There are certain patterns by which the temperature of the coolant in central heating changes. In order to adequately trace these fluctuations, there are special graphs.
Reasons for temperature changes
To begin with, it is important to understand a few points:
- When weather conditions change, this automatically entails a change in heat loss. With the onset of cold weather, an order of magnitude more thermal energy is spent to maintain an optimal microclimate in the home than during the warm period. At the same time, the level of consumed heat is not calculated by the exact temperature of the outdoor air: for this, the so-called. "delta" of the difference between the street and the interior. For example, +25 degrees in an apartment and -20 outside its walls will entail exactly the same heat costs as at +18 and -27, respectively.
- The constancy of the heat flow from the radiators is ensured by a stable temperature of the coolant. With a decrease in the temperature in the room, a certain rise in the temperature of the radiators will be observed: this is facilitated by an increase in the delta between the coolant and the air in the room. In any case, this will not be able to adequately compensate for the increase in heat loss through the walls. This is explained by the setting of restrictions for the lower temperature limit in the dwelling by the current SNiP at the level of + 18-22 degrees.
It is most logical to solve the problem of increasing losses by increasing the temperature of the coolant. It is important that its increase occurs in parallel with the decrease in air temperature outside the window: the colder it is, the greater the heat loss needs to be replenished. To facilitate orientation in this matter, at some stage it was decided to create special tables for reconciling both values. Based on this, we can say that the temperature graph of the heating system means the derivation of the dependence of the level of water heating in the supply and return pipelines in relation to the temperature regime on the street.
Features of the temperature graph
The above charts come in two varieties:
- For heating networks.
- For the heating system inside the house.
To understand how both of these concepts differ, it is advisable to first understand the features of the operation of centralized heating.
Link between CHP and heating networks
The purpose of this combination is to communicate the proper level of heating to the coolant, with its subsequent transportation to the place of consumption. Heating mains usually have a length of several tens of kilometers, with a total surface area of tens of thousands square meters. Although the main networks are subjected to thorough thermal insulation, it is impossible to do without heat losses.
In the direction of travel between the CHP (or boiler house) and residential premises, there is some cooling of process water. The conclusion itself suggests itself: in order to convey to the consumer an acceptable level of heating of the coolant, it must be supplied inside the heating main from the CHP in the most heated state. The temperature swing is limited by the boiling point. It can be shifted in the direction of increasing temperature if the pressure in the pipes is increased.
The standard pressure indicator in the supply pipe of the heating main is in the range of 7-8 atm. This level, despite the pressure loss in the course of transportation of the coolant, makes it possible to ensure efficient work heating system in buildings up to 16 floors high. In this case, additional pumps are usually not needed.
It is very important that such pressure does not pose a danger to the system as a whole: routes, risers, lines, mixing hoses and other components remain operational. long time. Given a certain margin for the upper limit of the supply temperature, its value is taken as +150 degrees. The passage of the most standard temperature curves for the supply of coolant to the heating system takes place between 150/70 - 105/70 (supply and return temperatures).
Features of the supply of coolant to the heating system
The house heating system is characterized by a number of additional restrictions:
- The value of the highest heating of the coolant in the circuit is limited to +95 degrees for a two-pipe system and +105 for a single-pipe heating system. It should be noted that preschool educational institutions are characterized by the presence of more stringent restrictions: there the temperature of the batteries should not rise above +37 degrees. To compensate for such a decrease in the supply temperature, it is necessary to increase the number of radiator sections. Interior spaces kindergartens located in regions with particularly harsh climatic conditions are literally crammed with batteries.
- It is desirable to achieve a minimum temperature delta of the heating supply schedule between the supply and return pipelines: otherwise, the degree of heating of the radiator sections in the building will have big difference. To do this, the coolant inside the system must move as quickly as possible. However, there is a danger here: due to the high speed of water circulation inside the heating circuit, its temperature at the outlet back to the route will be unnecessarily high. As a result, this can lead to serious violations in the operation of the CHP.
Influence of climatic zones on outdoor temperature
The main factor directly affecting the preparation of the temperature graph for heating season, is the estimated winter temperature. In the course of compilation, they try to ensure that the highest values \u200b\u200b(95/70 and 105/70) at maximum frosts guarantee the desired temperature for SNiP. The outdoor temperature for calculating heating is taken from a special table climatic zones.
Adjustment features
The parameters of thermal routes are in the area of responsibility of the management of CHPPs and heating networks. At the same time, ZhEK employees are responsible for the network parameters inside the building. Basically, residents' complaints about the cold relate to downward deviations. Situations are much less common when measurements inside thermal units indicate an increased return temperature.
There are several ways to normalize system parameters that you can implement yourself:
- Nozzle reaming. The problem of lowering the temperature of the liquid in the return can be solved by expanding the elevator nozzle. To do this, you need to close all the valves and valves on the elevator. After that, the module is removed, its nozzle is pulled out and reamed by 0.5-1 mm. After assembling the elevator, it is launched to bleed air in the reverse order. Paronite seals on the flanges are recommended to be replaced with rubber ones: they are made according to the size of the flange from the automobile chamber.
- Suction suppression. In extreme cases (with the onset of ultra-low frosts), the nozzle can be dismantled altogether. In this case, there is a threat that the suction will begin to perform the function of a jumper: in order to prevent this, it is jammed. For this, a steel pancake with a thickness of 1 mm is used. This method is emergency, because. this can provoke a jump in battery temperature up to +130 degrees.
- Delta control. A temporary way to solve the problem of temperature rise is to correct the differential with an elevator valve. To do this, it is necessary to redirect the DHW to the supply pipe: the return pipe is equipped with a pressure gauge. The inlet valve of the return pipeline is completely closed. Next, you need to gradually open the valve, constantly checking your actions with the readings of the pressure gauge.
Just a closed valve can cause a shutdown and defrosting of the circuit. The decrease in the difference is achieved due to an increase in the return pressure (0.2 atm./day). The temperature in the system must be checked every day: it must correspond to the heating temperature curve.
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). Work on this schedule heating network in Ufa (Bashkiria).
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.
| Temperature outdoor air Tnv, o C |
Temperature of network water in the supply pipeline T1, about C |
Water temperature in the supply pipe of the heating system T3, about C |
Water temperature after heating system T2, about C |
|||
|---|---|---|---|---|---|---|
| 150 | 130 | 115 | 105 | 95 | ||
| 8 | 53,2 | 50,2 | 46,4 | 43,4 | 41,2 | 35,8 |
| 7 | 55,7 | 52,3 | 48,2 | 45,0 | 42,7 | 36,8 |
| 6 | 58,1 | 54,4 | 50,0 | 46,6 | 44,1 | 37,7 |
| 5 | 60,5 | 56,5 | 51,8 | 48,2 | 45,5 | 38,7 |
| 4 | 62,9 | 58,5 | 53,5 | 49,8 | 46,9 | 39,6 |
| 3 | 65,3 | 60,5 | 55,3 | 51,4 | 48,3 | 40,6 |
| 2 | 67,7 | 62,6 | 57,0 | 52,9 | 49,7 | 41,5 |
| 1 | 70,0 | 64,5 | 58,8 | 54,5 | 51,0 | 42,4 |
| 0 | 72,4 | 66,5 | 60,5 | 56,0 | 52,4 | 43,3 |
| -1 | 74,7 | 68,5 | 62,2 | 57,5 | 53,7 | 44,2 |
| -2 | 77,0 | 70,4 | 63,8 | 59,0 | 55,0 | 45,0 |
| -3 | 79,3 | 72,4 | 65,5 | 60,5 | 56,3 | 45,9 |
| -4 | 81,6 | 74,3 | 67,2 | 62,0 | 57,6 | 46,7 |
| -5 | 83,9 | 76,2 | 68,8 | 63,5 | 58,9 | 47,6 |
| -6 | 86,2 | 78,1 | 70,4 | 65,0 | 60,2 | 48,4 |
| -7 | 88,5 | 80,0 | 72,1 | 66,4 | 61,5 | 49,2 |
| -8 | 90,8 | 81,9 | 73,7 | 67,9 | 62,8 | 50,1 |
| -9 | 93,0 | 83,8 | 75,3 | 69,3 | 64,0 | 50,9 |
| -10 | 95,3 | 85,6 | 76,9 | 70,8 | 65,3 | 51,7 |
| -11 | 97,6 | 87,5 | 78,5 | 72,2 | 66,6 | 52,5 |
| -12 | 99,8 | 89,3 | 80,1 | 73,6 | 67,8 | 53,3 |
| -13 | 102,0 | 91,2 | 81,7 | 75,0 | 69,0 | 54,0 |
| -14 | 104,3 | 93,0 | 83,3 | 76,4 | 70,3 | 54,8 |
| -15 | 106,5 | 94,8 | 84,8 | 77,9 | 71,5 | 55,6 |
| -16 | 108,7 | 96,6 | 86,4 | 79,3 | 72,7 | 56,3 |
| -17 | 110,9 | 98,4 | 87,9 | 80,7 | 73,9 | 57,1 |
| -18 | 113,1 | 100,2 | 89,5 | 82,0 | 75,1 | 57,9 |
| -19 | 115,3 | 102,0 | 91,0 | 83,4 | 76,3 | 58,6 |
| -20 | 117,5 | 103,8 | 92,6 | 84,8 | 77,5 | 59,4 |
| -21 | 119,7 | 105,6 | 94,1 | 86,2 | 78,7 | 60,1 |
| -22 | 121,9 | 107,4 | 95,6 | 87,6 | 79,9 | 60,8 |
| -23 | 124,1 | 109,2 | 97,1 | 88,9 | 81,1 | 61,6 |
| -24 | 126,3 | 110,9 | 98,6 | 90,3 | 82,3 | 62,3 |
| -25 | 128,5 | 112,7 | 100,2 | 91,6 | 83,5 | 63,0 |
| -26 | 130,6 | 114,4 | 101,7 | 93,0 | 84,6 | 63,7 |
| -27 | 132,8 | 116,2 | 103,2 | 94,3 | 85,8 | 64,4 |
| -28 | 135,0 | 117,9 | 104,7 | 95,7 | 87,0 | 65,1 |
| -29 | 137,1 | 119,7 | 106,1 | 97,0 | 88,1 | 65,8 |
| -30 | 139,3 | 121,4 | 107,6 | 98,4 | 89,3 | 66,5 |
| -31 | 141,4 | 123,1 | 109,1 | 99,7 | 90,4 | 67,2 |
| -32 | 143,6 | 124,9 | 110,6 | 101,0 | 94,6 | 67,9 |
| -33 | 145,7 | 126,6 | 112,1 | 102,4 | 92,7 | 68,6 |
| -34 | 147,9 | 128,3 | 113,5 | 103,7 | 93,9 | 69,3 |
| -35 | 150,0 | 130,0 | 115,0 | 105,0 | 95,0 | 70,0 |
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 a rather laborious and lengthy process, since several values must be calculated for each outdoor temperature: 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.
To calculate the heat loss of a house, it is necessary to know the thickness of the outer walls and the building material. The calculation of the surface power of the batteries is carried out according to the following formula: Psp \u003d P / Fact Where P is the maximum power, W, Fact is the radiator area, cm². The dependence of heat output on the temperature in the street According to the data obtained, it is compiled temperature regime for heating and a heat transfer schedule depending on the temperature outside. To timely change the heating parameters, a temperature heating controller is installed. This device connects to outdoor and indoor thermometers. Depending on the current indicators, the operation of the boiler or the volume of coolant inflow to the radiators is adjusted. The weekly programmer is the optimal temperature controller for heating. With its help, you can automate the operation of the entire system as much as possible.
Temperature chart of the heating system
Regulator benefits:
- The temperature regime is strictly maintained.
- Exclusion of liquid overheating.
- Economy of fuel and energy.
- The consumer, regardless of distance, receives heat equally.
Table with temperature graph Boiler operation mode depends on the weather environment. If we take various objects, for example, a factory building, a multi-storey building and a private house, all will have an individual heat chart.
Energy Blog
Attention
Looking through the statistics of visiting our blog, I noticed that search phrases such as, for example, “what should be the temperature of the coolant at minus 5 outside?” appear very often. I decided to lay out the old schedule for the quality regulation of heat supply based on the average daily outdoor temperature.
Important
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 the article regulating the temperature of the coolant). Thermal networks in Ufa (Bashkiria) operate according to this schedule.
I also want to draw attention to the fact that regulation takes place according to the average daily outdoor temperature, so if, for example, it is minus 15 degrees outside at night and minus 5 during the day, then the coolant temperature will be maintained in accordance with the schedule at minus 10 °C.
temperature graph
The temperature of the heat carrier at the inlet to the heating system with a qualitative regulation of the heat supply depends on the outside temperature, that is, the lower the outside temperature, the higher the temperature the coolant should enter the heating system. temperature graph is chosen when designing the heating system of the building, the size of the heating devices, the flow rate of the coolant in the system, and, consequently, the diameter of the distributing pipelines depend on it.
To indicate the temperature graph, two numbers are used, for example, 90-70 ° C - this means that at the estimated outdoor temperature (for Kyiv -22 ° C), to create comfortable temperature indoor air (for housing 20°C), the heating medium (water) must enter the heating system with a temperature of 90°C, and leave it with a temperature of 70°C.
Temperature chart of the heating system 95 70 snip table
Info
Analysis and adjustment of operating modes is carried out using a temperature scheme. For example, the return of a liquid with an elevated temperature will indicate high coolant costs.
Underestimated data will be considered as a consumption deficit. Previously, for 10-storey buildings, a scheme with calculated data of 95-70°C was introduced.
The buildings above had their chart 105-70°C. Modern new buildings may have a different scheme, at the discretion of the designer. More often, there are diagrams of 90-70°C, and maybe 80-60°C. Temperature graph 95-70: Temperature graph 95-70 How is it calculated? The control method is selected, then the calculation is made. The calculation-winter and reverse order of water inflow, the amount of outside air, the order at the break point of the diagram are taken into account. There are two diagrams, when one of them considers only heating, the second one considers heating with consumption hot water.
Heating temperature chart
At the same time, the degree of air heating in residential premises should be at the level of + 22 ° С. For non-residential, this figure is slightly lower - + 16 ° С. For centralized system drawing up the correct temperature schedule for the heating boiler room is required to ensure the optimal comfortable temperature in the apartments.
The main problem is the lack of feedback - it is impossible to adjust the parameters of the coolant depending on the degree of air heating in each apartment. That is why the temperature schedule of the heating system is drawn up. A copy of the heating schedule can be requested from the Management Company. With it, you can control the quality of the services provided. Heating system Temperature controller It is often not necessary to make similar calculations for autonomous heating systems of a private house.
Temperature schedule for the operation of sources and heating networks
Dependency graph may vary. A particular chart has a dependency on:
- Technical and economic indicators.
- Equipment for a CHP or boiler room.
- climate.
High performance of the coolant provides the consumer with a large thermal energy. An example of a circuit is shown below, where T1 is the temperature of the heat carrier, Tnv is the outdoor air: The diagram of the returned heat carrier is also used.
A boiler house or a CHP under such a scheme can evaluate source efficiency. It is considered high when the returned liquid arrives cooled. The stability of the scheme depends on the design values of the liquid flow of high-rise buildings. If the flow rate increases heating circuit, the water will return not chilled, as the flow rate will increase. And vice versa, when minimum flow, return water will be cool enough.
The supplier's interest is, of course, in the flow of return water in a chilled state. But there are certain limits to reduce the flow, since a decrease leads to losses in the amount of heat.
The consumer will begin to lower the internal degree in the apartment, which will lead to a violation of building codes and discomfort to the inhabitants. What does it depend on? The temperature curve depends on two quantities: outside air and heating medium. Frosty weather leads to an increase in the degree of coolant. When designing a central source, the size of the equipment, the building and the section of pipes are taken into account. The value of the temperature leaving the boiler room is 90 degrees, so that at minus 23°C, it would be warm in the apartments and have a value of 22°C. Then the return water returns to 70 degrees. Such norms correspond to normal and comfortable living in the house.
Temperature chart of the heating system - calculation procedure and ready-made tables
For networks operating according to temperature schedules of 95-70°С and 105-70°С (columns 5 and 6 of the table), the water temperature in the return pipeline of heating systems is determined by column 7 of the table. For consumers connected according to an independent connection scheme, the water temperature in the direct pipeline is determined according to column 4 of the table, and in the return pipeline according to column 8 of the table.
The temperature schedule for regulating the heat load is developed from the conditions of the daily supply of heat energy for heating, which ensures the need for buildings in heat energy depending on the outside temperature, in order to ensure that the temperature in the premises is constant at a level of at least 18 degrees, as well as covering the heat load of hot water supply with ensuring DHW temperature in places of water intake not lower than + 60 ° С, in accordance with the requirements of SanPin 2.1.4.2496-09 “Drinking water.
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 accepted according to the Joint Venture "Thermal protection of 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:
- Align heat loss during the supply of hot water to houses with an average daily outdoor temperature.
- Prevent insufficient heating of rooms.
- 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 is changed, 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 the central heating system, the most characteristic is a qualitative method, 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;
- the degree of heat transfer of heating devices;
- 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 a straight pipe, the better heat dissipation heating systems and higher indoor temperatures.
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 of temperatures of external and internal air are accepted 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 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 a more accurate value, it is necessary to take into account the area of \u200b\u200bglazing 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, the temperature regime of heating is selected 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.
- For large suppliers of thermal energy, coolant parameters are used 150-70ᵒС, 130-70ᵒС, 115-70ᵒС.
- For small systems with several apartment buildings parameters apply 90-70ᵒС (up to 10 floors), 105-70ᵒС (over 10 floors). A schedule of 80-60ᵒС can also be adopted.
- When arranging an autonomous heating system for an individual house, it is enough to control the degree of heating using sensors, you can not build a graph.
The performed measures allow determining the parameters of the coolant in the system at a certain point in 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.
Ph.D. Petrushchenkov V.A., Research Laboratory “Industrial Heat Power Engineering”, Peter the Great St. Petersburg State Polytechnic University, St. Petersburg
1. The problem of reducing the design temperature schedule for regulating heat supply systems nationwide
Over the past decades, in almost all cities of the Russian Federation, there has been a very significant gap between the actual and projected temperature curves for regulating heat supply systems. As you know, closed open systems district heating in the cities of the USSR they were designed using high-quality regulation with a temperature schedule for regulating the seasonal load of 150-70 ° С. Such a temperature schedule was widely used both for thermal power plants and for district boiler houses. But, starting from the end of the 1970s, significant deviations of network water temperatures appeared in the actual control curves from their design values at low outdoor air temperatures. Under the design conditions for the outside air temperature, the water temperature in the supply heat pipelines decreased from 150 °С to 85…115 °С. The lowering of the temperature schedule by the owners of heat sources was usually formalized as work on a project schedule of 150-70°С with a “cutoff” at a low temperature of 110…130°С. At lower coolant temperatures, the heat supply system was supposed to operate according to the dispatch schedule. Calculation justifications for such a transition are not known to the author of the article.
The transition to a lower temperature schedule, for example, 110-70 °С from the design schedule of 150-70 °С, should entail a number of serious consequences, which are dictated by the balance energy ratios. Due to the decrease in the calculated temperature difference of network water by 2 times, while maintaining the heat load of heating, ventilation, it is necessary to ensure an increase in the consumption of network water for these consumers also by 2 times. The corresponding pressure losses in the network water in the heating network and in the heat exchange equipment of the heat source and heat points with a quadratic law of resistance will increase by 4 times. The required increase in the power of network pumps should occur 8 times. It is obvious that neither the throughput of heat networks designed for a schedule of 150-70 ° C, nor the installed network pumps will allow the delivery of the coolant to consumers with a double flow rate compared to the design value.
In this regard, it is quite clear that in order to ensure a temperature schedule of 110-70 ° C, not on paper, but in reality, a radical reconstruction of both heat sources and the heat network with heat points will be required, the costs of which are unbearable for the owners of heat supply systems.
The ban on the use for heat networks of heat supply control schedules with “cutoff” by temperature, given in clause 7.11 of SNiP 41-02-2003 “Heat networks”, could not affect the widespread practice of its application. In the updated version of this document, SP 124.13330.2012, the mode with “cutoff” in temperature is not mentioned at all, that is, there is no direct ban on this method of regulation. This means that such methods of seasonal load regulation should be chosen, in which the main task will be solved - ensuring normalized temperatures in the premises and normalized water temperature for the needs of hot water supply.
Into the approved List of national standards and codes of practice (parts of such standards and codes of practice), as a result of which, on a mandatory basis, compliance with the requirements is ensured federal law dated December 30, 2009 No. 384-FZ "Technical Regulations on the Safety of Buildings and Structures" (Decree of the Government of the Russian Federation dated December 26, 2014 No. 1521) included the revisions of SNiP after updating. This means that the use of “cutting off” temperatures today is a completely legal measure, both from the point of view of the List of National Standards and Codes of Practice, and from the point of view of the updated edition of the profile SNiP “Heat Networks”.
Federal Law No. 190-FZ of July 27, 2010 “On heat supply”, “Rules and norms for the technical operation of the housing stock” (approved by Decree of the Gosstroy of the Russian Federation of September 27, 2003 No. 170), SO 153-34.20.501-2003 “Rules for the technical operation of power plants and networks Russian Federation” also do not prohibit the regulation of seasonal heat load with a “cut” in temperature.
In the 90s, good reasons that explained the radical decrease in the design temperature schedule were considered to be the deterioration of heating networks, fittings, compensators, as well as the inability to provide the necessary parameters at heat sources due to the state of heat exchange equipment. Despite the large volumes repair work conducted constantly in heat networks and heat sources in recent decades, this reason remains relevant today for a significant part of almost any heat supply system.
It should be noted that in specifications for connection to heating networks of most heat sources, a design temperature schedule of 150-70 ° C, or close to it, is still given. When coordinating the projects of central and individual heating points, an indispensable requirement of the owner of the heating network is to limit the flow of network water from the supply heat pipeline of the heating network during the entire heating period in strict accordance with the design, and not the actual temperature control schedule.
At present, the country is massively developing heat supply schemes for cities and settlements, in which also design schedules for regulating 150-70 ° С, 130-70 ° С are considered not only relevant, but also valid for 15 years ahead. At the same time, there are no explanations on how to ensure such schedules in practice, there is no clear justification for the possibility of providing the connected heat load at low outdoor temperatures under conditions of real regulation of seasonal heat load.
Such a gap between the declared and actual temperatures of the heat carrier of the heating network is abnormal and has nothing to do with the theory of operation of heat supply systems, given, for example, in.
Under these conditions, it is extremely important to analyze the actual situation with the hydraulic mode of operation of heating networks and with the microclimate of heated rooms at the calculated outdoor air temperature. The actual situation is such that, despite a significant decrease in the temperature schedule, while ensuring the design flow of network water in the heat supply systems of cities, as a rule, there is no significant decrease in the design temperatures in the premises, which would lead to resonant accusations of the owners of heat sources in failure to fulfill their main task: ensuring standard temperatures in the premises. In this regard, the following natural questions arise:
1. What explains such a set of facts?
2. Is it possible not only to explain the current state of affairs, but also to justify, based on the provision of the requirements of modern regulatory documentation, either a “cut” of the temperature graph at 115 ° С, or a new temperature graph of 115-70 (60) ° С with a qualitative regulation of the seasonal load?
This problem, of course, constantly attracts everyone's attention. Therefore, publications appear in the periodical press, which provide answers to the questions posed and provide recommendations for eliminating the gap between the design and actual parameters of the heat load control system. In some cities, measures have already been taken to reduce the temperature schedule and an attempt is being made to generalize the results of such a transition.
From our point of view, this problem is discussed most prominently and clearly in the article by Gershkovich V.F. .
It notes several extremely important provisions, which are, among other things, a generalization practical action on the normalization of the operation of heat supply systems under conditions of low-temperature “cutoff”. It is noted that practical attempts to increase the consumption in the network in order to bring it into line with the reduced temperature schedule have not been successful. Rather, they contributed to the hydraulic misalignment of the heating network, as a result of which the costs of network water between consumers were redistributed disproportionately to their heat loads.
At the same time, while maintaining the design flow in the network and reducing the temperature of the water in the supply line, even at low outdoor temperatures, in some cases, it was possible to ensure the air temperature in the premises at an acceptable level. The author explains this fact by the fact that in the heating load a very significant part of the power falls on the heating of fresh air, which ensures the normative air exchange of the premises. Real air exchange on cold days is far from the normative value, since it cannot be provided only by opening the vents and sashes of window blocks or double-glazed windows. The article emphasizes that Russian air exchange standards are several times higher than those of Germany, Finland, Sweden, and the USA. It is noted that in Kyiv, the decrease in the temperature schedule due to the “cutting off” from 150 ° C to 115 ° C was implemented and had no negative consequences. Similar work was done in the heating networks of Kazan and Minsk.
This article discusses the current state of the Russian requirements for regulatory documentation for indoor air exchange. On the example of model tasks with averaged parameters of the heat supply system, the influence of various factors on its behavior at a water temperature in the supply line of 115 °C under design conditions for the outdoor temperature, including:
Reducing the air temperature in the premises while maintaining the design water flow in the network;
Increasing the flow of water in the network in order to maintain the temperature of the air in the premises;
Reducing the power of the heating system by reducing the air exchange for the design water flow in the network while ensuring the calculated air temperature in the premises;
Estimation of the capacity of the heating system by reducing the air exchange for the actually achievable increased water consumption in the network while ensuring the calculated air temperature in the premises.
2. Initial data for analysis
As initial data, it is assumed that there is a source of heat supply with a dominant load of heating and ventilation, a two-pipe heating network, central heating and ITP, heating devices, heaters, taps. The type of heating system is not of fundamental importance. It is assumed that the design parameters of all links of the heat supply system ensure the normal operation of the heat supply system, that is, in the premises of all consumers, the design temperature is set to t w.r = 18 ° C, subject to the temperature schedule of the heating network of 150-70 ° C, the design value of the flow of network water , standard air exchange and quality regulation of seasonal load. The calculated outdoor air temperature is equal to the average temperature of the cold five-day period with a security factor of 0.92 at the time of the creation of the heat supply system. The mixing ratio of elevator units is determined by the generally accepted temperature curve for regulating heating systems 95-70 ° C and is equal to 2.2.
It should be noted that in the updated version of SNiP “Construction Climatology” SP 131.13330.2012 for many cities there was an increase in the design temperature of the cold five-day period by several degrees compared to the version of the document SNiP 23-01-99.
3. Calculations of operating modes of the heat supply system at a temperature of direct network water of 115 °C
The work in the new conditions of the heat supply system, created over decades according to modern standards for the construction period, is considered. The design temperature schedule for the qualitative regulation of the seasonal load is 150-70 °C. It is believed that at the time of commissioning, the heat supply system performed its functions exactly.
As a result of the analysis of the system of equations describing the processes in all links of the heat supply system, its behavior is determined at maximum temperature water in the supply line 115 °C at the estimated outdoor temperature, mixing ratios of elevator units 2.2.
One of the defining parameters of the analytical study is the consumption of network water for heating and ventilation. Its value is taken in the following options:
The design value of the flow rate in accordance with the schedule 150-70 ° C and the declared load of heating, ventilation;
The value of the flow rate, providing the design air temperature in the premises under the design conditions for the outside air temperature;
The actual maximum possible value of the network water flow, taking into account the installed network pumps.
3.1. Reducing the air temperature in the rooms while maintaining the connected heat loads
Let us determine how the average temperature in the premises will change at the temperature of the network water in the supply line t o 1 \u003d 115 ° С, the design consumption of network water for heating (we will assume that the entire load is heating, since the ventilation load is of the same type), based on the project schedule 150-70 °С, at outdoor air temperature t n.o = -25 °С. We consider that at all elevator nodes the mixing coefficients u are calculated and are equal to
For the design design conditions of operation of the heat supply system ( , , , ), the following system of equations is valid:
where - the average value of the heat transfer coefficient of all heating devices with a total heat exchange area F, - the average temperature difference between the coolant of the heating devices and the air temperature in the premises, G o - the estimated flow rate of network water entering the elevator units, G p - the estimated flow rate of water entering into heating devices, G p \u003d (1 + u) G o , s is the specific mass isobaric heat capacity of water, is the average design value of the heat transfer coefficient of the building, taking into account the transport of thermal energy through external fences with a total area A and the cost of thermal energy for heating the standard flow rate of the outdoor air.
At a low temperature of the network water in the supply line t o 1 =115 ° C, while maintaining the design air exchange, the average air temperature in the premises decreases to the value t in. The corresponding system of equations for design conditions for outdoor air will have the form
, (3)
where n is the exponent in the criterion dependence of the heat transfer coefficient of heating devices on the average temperature difference, see, table. 9.2, p.44. For the most common heating devices in the form of cast-iron sectional radiators and steel panel convectors of the RSV and RSG types, when the coolant moves from top to bottom, n=0.3.
Let us introduce the notation 
, , 
.
From (1)-(3) follows the system of equations
,
,
whose solutions look like:
, (4)
(5)
. (6)
For the given design values of the parameters of the heat supply system
,
Equation (5), taking into account (3) for a given temperature of direct water in the design conditions, allows us to obtain a ratio for determining the air temperature in the premises:
The solution to this equation is t in =8.7°C.
The relative thermal power of the heating system is equal to
Therefore, when the temperature of direct network water changes from 150 °C to 115 °C, the average air temperature in the premises decreases from 18 °C to 8.7 °C, the heating system's heat output drops by 21.6%.
The calculated values of water temperatures in the heating system for the accepted deviation from the temperature schedule are °С, °С.
The performed calculation corresponds to the case when the outdoor air flow during the operation of the ventilation and infiltration system corresponds to the design standard values up to the outdoor air temperature t n.o = -25°C. Since in residential buildings, as a rule, natural ventilation is used, organized by residents when ventilating with the help of vents, window sashes and micro-ventilation systems for double-glazed windows, it can be argued that at low outdoor temperatures, the flow of cold air entering the premises, especially after almost complete replacement of window blocks with double-glazed windows is far from the normative value. Therefore, the air temperature in residential premises is actually much higher. certain value t in \u003d 8.7 ° C.
3.2 Determining the power of the heating system by reducing the ventilation of indoor air at the estimated flow of network water
Let us determine how much it is necessary to reduce the cost of thermal energy for ventilation in the considered non-project mode of low temperature of the network water of the heating network in order for the average air temperature in the premises to remain at the standard level, that is, t in = t w.r = 18 ° C.
The system of equations describing the process of operation of the heat supply system under these conditions will take the form
The joint solution (2') with systems (1) and (3) similarly to the previous case gives the following relations for the temperatures of different water flows:
,
,
.
The equation for the given temperature of direct water under the design conditions for the outdoor temperature allows you to find the reduced relative load of the heating system (only the power of the ventilation system has been reduced, the heat transfer through the external fences is exactly preserved):
The solution to this equation is =0.706.
Therefore, when the temperature of the direct network water changes from 150°C to 115°C, maintaining the air temperature in the premises at the level of 18°C is possible by reducing the total heat output of the heating system to 0.706 of the design value by reducing the cost of heating the outside air. The heat output of the heating system drops by 29.4%.
The calculated values of water temperatures for the accepted deviation from the temperature graph are equal to °С, °С.
3.4 Increasing the consumption of network water in order to ensure the standard air temperature in the premises
Let us determine how the consumption of network water in the heating network for heating needs should increase when the temperature of the network water in the supply line drops to t o 1 \u003d 115 ° C under the design conditions for the outdoor temperature t n.o \u003d -25 ° C, so that the average temperature in the air in the premises remained at the normative level, that is, t in \u003d t w.r \u003d 18 ° C. The ventilation of the premises corresponds to the design value.
The system of equations describing the process of operation of the heat supply system, in this case, will take the form, taking into account the increase in the value of the flow rate of network water up to G o y and the flow rate of water through the heating system G pu \u003d G ou (1 + u) with a constant value of the mixing coefficient of elevator nodes u= 2.2. For clarity, we reproduce in this system the equations (1)
.
From (1), (2”), (3’) follows a system of equations of an intermediate form
The solution of the given system has the form:
° С, t o 2 \u003d 76.5 ° С,
So, when the temperature of the direct network water changes from 150 °C to 115 °C, maintaining the average air temperature in the premises at the level of 18 °C is possible by increasing the consumption of network water in the supply (return) line of the heating network for the needs of heating and ventilation systems in 2 .08 times.
It is obvious that there is no such reserve in terms of network water consumption both at heat sources and at pumping stations if available. In addition, such a high increase in network water consumption will lead to an increase in pressure losses due to friction in the pipelines of the heating network and in the equipment of heating points and heat sources by more than 4 times, which cannot be realized due to the lack of supply of network pumps in terms of pressure and engine power. . Consequently, an increase in network water consumption by 2.08 times due to an increase in only the number of installed network pumps, while maintaining their pressure, will inevitably lead to unsatisfactory operation of elevator units and heat exchangers in most of the heating points of the heat supply system.
3.5 Reducing the power of the heating system by reducing the ventilation of indoor air in conditions of increased consumption of network water
For some heat sources, the consumption of network water in the mains can be provided higher than the design value by tens of percent. This is due both to the decrease in thermal loads that has taken place in recent decades, and to the presence of a certain performance reserve of installed network pumps. Let's take the maximum relative value of network water consumption equal to 
=1.35 of the design value. We also take into account the possible increase in the calculated outdoor air temperature according to SP 131.13330.2012.
Let us determine how much it is necessary to reduce the average outdoor air consumption for ventilation of premises in the mode of reduced temperature of the network water of the heating network so that the average air temperature in the premises remains at the standard level, that is, tw = 18 °C.
For a reduced temperature of network water in the supply line t o 1 = 115 ° C, the air flow in the premises is reduced in order to maintain the calculated value of t at = 18 ° C in conditions of an increase in the flow of network water by 1.35 times and an increase in the calculated temperature of the cold five-day period. The corresponding system of equations for the new conditions will have the form
The relative decrease in the heat output of the heating system is equal to
. (3’’)
From (1), (2'''), (3'') follows the solution
,
,
.
For the given values of the parameters of the heat supply system and = 1.35:
; =115 °С; =66 °С; \u003d 81.3 ° С.
We also take into account the increase in the temperature of the cold five-day period to the value t n.o_ = -22 °C. The relative thermal power of the heating system is equal to
The relative change in the total heat transfer coefficients is equal to and due to a decrease in the air flow rate of the ventilation system.
For houses built before 2000, the share of heat energy consumption for ventilation of premises in the central regions of the Russian Federation is 40 ... .
For houses built after 2000, the share of ventilation costs increases to 50 ... 55%, a drop in the air consumption of the ventilation system by approximately 1.3 times will maintain the calculated air temperature in the premises.
Above in 3.2 it is shown that with the design values of network water consumption, indoor air temperature and design outdoor air temperature, a decrease in the network water temperature to 115 ° C corresponds to a relative power of the heating system of 0.709. If this decrease in power is attributed to a decrease in heating ventilation air, then for houses built before 2000, the air flow rate of the ventilation system of the premises should drop by approximately 3.2 times, for houses built after 2000 - by 2.3 times.
An analysis of measurement data from heat energy metering units of individual residential buildings shows that a decrease in heat energy consumption on cold days corresponds to a decrease in standard air exchange by a factor of 2.5 or more.
4. The need to clarify the calculated heating load of heat supply systems
Let the declared load of the heating system created in recent decades be . This load corresponds to the design temperature of the outside air, relevant during the construction period, taken for definiteness t n.o = -25 °С.
The following is an estimate of the actual reduction in the declared design heating load due to the influence of various factors.
Increasing the calculated outdoor temperature to -22 °C reduces the calculated heating load to (18+22)/(18+25)x100%=93%.
In addition, the following factors lead to a reduction in the calculated heating load.
1. Replacement of window blocks with double-glazed windows, which took place almost everywhere. The share of transmission losses of thermal energy through windows is about 20% of the total heating load. Replacing window blocks with double-glazed windows led to an increase in thermal resistance from 0.3 to 0.4 m 2 ∙K / W, respectively, the thermal power of heat loss decreased to the value: x100% \u003d 93.3%.
2. For residential buildings, the share of ventilation load in the heating load in projects completed before the early 2000s is about 40...45%, later - about 50...55%. Let's take the average share of the ventilation component in the heating load in the amount of 45% of the declared heating load. It corresponds to an air exchange rate of 1.0. According to modern STO standards, the maximum air exchange rate is at the level of 0.5, the average daily air exchange rate for a residential building is at the level of 0.35. Therefore, a decrease in the air exchange rate from 1.0 to 0.35 leads to a drop in the heating load of a residential building to the value:
x100%=70.75%.
3. The ventilation load of different consumers is demanded randomly, therefore, like the DHW load for a heat source, its value is summed not additively, but taking into account the coefficients of hourly unevenness. The share of the maximum ventilation load in the declared heating load is 0.45x0.5 / 1.0 = 0.225 (22.5%). The coefficient of hourly non-uniformity is estimated to be the same as for hot water supply, equal to K hour.vent = 2.4. Therefore, the total load of heating systems for the heat source, taking into account the reduction in the ventilation maximum load, the replacement of window blocks with double-glazed windows and the non-simultaneous demand for the ventilation load, will be 0.933x(0.55+0.225/2.4)x100%=60.1% of the declared load .
4. Taking into account the increase in the design outdoor temperature will lead to an even greater drop in the design heating load.
5. The performed estimates show that the clarification of the heat load of heating systems can lead to its reduction by 30 ... 40%. Such a decrease in the heating load allows us to expect that, while maintaining the design flow of network water, the calculated air temperature in the premises can be ensured by implementing the “cutoff” of the direct water temperature at 115 °C for low outdoor temperatures (see results 3.2). This can be argued with even greater reason if there is a reserve in the value of the network water consumption at the heat source of the heat supply system (see results 3.4).
The above estimates are illustrative, but it follows from them that, based on the current requirements of regulatory documentation, one can expect both a significant reduction in the total design heating load of existing consumers for a heat source, and a technically justified operating mode with a “cutoff” of the temperature schedule for regulating seasonal load at 115°C. The required degree of real reduction in the declared load of heating systems should be determined during field tests for consumers of a particular heat main. The calculated temperature of the return network water is also subject to clarification during field tests.
It should be borne in mind that the qualitative regulation of the seasonal load is not sustainable in terms of the distribution of thermal power among heating devices for vertical single-pipe heating systems. Therefore, in all calculations given above, while ensuring the average design air temperature in the rooms, there will be some change in the air temperature in the rooms along the riser during the heating period at different temperature outside air.
5. Difficulties in the implementation of the normative air exchange of premises
Consider the cost structure of the thermal power of the heating system of a residential building. The main components of heat losses compensated by the flow of heat from heating devices are transmission losses through external fences, as well as the cost of heating the outside air entering the premises. Fresh air consumption for residential buildings is determined by the requirements of sanitary and hygienic standards, which are given in section 6.
IN residential buildings the ventilation system is usually natural. The air flow rate is provided by the periodic opening of the vents and window sashes. At the same time, it should be borne in mind that since 2000 the requirements for the heat-shielding properties of external fences, primarily walls, have increased significantly (by 2–3 times).
From the practice of developing energy passports for residential buildings, it follows that for buildings built from the 50s to the 80s of the last century in the central and northwestern regions, the share of thermal energy for standard ventilation (infiltration) was 40 ... 45%, for buildings built later, 45…55%.
Before the advent of double-glazed windows, air exchange was regulated by vents and transoms, and on cold days the frequency of their opening decreased. With the widespread use of double-glazed windows, ensuring standard air exchange has become even more bigger problem. This is due to a tenfold decrease in uncontrolled infiltration through cracks and the fact that frequent ventilation by opening window sashes, which alone can provide standard air exchange, does not actually occur.
There are publications on this topic, see, for example,. Even during periodic ventilation, there are no quantitative indicators indicating the air exchange of the premises and its comparison with the standard value. As a result, in fact, the air exchange is far from the normative one and a number of problems arise: relative humidity, condensation forms on the glazing, mold appears, persistent odors appear, the carbon dioxide content in the air rises, which together led to the emergence of the term “sick building syndrome”. In some cases, due to a sharp decrease in air exchange, a rarefaction occurs in the premises, leading to an overturning of the air movement in the exhaust ducts and to the flow of cold air into the premises, overflowing dirty air from one apartment to another, freezing of the walls of the channels. As a result, builders are faced with the problem of using more advanced ventilation systems that can save heating costs. In this regard, it is necessary to use ventilation systems with controlled air supply and removal, heating systems with automatic regulation of heat supply to heating devices (ideally, systems with apartment connection), sealed windows and entrance doors to apartments.
Confirmation of the fact that the ventilation system of residential buildings operates with a performance that is significantly less than the design one is the lower, in comparison with the calculated, heat energy consumption during the heating period, recorded by the heat energy metering units of buildings.
The calculation of the ventilation system of a residential building performed by the staff of the St. Petersburg State Polytechnical University showed the following. natural ventilation in the free air flow mode, on average for the year, almost 50% of the time is less than the calculated one (section exhaust duct designed according to the current ventilation standards for multi-apartment residential buildings for the conditions of St. Petersburg for standard air exchange for an outside temperature of +5 ° C), in 13% of the time ventilation is more than 2 times less than the calculated one, and in 2% of the time there is no ventilation. For a significant part of the heating period, at an outside air temperature of less than +5 °C, ventilation exceeds the standard value. That is, without special adjustment at low outdoor temperatures, it is impossible to ensure standard air exchange; at outdoor temperatures of more than +5 ° C, air exchange will be lower than standard if the fan is not used.
6. Evolution of regulatory requirements for indoor air exchange
The costs of heating the outdoor air are determined by the requirements given in the regulatory documentation, which have undergone a number of changes over the long period of building construction.
Consider these changes on the example of residential apartment buildings.
In SNiP II-L.1-62, part II, section L, chapter 1, in force until April 1971, air exchange rates for living rooms were 3 m 3 / h per 1 m 2 of room area, for a kitchen with electric stoves, the air exchange rate is 3, but not less than 60 m 3 / h, for a kitchen with gas stove- 60 m 3 / h for two-burner stoves, 75 m 3 / h - for three-burner stoves, 90 m 3 / h - for four-burner stoves. Estimated temperature of living rooms +18 °С, kitchens +15 °С.
In SNiP II-L.1-71, Part II, Section L, Chapter 1, in force until July 1986, similar standards are indicated, but for a kitchen with electric stoves, the air exchange rate of 3 is excluded.
In SNiP 2.08.01-85, which were in force until January 1990, the air exchange rates for living rooms were 3 m 3 / h per 1 m 2 of room area, for the kitchen without indicating the type of plates 60 m 3 / h. Despite the different standard temperature in living quarters and in the kitchen, for heat engineering calculations, it is proposed to take the temperature of the internal air to +18°C.
In SNiP 2.08.01-89, which were in force until October 2003, the air exchange rates are the same as in SNiP II-L.1-71, Part II, Section L, Chapter 1. The indication of the internal air temperature +18 ° WITH.
In the SNiP 31-01-2003 that are still in force, new requirements appear, given in 9.2-9.4:
9.2 The design parameters of air in the premises of a residential building should be taken according to optimal standards GOST 30494. The air exchange rate in the premises should be taken in accordance with Table 9.1.
Table 9.1
| room | Multiplicity or magnitude air exchange, m 3 per hour, not less |
|
| in non-working | in mode service |
|
| Bedroom, shared, children's room | 0,2 | 1,0 |
| Library, office | 0,2 | 0,5 |
| Pantry, linen, dressing room | 0,2 | 0,2 |
| Gym, billiard room | 0,2 | 80 m 3 |
| Laundry, ironing, drying | 0,5 | 90 m 3 |
| Kitchen with electric stove | 0,5 | 60 m 3 |
| Room with gas-using equipment | 1,0 | 1.0 + 100 m 3 |
| Room with heat generators and solid fuel stoves | 0,5 | 1.0 + 100 m 3 |
| Bathroom, shower room, toilet, shared bathroom | 0,5 | 25 m 3 |
| Sauna | 0,5 | 10 m 3 for 1 person |
| Elevator engine room | - | By calculation |
| Parking | 1,0 | By calculation |
| Garbage chamber | 1,0 | 1,0 |
The air exchange rate in all ventilated rooms not listed in the table in non-operating mode should be at least 0.2 room volume per hour.
9.3 In the course of thermotechnical calculation of enclosing structures of residential buildings, the temperature of the internal air of heated premises should be taken as at least 20 °C.
9.4 The heating and ventilation system of the building must be designed to ensure that the indoor air temperature in the premises during the heating period is within the optimal parameters established by GOST 30494, with the design parameters of the outdoor air for the respective construction areas.
From this it can be seen that, firstly, the concepts of the maintenance mode of the premises and the non-working mode appear, during which, as a rule, very different quantitative requirements are imposed on air exchange. For residential premises (bedrooms, common rooms, children's rooms), which make up a significant part of the area of the apartment, the air exchange rates under different modes differ by 5 times. The air temperature in the premises when calculating the heat losses of the designed building should be taken at least 20°C. In residential premises, the frequency of air exchange is normalized, regardless of the area and number of residents.
The updated version of SP 54.13330.2011 partially reproduces the information of SNiP 31-01-2003 in the original version. Air exchange rates for bedrooms, common rooms, children's rooms with a total area of \u200b\u200bthe apartment per person less than 20 m 2 - 3 m 3 / h per 1 m 2 of room area; the same when the total area of the apartment per person is more than 20 m 2 - 30 m 3 / h per person, but not less than 0.35 h -1; for a kitchen with electric stoves 60 m 3 / h, for a kitchen with a gas stove 100 m 3 / h.
Therefore, to determine the average daily hourly air exchange, it is necessary to assign the duration of each of the modes, determine the air flow in different rooms during each mode and then calculate the average hourly need for fresh air in the apartment, and then the house as a whole. Multiple changes in air exchange in a particular apartment during the day, for example, in the absence of people in the apartment during working hours or on weekends, will lead to a significant unevenness of air exchange during the day. At the same time, it is obvious that the non-simultaneous operation of these modes in different apartments will lead to equalization of the load of the house for the needs of ventilation and to the non-additive addition of this load for different consumers.
It is possible to draw an analogy with the non-simultaneous use of the DHW load by consumers, which obliges to introduce the coefficient of hourly unevenness when determining the DHW load for the heat source. As you know, its value for a significant number of consumers in the regulatory documentation is taken equal to 2.4. A similar value for the ventilation component of the heating load allows us to assume that the corresponding total load will also in fact decrease by at least 2.4 times due to the non-simultaneous opening of vents and windows in different residential buildings. In public and industrial buildings, a similar picture is observed with the difference that during non-working hours ventilation is minimal and is determined only by infiltration through leaks in light barriers and external doors.
Accounting for the thermal inertia of buildings also makes it possible to focus on the average daily values of thermal energy consumption for air heating. Moreover, in most heating systems there are no thermostats that maintain the air temperature in the premises. It is also known that the central regulation of the temperature of network water in the supply line for heating systems is carried out according to the outdoor temperature, averaged over a period of about 6-12 hours, and sometimes for more time.
Therefore, it is necessary to perform calculations of the normative average air exchange for residential buildings different series in order to clarify the calculated heating load of buildings. Similar work needs to be done for public and industrial buildings.
It should be noted that these current regulatory documents apply to newly designed buildings in terms of designing ventilation systems for premises, but indirectly they not only can, but should also be a guide to action when clarifying the thermal loads of all buildings, including those that were built according to other standards listed above.
The standards of organizations regulating the norms of air exchange in the premises of multi-apartment residential buildings have been developed and published. For example, STO NPO AVOK 2.1-2008, STO SRO NP SPAS-05-2013, Energy saving in buildings. Calculation and design of ventilation systems for residential multi-apartment buildings (Approved by the general meeting of SRO NP SPAS dated March 27, 2014).
Basically, in these documents, the standards cited correspond to SP 54.13330.2011, with some reductions in individual requirements (for example, for a kitchen with a gas stove, a single air exchange is not added to 90 (100) m 3 / h, during non-working hours in a kitchen of this type air exchange is allowed 0 .5 h -1, while in SP 54.13330.2011 - 1.0 h -1).
Reference Appendix B STO SRO NP SPAS-05-2013 provides an example of calculating the required air exchange for a three-room apartment.
Initial data:
The total area of the apartment F total \u003d 82.29 m 2;
The area of residential premises F lived \u003d 43.42 m 2;
Kitchen area - F kx \u003d 12.33 m 2;
Bathroom area - F ext \u003d 2.82 m 2;
The area of the restroom - F ub \u003d 1.11 m 2;
Room height h = 2.6 m;
The kitchen has an electric stove.
Geometric characteristics:
The volume of heated premises V \u003d 221.8 m 3;
The volume of residential premises V lived \u003d 112.9 m 3;
Kitchen volume V kx \u003d 32.1 m 3;
The volume of the restroom V ub \u003d 2.9 m 3;
The volume of the bathroom V ext \u003d 7.3 m 3.
From the above calculation of air exchange, it follows that the ventilation system of the apartment must provide the calculated air exchange in the maintenance mode (in the design operation mode) - L tr work = 110.0 m 3 / h; in idle mode - L tr slave \u003d 22.6 m 3 / h. The given air flow rates correspond to the air exchange rate of 110.0/221.8=0.5 h -1 for the service mode and 22.6/221.8=0.1 h -1 for the off mode.
The information given in this section shows that in the existing regulatory documents, with different occupancy of apartments, the maximum air exchange rate is in the range of 0.35 ... This means that when determining the capacity of the heating system that compensates for the transmission losses of thermal energy and the costs of heating the outdoor air, as well as the consumption of network water for heating needs, one can focus, as a first approximation, on the daily average value of the air exchange rate of residential multi-apartment buildings 0.35 h - 1 .
An analysis of the energy passports of residential buildings developed in accordance with SNiP 23-02-2003 “Thermal protection of buildings” shows that when calculating the heating load of a house, the air exchange rate corresponds to the level of 0.7 h -1, which is 2 times higher than the recommended value above, not contradicting the requirements of modern service stations.
It is necessary to clarify the heating load of buildings built according to standard projects, based on the reduced average value of the air exchange rate, which will comply with the existing Russian standards and will make it possible to approach the standards of a number of EU countries and the USA.
7. Rationale for lowering the temperature graph
Section 1 shows that the temperature graph of 150-70 °C due to the actual impossibility of its use in modern conditions must be lowered or modified by justifying the “cutoff” in terms of temperature.
The above calculations of various modes of operation of the heat supply system in off-design conditions allow us to propose the following strategy for making changes to the regulation of the heat load of consumers.
1. For the transitional period, introduce a temperature chart of 150-70 °С with a “cutoff” of 115 °С. With such a schedule, the consumption of network water in the heating network for the needs of heating and ventilation should be kept at current level corresponding to the design value, or slightly exceeding it, based on the performance of the installed network pumps. In the range of outdoor air temperatures corresponding to the “cutoff”, consider the calculated heating load of consumers reduced in comparison with the design value. The decrease in the heating load is attributed to the reduction in the cost of thermal energy for ventilation, based on the provision of the necessary average daily air exchange of residential multi-apartment buildings according to modern standards at the level of 0.35 h -1 .
2. Organize work to clarify the loads of heating systems in buildings by developing energy passports for residential buildings, public organizations and enterprises, paying attention, first of all, to the ventilation load of buildings, which is included in the load of heating systems, taking into account modern regulatory requirements for indoor air exchange. To this end, it is necessary for houses of different heights, first of all, standard series carry out the calculation of heat losses, both transmission and ventilation in accordance with the modern requirements of the regulatory documentation of the Russian Federation.
3. On the basis of full-scale tests, take into account the duration of the characteristic modes of operation of ventilation systems and the non-simultaneity of their operation for different consumers.
4. After clarifying the thermal loads of consumer heating systems, develop a schedule for regulating the seasonal load of 150-70 °С with a “cutoff” by 115°С. The possibility of switching to the classic schedule of 115-70 °С without “cutting off” with high-quality regulation should be determined after clarifying the reduced heating loads. Specify the temperature of the return network water when developing a reduced schedule.
5. Recommend to designers, developers of new residential buildings and repair organizations performing overhaul old housing stock, application modern systems ventilation, allowing for the regulation of air exchange, including mechanical ones with systems for recuperating the thermal energy of polluted air, as well as the introduction of thermostats to adjust the power of heating devices.
Literature
1. Sokolov E.Ya. Heat supply and heat networks, 7th ed., M.: MPEI Publishing House, 2001
2. Gershkovich V.F. “One hundred and fifty ... Norm or bust? Reflections on the parameters of the coolant…” // Energy saving in buildings. - 2004 - No. 3 (22), Kyiv.
3. Internal sanitary devices. At 3 p.m. Part 1 Heating / V.N. Bogoslovsky, B.A. Krupnov, A.N. Scanavi and others; Ed. I.G. Staroverov and Yu.I. Schiller, - 4th ed., Revised. and additional - M.: Stroyizdat, 1990. -344 p.: ill. – (Designer's Handbook).
4. Samarin O.D. Thermophysics. Energy saving. Energy efficiency / Monograph. M.: DIA Publishing House, 2011.
6. A.D. Krivoshein, Energy saving in buildings: translucent structures and ventilation of premises // Architecture and construction of the Omsk region, No. 10 (61), 2008
7. N.I. Vatin, T.V. Samoplyas “Ventilation systems for residential premises of apartment buildings”, St. Petersburg, 2004
