The dependence of the coolant temperature on the outside air temperature. D.V

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. graph of quality regulation of heat supply based on the average daily outdoor temperature. I want to warn those who, on the basis of these figures, will try to sort out relations with the housing department or heating networks: the heating schedules for each individual settlement 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 network work 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

Method of calculation temperature chart described in the handbook (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.

Optimization of operating modes of heat networks refers to organizational and technical measures that do not require significant financial costs for implementation, but lead to a significant economic result and reduce the cost of fuel and energy resources.

Almost all structural subdivisions of "Thermal Networks" are involved in the work on managing and adjusting the operating modes of thermal networks, which develop optimal thermal and hydraulic modes and measures for their organization, analyze the actual modes, carry out the developed measures and adjust systems automatic regulation(SAR), as well as operationally manage the modes and control the consumption of thermal energy, etc.

The development of modes (during the heating and non-heating periods) is carried out annually, taking into account the analysis of the operating modes of heat networks in previous periods, clarification of characteristics for heat networks and heat consumption systems, the expected connection of new loads, plans overhaul, reconstruction and technical re-equipment. Using this information, thermohydraulic calculations are carried out with a list of adjustment measures, including the calculation of throttle devices (throttle diaphragms and elevator nozzles). The calculation of throttle devices is carried out for each thermal node taking into account the decrease in the temperature of the coolant due to the loss of thermal energy through pipelines from the source to the thermal unit. Calculations for the heating period are carried out in 3 modes: commissioning (ratio of shares DHW open schemes from the supply and return pipelines, respectively, 60 and 40%), as a result of which the diameters of the throttle devices are determined, winter (at the design temperature of the outdoor air and DHW open circuit 100% from the return pipeline) and transitional (at an outdoor temperature corresponding to the beginning / end of the heating period and open circuit DHW 100% from the supply pipeline). When making calculations in the last two years, increasing or decreasing coefficients are applied to the calculated (contractual) loads, determined by the actual consumption of thermal energy. Taking into account the actual thermal loads allows more accurate calculation of modes, adjustment and, ultimately, minimization of deviations from the calculated modes.

The development of operating modes of heat networks over the past 10 years has been carried out using software SKF-TS. By system district heating city ​​of Omsk formed detailed diagram heating networks and a database containing the characteristics of all elements of the scheme (sections of main and intra-quarter pipelines, pumping equipment, stop and control valves, PNS, TsTP and TPNS, connection schemes and loads of thermal units (consumers). Currently, the database contains characteristics of more than 130 thousand elements (figure).

In addition to calculations optimal modes and development of adjustment measures "SKF-TS" also allows operational and engineering personnel to perform in a single information space:

1) analysis technical condition heat supply systems, the actual state of networks, modes, pipeline damage;

2) simulation of emergency situations, including emergencies;

3) optimization of pipeline replacement planning with prioritization of replacement;

4) design and modernization of heat supply systems, including optimization of planning for the modernization and development of heat networks.

The main criterion for the optimization task in developing modes and redistributing heat loads is to reduce the cost of production and transportation of thermal energy (in particular, loading the most economical heat sources of CHPP-5 and CHPP-3, unloading the PNS) with the existing technological limitations (available capacities and equipment characteristics heat sources, throughput heating networks and characteristics of pumping equipment pumping stations, permissible operating parameters of heat consumption systems, etc.).

The developed modes of operation of heat networks are coordinated with heat sources, approved and sent for management and planning of equipment operation modes to heat sources and operational units. When developing regimes, also developed and approved necessary measures on the organization of regimes for main heat networks and for heat consumption systems, which are issued to operational areas and consumers for execution before the start of the heating period. For heat consumption systems, the installation of throttle devices is carried out by housing management companies and other owners under the supervision of the personnel of the subscriber departments of thermal regions upon acceptance for re-operation. In addition, specialists monitor the implementation of these measures, including selectively for heat consumption systems. After the start of the heating season, commissioning work at control nodes, regulators are adjusted, adjustment work is carried out on heat consumption systems.

During the heating period, a multi-level control and analysis of the supply and consumption of thermal energy is carried out.

1) operational control the dispatching service is carried out by remotely transmitted data from heat sources metering devices, as well as by periodically transmitted data from control points.

2) Daily monitoring of the parameters of the coolant, the supply of thermal energy and the coolant for each heating main and in general for heat source transferred to the server (flow rates of network, make-up and source water, temperature and pressure of the coolant) with the introduction of operational adjustments to the dispatcher schedule of heat loads.

3) Control over the consumption of thermal energy by consumers is carried out by inspectors and specialists of subscriber departments with a frequency of 1 time per month. Also, based on printouts from metering devices, an analysis is made of the consumption modes of consumers with metering devices to identify violations of the consumption of thermal energy (increased consumption, excess temperature of the return network water, etc.).

4) Monitoring the temperature of the return network water along the boundaries and branches (carried out weekly by the personnel of the thermal district to identify branches with elevated temperature return network water and adjustment).

On the issues of regulation of heat supply regimes and adjustment, working meetings are held weekly, in which managers and specialists of management, inspection, subscriber departments, operational and repair personnel of thermal regions participate. In addition, weekly meetings are held at the Thermal Networks JV on the issue of passing the heating period with consideration of all problematic issues in heat supply and hot water supply of the city. These meetings are attended by representatives of the Management Companies housing stock, the transporting organization MP "Thermal Company", OAO "Omskvodokanal", City Administration.

The adjustment of hydraulic regimes is inextricably linked with the regulation of temperature regimes from heat sources. The main task of regulation in heat supply systems is to maintain the air temperature inside the heated premises within the specified allowable limits when external and internal disturbing factors change.

According to the rules technical operation» the temperature of the water in the supply line of the water heating network, in accordance with the schedule, is set according to the average outdoor temperature over 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. Due to the lack of developed methods and recommendations, the determination of the specified coolant parameters (temperature, pressure) and the task time, as a rule, was carried out on the basis of the dispatcher's experience and intuition.

An increase in the share of automation of heat consumption systems and the transition to quantitative and qualitative regulation at low hydraulic stability system leads to a significant variability of hydraulic modes, therefore, the requirements for the organization and operational management of thermal and hydraulic modes DH systems are increasing significantly.

Analysis of the dynamics of changes in the average daily outdoor temperature in Omsk in heating periods shows that the change in temperature is random, while in some periods there are significant amplitudes of changes in daily temperatures (up to 15÷17 ° C), which at quality regulation assumes a temperature change in the supply pipelines of more than 30 ° C.

Constant changes in external disturbing factors lead to the need to change the heat load, modes and composition of the operating equipment of the CHPP, as well as to the occurrence of alternating stresses in the pipelines of heat networks, which increases the likelihood of damage and reduces reliability.

In order to exclude negative moments during the operational regulation of heat loads in the heat networks of the Omsk branch of JSC "TGC-11", simplifying the process of developing a dispatch schedule for heat loads, an "Instruction for setting the temperature regime of operation of heat sources" and a calculation form temperature parameters for the following days. The main provisions of this instruction are based on a model that takes into account the dynamic characteristics of the heat supply system, the storage capacity of buildings, as well as the dynamics of change and the influence of the main disturbing influences (outside air temperature) over several days (actual and forecast) on the thermal regime of heated buildings.

When forming the dispatching schedule, the task adjustment is also provided, which can be introduced on an external initiative, or in case of a significant deviation of the actual temperatures from the predicted ones. This temperature can be set for a regulation period or, subject to correction, for several regulation periods.

Since 2009, the heating networks of the Omsk branch of OAO TGC-11 have been regulated taking into account the dynamic characteristics of the heat supply system. As practice has shown, within certain limits of change external factors allow to increase the regulation periods up to 24-72 hours or more, while the increase in the period practically does not affect the quality of heat supply to consumers, which makes it possible to operate the equipment of heat sources and heat networks in a more “sparing” mode.

In the DH system from heat sources of the Omsk branch of OAO TGC-11, as a result of systematic work to optimize and adjust the modes of operation of heat networks over the past 6-7 years, the quality of heat supply to consumers has dramatically improved and the efficiency of the entire district heating system from heat sources of OAO TGC-11, namely:

1) issues of heat supply and hot water supply in entire microdistricts of the city (settlement of 40 years of October, settlement of Sibzavod, settlement of Sverdlov, microdistricts No. 5, No. 6, No. 10, No. 11 of the Left Bank, Central part of the city, residential areas on the street Poselkovaya, Tyulenina St., Truda St.), as well as individual consumers;

2) the work of heat consumption systems “for discharge” is completely excluded due to insufficient available pressure;

3) excessive fuel consumption was reduced due to overheating of consumers during transitional periods;

4) the cost of electricity for pumping the coolant was reduced by 14% (from 53 to 46 million kWh) due to a reduction in the circulation flow of the coolant while connecting new consumers;

5) reduced fuel consumption for power generation by reducing and normalizing the temperature of the return network water;

6) make-up water consumption was reduced by 21% (from 40.2 to 31.9 million m3);

7) new consumers are connected;

8) pipeline damage is reduced. Thus, at integrated approach to the process of managing operating modes, modes can be optimized and the efficiency of the DH system can be significantly increased.

Literature

1. Rules for the technical operation of power plants and networks Russian Federation. - M.: NTs ENAS, 2008. - 264 p.

2. Zhukov D.V., Dmitriev V.Z. Improving the efficiency of district heating systems by optimizing thermal-hydraulic modes. - Sat. “Proceedings of the VNPK “Improving the Reliability and Efficiency of Operation of Power Plants and energy systems» - Energo - 2010. In 2 volumes. - M.: MPEI Publishing House, 2010. - T. 1. 304 p. ill. pp. 229-232.

What laws are subject to changes in the temperature of the coolant in systems central heating? What is it - the temperature graph of the heating system 95-70? How to bring the heating parameters in accordance with the schedule? Let's try to answer these questions.

What it is

Let's start with a couple of abstract theses.

• With change weather conditions heat losses of any building change after them. In frosts, in order to maintain a constant temperature in the apartment, much more thermal energy is required than in warm weather.

To clarify: heat costs are determined not by the absolute value of the air temperature in the street, but by the delta between the street and the interior.
So, at +25C in the apartment and -20 in the yard, the heat costs will be exactly the same as at +18 and -27, respectively.

• The heat flow from the heater at a constant coolant temperature will also be constant.
  A drop in room temperature will slightly increase it (again, due to an increase in the delta between the coolant and the air in the room); however, this increase will be categorically insufficient to compensate for the increased heat loss through the building envelope. Simply because the current SNiP limits the lower temperature threshold in an apartment to 18-22 degrees.

An obvious solution to the problem of increasing losses is to increase the temperature of the coolant.

Obviously, its growth should be proportional to the decrease in street temperature: the colder it is outside the window, the greater the heat loss will have to be compensated. Which, in fact, brings us to the idea of ​​creating a specific table for matching both values.

So the chart temperature system heating is a description of the dependence of the temperatures of the supply and return pipelines on the current weather outside.

How it all works

There are two different types charts:

1. For heating networks.
2. For intra-house heating system.

To clarify the difference between these concepts, it is probably worth starting with a brief digression into how central heating works.

CHP - heat networks

The function of this bundle is to heat the coolant and deliver it to the end user. The length of heating mains is usually measured in kilometers, the total surface area - in thousands and thousands. square meters. Despite the measures for thermal insulation of pipes, heat losses are inevitable: having passed the path from the CHP or boiler house to the border of the house, process water cool down partially.

Hence the conclusion: in order for it to reach the consumer, while maintaining an acceptable temperature, the supply of the heating main at the exit from the CHP should be as hot as possible. The limiting factor is the boiling point; however, with increasing pressure, it shifts in the direction of increasing temperature:

Typical pressure in the supply pipeline of the heating main is 7-8 atmospheres. This value, even taking into account pressure losses during transportation, allows you to start the heating system in houses up to 16 floors high without additional pumps. At the same time, it is safe for routes, risers and inlets, mixer hoses and other elements of heating and hot water systems.

With some margin, the upper limit of the supply temperature is taken equal to 150 degrees. The most typical heating temperature curves for heating mains lie in the range of 150/70 - 105/70 (supply and return temperatures).

House

There are a number of additional limiting factors in the home heating system.

• The maximum temperature of the coolant in it cannot exceed 95 C for a two-pipe and 105 C for.

By the way: in preschool educational institutions, the restriction is much more stringent - 37 C.
The price of lowering the supply temperature is an increase in the number of radiator sections: in the northern regions of the country, group rooms in kindergartens are literally surrounded by them.

• The temperature delta between the supply and return pipelines, for obvious reasons, should be as small as possible - otherwise the temperature of the batteries in the building will vary greatly. This implies a fast circulation of the coolant.
  However, too fast circulation through house system heating will cause the return water to return to the route with exorbitant high temperature, which is unacceptable due to a number of technical limitations in the operation of the CHPP.

The problem is solved by installing one or more elevator units in each house, in which the return flow is mixed with the water stream from the supply pipeline. The resulting mixture, in fact, ensures the rapid circulation of a large volume of coolant without overheating the return pipeline of the route.

For intra-house networks, a separate temperature graph is set, taking into account the elevator operation scheme. For two-pipe circuits, a heating temperature graph of 95-70 is typical, for single-pipe circuits (which, however, is rare in apartment buildings) — 105-70.

Climate zones

The main factor that determines the scheduling algorithm is the estimated winter temperature. The heat carrier temperature table should be drawn up in such a way that the maximum values ​​\u200b\u200b(95/70 and 105/70) at the peak of frost provide the temperature in residential premises corresponding to SNiP.

Here is an example of an intra-house schedule for the following conditions:

• Heating devices - radiators with a coolant supply from the bottom up.
• Heating - two-pipe, co.

• The estimated outdoor air temperature is -15 C.

Nuance: when determining the parameters of the route and the in-house heating system, the average daily temperature is taken.
If it is -15 at night and -5 during the day, -10C appears as the outside temperature.

And here are some values ​​​​of calculated winter temperatures for Russian cities.

In the photo - winter in Verkhoyansk.

Adjustment

If the management of the CHPP and heating networks is responsible for the parameters of the route, then the responsibility for the parameters of the intra-house network rests with the residents. A very typical situation is when, when residents complain about the cold in apartments, measurements show downward deviations from the schedule. It happens a little less often that measurements in the wells of heat pumps show an overestimated return temperature from the house.

How to bring the heating parameters in line with the schedule with your own hands?

Nozzle reaming

With low mixture and return temperatures, the obvious solution is to increase the diameter of the elevator nozzle. How it's done?

The instruction is at the service of the reader.

1. All valves or gates are closed in elevator node(input, house and hot water supply).
2. The elevator is dismantled.
3. The nozzle is removed and reamed by 0.5-1 mm.
4. The elevator is assembled and started with air bleeding in the reverse order.

Tip: instead of paronite gaskets on the flanges, you can put rubber ones cut to the size of the flange from the car chamber.

An alternative is to install an elevator with an adjustable nozzle.

Suction suppression

In a critical situation extreme cold and freezing flats) the nozzle can be completely removed. So that the suction does not become a jumper, it is suppressed with a pancake made of steel sheet with a thickness of at least a millimeter.

Attention: this is an emergency measure, used in extreme cases, since in this case the temperature of the radiators in the house can reach 120-130 degrees.

Differential adjustment

At elevated temperatures as a temporary measure until the end heating season practice is to adjust the differential on the elevator with a valve.

1. The DHW is switched to the supply pipe.
2. A manometer is installed on the return.
   
3. The inlet gate valve on the return pipeline closes completely and then gradually opens with pressure control on the pressure gauge. If you just close the valve, the subsidence of the cheeks on the stem can stop and unfreeze the circuit. The difference is reduced by increasing the return pressure by 0.2 atmospheres per day with daily temperature control.

Conclusion

The temperature graph represents the dependence of the degree of heating of water in the system on the temperature of cold outside air. After the necessary calculations, the result is presented in the form of two numbers. The first means the temperature of the water at the inlet to the heating system, and the second at the outlet.

For example, the entry 90-70ᵒС means that under given climatic conditions, for heating a certain building, it will be necessary that the coolant at the inlet to the pipes has a temperature of 90ᵒС, and at the outlet 70ᵒС.

All values ​​are presented for the outside air temperature for the coldest five-day period. This design temperature is taken according to the joint venture " Thermal protection buildings." According to the norms, the internal temperature for residential premises is 20ᵒС. The schedule will ensure the correct supply of coolant to the heating pipes. This will avoid hypothermia of the premises and waste of resources.

The need to perform constructions and calculations

The temperature schedule must be developed for each settlement. It allows you to provide the most competent work heating systems, namely:

1. Align heat loss at the time of filing hot water at home with average daily temperature outside air.
2. Prevent insufficient heating of rooms.
3. Oblige thermal power plants to supply consumers with services that meet technological conditions.

Such calculations are necessary both for large heating stations and for boiler houses in small settlements. In this case, the result of calculations and constructions will be called the boiler house schedule.

Ways to control the temperature in the heating system

Upon completion of the calculations, it is necessary to achieve the calculated degree of heating of the coolant. You can achieve it in several ways:

• quantitative;
• quality;
• temporary.

In the first case, the flow rate of water entering the heating network, in the second, the degree of heating of the coolant is regulated. The temporary option involves a discrete supply of hot liquid to the heating network.

For central system heat supply is most characteristic of high-quality, while the volume of water entering the heating circuit remains unchanged.

Graph types

Depending on the purpose of the heating network, the execution methods differ. The first option is the normal heating schedule. It is a construction for networks that work only for space heating and are centrally regulated.

The increased schedule is calculated for heating networks that provide heating and hot water supply. It is built for closed systems and shows the total load on the hot water supply system.

The adjusted schedule is also intended for networks operating both for heating and for heating. Here, heat losses are taken into account when the coolant passes through the pipes to the consumer.

Drawing up a temperature chart

The constructed straight line depends on the following values:

• normalized air temperature in the room;
• outdoor air temperature;
• the degree of heating of the coolant when it enters the heating system;
• the degree of heating of the coolant at the outlet of the building networks;
• degree of heat transfer heating appliances;
• thermal conductivity of the outer walls and the overall heat loss of the building.

To perform a competent calculation, it is necessary to calculate the difference between the water temperatures in the direct and return pipes Δt. The higher the value in the straight pipe, the better the heat transfer of the heating system and the higher the indoor temperature.

In order to rationally and economically consume the coolant, it is necessary to achieve the minimum possible value of Δt. This can be achieved, for example, by working on additional insulation external structures of the house (walls, coverings, ceilings over a cold basement or technical underground).

Calculation of the heating mode

First of all, you need to get all the initial data. Standard values temperatures of outdoor and indoor air are taken according to the joint venture "Thermal protection of buildings". To find the power of heating devices and heat losses, you will need to use the following formulas.

Heat loss of the building

In this case, the input data will be:

• the thickness of the outer walls;
• thermal conductivity of the material from which the enclosing structures are made (in most cases it is indicated by the manufacturer, denoted by the letter λ);
• surface area of ​​the outer wall;
• climatic area of ​​construction.

First of all, the actual resistance of the wall to heat transfer is found. In a simplified version, you can find it as a quotient of the wall thickness and its thermal conductivity. If a outdoor structure consists of several layers, individually find the resistance of each of them and add the resulting values.

Thermal losses of walls are calculated by the formula:

Q = F*(1/R 0)*(t inside air -t outside air)

Here Q is the heat loss in kilocalories and F is the surface area of ​​the exterior walls. For more exact value it is necessary to take into account the area of ​​​​the glazing and its heat transfer coefficient.

Calculation of the surface power of batteries

Specific (surface) power is calculated as a quotient maximum power device in W and heat transfer surface area. The formula looks like this:

R beats \u003d R max / F act

Calculation of the coolant temperature

Based on the obtained values, temperature regime heating and a direct heat transfer is built. On one axis, the values ​​​​of the degree of heating of the water supplied to the heating system are plotted, and on the other, the outside air temperature. All values ​​are taken in degrees Celsius. The results of the calculation are summarized in a table in which the nodal points of the pipeline are indicated.

It is rather difficult to carry out calculations according to the method. To perform a competent calculation, it is best to use special programs.

For each building, this calculation is carried out individually. management company. For an approximate definition of water at the inlet to the system, you can use the existing tables.

1. For large suppliers of thermal energy, coolant parameters are used 150-70ᵒС, 130-70ᵒС, 115-70ᵒС.
2. For small systems for a few apartment buildings parameters apply 90-70ᵒС (up to 10 floors), 105-70ᵒС (over 10 floors). A schedule of 80-60ᵒС can also be adopted.
3. When arranging autonomous system heating for individual home it is enough to control the degree of heating with the help of sensors, you can not build a graph.

The measures taken make it possible to determine the parameters of the coolant in the system in certain moment time. By analyzing the coincidence of the parameters with the schedule, you can check the efficiency of the heating system. The temperature chart table also indicates the degree of load on the heating system.