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Heat pump installations of a new generation and their use as a highly efficient energy-saving and environmentally friendly energy technology for hot water supply. Heat pump installations

Heat supply in Russia, with its long and rather severe winters, requires very high fuel costs, which are almost 2 times higher than the costs of electricity supply. The main disadvantages of traditional sources of heat supply are low energy, economic and environmental efficiency. In addition, high transport tariffs for the delivery of energy carriers exacerbate the negative factors inherent in traditional heat supply.

A very indicative benchmark for assessing the possibility of using heat pump installations in Russia is foreign experience. It is different in different countries and depends on climatic and geographical features, the level of economic development, the fuel and energy balance, the ratio of prices for the main types of fuel and electricity, traditionally used heat and power supply systems, etc. Under similar conditions, taking into account the state of the Russian economy, foreign experience should considered as a real way of development in the future.

A feature of heat supply in Russia, in contrast to most countries of the world, is the widespread use of systems district heating in big cities.

Although over the past few decades, the production of heat pumps has increased dramatically all over the world, but in our country HPPs have not yet found wide application. There are several reasons here:

Traditional focus on district heating;

Unfavorable ratio between the cost of electricity and fuel;

The manufacture of HP is carried out, as a rule, on the basis of the closest refrigerating machines in terms of parameters, which does not always lead to optimal characteristics of HP;

In the recent past, there was a very long way from the design of a HP to its commissioning.

In our country, HP design issues have been dealt with since 1926 /27/. Since 1976, HP has been working in industry at a tea factory (Samtredia, Georgia) /13/, at the Podolsk Chemical and Metallurgical Plant (PCMZ) since 1987 /24/, at the Sagarejo Dairy Plant, (Georgia), in the Moscow region dairy farm "Gorki-2" since 1963

In addition to industry, HPs are used in mall(Sukhumi) for heat and cold supply, in a residential building (settlement Bucuria, Moldova), in the boarding house "Druzhba" (Yalta), climatological hospital (Gagra), resort hall of Pitsunda.

Back in the seventies, efficient heat recovery with the help of a heat pump installation was carried out at the Pauzhetskaya geothermal station in Kamchatka. The TNU successfully used the experimental system of geothermal heat supply for the residential area and the Sredne-Parutinsky greenhouse facility in Kamchatka. In these cases, geothermal sources /12/ were used as low-potential energy sources.

The use and especially the production of heat pumps in our country is developing with a great delay. The pioneer in the field of creation and implementation of heat pumps in the former USSR was VNIIholodmash. In 1986-1989 VNIIkholodmash has developed a number of vapor-compression heat pumps with heat output from 17 kW to 11.5 MW in twelve water-to-water sizes. Also, sea water as a source of low-temperature heat for heat pumps with a heat output of 300 - 1000 kW "water-air" heat pumps for 45 and 65 kW. Most of the heat pumps of this series have passed the stage of manufacturing and testing, prototypes at five refrigeration engineering plants. Four standard sizes were mass-produced heat pumps with a heat output of 14; 100; 300; 8500 kW. Their total release until 1992 was 3,000 units. The thermal power of the operating fleet of these heat pumps is estimated at 40 MW /16, 17/.

During this period, a number of fundamentally new heat pumps were developed - absorption, compression-resorption, compression, working on butane and water as a working substance, etc.

In the future, there was a decline in demand for heat pumps. Many mastered machines and new developments were unclaimed.

However, in last years the picture began to change. There are real economic incentives for energy conservation. This is due to the increase in energy prices, as well as changes in the ratio of tariffs for electricity and various types of fuel. In many cases, the requirements of environmental cleanliness of heat supply systems come to the fore. In particular, this applies to elite individual houses. New specialized firms appeared in Moscow, Novosibirsk, Nizhny Novgorod and other cities, designing heat pump installations and producing only heat pumps. Through the efforts of these firms, a fleet of heat pumps with a total thermal capacity of about 50 MW has been put into operation by now.

In a real market economy in Russia, heat pumps have the prospect of further expansion of use, and the production of heat pumps can become commensurate with the production of refrigeration machines of the corresponding classes. This prospect can be assessed when considering the conditions of heat and power supply in the main areas of application of heat pump installations: the housing and communal sector, industrial enterprises, health resorts and sports complexes, and agricultural production.

In the housing and communal sector, heat pump installations are most widely used in world and Russian practice, mainly for heating and hot water supply (DHW). Main directions:

Autonomous heat supply from heat pump installations;

The use of heat pump systems since existing systems district heating.

For autonomous heat supply of individual buildings, urban areas, settlements, mainly vapor-compression heat pumps with a thermal power of 10–30 kW are used in a unit of equipment of a separate building and up to 5 MW of districts and settlements.

Now the program "Development of non-traditional energy in Russia" is being implemented. It includes a section on the development of heat pump installations. The development forecast is based on estimates of heat pump manufacturers, as well as their users in the regions of the country, needs different power and the possibilities of their production. Most of the approximately 30 large projects envisage the use of heat pumps for the housing and communal sector, including in the district heating system.

A number of works are carried out within the framework of regional programs for energy saving and replacement of traditional heat supply systems with heat pump units: Novosibirsk Region, Nizhny Novgorod Region, Norilsk, Neryungri, Yakutia, Divnogorsk, Krasnoyarsk region. The average annual input of thermal capacities will be about 100 MW.

Under these conditions, heat generation by all operating heat pumps in 2005 amounted to 2.2 million Gcal, and replacement of organic fuel - 160 thousand tons of reference fuel, the total annual thermal output of 300 MW. Thus, a breakthrough in the distribution of heat pump installations is planned in Russia.

As for heat pumps with large thermal output from 500 kW to 40 MW, after 2005 the annual input of thermal outputs is on average 280 MW, and after 2010 - up to 800 MW. This is due to the fact that during this period it is planned to widely use heat pumps in district heating systems.

In agricultural production, the main areas of application of heat pumps are the primary processing of milk and heat supply to stalls.

On dairy farms, a significant share of energy costs up to 50% falls on the drive of compressors of refrigeration machines designed to cool freshly milked milk and heat water for sanitary and technological needs. This combination of demand for heat and cold creates favorable conditions for heat pump applications. A significant amount of heat is removed with the ventilated air of the stalls, which can be successfully used as a low-potential source for small heat pumps. On livestock farms, a heat pump unit provides simultaneous air conditioning in the stall rooms and heat supply to the production facilities.

The use of decentralized heat supply systems based on heat pump installations in areas where there are no heat networks, or in new residential areas, makes it possible to avoid many technological, economic and environmental disadvantages of district heating systems. Competitive with them in terms of economic parameters can only be district boiler houses operating on gas.

A significant number of such installations are currently in operation. And in the future, the need for them will grow rapidly.

Saving, substitution, organic fuel with the help of heat pumps occurs due to the useful involvement of emissions of low-grade heat at the CHP. This is achieved in two ways:

Direct use of cooling technical water CHP as a source of low-grade heat for a heat pump;

Use as a source of low-grade heat for a heat pump return network water returned to the CHPP, the temperature of which is reduced to 20 - 25 °C.

The first method is implemented when the heat pump is located near the CHP, the second - when it is used near heat consumers. In both cases, the temperature level of the source of low-potential heat is quite high, which creates the prerequisites for the operation of a heat pump with a high conversion factor.

The use of heat pumps in district heating systems can significantly improve the technical and economic performance of urban energy systems, providing:

An increase in thermal power by the amount of utilized heat previously released into the process water cooling system;

Reduction of heat losses during transportation of network water in main pipelines;

Ascending heating load by 15 - 20% with the same consumption of primary network water and a decrease in the deficit in network water at the central heating station in microdistricts remote from the CHPP;

The emergence of a backup source to cover peak heat loads.

To work in a district heating system, large heat pumps are required with a heating capacity from several megawatts for installation in heating substations and up to several tens of megawatts for use in thermal power plants.

At industrial enterprises, heat pump installations are used to utilize the heat of water circulation systems, the heat of ventilation emissions and the heat of waste water.

With the help of HPP, it is possible to transfer most of the waste heat to the heating network, about 50 - 60%. Wherein:

It is not necessary to expend additional fuel to produce this heat;

The ecological situation would improve;

By lowering the temperature circulating water the vacuum in the turbine condenser will significantly improve and the electrical output from the turbines will increase;

The loss of circulating water and the cost of its pumping will be reduced.

Until recently, it was believed that the use of heat pump installations in enterprises supplied with heat from CHPPs is obviously uneconomical. These estimates are now being revised. First, they take into account the possibility of using the technologies discussed above in the housing and communal sector with district heating. Secondly, the real price ratios for electricity, heat from CHPPs and fuel are forcing some enterprises to switch to their own generators of heat and even electricity. With this approach, the use of heat pump installations is most effective. Particularly large fuel savings are provided by "mini-CHP", based on a natural gas diesel generator, which simultaneously drives the heat pump compressor. Thermal installation at the same time provides heating and hot water supply of the enterprise.

It is also promising for enterprises to use a heat pump installation in combination with the use of heat from ventilation emissions. air heating characteristic of many industrial enterprises. Installations for the recovery of heat from ventilation emissions make it possible to preheat the outside air entering the workshop to 8 0 С. transformations.

Many industrial enterprises need artificial cold at the same time. So, in the factories of artificial fiber in the main production workshops, technological air conditioning is used to maintain temperature and humidity. Combined heat pump systems heat pump - refrigeration machine, which simultaneously produce heat and cold, are the most economical.

At present, HPPs are manufactured in Russia by individual orders by various companies. So, for example, in Nizhny Novgorod, the Triton company produces HP with a heat output from 10 to 2000 kW with a compressor power from 3 to 620 kW. The working substance is R-142; m≈ 3; the cost of TN from 5,000 to 300,000 US dollars. Payback period 2 - 3 years.

Before today CJSC Energia remains practically the only serial manufacturer of vapor-compression heat pumps in our country. Currently, the company is mastering the production of absorption heat pump units, as well as turbocompressor heat pumps with a large unit capacity of over 3 MW.

Firm "Energy" has manufactured and launched about 100 heat pump units of various capacities throughout the territory former USSR. The first units were installed in Kamchatka.

On fig. 8.1. Some of the objects where the heat pumps of CJSC "Energia" operate.

CJSC Energia manufactures heat pumps with a heating capacity of 300 to 2500 kW with a guarantee of operation from 35 to 45 thousand hours. The price of a heat pump is set at the rate of 160 - 180 USD. for 1 kW of heat output (Q in).

Since its foundation, CJSC Energia has put into operation heat pump units of various capacities in the CIS and neighboring countries. In total, from 1990 to 2004 CJSC ENERGIA introduced 125 heat pumps of various capacities at 63 facilities in Russia and neighboring countries.

Rice. 8.1. Heat pumps CJSC "Energia" installed:

Heat pump unit in school No. 1, Karasuk, Novosibirsk region and heat pump NT - 1000 at the CHPP in Rechkunovka village, Novosibirsk

Below is a brief annotation of the largest object presented by CJSC Energia, Novosibirsk, Table. 8.1..

Table 8.1. Some objects where heat pumps of CJSC Energia operate

Object name	Heat source	Total power, kW	Type of heat pumps	Year of launch
Tyumen, Velizhansky water intake, heating of the village	Drinking water 7-9 °C		2 pumps NT-3000
Karasuk, Novosibirsk region, heating of secondary school No. 1	Ground water 24 °С		2 pumps NKT-300
Gornoaltaysk, CSB, building heating	Ground water 7 - 9 °С		1 pump NKT-300
P / household "Mirny", Altai Territory, heating of the village	Ground water 23 °С		3 pumps NKT-300
Lithuania, Kaunas, artificial fiber plant, plant shop heating.	Technological discharges - water 20 °С		2 pumps NT-3000	1995 1996
Moscow, Interstroyplast (People's Windows), water cooling for extruders	Process water 16 °C		1 pump NT-500
Kazakhstan, Ust-Kamenogorsk, Kazzinc JSC, heating feed water before chemical water treatment from 8 to 40 °С	Recycled process water (cooling tower replacement)		1 pump NT-3000
Krasnoyarsk, Moscow Scientific Center, heating of the Institute of Ecology	Yenisei - water in winter is about 2 ° C		1 pump NT-500
Yelizovo, Kamchatka region, water intake, building heating	Drinking water 2 - 9 °С		1 pump NKT-300

In the Nizhny Novgorod region, the development and production of HP with

1996 CJSC Research and Production Company Triton Ltd. Over the past period, HPs of various capacities have been designed and installed:

TN-24, Q = 24 kW, residential heating F = 200 m 2. BAT - groundwater. Installed in the village of Bolshiye Orly, Borsky District, Nizhny Novgorod Region, 1998.

ТН-45, Q = 45 kW, complex heating administrative buildings, warehouses and garages, F > 1200 m 2 , NIT - groundwater. Installed in the Moscow region, Nizhny Novgorod in 1997. The owner is Symbol LLP.

ТН-600, Q = 600 kW, heating, hot water supply of the hotel complex and three cottages, F > 7000 m 2 , NIT - groundwater. Installed in Avtozavodsky district, Nizhny Novgorod, 1996. Owner - GAZ.

ТН-139, Q = 139 kW, heating, DHW production building F > 960 m 2, NIT - ground. Installed in Kanavinsky district, Nizhny Novgorod, 1999. Owner - GZD.

ТН-119, Q = 119 kW, heating, hot water supply of dispensary F > 770 m 2 , NIT - groundwater. Installed in Borsky district, Nizhny Novgorod region in 1999. The owner is Tsentrenergostroy.

ТН-300, Q = 300 kW, heating, school hot water supply F > 3000 m 2 , BAT - groundwater. It was put into operation in Avtozavodsky district, Nizhny Novgorod in 1999. The owner is the education department of the district administration.

TN-360, Q = 360 kW, heating, hot water supply of the recreation center F > 4000 m 2, NIT - groundwater. It was put into operation in Dalnekonstantinovsky district, Nizhny Novgorod region in 1999. The owner is Gidromash.

ТН-3500, Q = 3500 kW, heating, hot water supply, ventilation of the administrative building of the new depot F > 15000 m 2 , NIT - return water, heat supply systems of the Sormovskaya CHPP. Kanavinsky district, Nizhny Novgorod 2000 Owner - GZD.

Two HP Q = 360 and 200 kW, for Penza region, 2 Gcal - for Tuapse.

With the participation of specialists from the Institute for High Temperatures of the Russian Academy of Sciences (IHT RAS), a number of experimental and demonstration installations and systems using heat pumps for heat supply to various objects /48/ have been developed and created.

In the suburbs of der. In Gribanovo, in 2001, a solar-heat pump heat supply system for the laboratory building was put into trial operation on the territory of the NPO Astrophysics test site. As a source of low-grade heat for the heat pump, a vertical ground heat exchanger with a total length of about 30 m was used (technology of OAO Insolar-Invest). Heating devices - fancoils and floor heater. Solar collectors provide hot water supply, excess solar heat in the summer is pumped into the soil to accelerate the restoration of its temperature regime.

In 2004 JSC "Insolar-Invest" an experimental automated heat pump unit (ATNU) was put into operation, designed to heat tap water in front of the boilers of the Zelenograd district heating plant. Table. 8.2.

As a low-grade source of heat, untreated domestic wastewater is used, which is accumulated in the receiving tank of the main sewage pumping station (GKNS). ATNU is designed to test the technology for utilizing the heat of raw wastewater, determine the effect of the operation of the installation on the regime parameters of the thermal power plant, check the economic efficiency and develop recommendations for the creation of similar installations in the Moscow city economy.

Table 8.2. Main design and operational parameters of ATNU

ATNU includes five main parts:

Heat pump heat unit (TTU);

Pipelines of the low-grade heat collection system (SSNT);

heat exchanger;

Pressure sewer pipelines;

A group of feeding fecal pumps in the GKNS.

Untreated wastewater, having a temperature of 20 0 C, from the receiving tank, fecal pumps Flygt firms are fed into the waste heat exchanger, where they give off heat to the intermediate heat carrier (water), cooling to a temperature of 15.4 0 С, and then return to the tank. The total consumption of wastewater - 400 m 3 / h.

The raw wastewater circulation circuit is designed taking into account the practice of operating pressure pipelines in sewerage systems. The flow rate in the channels of the heat exchanger ensures the absence of deposits on the heat exchange surfaces.

Heated in the waste heat exchanger to a temperature of 13 0 C, the intermediate heat carrier is supplied to the heat pumps, where it is cooled to a temperature of 8 0 C, giving off heat to the freon of the vapor-compression circuit, and again sent to the waste heat exchanger.

The use of heat pumps in the ring circuit in Russia.

In general, examples of the use of single heat pump installations are considered. These installations include one or more heat pumps that operate independently of each other and perform a specific heat supply function. There is an integrated ring heat pump system that allows you to achieve maximum efficiency and savings. Several HPs are installed in the ring system, which are used to produce both heat and cold, depending on the needs of different parts of the building. There is very little information about such systems.

Some time ago, a company supplying heat pumps in Russia implemented a project to modernize the heating and air conditioning system in one of the Moscow hotel and entertainment centers /54/. Let's see how this system works. 8.2.

The water circuit consists of a water pump and a low-temperature storage tank, due to the volume of which the accumulation of heat increases and the temperature of the water in the circuit stabilizes. All VTs are connected to this circuit.

The arrows show the direction of heat movement. Behind the circulation pump, heat pumps of the "water - water" type are installed, which heat the water in the pools of the complex. Pools can be several, different volumes and with different water temperatures. For each of the pools, a TN is established.

HP "water - air", cooling air in kitchen areas, which serve restaurants, bars, cafes, canteen for staff. In these rooms, there is always a large heat release and the HP cools the air in them, taking heat into the common water circuit.

Rice. 8.2. An example of an annular heat pump.

HP "water - water" is used to utilize excess heat through the hot water supply system (DHW). Heat is taken from the water circuit of administrative and office space. For air conditioning, each of these rooms has its own reversible heat pump for heat or cold. In the warm season, all these pumps will cool the air, and in the cold season, they will heat it up.

All these HPs are combined in one ring with HPs in other parts of the building with their needs for heat and its surpluses (technical and functional rooms, cafes, restaurants, winter gardens, refrigeration rooms) and heat is exchanged between them.

For normal operation The HP temperature of the water in the circuit must be between 18 0 С and 35 0 С. If the number of HPs operating in heating mode is equal to the number of HPs operating in cooling mode, then the system does not require heat input from the outside or its removal to the outside. The ring system operates most efficiently at outdoor temperatures from -4 0 С to +14 0 С. The energy costs for the operation of the entire ring circuit are only in the cost of work circulation pump and individual heat pumps in the premises. There is no need for expensive sources of thermal energy, gas or electric heaters or its receipt from the outside.

With more low temperatures outdoor air and lack of heat in the water circuit, the temperature in it can drop below 18 0 C. Then, to heat the water circuit to the required parameter, you can use external sources of the city heating plant, a boiler or a geothermal heat pump that pumps heat from groundwater or from a nearby reservoir . Sources such as ground water or a river with a temperature of 4 0 C will be enough to heat the water in the circuit to a level of 18 0 C and thus for the normal operation of all building heat pumps.

Unfortunately, in Russia this approach has so far been restrained. at great expense at the design stage and the lack of economic incentives for energy-saving and environmentally friendly solutions. Other sources of low-grade heat can also be used in ring heat pump systems. In many facilities: large laundries, enterprises using water in technological processes, there is a significant flow of wastewater at a sufficiently high temperature. In this case, it makes sense to include a heat pump in the ring system that utilizes this heat.

The water circuit also includes a low-temperature storage tank. The larger the volume of this tank, the more heat that can be used if necessary, the system is able to accumulate. The ring system can completely take over the heating function - a monovalent system. However, it is possible to use heat pumps simultaneously with a traditional heating system - a bivalent system. If there are enough heat sources connected to the ring at the site, and if there is a small need for hot water, the ring system can fully satisfy these needs.

The ring heat pump system can only be used for air conditioning in rooms where there is only such a need. But ring air conditioning systems are especially effective in buildings where there are many rooms with different purposes that require different air temperatures. HP as an air conditioner works more efficiently than many other known air conditioning devices.

The basis of the high efficiency of heat pumps lies precisely in the fact that the energy spent inside the building to produce heat is not discharged "into the pipe", but is used inside the building where there is a need for it. Heat is stored and efficiently transferred within the ring system.

The second important factor of economic efficiency is the possibility of using low-potential "gratuitous" heat sources - artesian wells, reservoirs, sewers. With the help of compressors, using a source with a temperature of 4 ° C, we get hot water 50 - 60 0 C, spending 1 kW of electricity to obtain 3 - 4 kW of thermal energy. If when using a conventional steam heating system, the efficiency is only 30 - 40%, then with heat pumps, the efficiency increases several times.

In particular, the following results were achieved in the described hotel and entertainment center.

Reduced capital costs for the purchase and installation of equipment by 13 - 15% compared to the chiller-fan coil system. The system of engineering communications has been simplified in comparison with the central air conditioning system. A comfortable microclimate has been created in the premises: compliance of air pressure, humidity and temperature with hygienic requirements. The total cost of heating and hot water supply is reduced by more than 50% compared to central heating.

An annular heat pump system does not require complex and expensive control and monitoring devices to optimize its operation. It is enough with the help of several thermal relays, thermostats to keep the temperature in the water circuit within the specified limits. For additional convenience and visual control, expensive automation can also be used.

With a given temperature range in the water circuit of the ring system of 18 - 35 0 C, no condensate forms on the pipes and there is no noticeable heat loss. This is an important factor with a significant branching of the system (distribution, risers, connections, which can be quite a lot in buildings with complex architecture).

When using a HP in a room ventilation system, the number and total length of air ducts can be reduced compared to central air conditioning units. Heat pump installations are placed directly in air-conditioned rooms or in adjacent ones, that is, the air is conditioned right on the spot. This avoids the transportation of finished air through long ducts.

In Russia, the first such TH-based system was installed in 1990 at the Iris Congress Hotel. This is an annular bivalent air conditioning system of the American company ClimateMaster. For heating in the hotel, a heating kitchen, laundry, technical rooms, refrigeration units and freezers, there is an exchange of heat during the air conditioning of hotel rooms, conference rooms, a fitness center, restaurants, and administrative premises. 15 years of operation of the system have shown the reliability of the equipment and the feasibility of its use in our climate.

When designing a heat pump system for an object, it is necessary, first of all, to study all possible low-potential heat sources and all possible consumers of high-potential heat at this object, to evaluate all heat gains and all heat losses. It is necessary to choose those sources for utilization where the heat is released fairly evenly and for a long time. Neat and accurate calculations ensure stable and cost-effective operation of HP. The total capacity of waste heat pumps should not be uselessly redundant. The system must be balanced, but this does not mean at all that the total capacities of heat sources and consumers should be close, they may differ, and their ratio may also change significantly when the operating conditions of the system change. The flexibility of the system allows you to choose when designing it best option and lay the groundwork for its further expansion. It is also necessary to take into account the peculiarities of the climatic conditions of the region. Climatic conditions are the key to choosing an efficient climate system.

In the southern latitudes, the main task is to cool the air and release heat to the outside, the utilization of which for heating is meaningless. Traditional chiller systems - fan coils or the like are quite suitable here. AT northern latitudes too much energy is required to heat the facility, a lot of high-potential heat that will have to be supplied to the system. Therefore, it will be necessary to install a bivalent system, HP in combination with a heating system. In a temperate climate of mid-latitudes, it is advisable to use a monovalent ring system, where its efficiency is maximum.

To date, it is widely believed that TN is too expensive. The costs for the installation and installation of equipment are high, and with the existing heat prices in Russia, the payback period is too long. However, practice shows that the installation of heat pump systems in large and medium-sized facilities can save 10 - 15% on capital investments, not to mention operating costs. In addition, ring systems reduce the consumption of energy resources as much as possible, the prices of which are increasing more and more rapidly.

According to Research.Techart calculations, 5.3 MW of heat pumps were installed in Russia in 2009. The dynamics of the Russian market of geothermal pumps, according to Research.Techart forecasts, will be low in the medium term, due to the crisis in the economy. However, in some regions the market can develop very actively.

The upward trend in demand from the infrastructure and housing sectors will continue, and the bulk of sales will be 15-38kW PTNs. The structure of consumption in relation to the types of PTN will not change. An increase in the share of domestic products in the total market volume is predicted.

In the long term, the leading factor in the development of the market will be the implementation of the state energy strategy. After 2016, active market growth is predicted. In the area of performance, a transition to PTN with carbon refrigerants is expected. At the same time, the consumption of both low- and medium-power, and high-power heat pumps will increase, which is due to the prospects for using wastewater heat recovery systems. Against the background of increasing demand, the active development of the domestic production base will begin - the number Russian manufacturers will increase and they will take a leading position in the market.

By 2020, the size of the CVT market may reach 8,000 - 11,000 units, 460 - 500 MW. Forecast of the size of the PTN market for 2030 - the moment of completion of the implementation of the current Energy Strategy of Russia - 11,000 - 15,000 units, 500 - 700 MW.

Over the past year, heat pumps have occupied their niche in the Russian climate market, among other popular technologies. Discussion of the advantages and disadvantages of heat pump installations (HPU) took place both on the pages of the industry press, and at thematic conferences and round tables. A lot of information has recently appeared about heat pumps - both in the Russian-language Internet and in specialized media. However, there are still very few publications on integrated heat pump systems. The purpose of this article is to somewhat fill this gap, to summarize some of the questions that arise in specialists when they first get acquainted with ring heat transfer systems, and to briefly answer them.

So, it is known about heat pumps that this is climatic equipment capable of utilizing the heat of the environment, using a compressor to raise the temperature of the coolant to the desired level and transfer this heat to where it is needed.

It is almost always possible to extract heat from the environment. After all " cold water"- a subjective concept based on our feelings. Even the coldest river water contains a certain amount of heat. But it is known that heat only passes from a hotter body to a colder one. Heat can be forcibly directed from a cold body to a warm one, then the cold body is even more cool down, and the warm heat up.Using a heat pump that "pumps out" heat from the air, river water or earth, lowering their temperature even more, it is possible to heat the building.In the classical case, it is considered that, spending 1 kW of electricity on work, HPP can produce from 3 to 6 kW of thermal energy.In practice, this means that the power of two or three household light bulbs in winter period can be heated living room medium sizes. In summer, by operating in reverse mode, the heat pump can cool the air in the rooms of the building. The heat from the building will be removed by being absorbed by the atmosphere, river or earth.

Currently, there is a huge variety of heat pump installations, which allows them to be widely used in industry, agriculture, in housing and communal services. As an example of the use of HPP, at the end of the article we will consider two projects - one of them is a large-scale ring system project implemented in the Krasnodar Territory, the second is a small-scale construction facility in the Moscow region.

What are heat pumps?

Heat pumps come in a variety of heat outputs ranging from a few kilowatts to hundreds of megawatts. They can work with various sources heat in different states of aggregation. In this regard, they can be divided into the following types: water-water, water-air, air-water, air-air. Heat pumps are produced, designed to work with sources of low-grade heat of various temperatures, up to negative. They can be used as a receiver of high potential heat requiring different temperature even above 1000C. Depending on this, heat pumps can be divided into low temperature, medium temperature and high temperature.

Heat pumps also differ in terms of technical device. In this regard, two directions can be distinguished: vapor compression and absorption HPP. Heat pumps can also use other types of energy for their work, in addition to electricity, for example, they can run on different types of fuel.

Various combinations of types of low-potential heat sources and high-grade heat receivers provide a wide variety of types of heat pumps. Here are some examples:

HPP, using the heat of groundwater for heating;
HPP, using the heat of a natural reservoir for hot water supply;
HPU - air conditioner using sea water as a source and receiver of heat;
HPI - air conditioner using outside air as a source and receiver of heat;
HPI for heating the water of the swimming pool, using the heat of the outside air;
HPP, utilizing wastewater heat in the heat supply system;
HPP, utilizing the heat of engineering and technical equipment in the heat supply system;
HPP for cooling milk and at the same time heating water for hot water supply on dairy farms;
HPP for heat recovery from technological processes in the primary heating of supply air.

A wide variety of heat pump equipment is mass-produced, but heat pumps can also be manufactured according to special projects. There are experimental installations, pilot samples, as well as many theoretical developments.

If the facility provides for the use of several heat pumps, which will be designed to produce both heat and cold, their efficiency will increase many times if they are combined into a single system. These are the so-called ring heat pump systems (KHNS). Such systems are expedient to use on average and large objects.

Ring air conditioning systems

These systems are based on water-air heat pumps that perform the functions of air conditioning in the premises. In the room where air conditioning is provided (or next to it), a heat pump is installed, the power of which is selected in accordance with the parameters of the room, its purpose, the characteristics of the required supply air - exhaust ventilation, the possible number of people present, the equipment installed in it and other criteria. All HPPs are reversible, that is, they are designed for both cooling and heating air. All of them are connected by a common water circuit - pipes in which water circulates. Water is both a source and a receiver of heat for all HPI. The temperature in the circuit can vary from 18 to 320C. Between heat pumps that heat the air and those that cool it, heat is exchanged through a water circuit. Depending on the characteristics of the premises, as well as on the time of year and time of day, either heating or cooling of the air may be required in different rooms. With simultaneous operation in the same building of HPI producing heat and cold, heat is transferred from rooms where it is in excess to rooms where it is not enough. Thus, there is an exchange of heat between the zones, united in a single ring.

In addition to HPP performing the function of air conditioning, HPP for other purposes may also be included in the HPP. If there are sufficient heat requirements at the facility, waste heat can be efficiently utilized through the ring system using HPI. For example, in the presence of an intensive wastewater flow, it makes sense to install a water-to-water HPI, which will allow waste heat to be utilized by means of a HPS. Such a heat pump will be able to extract heat from wastewater, transfer it using a ring circuit, and then use it to heat rooms.

The air removed from the building by exhaust ventilation also contains a large amount of heat. In the absence of a large amount of impurities in the exhaust air that impede the operation of the HPI, it is possible to utilize the heat of the exhaust air by installing an air-to-water HPI. Through CHP this heat can be used by all consumers in the building, which is difficult to achieve using traditional regenerators and recuperators. In addition, the recycling process in this case can be more efficient, since it does not depend on the temperature of the outside air taken in by the supply ventilation, and on the set temperature for heating the air injected into the premises.

In addition, when operating reversible heat pumps in both wastewater and exhaust ventilation, they can be used to remove excess heat from the water circuit during the warm season, and thereby reduce the required capacity of the cooling tower.

In the warm season, with the help of heat pumps, excess heat in the water circuit is utilized through consumers available at the facility. For example, a water-to-water HPI can be connected to the ring system, transferring excess heat to the hot water supply system (DHW). In a facility with little need for hot water, this heat pump may be enough to fully satisfy them.

If the facility has one or more swimming pools, for example, in health care facilities, rest homes, entertainment complexes and hotels, the pool water can also be heated using a water-to-water heat pump by connecting it to the KTS.

Combination of ring systems with other systems

The ventilation system in buildings using an annular heat pump system must be developed taking into account the peculiarities of the operation of HPPs that condition air. It is obligatory to recirculate air in the volume that is necessary for the stable operation of these heat pumps, maintaining the set temperature in the room and efficient heat recovery (the exception is those cases where recirculation is undesirable, for example, swimming pool halls, local kitchen hoods). There are some other features in the development of ventilation with CTNS.

However, at the same time, the ring system provides for more simple systems ventilation than other types of air conditioning. Heat pumps carry out air conditioning directly on site, in the room itself, which eliminates the need to transport the finished air through long, heat-insulated air ducts, as happens, for example, with central air conditioning.

The ring system can fully take over the functions of heating, but joint use with the heating system is not excluded. In this case, a less powerful and technically simpler heating system is used. Such a bivalent system is more suitable in northern latitudes, where more heat is needed for heating, and it will have to be brought in more from a high potential source. If the building has individual systems air conditioning and heating, these systems often literally interfere with each other, especially during transitional periods. The use of a ring system in conjunction with a heating system does not give rise to such problems, since its operation is completely dependent on the actual state of the microclimate in each individual zone.

At enterprises, ring heat pump systems can be involved in heating or cooling water or air for technological purposes, and these processes will be included in the balance of the general heat supply of the enterprise.

Speaking about traditional heat supply systems, it is difficult to agree with their limited efficiency. Heat is partially used, quickly dissipated into the atmosphere (during heating and ventilation), removed from sewage(through hot water supply, technological processes) and in other ways. It is also good if, for some economy, air-to-air heat exchangers are installed in the ventilation system, or water-to-water heat exchangers for heat recovery, for example, refrigeration units, or some other local heat recovery devices. KTNS, on the other hand, solves this problem in a complex manner, in many cases making it possible to make heat recovery more efficient.

Automated control of ring systems

To the dismay of many manufacturers of expensive automation systems, heat pump systems do not require complex automation controls. All regulation here is reduced only to maintaining a certain value of the water temperature in the circuit. In order to prevent water cooling below the set limit, it is necessary to turn on the additional heater in time. And vice versa, in order not to exceed the upper limit, it is necessary to turn on the cooling tower in a timely manner. Automatic control this simple process can be implemented using several thermostats. Since the water temperature in the HPNS circuit can vary over a fairly wide range (usually from 18 to 320C), there is also no need to use precise control valves.

As for the process of heat transfer from the heat pump to the consumer, it is controlled by automation built into each heat pump. For example, HPI for air conditioning have a temperature sensor (thermostat) installed directly in the room. This ordinary thermostat is quite enough to control the operation of the HP.

The heat pump fully provides the necessary temperature parameters air in the premises, which makes it possible to refuse control dampers in the ventilation system and control valves in the heating system (with a bivalent system). All these circumstances contribute to reducing the cost and increasing the reliability of engineering systems as a whole.

At large facilities where the ring system includes a large number of heat pumps and where various types of HPPs are installed (for air conditioning, heat recovery and for ensuring technological processes), it often makes sense to implement a more complex automated control system that allows optimizing the operation of the entire system.

The operation of an annular heat pump system is affected by the following factors:

Firstly, the temperature of the water in the circuit. The heat conversion coefficient (COP) depends on it, that is, the ratio of the amount of heat supplied to the consumer to the amount of energy consumed by the heat pump;
secondly, the outside air temperature;
thirdly, the operating parameters of the cooling tower. For the same amount of heat removed at different conditions different amounts of energy consumed by the cooling tower can be expended. This, in turn, also depends on the temperature of the outside air, its humidity, the presence of wind and other conditions;
fourthly, from the number of employees in this moment in the heat pump system. Here, the total power of the HPI, which take heat from the water circuit, is important in comparison with the power of all HPI, which transfer heat to the circuit, that is, the amount of heat entering the circuit or removed from it.

Good for the kids, good for the budget

Let's move on to the description of projects using ring heat pump systems.

The first project is the reconstruction of a conventional secondary school in the south of Russia. Last summer, the administration of the Krasnodar Territory implemented this project in the city of Ust-Labinsk (city school No. 2). During the reconstruction, the highest standards were maintained in ensuring sanitary requirements and a comfortable stay for children at school. In particular, a full-fledged climate system was installed in the building, providing zone-by-zone control over temperature, fresh air inflow and humidity.

When implementing this project, engineers, firstly, wanted to ensure the proper level of comfort, individual control in each class. Secondly, it was assumed that the ring system would significantly reduce the cost of heating the school and solve the problem of low water temperature in the heating plant on the school site. The system consists of more than fifty heat pumps manufactured by Climatemaster (USA) and a cooling tower. It receives additional heat from the heating plant of the city. The climate system is under automated control and is able to independently maintain the most comfortable for a person and at the same time economical modes of operation.

The operation of the described system in the winter months gave the following results:

before modernization (before the installation of heat pumps), the monthly heating costs for 2,500 m2 were 18,440 rubles;
after the modernization of the building, the heated area increased to 3000 m2, and the monthly heating costs decreased to 9800 rubles.

Thus, the use of heat pumps made it possible to more than halve the cost of heating the building, the heated area of which increased by almost 20%.

Autonomous heat

The problems of cottage construction in the Moscow region today are due to the fact that the infrastructure (electrical networks, water pipes) often does not allow new settlements to grow. The existing transformer substations cannot cope with the increased loads. Constant interruptions in the supply of electricity (accidents at old substations, breaks in dilapidated wires) force consumers to look for ways of autonomous power supply.

In the described project, the engineers were faced with the task of providing a multi-room two-story cottage with an attic with heat and electricity. The total heated area of the house was 200 m2. Of the summed communications - artesian water and electricity.

Since the requirement of energy efficiency was put at the forefront, it was decided to install solar panels. 3.5 kW solar photovoltaic modules were purchased and installed right on the site behind the house. According to the calculations of the engineers, this should have been enough to recharge the batteries, which, in turn, would uninterruptedly feed the house and the heating system. The total cost of the system was about 27,000 US dollars. Given that the received source free electricity, and this item will be crossed out from the family budget, it turns out that the installation costs solar battery payback in less than 10 years. And if we consider that otherwise we would have to build a substation or live with constant power outages, then the costs can already be considered paid off.

For heating, it was decided to use a geothermal heat pump system. An American water-to-water heat pump was purchased. This type of heat pump produces hot water using heat exchangers, which can be used for hot water supply and heating with radiator batteries. The circuit itself, supplying low-grade heat to the heat pump, was laid directly on the site adjacent to the cottage, at a depth of 2 m. The circuit is a polyethylene pipe with a diameter of 32 mm and a length of 800 m. at 10,000 US dollars.

Thus, having spent about 40,000 US dollars on organizing his own autonomous energy system, the owner of the cottage excluded the cost of heat supply from his budget and provided reliable autonomous heating.

Possibilities of application of ring systems

From the foregoing, it follows that the possibilities of using an annular heat pump system are unusually wide. They can be used on a wide variety of objects. These are administrative, public buildings, medical and health institutions, rest houses, entertainment and sports complexes, various industrial enterprises. The systems are so flexible that their application is possible in a variety of cases and in very in large numbers options.

When developing such a system, first of all, it is necessary to assess the needs for heat and cold of the object being designed, to study all possible heat sources inside the building and all prospective heat receivers, to determine heat gains and heat losses. The most suitable heat sources can be used in the ring system if this heat is required. The total capacity of the heat recovery heat pumps should not be needlessly redundant. Under certain conditions, the most profitable option may be the installation of HPP using external environment as a source and receiver of heat. The system must be balanced in terms of heat, but this does not mean at all that the total capacities of heat sources and consumers should be equal, they can differ, since their ratio can change significantly when the operating conditions of the system change.

How to deal with the fire hazard of air ducts

Behind recent times the number of fires and even explosions inside the air ducts of ventilation and air conditioning systems has sharply increased. Although such fires have always occurred, recent changes have led to much larger fires involving more of people.

Analysis of advanced heat supply systems

This report discusses issues related to the transition of district heating systems to decentralized. The positive and negative aspects of both systems are considered. The results of the comparison of these systems are presented.

Heat pump units (HPU) use natural renewable low-potential thermal energy of the environment (water, air, soil) and increase the potential of the main heat carrier to more high level, while spending several times less primary energy or organic fuel. Heat pump installations operate according to the Carnot thermodynamic cycle, in which low-temperature liquids (ammonia, freon, etc.) serve as the working fluid. The transfer of heat from a source of low potential to a higher temperature level is carried out by the supply of mechanical energy in the compressor (steam-pressure HPI) or additional heat supply (in absorption HPI).

The use of HPP in heat supply systems is one of the most important intersections of low temperature technology with thermal power engineering, which leads to energy saving of non-renewable energy sources and environmental protection by reducing CO2 and NOx emissions into the atmosphere. The use of HPP is very promising in combined systems heat supply in combination with other technologies for the use of renewable energy sources (solar, wind, bioenergy) and allows you to optimize the parameters of the associated systems and achieve the highest economic performance.

Let us choose as a working refrigerant - R 22, which has the following parameters: refrigerant flow Oa \u003d 0.06 kg / s; boiling point Т0 = 3 °С; condensation temperature Тk = 55 °С; coolant temperature at the inlet to the evaporator from a low potential source Ґн = 8 °С; coolant (water) temperature at the condenser outlet f = 50 °C; coolant flow rate in the condenser Ok = 0.25 kg/s; coolant temperature difference in the condenser D4 = 15 °C; power consumed by the compressor, N = 3.5 kW; HPI heat output = 15.7 kW; conversion factor tsnt = 4.5.

circuit diagram vapor compression HPI is shown in fig. 7.2 and includes the evaporator, compressor, condenser and throttle.

4 - expansion throttle valve; 5 - refrigerant evaporation coil;

6 - evaporation tank; 7 - water low-grade energy source

8 - drain to NIE; 9 - water from the heating system or plumbing;

It is almost always possible to extract heat from the environment. After all, "cold water" is a subjective concept, based on our feelings. Even the coldest river water contains some heat. But it is known that heat passes only from a hotter body to a colder one. Heat can be forcibly directed from a cold body to a warm one, then the cold body will cool down even more, and the warm one will heat up. Using a heat pump that "pumps out" heat from the air, river water or earth, lowering their temperature even more, it is possible to heat the building. In the classical case, it is considered that, spending 1 kW of electricity on operation, HPI can produce from 3 to 6 kW of thermal energy. In practice, this means that the power of two or three household light bulbs in winter can heat a medium-sized living room. In summer, by operating in reverse mode, the heat pump can cool the air in the rooms of the building. The heat from the building will be removed by being absorbed by the atmosphere, river or earth.

Currently, there is a huge variety of heat pump installations, which allows them to be widely used in industry, agriculture, housing and communal services. As an example of the use of HPP, at the end of the article we will consider two projects - one of them is a project of a large-scale ring system implemented in the Krasnodar Territory, the second is a small-scale construction facility in the Moscow region.

What are heat pumps?

Heat pumps come in a variety of heat outputs ranging from a few kilowatts to hundreds of megawatts. They can work with various heat sources in different states of aggregation. In this regard, they can be divided into the following types: water-water, water-air, air-water, air-air. Heat pumps are produced, designed to work with sources of low-grade heat of various temperatures, up to negative. They can be used as a receiver of high potential heat requiring different temperatures, even above 1000C. Depending on this, heat pumps can be divided into low temperature, medium temperature and high temperature.

Heat pumps also differ in their technical design. In this regard, two directions can be distinguished: vapor compression and absorption HPP. Heat pumps can also use other types of energy for their work, in addition to electricity, for example, they can run on different types of fuel.

Various combinations of types of low-potential heat sources and high-grade heat receivers provide a wide variety of types of heat pumps. Here are some examples:

HPP, using the heat of groundwater for heating;
HPP, using the heat of a natural reservoir for hot water supply;
HPI-air conditioner using sea water as a source and receiver of heat;
HPI-air conditioner using outside air as a source and receiver of heat;
HPI for heating the water of the swimming pool, using the heat of the outside air;
HPP, utilizing wastewater heat in the heat supply system;
HPP, utilizing the heat of engineering and technical equipment in the heat supply system;
HPP for cooling milk and at the same time heating water for hot water supply on dairy farms;
HPP for heat recovery from technological processes in the primary heating of supply air.

A wide variety of heat pump equipment is mass-produced, but heat pumps can also be manufactured according to special projects. There are experimental installations, pilot industrial samples, as well as many theoretical developments.

Ring air conditioning systems

These systems are based on water-air heat pumps that perform the functions of air conditioning in the premises. In the room where air conditioning is provided (or near it), a heat pump is installed, the power of which is selected in accordance with the parameters of the room, its purpose, the characteristics of the required supply and exhaust ventilation, the possible number of people present, the equipment installed in it and other criteria. All HPPs are reversible, that is, they are designed for both cooling and heating air. All of them are connected by a common water circuit - pipes in which water circulates. Water is both a source and a receiver of heat for all HPI. The temperature in the circuit can vary from 18 to 320C. Between heat pumps that heat the air and those that cool it, heat is exchanged through a water circuit. Depending on the characteristics of the premises, as well as on the time of year and time of day, either heating or cooling of the air may be required in different rooms. With simultaneous operation in the same building of HPI producing heat and cold, heat is transferred from rooms where it is in excess to rooms where it is not enough. Thus, there is an exchange of heat between the zones, united in a single ring.

If the facility has one or more swimming pools, for example, in health facilities, rest homes, entertainment complexes and hotels, the pool water can also be heated using a water-to-water heat pump by connecting it to the KTN.

Combination of ring systems with other systems

The ventilation system in buildings using an annular heat pump system must be developed taking into account the peculiarities of the operation of HPPs that condition air. It is obligatory to recirculate air in the amount necessary for the stable operation of these heat pumps, maintaining the set temperature in the room and efficient heat recovery (the exception is those cases where recirculation is undesirable, for example, swimming pool halls, local kitchen hoods). There are some other features in the development of ventilation with CTNS.

However, at the same time, the ring system provides for simpler ventilation systems than with other air conditioning methods. Heat pumps carry out air conditioning directly on site, in the room itself, which eliminates the need to transport the finished air through long, heat-insulated air ducts, as happens, for example, with central air conditioning.

The ring system can fully take over the functions of heating, but joint use with the heating system is not excluded. In this case, a less powerful and technically simpler heating system is used. Such a bivalent system is more suitable in northern latitudes, where more heat is needed for heating, and it will have to be supplied in larger quantities from a high-potential source. If separate air conditioning and heating systems are installed in the building, then these systems often literally interfere with each other, especially during transitional periods. The use of a ring system in conjunction with a heating system does not give rise to such problems, since its operation is completely dependent on the actual state of the microclimate in each individual zone.

Speaking about traditional heat supply systems, it is difficult to agree with their limited efficiency. Heat is partially used, quickly dissipated into the atmosphere (during heating and ventilation operation), removed with wastewater (through hot water supply, technological processes) and in other ways. It is also good if, to provide some efficiency, air-to-air heat exchangers are installed in the ventilation system, or water-to-water heat exchangers for heat recovery, for example, refrigeration units, or some other local heat recovery devices. KTNS, on the other hand, solves this problem in a complex manner, in many cases making it possible to make heat recovery more efficient.

Automated control of ring systems

To the dismay of many manufacturers of expensive automation systems, heat pump systems do not require complex automation controls. All regulation here is reduced only to maintaining a certain value of the water temperature in the circuit. In order to prevent water cooling below the set limit, it is necessary to turn on the additional heater in time. And vice versa, in order not to exceed the upper limit, it is necessary to turn on the cooling tower in a timely manner. Automatic control of this simple process can be implemented using several thermostats. Since the water temperature in the HPNS circuit can vary over a fairly wide range (usually from 18 to 320C), there is also no need to use precise control valves.

The heat pump fully provides the necessary temperature parameters of the air in the premises, which makes it possible to refuse control dampers in the ventilation system and control valves in the heating system (with a bivalent system). All these circumstances contribute to reducing the cost and increasing the reliability of engineering systems as a whole.

The operation of an annular heat pump system is influenced by the following factors:

Firstly, the temperature of the water in the circuit. The heat conversion coefficient (COP) depends on it, that is, the ratio of the amount of heat supplied to the consumer to the amount of energy consumed by the heat pump;
secondly, the outside air temperature;
thirdly, the operating parameters of the cooling tower. For the same amount of heat removed under different conditions, different amounts of energy consumed by the cooling tower can be expended. This, in turn, also depends on the temperature of the outside air, its humidity, the presence of wind and other conditions;
fourthly, on the number of heat pumps currently working in the system. Here, the total power of the HPI, which take heat from the water circuit, is important in comparison with the power of all HPI, which transfer heat to the circuit, that is, the amount of heat entering the circuit or removed from it.

Good for the kids, good for the budget

Let's move on to the description of projects using ring heat pump systems.

The first project is the reconstruction of an ordinary general education school in the south of Russia. Last summer, the administration of the Krasnodar Territory implemented this project in Ust-Labinsk (city school No. 2). During the reconstruction, the highest standards were maintained in ensuring sanitary requirements and a comfortable stay for children at school. In particular, a full-fledged climate system was installed in the building, providing zone-by-zone control over temperature, inflow fresh air and humidity.

The operation of the described system in the winter months gave the following results:

before modernization (before the installation of heat pumps), the monthly heating costs for 2,500 m2 were 18,440 rubles;
after the modernization of the building, the heated area increased to 3000 m2, and the monthly heating costs decreased to 9800 rubles.

Thus, the use of heat pumps made it possible to more than halve the cost of heating the building, the heated area of which increased by almost 20%.

Autonomous heat

Since the requirement of energy efficiency was put at the forefront, it was decided to install solar panels. 3.5 kW solar photovoltaic modules were purchased and installed right on the site behind the house. According to the calculations of the engineers, this should have been enough to recharge the batteries, which, in turn, would uninterruptedly feed the house and the heating system. The total cost of the system was about 27,000 US dollars. If we take into account that a source of free electricity has been received, and this item will be crossed out from the family budget, it turns out that the cost of installing a solar battery will pay off in less than 10 years. And if we consider that otherwise we would have to build a substation or live with constant power outages, then the costs can already be considered paid off.

Possibilities of application of ring systems

When developing such a system, first of all, it is necessary to assess the needs for heat and cold of the object being designed, to study all possible heat sources inside the building and all prospective heat receivers, to determine heat gains and heat losses. The most suitable heat sources can be used in the ring system if this heat is required. The total capacity of the heat recovery heat pumps should not be needlessly redundant. Under certain conditions, the most profitable option may be the installation of HPPs that use the external environment as a source and receiver of heat. The system must be balanced in terms of heat, but this does not mean at all that the total capacities of heat sources and consumers should be equal, they can differ, since their ratio can change significantly when the operating conditions of the system change.

Thus, the ring heat pump system performs the functions of both heating and air conditioning, and efficient heat recovery. The use of one system instead of several is always more profitable in terms of capital and operating costs.

Article provided by the company "AEROCLIMATE"

Question 26. Beneficial use of low-potential energy resources. Heat pump installations

Recently there has been real opportunity in a fundamentally new way to solve the issues of integrated energy supply of industrial enterprises through the use of heat pumps that use low-potential emissions to generate both heat and cold. The simultaneous production of these energy carriers by heat pumps is almost always more efficient than the separate production of heat and cold in traditional plants, since in this case the irreversible losses of the refrigeration cycle are used to generate heat that is given to the consumer.

In heat pump installations, the temperature of the heat sink is equal to or slightly higher than the ambient temperature, and the temperature of the heat receiver is much higher than the ambient temperature, i.e. T n >T about. Heat pumps are devices that transfer energy in the form of heat from a lower to a higher temperature level required for heat supply. The main purpose of these installations is to use the heat of low-potential sources, such as the environment.

Currently, three main groups of heat pumps have been developed and are being used: compression (steam); jet (ejector type); absorption.

Compression heat pumps are used for heat supply of individual buildings or groups of buildings, as well as for heat supply of individual industrial workshops or installations.

Freons are usually used as a working agent in heat pump installations.

Figure 4 shows a schematic diagram of an ideal vapor compression heat pump. Available low-potential heat at temperature Tn is supplied to evaporator I. Vapors of the working agent come from the evaporator I to the compressor II in state 1 and are compressed to a pressure pk and the corresponding saturation temperature Tk. In state 2, the compressed vapors of the working agent enter condenser III, where they transfer heat to the heat carrier of the heat supply system. In the condenser, the vapors of the working agent are condensed. From the condenser, the working agent enters in liquid form into the expander IV (a device in which the expansion of the working fluid, produced together with cooling, occurs with the performance of useful work), where the working agent expands from pressure p to pressure p o, accompanied by a decrease in its temperature and heat transfer. From the expander, the working agent enters the evaporator I and the cycle is closed.

The scheme of heat pumps operating in a closed cycle is fundamentally no different from the scheme of steam compression refrigeration units. However, the connection of consumers is carried out in different ways. In refrigeration circuits, the cold consumer is connected to the evaporator, and in heat pump systems, the heat consumer is connected to the condenser.

Heat pumps belong to heat transformation plants, which also include refrigeration ( 120 K), cryogenic ( = 0 ... 120 K) and combined ( , ) plants. All these installations operate according to reverse thermodynamic cycles, in which at a cost external work there is a transfer of thermal energy from bodies with a low temperature (heat sinks) to bodies with a high temperature (heat sinks). But if the function of refrigeration and cryogenic installations is to cool bodies and maintain a low temperature in cold store, i.e. heat removal, the main function of heat pumps is to supply heat to a high-temperature source using low-temperature thermal energy. At the same time, it is advantageous that the amount of high-temperature heat obtained can be several times higher than the work expended.

The heat transformer can operate simultaneously as a refrigeration and heat pump unit; while T n< Т о и Т н >That. Such a process is called combined. In the combined process, heat and cold are generated simultaneously - medium A is cooled and medium B is heated. Thus, in refrigeration units, artificial cooling of bodies is carried out, the temperature of which is lower than the ambient temperature. In heat pump installations, the heat of the environment or other low-potential environments is used for heat supply purposes.

Ideal Cycles Carnot installations heat transformations are shown in Fig.5.

The efficiency of refrigeration machines ( - useful effect, the amount of heat taken from a colder coolant) is estimated by the coefficient of performance. For a heat pump, the concept of transformation ratio is used ( - useful effect, the amount of heat given to the heated coolant) or heating coefficient, i.e. the amount of heat produced per unit of work expended.

, ,

, .

For real heat pumps = 2 - 5.

A real installation has losses caused by the irreversibility of the compression (internal) and heat exchange (external) processes. Internal irreversibility is due to the viscosity of the refrigerant and the release of heat of internal friction during compression in the compressor (entropy increases). The actual work of compression, where - perfect job in a reversible process; - relative internal efficiency of the compressor; - electromechanical efficiency of the drive.

External irreversibility is explained by the need to have a temperature difference for the occurrence of heat transfer, which is set (determined) by the area of the heat exchange surface at a given heat flux.

That's why ,

where , - temperatures respectively in the evaporator and condenser of the installation.

Jet heat pumps of ejector type are currently widely used. High-pressure steam enters the jet apparatus, and due to the use of the energy of the working flow, the injected flow is compressed. A mixture of two streams comes out of the apparatus. Thus, when the injected vapor is compressed, its temperature simultaneously rises. The compressed steam stream is then withdrawn from the plant.

High-pressure steam with parameters p p and T p enters the jet apparatus (Fig. 6). Due to the use of the energy of the working flow, the injected flow is compressed with the parameters r n and T n. A mixture of streams with parameters comes out of the apparatus r s and T s. Thus, when the injected vapor is compressed, its temperature (and, consequently, the enthalpy) also increases. The compressed steam stream is then withdrawn from the plant. Pressure ratio r s / r n in such devices, called jet compressors, is relatively small and is within 1.2 ≤ r s / r n≤ 4.

Jet heat pumps are currently the most widely used due to ease of maintenance, compactness, and the absence of expensive elements.

Absorption heat pumps work on the principle of absorption of water vapor by aqueous solutions of alkalis (NaOH, KOH). The process of absorption of water vapor occurs exothermically, i.e. with heat release. This heat is spent on heating the solution to a temperature significantly higher than the temperature of the absorbed vapor. After leaving the absorber, the heated alkali solution is directed to a surface evaporator, where secondary steam is generated at a higher pressure than the primary steam entering the absorber. Thus, in absorption heat pumps, the process of obtaining high-pressure steam is carried out by using heat supplied from outside.

A schematic diagram of an absorption heat pump is shown in Fig. 7.

As a working substance in absorption heat pumps, a solution of two substances (binary mixture) is used, which differs in boiling point at the same pressure. One substance absorbs and dissolves the second substance, which is a working agent. The working cycle of an absorption heat pump is as follows. In the evaporator 3, through the walls of the heat exchanger, low-potential heat is supplied to the binary solution at a temperature Tо. The supplied heat ensures the evaporation of the working agent from the binary mixture at a pressure p o. The resulting vapors of the working agent from the evaporator through the pipeline enter the absorber 2, where they are absorbed by the solvent (absorbent), and the heat of absorption Q a is released. The strong liquid solution formed in the absorber is pumped by pump 1 to generator 6. Heat Q g is supplied to the generator, which is spent on evaporating the working agent at high pressure p to, and, accordingly, high temperature T to. When evaporating above the surface of the solution, vapors of the working agent are formed, and the solution itself becomes weak. A weak solution is sent through the pipeline to the absorber 2, lowering the pressure in the auxiliary thermostatic valve 7 to the pressure in the evaporator p about. The working agent vapor formed in the generator enters the condenser 5, where, through the separating wall, they give off the heat of condensation Q k at a high temperature T k. The working agent condensed in the condenser lowers the pressure in the thermostatic valve from p to p o, with which it enters the evaporator. Then the process is repeated.

The operation of an ideal absorption heat pump is characterized by the following heat balance equation:

where Q n- the amount of heat of low potential, summed up in the evaporator;

Q g - the amount of high potential heat supplied to the generator;

Q us - heat equivalent to pump operation;

Q to- the amount of high potential heat removed in the condenser;

Q a - the amount of low potential heat removed in the absorber.

The working agent is usually water and the absorbent is lithium bromide.

For chemical, petrochemical and oil refineries that have a large volume of water for cooling technological units, the temperature of which is in the range from 20 to 50 ° C, it is necessary to use absorption lithium bromide heat pumps, which will operate in cooling mode in summer recycled water, and in winter time Waste heat of circulating water is used to generate hot water for heating workshops. Table 6 shows the parameters of absorption lithium bromide heat pumps (ABTN).

Absorption heat pumps are highly efficient, have no moving parts and can be easily manufactured. However, absorption pumps require a high specific metal consumption, which makes them bulky. The possibility of metal corrosion requires the manufacture of equipment from alloyed steel. Therefore, absorption heat pumps are not widely used in industry.

Table 6

ABTN parameters

Working agents and coolants (coolants)

in heat transformers

For the implementation of processes in heat transformers, working substances (agents) are used that have the necessary thermodynamic, physicochemical properties. They can be homogeneous or are a mixture of several, usually two, substances. In most heat transformers, the working substances undergo phase transformations. Currently, the following working substances are used in heat transformers:

a) refrigerants - substances that have a low boiling point at atmospheric pressure from +80 to -130 ° C. Refrigerants with a boiling point from +80 to -30 °C are usually used in heat pump installations, and with lower boiling points from 0 to -130 °C - in moderate cold installations;

b) gases and gas mixtures (also air) with low boiling points;

c) working agents and absorbents of absorption plants;

d) water used in its own way thermophysical properties in refrigeration units, where the temperature of the lower source, heat tn> 0 ° C, for example, for air conditioning.

For economical and safe work heat transformers, refrigerants must meet the following requirements:

a) have a low overpressure at the boiling and condensing temperatures, a large heat output of 1 kg of the agent, a small specific volume of steam (for reciprocating compressors), a low heat capacity of the liquid and high thermal conductivity and heat transfer coefficients;

b) have a low viscosity, possibly a lower solidification point, do not dissolve in oil (for reciprocating compressors);

c) be chemically resistant, non-flammable, non-explosive, non-corrosive to metals;

d) be harmless to the human body;

e) be non-scarce and inexpensive.

The working agents of gas refrigeration units must have a low normal temperature boiling, low viscosity, high thermal conductivity and heat capacity Ср, which depends little on temperature and pressure.

The working agents of absorption plants, in addition to meeting the above requirements, must be well absorbed and desorbed in combination with appropriate sorbents.

Economic efficiency The use of heat pumps depends on:

The temperatures of a low-potential source of thermal energy and will be the higher, the more high temperature he will have;

The cost of electricity in the region;

The cost of thermal energy produced using various types of fuel.

The use of heat pumps instead of traditionally used sources of thermal energy is economically beneficial due to:

No need to purchase, transport, store fuel and spend money associated with it;

The release of a large area necessary for the placement of a boiler house, access roads and a fuel warehouse.

The greatest energy saving potential exists in the area of heat supply: 40-50% of the country's total heat consumption. The equipment of existing CHPPs is physically and morally worn out, operated with excessive fuel consumption, heating networks are a source of large energy losses, small heat sources are characterized by low energy efficiency, a high degree of environmental pollution, increased unit costs and labor costs for maintenance.

TNU provide an opportunity to:

1) minimize the length of heat networks (approximate thermal power to places of consumption);

2) receive in heating systems 3 - 8 kW of equivalent thermal energy (depending on the temperature of the low-potential source, while spending 1 kW of electricity).

To date, the scale of introduction of heat pumps in the world is as follows:

In Sweden, 50% of all heating is provided by heat pumps; in recent years alone, more than 100 (from 5 to 80 MW) heat pump stations have been commissioned;

Germany provides for a state subsidy for the installation of heat pumps in the amount of DM 400 for each kilowatt of installed capacity;

In Japan, about 3 million heat pumps are produced annually;

In the USA, 30% of residential buildings are equipped with heat pumps, about 1 million heat pumps are produced annually;

In Stockholm, 12% of the entire heating of the city is provided by heat pumps with a total capacity of 320 MW, using the Baltic Sea as a heat source with a temperature of + 8 ° C;

In the world, according to the forecasts of the World Energy Committee, by 2020 the share of heat pumps in heat supply (municipal sector and production) will be 75%.

The reasons for the mass acceptance of heat pumps are as follows:

Profitability. To transfer 1 kW of thermal energy to the heating system, the heat pump needs only 0.2 - 0.35 kW of electricity;

Ecological purity. The heat pump does not burn fuel and does not produce harmful emissions into the atmosphere;

Minimum Maintenance . Heat pumps have a long service life up to overhaul(up to 10 - 15 heating seasons) and operate fully automatically. Maintenance of installations consists of seasonal technical inspection and periodic monitoring of the operating mode. To operate a heat pump station with a capacity of up to 10 MW, more than one operator per shift is not required;

Easy adaptation to the existing heating system;

Short payback period . Due to the low cost of the heat produced, the heat pump pays off in an average of 1.5 - 2 years (2 - 3 heating seasons).

Now there are two directions of TNU development:

Large heat pump stations (HPS) for district heating, including vapor compression HPP and peak hot water boilers used at low air temperatures. The electrical (consumed) power of the HPI is 20 - 30 MW, the thermal power is 110 - 125 MW. Compared to conventional boilers, fuel savings of 20 - 30% are achieved, air pollution is reduced (no boilers!);

decentralized individual heat supply(low-power vapor compression heat pumps and thermoelectric semiconductor heat pumps). Fuel economy compared to small boiler houses is 10 - 20%. Refrigeration possible. Accompanied by high unit costs fuel, investment and labor costs.

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