Heating schedule for quality regulation of heat supply based on the average daily outdoor temperature. Temperature chart of the heating system

The temperature schedule for the operation of heat networks is the basis of all technical and economic policy large thermal power system of the city. When organizing heat supply to tens of thousands of consumers from heat networks that combine different kinds sources of heat (CHP, boiler houses), a single technological document is needed that links the interests of all parties to the heat and power process: buyers, producers of thermal energy, adjusters of hydraulic and temperature conditions heating networks, inspectors of the State Energy Supervision Authority, designers of heating systems. The temperature chart is a “backbone” that determines the entire economics of thermal power engineering big city. As a conductor controls an orchestra, so the temperature schedule of heat networks controls all elements of a heat and power system: production, distribution and consumption of heat, determines the possible ranges of combined production of heat and electricity. In itself, the use of one or another temperature schedule for the operation of heating networks does not bring direct savings or cost overruns for the consumer. However, the costs of providing one or another temperature schedule of heat networks differ significantly both in the construction of heat networks and in the operation of heat networks. Comparative characteristics of temperature graphs, see Table 3

Table 3 Comparative characteristics temperature heat network schedules

The results of the feasibility study show that the temperature schedules of 150 -70 and 170-70º C are the most economical schedules, both in terms of initial capital costs, a) in terms of metal consumption in building construction, and operating costs: b) to reduce specific heat losses through thermal insulation, c) to reduce the cost of pumping network water. Wherein:

• - transition from the schedule 150-70°С to the schedule 110-70є С, causes an increase in initial investments in the construction of heating networks by 200%;
• - transition from the 150-70ºC schedule to the 110-70ºC schedule causes an increase in specific standard losses from 8.4% to 15.0% (Assuming equal circulation and 100% pipeline loading in both cases);
• - the transition to the actual mode of operation of heat networks according to the schedule of 110º C against the project schedule of 150-70º C requires a simultaneous increase in circulation by 2 times more network water. To provide transmission of an equal amount of heat requires an increase in the pressure drop of network water at the CHP from 120 m.w.s up to 480 m.w.s. Since this is practically impossible, then consumers will certainly be limited in terms of heat by 2 times;
• - if heating network were designed for a schedule of 110-70ºС, then the transition to a temperature graph of 150-70°С will reduce the available head at the CHP from 120 m.w.s. up to 30.0 m.w.s.

However, it should be noted that the above conclusions are fully valid only with cheap fuel, as we have in Russia. With a very expensive fuel cost, as in Denmark, for example, in order to maximize the generation of electricity from heat consumption at a CHP, they tend to reduce the temperature of the direct network water from the CHP as low as possible, down to the lowest possible - 80 ° C. Effective pricing policy for heat and electrical energy, mass application of quantitative regulation of heat supply, by changing the flow of network water, allow Denmark to design main heating networks with a pipe cross section 2-3 times larger than in Russia. In-house heating systems also require the use of radiators with large at 2-3 times heating surfaces. For a new perspective design of heating systems from CHPPs, with a significant increase in the cost of fuel in Russia, it is also necessary to switch to an energy-efficient schedule of 80-35°C. But until we understand that in the heating systems of Russia, instead of “fashionable” heat meters, it is necessary, first of all, to install really energy-saving devices such as: battery temperature controllers of the Danfoss type, flow and pressure controllers, until we build a sufficient number of heating mains from the CHP one can only dream of an energy-saving temperature chart of 80-35°C for CHPPs. Demand for these solutions will be when the price gas for within the Russian consumer from 40$ per thousand m3 will rise to world level prices gas before 160$ and more per thousand m3 of gas.

Compliance with the actual temperature of the network water normative value according to the temperature graph is one of the main indicators characterizing the quality of the entire heat and power system. According to the rules technical operation(PTE), the subcooling of the "direct" network water should not be more than ± (2.1h4.5 ° С). However, the actual subcooling of direct network water is 30-60°С, which is 10 times more than allowed by PTE. In turn, the consumer must also ensure the full use of heat and the temperature of the "return" to the CHP should not be higher than + (1.2h2.1єС) from the standard. The actual underutilization of heat by the consumer is up to 12-30°C, which is also 10 times more than allowed by PTE. Horror! What kind of tariff reductions can we talk about !! What kind of energy-saving technology can be in such barbarous conditions of operation of the city's heat and power systems?

In modern economic conditions the implementation of the temperature graph is not so much a technical task as economic, related to non-payments of the municipality for thermal energy. Due to the lack of the necessary funds from the municipality to pay for heat in accordance with the project schedule of 150-70°C and the transfer of heat networks to the actual temperature of direct network water not higher than 95-100°C, it leads to irreparable technological damage in the form of a complete misalignment of the hydraulic regime of heat networks , and, ultimately, to economic damage for both consumers and heat producers.

Due to the overestimated growth of network water circulation, a massive reduction in pressure drops at the end heat consumers, at outdoor temperatures below -20-25 ° C, an uncontrollable emergency situation is created. fine tuning hydraulic modes with the installation of the required diameters of the control washers and nozzles, heating network specialists have been working for months, but it is enough once not to provide the required temperature for 2-4 days as all thin commissioning work falling apart. But most importantly, no real savings At the same time, there is no fuel for the heat supply of the city. On the contrary, there is a constant excess fuel consumption due to “overheating” above +22°C, nearby heat consumers ~ 60%, and massive “underheating” below +18°C, remote heat consumers ~ 30%. When the outdoor air temperature drops below minus 28°C, mass uncontrolled “underheating” of the population with temperatures below +18°C can occur already for ~ 60% of consumers, and urban heating systems may experience uncontrollable emergency situation requiring the intervention of the Ministry of Emergency Situations.

The cost of damage due to deviation of the actual temperature schedule from the normative temperature schedule of 150-70°C for Omsk, only in terms of the cost of excess pumping of network water, is about 40 million rubles per year. AT recent times in heat supply systems, a “fashionable” and effectively lobbied trend has been established to install heat meters, supposedly allowing to save money on heat supply to consumers. Yes, heat meters allow you to legally show the actual heat consumed. But they do not bring any real savings in fuel and energy resources. Instead of spending huge amounts of money on the evidence side of the shortcomings of heat supply in the form of installing very expensive heat meters (30,000-80,000 rubles) in conditions of limited funding, it is necessary to install “real hard workers” in home heating systems - flow regulators, temperature regulators, pressure regulators. Here they really reduce energy costs and allow work strictly according to the temperature schedule of heating networks. And to conduct effective claims work with any supplier and consumer of thermal energy, three ordinary thermometers worth 100 rubles each, and a temperature chart on one page, are enough.

But the main energy-saving effect lies not so much in reducing the cost of pumping network water, but primarily in the possibility of providing joint work CHP plants in base mode with maximum electricity generation based on heat consumption and boiler plants in peak mode. For the city of Omsk, the cost of the energy-saving effect is at least 800 million rubles. rubles a year! It is the temperature of the return network water from the heat consumer to the CHPP that is the key indicator of the “health” of the energy-saving heat power industry of the region, city, and enterprise. Until, instead of a window, each apartment battery receiving heat from a CHP plant has an individual room temperature controller, we will not be able to actually save up to 50% of fuel for electricity.

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Temperature drop return water against the schedule is not limited.

Thus, the first task is to reduce the temperature of the return water from the heating systems at the design point to 60 C.

This scheme gives a very large savings in thermal energy and a decrease in the return water temperature when the heating network is operating with a cutoff schedule for hot water supply, since it allows obtaining a variable temperature at a constant temperature of the network water in the supply line supply air according to the outside temperature.

Many heating networks successfully withstand this limit and even achieve a decrease in the return water temperature below the established schedule, thereby increasing the technical and economic performance of the entire system as a whole.

Energy savings for coolant pumping, fuel savings at CHPPs and a decrease in the return water temperature with three-pulse isodromic control pays for all the costs of bushing automation.

The use of surface condensing boilers and economizers for heating is therefore advisable, provided that the return water temperature is reduced heating system. Accordingly, the average water temperature and, as shown above, the temperature of direct water entering the system also decrease. Therefore, the use of surface condensing boilers and economizers for heating water in heating systems is inevitably associated with a certain excess consumption of metal for the construction of heating systems. Nevertheless, abroad, condensing boilers and economizers are mainly used for heating systems.

The average daily temperature of the return water from the heating network must not exceed the set value by more than 2 C. The decrease in the temperature of the return water against the schedule is not limited.

When the return water temperature drops to calculated value some decrease in the flue gas temperature should be expected.

Let's define optimal temperature return water coming from the heating system of the building to the FNKV-1 contact-surface water heater. As the return water temperature tz decreases, the efficiency of gas use in the apparatus increases due to the use of heat released during the condensation of water vapor in the gas combustion products. Therefore, the determination of the value of n is practically necessary.

raw water for chemical water treatment they are taken from the waste circulation conduit at a temperature of 20 - 35 C, which makes it possible to utilize waste heat. A significant increase in the specific output at heat consumption results in a decrease in the temperature of the return water, which is obtained as a result of mixing the return and colder make-up water.

The bellows is the regulating body. With an increase in the temperature of the water leaving the heater, the liquid in the bellows heats up and expands, which leads to a decrease in the valve flow area and a reduction in the network water flow rate, and, consequently, to a decrease in the return water temperature.

Thus, for the considered scheme of proportional control of the temperature in the room, it is always necessary to provide automatic protection against freezing of heaters. According to this scheme, a manometric temperature sensor is installed in the return water pipeline after the heater and is adjusted to a temperature of 25 - 30 C. When the return water temperature drops to the set value, the sensor gives a signal, and the on-off controller is triggered, opening a passage for water through the bypass branch using a solenoid valve .

To obtain a uniform temperature field after the heater, which is especially important in air conditioners in which an irrigation chamber is installed immediately after the first heating, it is desirable to significantly reduce the temperature of the water supplied to the heater while simultaneously reducing the temperature difference between the direct and return water. Some increase in the required heating surface of the heaters is compensated by a decrease in the return water temperature.

To reduce the temperature of the water leaving the CHP and reduce heat loss at night, it is advisable to switch the circulation line of the hot water supply system to the pipeline for this time cold water in front of the 1st stage of the water heater. At the same time, the setting of the hot water temperature controller should be reduced from 60 to 50 C. During the day, the circulation line should be connected to the pipeline of heated water before stage II or, more rationally, to the pipeline between sections of stage II of the water heater, the water temperature in which is equal to the accepted water temperature in circulating pipeline (approximately in front of the last three sections in the direction of the heated water), as shown in fig. 3.19. Switching is carried out automatically: the time relay closes valve 5, for example, at 0000, directing the circulation flow to stage I, and through the electro-hydraulic relay, the impulse is switched to the temperature controller from the sensor configured to maintain the hot water temperature of 60 C, to another sensor with a setting of 45 - 50 C. At 6 o'clock the time relay makes reverse switching, at open valve 5 through it will flow circulating water, since the water pressure before stage I is much higher than at the point of inclusion of the pipeline on which the valve is installed. With automatic control of the heat supply to heating, when the temperature of the water from the heating system is below 40 - 45 C, it is not advisable to switch the circulation pipeline in front of the 1st stage of the water heater at such temperatures. In this regard, a temperature sensor is installed on the return pipe of the heating system, on the signal of which, when the return water temperature drops below 40 - - 45 C, valve 5 remains open at night.

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Looking through the statistics of visits to our blog, I noticed that search phrases such as, for example, appear very often “What should be the temperature of the coolant at minus 5 outside?”. Decided to post the old one. schedule quality regulation heat release by average daily temperature outside air. I want to warn those who, on the basis of these figures, will try to sort things out with housing departments or heating networks: heating schedules for each individual locality are different (I wrote about this in an article). Thermal networks in Ufa (Bashkiria) operate according to this schedule.

I also want to draw attention to the fact that regulation occurs according to average daily outside temperature, so if, for example, outside at night minus 15 degrees, and during the day minus 5, then the coolant temperature will be maintained in accordance with the schedule minus 10 o C.

As a rule, the following temperature charts are used: 150/70 , 130/70 , 115/70 , 105/70 , 95/70 . The schedule is selected depending on the specific local conditions. House heating systems operate according to schedules 105/70 and 95/70. According to schedules 150, 130 and 115/70, main heat networks operate.

Let's look at an example of how to use the chart. Suppose the temperature outside is minus 10 degrees. Heating networks operate according to the temperature schedule 130/70 , which means at -10 o С the temperature of the heat carrier in the supply pipeline of the heating network must be 85,6 degrees, in the supply pipeline of the heating system - 70.8 o C with a schedule of 105/70 or 65.3 about C on a 95/70 schedule. The temperature of the water after the heating system must be 51,7 about S.

As a rule, the temperature values ​​in the supply pipeline of heat networks are rounded off when setting the heat source. For example, according to the schedule, it should be 85.6 ° C, and 87 degrees are set at the CHP or boiler house.

Please do not focus on the diagram at the beginning of the post - it does not correspond to the data from the table.

Calculation of the temperature graph

The method for calculating the temperature graph is described in the reference book (Chapter 4, p. 4.4, p. 153,).

This is quite laborious and long process, since for each outdoor temperature several values ​​\u200b\u200bmust be considered: T 1, T 3, T 2, etc.

To our joy, we have a computer and a MS Excel spreadsheet. A colleague at work shared with me a ready-made table for calculating the temperature graph. She was once made by his wife, who worked as an engineer for a group of regimes in thermal networks.

In order for Excel to calculate and build a graph, it is enough to enter several initial values:

• design temperature in the supply pipeline of the heating network T 1
• design temperature in the return pipeline of the heating network T 2
• design temperature in the supply pipe of the heating system T 3
• Outside temperature T n.v.
• Indoor temperature T v.p.
• coefficient " n» (it is usually not changed and is equal to 0.25)
• Minimum and maximum cut of the temperature graph Cut min, Cut max.

All. nothing more is required of you. The results of the calculations will be in the first table of the sheet. It is highlighted in bold.

The charts will also be rebuilt for the new values.

The table also considers the temperature of direct network water, taking into account wind speed.

When organizing heat supply to tens of thousands of consumers from heat networks that combine various types of heat sources (CHP, boiler houses), a single technological document is needed that links the interests of all parties to the heat and power process: buyers, producers of heat energy, adjusters of hydraulic and temperature regimes of heat networks, inspectors of the State Energy Supervision Authority , designers of heating systems.

The temperature chart is a “backbone” that determines the entire economy of the thermal power industry of a large city. As a conductor controls an orchestra, so the temperature schedule of heat networks controls all elements of a heat and power system: production, distribution and consumption of heat, determines the possible ranges of combined production of heat and electricity. In itself, the use of one or another temperature schedule for the operation of heating networks does not bring direct savings or cost overruns for the consumer. However, the costs of providing one or another temperature schedule of heat networks differ significantly both during the construction and operation of heat networks. Comparative characteristics temperature graphs are given in the table.

The results of the feasibility study show that the temperature charts 150‑70 °С and 170‑70 ºС are the most economical graphs:

a) initial capital cost
b) metal consumption in building structures and operating costs,
c) to reduce specific heat loss through thermal insulation,
d) to reduce the cost of pumping network water.

Wherein:

The transition from the 150‑70 °C schedule to the 110‑70 °C schedule causes an increase in initial investment in the construction of heat networks by 200 percent;
transition from the 150‑70 ºС schedule to the 110‑70 ºС schedule causes an increase in specific standard losses from 8.4 percent to 15.0 percent (assuming equal circulation and 100 percent pipeline loading in both cases);
transition to the actual mode of operation of heat networks according to the schedule of 110 ºС against the project schedule of 150‑70 ºС requires a simultaneous increase in circulation twice more network water. To ensure the transfer of an equal amount of heat, an increase in the pressure drop of network water at the CHP from 120 m.w.s. up to 480 m.w.s. Since this is practically impossible, then consumers will certainly be limited in terms of heat twice;
if the heating networks were designed for a schedule of 110‑70 ºС, then the transition to a temperature graph of 150‑70 °С will reduce the available pressure at the CHP from 120 m.w.s. up to 30 m.w.s.

However, it should be noted that the above conclusions are fully valid only with cheap fuel, as we have in Russia. At very high cost fuel, as, for example, in Denmark, in order to maximize the generation of electricity from heat consumption at CHPPs, they tend to reduce the temperature of direct network water from CHPPs as low as possible, down to the minimum possible (80 °C). An effective pricing policy for heat and electricity, the massive use of quantitative regulation of heat supply by changing the flow of network water allow Denmark to design main heat networks with a pipe cross section two to three times larger than in Russia. In-house heating systems also require the use of radiators with two to three times large surfaces heating.

For a new promising design of heating systems from CHPPs, with a significant increase in the cost of fuel in Russia, it is necessary to switch to an energy-efficient schedule of 80‑35 °С. But until we understand that in the heating systems of Russia, instead of “fashionable” heat meters, it is necessary, first of all, to install really energy-saving devices, such as Danfoss-type battery temperature controllers, flow and pressure regulators, until we build a sufficient number of heating mains from the CHP , one can only dream of an energy-saving temperature schedule of 80‑35 °С for CHPPs. These solutions will be in demand when the price of gas for the Russian consumer rises from the current $128 per thousand cubic meters to the level of the world gas price - $400 or more per thousand cubic meters.

Compliance of the actual temperature of the network water with the standard value according to the temperature graph is one of the main indicators characterizing the quality of the entire heat and power system. According to the technical operation rules (PTE), the subcooling of the “direct” network water should not be more than ±2.1‑4.5 °С. However, the actual subcooling of direct network water is 30-60 °C, which is ten times more than the allowable value according to PTE.

In turn, the consumer must also ensure the full use of heat, and the temperature of the "return" to the CHP should not be higher than +1.2‑2.1 ºС from the standard. The actual underutilization of heat by the consumer is up to 12‑30 °C, which is also ten times more than allowed by the PTE! What kind of tariff reduction can we talk about here, what Energy Saving Technologies can be used in such barbarous conditions of operation of thermal power systems of cities?

In modern economic conditions, the implementation of the temperature schedule is not so much a technical task as an economic one, associated with non-payments of municipalities for thermal energy. Due to the lack of necessary funds from the municipalities to pay for heat in accordance with the project schedule of 150-70 °C and the transfer of heat networks to the actual temperature of direct network water not higher than 95-100 °C, irreparable technological damage occurs in the form of a complete misalignment of the hydraulic regime of heat networks and, ultimately, economic damage to both consumers and heat producers.

Due to the overestimated growth of network water circulation, a massive reduction in pressure drops at the end heat consumers at outdoor air temperatures below –20‑25 °С, an uncontrollable emergency situation is created. Specialists of thermal networks have been engaged in fine adjustment of hydraulic modes with the installation of the required diameters of control washers and nozzles for months, but it is enough not to provide the required temperature once for two to four days, as all the fine adjustment work falls apart. But the most important thing is that there is no real fuel saving on the city's heat supply. On the contrary, there is a constant excess fuel consumption due to “overheating” above +22 °C of nearby heat consumers (about 60 percent of consumers) and massive “underheating” below +18 °C of remote consumers (about 30 percent of consumers) - that is, heat only about 10 percent of consumers receive standards! When the outdoor air temperature drops below -28 °C, mass uncontrolled “underheating” of the population with temperatures below +18 °C can occur for about 60 percent of consumers, and an uncontrollable emergency situation may occur in urban heating systems requiring the intervention of the Ministry of Emergency Situations.

So, for Omsk, the cost of damage due to the deviation of the actual temperature schedule from the normative temperature schedule of 150-70 °C, only in terms of the cost of excess pumping of network water, is about 120 million rubles a year. Recently, a “fashionable” and effectively lobbied trend has been established in heat supply systems to install heat meters, supposedly allowing to save money on heat supply to consumers. Yes, heat meters allow you to legally show the actual heat consumed. But they do not bring any real savings in fuel and energy resources. Instead of spending huge amounts of money on the evidence side of heat supply shortcomings in the form of installing very expensive heat meters (30-80 thousand rubles) in conditions of limited funding, it is necessary to install “real hard workers” in home heating systems - flow regulators, temperature regulators, pressure regulators. Here they really reduce energy costs and allow you to work strictly according to the temperature schedule of heating networks. And to conduct effective claims work with any supplier and consumer of thermal energy, three ordinary thermometers worth 100 rubles each and a temperature graph on one page are enough.

But the main energy-saving effect lies not so much in reducing the cost of pumping network water, but, first of all, in the possibility of ensuring the joint operation of CHPPs in the base mode with maximum electricity generation for heat consumption and boiler houses in peak mode. For the city of Omsk, the price of the energy-saving effect is at least 2,400,000,000 rubles a year! It is the temperature of the return network water from the heat consumer to the CHP that serves as a key indicator of the "health" of the energy-saving heat power industry of the region, city, and enterprise. Until an individual room temperature controller appears instead of a window on each apartment battery that receives heat from a CHP, we will not be able to actually save up to 50 percent of fuel for electricity.

In this article I want to tell you how and on the basis of what the temperature of the coolant is regulated. I don't think that this article will be useful or interesting to heat power workers, since they won't learn anything new from it. But for ordinary citizens, I hope it will be useful.

4.11.1. The mode of operation of the heating plant of the power plant and the district boiler house (pressure in the supply and return pipelines and temperature in the supply pipelines) must be organized in accordance with the task of the heat network manager.

The temperature of the network water in the supply pipelines in accordance with the approved for the heat supply system temperature graph should be set according to the average outdoor air temperature for a period of time within 12 - 24 hours, determined by the heat network dispatcher, depending on the length of the networks, climatic conditions and other factors.

The temperature schedule is developed for each city, depending on local conditions. It clearly defines what should be the temperature of the network water in the heating network at a specific outdoor temperature. For example, at -35 ° the temperature of the coolant should be 130/70. The first digit determines the temperature in the supply pipe, the second - in the return. The heat network manager sets this temperature for all heat sources (CHP, boiler houses).

The rules allow deviations from the given parameters:

4.11.1. Deviations from the set mode behind the head valves of the power plant (boiler house) should be no more than:

• by the temperature of the water entering the heating network, ± 3%;
• by pressure in the supply pipelines ± 5%;
• pressure in return pipelines ±0.2 kgf/cm2 (±20 kPa).

4.12.36. For water heating systems, the heat supply regime should be based on a schedule of central quality control. It is allowed to use qualitative-quantitative and quantitative schedules for regulating heat supply at required level equipping thermal energy sources, heating networks and heat consumption systems with means automatic regulation, development of appropriate hydraulic regimes.

So, dear citizens, do not try to somehow influence the heating networks if you become very hot in the spring. They will not do anything for you, because they have neither the right nor the opportunity. Complain to the administration, then perhaps they will order to stop heating season before. But remember that in spring the temperature outside is changeable, and if today it is warm and you have turned off the heating, then tomorrow it can become very cold, and turning off the equipment is much faster than turning it on.

Now let's talk about how cold it is in an apartment in winter, especially when it is thoroughly "frost". If the apartment is cold Who is usually to blame? That's right - heating networks! This is what most people think. In part, they are right, but not everything is so simple.

Let's start with the fact that in severe frosts, gas supply organizations can introduce restriction on gas supplies. Because of this, boiler houses have to maintain the temperature of the coolant "as much as possible". As a rule, it is 10 degrees lower than what is laid down in the temperature chart. It is easier for power plants - they switch to burning fuel oil, and boiler houses, which often stand almost in the middle of residential areas, are allowed to burn fuel oil only in emergency cases (for example, a complete cessation of gas supply) so that people do not freeze completely. Due to gas supply restrictions, even disable hot water to reduce heat carrier costs and thereby maintain the temperature in heating systems at the desired level. So don't be surprised if something happens.

Also, the reason that it is cold in apartments in winter is the high degree of deterioration of the heating networks themselves, and in particular thermal insulation of pipelines. As a result, in houses that are located quite far from the heat source, the coolant “reaches” already cooled down in order.

Well, the last reason that I will talk about is the unsatisfactory thermal insulation of the apartments and houses themselves. Slots in windows, doors, lack of thermal insulation of the house itself - all this leads to the fact that heat goes into environment and we are cold. You can eliminate this cause yourself. Install new windows, make the thermal insulation of the apartment, change the heating radiators to new ones, because over time cast iron batteries clogged and heat transfer is significantly reduced. By the way, if paint the battery black, then it will heat better. This is not a joke, experiments confirm this fact.

Well, that seems to be all I wanted to tell in this article. I also want to make a reservation that I wrote the article, based largely on personal experience. AT different regions our country, the situation may be different and radically different from what I wrote here. But in general, I think the situation is similar. At least in big cities.