Temperature curve of the heating system for industrial premises. Temperature chart of the heating system: variations, application, shortcomings

Most city apartments are connected to the central heating network. The main source of heat in major cities usually are boiler houses and CHP. A coolant is used to provide heat in the house. Typically, this is water. It is heated to a certain temperature and fed into the heating system. But the temperature in the heating system can be different and is related to the temperature indicators of the outside air.

To effectively provide city apartments with heat, regulation is necessary. Observe set mode heating helps the temperature chart. What is the heating temperature chart, what types of it are, where is it used and how to compile it - the article will tell about all this.

Under the temperature graph is understood a graph that shows the required mode of water temperature in the heat supply system, depending on the level of outdoor temperature. Most often the chart temperature regime heating is determined for central heating. According to this schedule, heat is supplied to city apartments and other objects that are used by people. This schedule allows you to maintain the optimum temperature and save heating resources.

When is a temperature chart needed?

Apart from district heating the schedule is widely used in domestic autonomous heating systems. In addition to the need to adjust the temperature in the room, the schedule is also used in order to provide for safety measures during operation. household systems heating. This is especially true for those who install the system. Since the choice of equipment parameters for heating an apartment directly depends on the temperature graph.

Based on the climatic features and the temperature schedule of the region, a boiler and heating pipes are selected. The power of the radiator, the length of the system and the number of sections also depend on the temperature established by the standard. After all, the temperature of the heating radiators in the apartment should be within the standard. ABOUT technical specifications cast iron radiators can be read.

What are temperature charts?

Graphs may vary. The standard for the temperature of the apartment heating batteries depends on the option chosen.

The choice of a specific schedule depends on:

1. climate of the region;
2. boiler room equipment;
3. technical and economic indicators heating system.

Allocate schedules of one- and two-pipe heat supply systems.

Designate the heating temperature graph with two digits. For example, the temperature graph for heating 95-70 is deciphered as follows. To maintain the desired air temperature in the apartment, the coolant must enter the system with a temperature of +95 degrees, and exit - with a temperature of +70 degrees. As a rule, such a schedule is used for autonomous heating. All old houses with a height of up to 10 floors are designed for heating schedule 95 70. But, if the house has a large number of storeys, then the heating temperature chart of 130 70 is more suitable.

In modern new buildings, when calculating heating systems, the schedule 90-70 or 80-60 is most often adopted. True, another option may be approved at the discretion of the designer. The lower the air temperature, the coolant must have a higher temperature when entering the heating system. The temperature schedule is chosen, as a rule, when designing the heating system of a building.

Features of scheduling

The temperature graph indicators are developed based on the capabilities of the heating system, the heating boiler, and temperature fluctuations in the street. By creating a temperature balance, you can use the system more carefully, which means it will last much longer. Indeed, depending on the materials of the pipes, the fuel used, not all devices are always able to withstand sudden temperature changes.

When choosing the optimal temperature, they are usually guided by the following factors:

It should be noted that the temperature of the water in the central heating batteries should be such that it will warm the building well. For different rooms different standards have been developed. For example, for a residential apartment, the air temperature should not be less than +18 degrees. In kindergartens and hospitals, this figure is higher: +21 degrees.

When the temperature of the heating batteries in the apartment is low and does not allow the room to warm up to +18 degrees, the owner of the apartment has the right to contact the utility service to increase the efficiency of heating.

Since the temperature in the room depends on the season and climatic features, the temperature standard for heating batteries may be different. Heating of water in the heat supply system of the building can vary from +30 to +90 degrees. When the temperature of the water in the heating system is above +90 degrees, then the decomposition of the paintwork and dust begins. Therefore, above this mark, heating the coolant is prohibited by sanitary standards.

It must be said that the design outdoor air temperature for heating design depends on the diameter of the distributing pipelines, the size heating devices and coolant flow in heating system. There is a special table of heating temperatures that facilitates the calculation of the schedule.

The optimal temperature in heating batteries, the norms of which are set according to the heating temperature chart, allows you to create comfortable conditions residence. More details about bimetallic radiators heating can be found.

The temperature schedule is set for each heating system.

Thanks to him, the temperature in the home is maintained at optimal level. Graphs may vary. Many factors are taken into account in their development. Any schedule before being put into practice needs approval from the authorized institution of the city.

The temperature chart of the heating system 95 -70 degrees Celsius is the most demanded temperature chart. By and large, we can say with confidence that all central heating systems operate in this mode. The only exceptions are buildings with autonomous heating.

But also in autonomous systems there may be exceptions when using condensing boilers.

When using boilers operating on the condensation principle, the temperature curves of heating tend to be lower.

Application of condensing boilers

For example, when maximum load for a condensing boiler, there will be a mode of 35-15 degrees. This is due to the fact that the boiler extracts heat from the exhaust gases. In a word, with other parameters, for example, the same 90-70, it will not be able to work effectively.

Distinctive properties of condensing boilers are:

• high efficiency;
• profitability;
• optimal efficiency at minimum load;
• quality of materials;
• high price.

You have heard many times that the efficiency of a condensing boiler is about 108%. Indeed, the manual says the same thing.

But how can this be, because we are still with school desk taught that more than 100% does not happen.

1. The thing is that when calculating the efficiency of conventional boilers, exactly 100% is taken as a maximum.
   But ordinary ones simply throw flue gases into the atmosphere, and condensing ones utilize part of the outgoing heat. The latter will go to heating in the future.
2. The heat that will be utilized and used in the second round and added to the efficiency of the boiler. Typically, a condensing boiler utilizes up to 15% of flue gases, this figure is adjusted to the efficiency of the boiler (approximately 93%). The result is a number of 108%.
3. Undoubtedly, heat recovery is a necessary thing, but the boiler itself costs a lot of money for such work..
   The high price of the boiler due to stainless heat exchange equipment, which utilizes heat in the last path of the chimney.
4. If instead of such stainless equipment we put ordinary iron equipment, then it will become unusable after a very short span time . Since the moisture contained in the flue gases has aggressive properties.
5. The main feature of condensing boilers is that they achieve maximum efficiency with minimum loads.
   Conventional boilers (), on the contrary, reach the peak of economy at maximum load.
6. The beauty of it useful property that during all heating period, the heating load is not always at its maximum.
   On the strength of 5-6 days, an ordinary boiler works at maximum. Therefore, a conventional boiler cannot match the performance of a condensing boiler, which has maximum performance with minimal loads.

You can see a photo of such a boiler a little higher, and a video with its operation can be easily found on the Internet.

conventional heating system

It is safe to say that the heating temperature schedule of 95 - 70 is the most in demand.

This is explained by the fact that all houses that receive heat from central heat sources are designed to work in this mode. And we have more than 90% of such houses.

The principle of operation of such heat production occurs in several stages:

• heat source (district boiler house), produces water heating;
• heated water, through the main and distribution networks moves towards consumers;
• in the home of consumers, most often in the basement, through elevator unit hot water is mixed with water from the heating system, the so-called return, the temperature of which is not more than 70 degrees, and then heated to a temperature of 95 degrees;
• further heated water (the one that is 95 degrees) passes through the heaters of the heating system, heats the premises and again returns to the elevator.

Advice. If you have a cooperative house or a society of co-owners of houses, then you can set up the elevator with your own hands, but this requires you to strictly follow the instructions and correctly calculate the throttle washer.

Poor heating system

Very often we hear that people's heating does not work well and their rooms are cold.

There can be many reasons for this, the most common are:

• schedule temperature system heating is not observed, the elevator may be incorrectly calculated;
• the house heating system is heavily polluted, which greatly impairs the passage of water through the risers;
• fuzzy heating radiators;
• unauthorized change of the heating system;
• poor thermal insulation of walls and windows.

A common mistake is an incorrectly dimensioned elevator nozzle. As a result, the function of mixing water and the operation of the entire elevator as a whole is disrupted.

This could happen for several reasons:

• negligence and lack of training of operating personnel;
• incorrectly performed calculations in the technical department.

During the many years of operation of heating systems, people rarely think about the need to clean their heating systems. By and large, this applies to buildings that were built during the Soviet Union.

All heating systems must be hydropneumatic flushing before each heating season. But this is observed only on paper, since ZhEKs and other organizations carry out these works only on paper.

As a result, the walls of the risers become clogged, and the latter become smaller in diameter, which violates the hydraulics of the entire heating system as a whole. The amount of transmitted heat decreases, that is, someone simply does not have enough of it.

You can do hydropneumatic purge with your own hands, it is enough to have a compressor and a desire.

The same applies to cleaning radiators. Over many years of operation, radiators inside accumulate a lot of dirt, silt and other defects. Periodically, at least once every three years, they need to be disconnected and washed.

Dirty radiators greatly impair the heat output in your room.

The most common moment is an unauthorized change and redevelopment of heating systems. When replacing old metal pipes with metal-plastic ones, diameters are not observed. And sometimes various bends are added, which increases local resistance and worsens the quality of heating.

Very often, with such unauthorized reconstruction, the number of radiator sections also changes. And really, why not give yourself more sections? But in the end, your housemate, who lives after you, will receive less of the heat he needs for heating. And the last neighbor, who will receive less heat the most, will suffer the most.

An important role is played thermal resistance building envelopes, windows and doors. As statistics show, up to 60% of heat can escape through them.

Elevator node

As we said above, all water jet elevators are designed to mix water from the supply line of heating networks into the return line of the heating system. Thanks to this process, system circulation and pressure are created.

As for the material used for their manufacture, both cast iron and steel are used.

Consider the principle of operation of the elevator in the photo below.

Through pipe 1, water from heating networks passes through the ejector nozzle and with high speed enters the mixing chamber 3. There, water is mixed with it from the return of the heating system of the building, the latter is supplied through pipe 5.

The resulting water is sent to the heating system supply through diffuser 4.

In order for the elevator to function correctly, it is necessary that its neck be correctly selected. To do this, calculations are made using the formula below:

Where ΔРnas is the design circulation pressure in the heating system, Pa;

Gcm - water consumption in the heating system kg / h.

For your information!
True, for such a calculation, you need a building heating scheme.

After installing the heating system, it is necessary to adjust the temperature regime. This procedure must be carried out in accordance with existing standards.

The requirements for the temperature of the coolant are set out in normative documents that establish the design, installation and use engineering systems residential and public buildings. They are described in the State building codes and rules:

• DBN (B. 2.5-39 Heat networks);
• SNiP 2.04.05 "Heating, ventilation and air conditioning".

For the calculated temperature of the water in the supply, the figure is taken that is equal to the temperature of the water at the outlet of the boiler, according to its passport data.

For individual heating to decide what should be the temperature of the coolant, should be taking into account such factors:

1. Beginning and end heating season on average daily temperature outside +8 °C for 3 days;
2. The average temperature inside heated premises of housing and communal and public importance should be 20 ° C, and for industrial buildings 16 ° C;
3. The average design temperature must comply with the requirements of DBN V.2.2-10, DBN V.2.2.-4, DSanPiN 5.5.2.008, SP No. 3231-85.

According to SNiP 2.04.05 "Heating, ventilation and air conditioning" (clause 3.20), the coolant limit values ​​are as follows:

Depending on the external factors, the water temperature in the heating system can be from 30 to 90 °C. When heated above 90 ° C, dust begins to decompose and paintwork. For these reasons sanitary norms prohibit more heating.

For calculation optimal performance special charts and tables can be used that define the norms depending on the season:

• With an average value outside the window of 0 °С, the supply for radiators with different wiring is set at a level of 40 to 45 °С, and the return temperature is from 35 to 38 °С;
• At -20 °С, the supply is heated from 67 to 77 °С, while the return rate should be from 53 to 55 °С;
• At -40 ° C outside the window for all heating devices set the maximum allowed values. At the supply it is from 95 to 105 ° C, and at the return - 70 ° C.

Optimal values ​​in an individual heating system

Heating system helps to avoid many of the problems that arise with centralized network, but optimum temperature The coolant can be adjusted according to the season. In the case of individual heating, the concept of norms includes the heat transfer of a heating device per unit area of ​​​​the room where this device is located. The thermal regime in this situation is provided design features heating appliances.

It is important to ensure that the heat carrier in the network does not cool below 70 ° C. 80 °C is considered optimal. FROM gas boiler it is easier to control heating, because manufacturers limit the possibility of heating the coolant to 90 ° C. Using sensors to adjust the gas supply, the heating of the coolant can be controlled.

A little more difficult with solid fuel devices, they do not regulate the heating of the liquid, and can easily turn it into steam. And it is impossible to reduce the heat from coal or wood by turning the knob in such a situation. At the same time, the control of heating of the coolant is rather conditional with high errors and is performed by rotary thermostats and mechanical dampers.

Electric boilers allow you to smoothly adjust the heating of the coolant from 30 to 90 ° C. They are equipped with an excellent overheating protection system.

One-pipe and two-pipe lines

The design features of a single-pipe and two-pipe heating network determine different norms for heating the coolant.

For example, for a single-pipe line, the maximum rate is 105 ° C, and for a two-pipe line - 95 ° C, while the difference between the return and supply should be, respectively: 105 - 70 ° C and 95 - 70 ° C.

Matching the temperature of the heat carrier and the boiler

Regulators help to coordinate the temperature of the coolant and the boiler. These are devices that create automatic control and correction of the return and supply temperatures.

The return temperature depends on the amount of liquid passing through it. The regulators cover the liquid supply and increase the difference between the return and supply to the level that is needed, and the necessary pointers are installed on the sensor.

If it is necessary to increase the flow, then a boost pump can be added to the network, which is controlled by a regulator. To reduce the heating of the supply, a “cold start” is used: that part of the liquid that has passed through the network is again transferred from the return to the inlet.

The regulator redistributes the supply and return flows according to the data taken by the sensor, and ensures strict temperature norms heating networks.

Ways to reduce heat loss

The above information will help to be used for the correct calculation of the coolant temperature norm and will tell you how to determine the situations when you need to use the regulator.

But it is important to remember that the temperature in the room is affected not only by the temperature of the coolant, outdoor air and wind strength. The degree of insulation of the facade, doors and windows in the house should also be taken into account.

To reduce the heat loss of housing, you need to worry about its maximum thermal insulation. Insulated walls, sealed doors, metal-plastic windows help reduce heat loss. It will also reduce heating costs.

When autumn confidently walks across the country, snow flies beyond the Arctic Circle, and in the Urals night temperatures stay below 8 degrees, then the word form “heating season” sounds appropriate. People recall past winters and try to understand the normal temperature of the coolant in the heating system.

Prudent owners of individual buildings carefully revise the valves and nozzles of boilers. Residents apartment building by October 1 they are waiting like Santa Claus, a plumber from management company. The ruler of valves and valves brings warmth, and with it - joy, fun and confidence in the future.

The Gigacalorie Path

Megacities sparkle with high-rise buildings. A cloud of renovation hangs over the capital. Outback prays on five-story buildings. Until demolished, the house has a calorie supply system.

Heating of an economy-class apartment building is carried out through centralized system heat supply. The pipes are included in basement buildings. The supply of heat carrier is regulated by inlet valves, after which water enters the mud collectors, and from there it is distributed through risers, and from them it is supplied to batteries and radiators that heat housing.

The number of gate valves correlates with the number of risers. While doing repair work in a single apartment, it is possible to turn off one vertical, and not the whole house.

The spent liquid partially leaves through the return pipe, and partially is supplied to the hot water supply network.

degrees here and there

Water for the heating configuration is prepared at a CHP plant or in a boiler house. The water temperature standards in the heating system are prescribed in building regulations ax: the component must be heated to 130-150 °C.

The supply is calculated taking into account the parameters of the outside air. So, for the South Ural region, minus 32 degrees is taken into account.

To prevent the liquid from boiling, it must be supplied to the network under a pressure of 6-10 kgf. But this is a theory. In fact, most networks operate at 95-110 ° C, since the network pipes of most settlements are worn out and high pressure tear them up like a heating pad.

An extensible concept is the norm. The temperature in the apartment is never equal to the primary indicator of the heat carrier. Here, the elevator unit performs an energy-saving function - a jumper between the direct and return pipes. The norms for the temperature of the coolant in the heating system on the return in winter allow the preservation of heat at a level of 60 ° C.

The liquid from the straight pipe enters the elevator nozzle, mixes with return water and again goes into the house network for heating. The carrier temperature is lowered by mixing the return flow. What affects the calculation of the amount of heat consumed by residential and utility rooms.

hot gone

Temperature hot water according to sanitary rules at the points of analysis, it should lie in the range of 60-75 ° C.

In the network, the coolant is supplied from the pipe:

• in winter - from the reverse, so as not to scald users with boiling water;
• in summer - with a straight line, since in summer the carrier is heated no higher than 75 ° C.

A temperature chart is drawn up. Average daily temperature return water should not exceed the schedule by more than 5% at night and 3% during the day.

Parameters of distributing elements

One of the details of warming a home is a riser through which the coolant enters the battery or radiator from the temperature norms of the coolant in the heating system require heating in the riser in winter time in the range of 70-90 °C. In fact, the degrees depend on the output parameters of the CHP or boiler house. In the summer, when hot water is needed only for washing and showering, the range moves to the range of 40-60 ° C.

Observant people may notice that in a neighboring apartment, the heating elements are hotter or colder than in his own.

The reason for the temperature difference in the heating riser is the way the hot water is distributed.

In a single-pipe design, the heat carrier can be distributed:

• above; then the temperature is upper floors higher than on the bottom;
• from below, then the picture changes to the opposite - it is hotter from below.

IN two-pipe system the degree is the same throughout, theoretically 90 ° C in the forward direction and 70 ° C in the opposite direction.

Warm like a battery

Suppose that the structures of the central network are reliably insulated along the entire route, the wind does not walk through the attics, stairwells and basements, the doors and windows in the apartments are insulated by conscientious owners.

We assume that the coolant in the riser complies with the building regulations. It remains to find out what is the norm for the temperature of the heating batteries in the apartment. The indicator takes into account:

• outdoor air parameters and time of day;
• the location of the apartment in terms of the house;
• residential or utility room in the apartment.

Therefore, attention: it is important, not what is the degree of the heater, but what is the degree of air in the room.

Happy in corner rooms the thermometer should show at least 20 ° C, and 18 ° C is allowed in centrally located rooms.

At night, air in the dwelling is allowed to be 17 ° C and 15 ° C, respectively.

Theory of linguistics

The name "battery" is household, denoting a number of identical items. In relation to the heating of housing, this is a series of heating sections.

The temperature standards of heating batteries allow heating no higher than 90 ° C. According to the rules, parts heated above 75 ° C are protected. This does not mean that they need to be sheathed with plywood or bricked. Usually they put a lattice fence that does not interfere with air circulation.

Cast iron, aluminum and bimetallic devices are common.

Consumer choice: cast iron or aluminum

The aesthetics of cast-iron radiators is a byword. They require periodic painting, as regulations require that the work surface be smooth and allow dust and dirt to be easily removed.

A dirty coating forms on the rough inner surface of the sections, which reduces the heat transfer of the device. But the technical parameters cast iron products on high:

• little susceptible to water corrosion, can be used for more than 45 years;
• they have a high thermal power per 1 section, therefore they are compact;
• they are inert in heat transfer, therefore they smooth out temperature fluctuations in the room well.

Another type of radiators is made of aluminum. Lightweight construction, painted in the factory, does not require painting, easy to clean.

But there is a drawback that overshadows the advantages - corrosion in aquatic environment. Certainly, inner surface heaters are insulated with plastic to avoid contact of aluminum with water. But the film may be damaged, then it will begin chemical reaction with the release of hydrogen, when creating overpressure gas aluminum appliance may burst.

The temperature standards of heating radiators are subject to the same rules as batteries: it is not so much heating that matters metal object how much air heating in the room.

In order for the air to warm up well, there must be sufficient heat removal from working surface heating structure. Therefore, it is strongly not recommended to increase the aesthetics of the room with shields in front of the heating device.

Stairwell heating

Since we are talking about apartment building, then it should be mentioned stairwells. The norms for the temperature of the coolant in the heating system state: the degree measure on the sites should not fall below 12 ° C.

Of course, the discipline of the tenants requires that the doors be closed tightly. entrance group, do not leave the transoms of stair windows open, keep the glass intact and promptly report any problems to the management company. If the management company does not take timely measures to insulate the points of probable heat loss and maintain the temperature regime in the house, an application for recalculation of the cost of services will help.

Changes in heating design

Replacement of existing heating devices in the apartment is carried out with the obligatory coordination with the management company. Unauthorized change in the elements of warming radiation can disrupt the thermal and hydraulic balance of the structure.

The heating season will begin, a change in the temperature regime in other apartments and sites will be recorded. Technical inspection premises will reveal unauthorized changes in the types of heating devices, their number and size. The chain is inevitable: conflict - trial - fine.

So the situation is resolved like this:

• if not old ones are replaced with new radiators of the same size, then this is done without additional approvals; the only thing to apply to the Criminal Code is to turn off the riser for the duration of the repair;
• if new products differ significantly from those installed during construction, then it is useful to interact with the management company.

Heat meters

Let us recall once again that the heat supply network of an apartment building is equipped with heat energy metering units, which record both the consumed gigacalories and the cubic capacity of water passed through the house line.

In order not to be surprised by bills containing unrealistic amounts for heat at temperatures in the apartment below the norm, before the start of the heating season, check with the management company whether the meter is in working order, whether the verification schedule has been violated.

Build for closed system heat supply schedule of the central quality regulation heat supply for the combined load of heating and hot water supply (increased or adjusted temperature schedule).

Take the estimated temperature of the network water in the supply line t 1 = 130 0 С in the return line t 2 = 70 0 С, after the elevator t 3 = 95 0 С. indoors tv = 18 0 C. Estimated heat flows accept the same. Hot water temperature in hot water supply systems tgv = 60 0 C, temperature cold water t c \u003d 5 0 C. Balance coefficient for the load of hot water supply a b \u003d 1.2. The scheme for switching on water heaters of hot water supply systems is two-stage sequential.

Solution. Let us preliminarily perform the calculation and construction of a heating and household temperature graph with the temperature of the network water in the supply pipeline for the break point = 70 0 C. The values ​​of the temperatures of the network water for heating systems t 01 ; t 02 ; t 03 will be determined using the calculated dependencies (13), (14), (15) for outdoor air temperatures t n = +8; 0; -10; -23; -31 0 С

Let us determine, using formulas (16),(17),(18), the values ​​of the quantities

For t n = +8 0С values t 01, t 02 ,t 03 respectively will be:

Calculations of network water temperatures are performed similarly for other values t n. Using the calculated data and taking minimum temperature network water in the supply pipeline \u003d 70 0 С, we will build a heating and household temperature graph (see Fig. 4). The breaking point of the temperature graph will correspond to the network water temperature = 70 0 С, = 44.9 0 С, = 55.3 0 С, outdoor air temperature = -2.5 0 С. in table 4. Next, we proceed to the calculation of the elevated temperature graph. Given the value of subheating D t n \u003d 7 0 С, we determine the temperature of the heated tap water after the water heater of the first stage

Let us determine by formula (19) the balance load of hot water supply

Using formula (20), we determine the total temperature difference of network water d in both stages of water heaters

Let us determine by formula (21) the temperature difference of the network water in the water heater of the first stage for the range of outdoor air temperatures from t n \u003d +8 0 C to t" n \u003d -2.5 0 C

Let us determine for the specified range of outdoor air temperatures the temperature difference of network water in the second stage of the water heater

Using formulas (22) and (25), we determine the values ​​of the quantities d 2 and d 1 for outdoor temperature range t n from t" n \u003d -2.5 0 C to t 0 \u003d -31 0 C. So, for t n \u003d -10 0 C, these values ​​\u200b\u200bwill be:

Similarly, we will calculate the quantities d 2 and d 1 for values t n \u003d -23 0 C and tн = –31 0 С. The temperature of the network water and in the supply and return pipelines for the increased temperature graph will be determined by formulas (24) and (26).

Yes, for t n \u003d +8 0 C and t n \u003d -2.5 0 C, these values ​​will be

for t n \u003d -10 0 C

Similarly, we perform calculations for the values t n \u003d -23 0 С and -31 0 С. The obtained values ​​of the quantities d 2, d 1, , we summarize in table 4.

To plot the temperature of network water in the return pipeline after the heaters of ventilation systems in the range of outdoor air temperatures t n \u003d +8 ¸ -2.5 0 С use formula (32)

Let's define the value t 2v for t n \u003d +8 0 C. We first set the value to 0 C. We determine the temperature differences in the heater and, accordingly, for t n \u003d +8 0 C and t n \u003d -2.5 0 C

Calculate the left and right sides of the equation

Left side

Right part

Insofar as numerical values the right and left parts of the equation are close in value (within 3%), we will take the value as final.

For ventilation systems with air recirculation, we determine, using formula (34), the temperature of the network water after the heaters t 2v for t n = t nro = -31 0 C.

Here the values ​​of D t ; t ; t correspond t n = t v \u003d -23 0 С. Since this expression is solved by the selection method, we first set the value t 2v = 51 0 C. Let us determine the values ​​of D t to and D t

Since the left side of the expression is close in value to the right (0.99"1), the previously accepted value t 2v = 51 0 С will be considered final. Using the data in Table 4, we will construct a heating and domestic and increased temperature control graphs (see Fig. 4).

Table 4 - Calculation of temperature control curves for a closed heat supply system.

Fig.4. Temperature control charts for a closed heat supply system (¾ heating and domestic; --- elevated)

Build for open system heat supply of the adjusted (increased) schedule of the central quality regulation. Accept the balance coefficient a b = 1.1. Take the minimum temperature of the network water in the supply pipeline for the break point of the temperature graph 0 C. Take the rest of the initial data from the previous part.

Solution. First, we build temperature graphs , , , using calculations using formulas (13); (fourteen); (15). Next, we will build a heating and household schedule, the break point of which corresponds to the temperature values ​​of the network water 0 С; 0C; 0 C, and outdoor temperature 0 C. Next, we proceed to calculate the adjusted schedule. Determine the balance load of hot water supply

Let us determine the ratio of the balance load for hot water supply to the calculated load for heating

For a range of outdoor temperatures t n \u003d +8 0 C; -10 0 С; -25 0 С; -31 0 C, we determine the relative heat consumption for heating according to the formula (29)`; For example for t n \u003d -10 will be:

Then, taking the values ​​known from the previous part t c; t h q; Dt define, using formula (30), for each value t n relative costs of network water for heating.

For example, for t n \u003d -10 0 C will be:

Let's do the calculations for other values ​​in the same way. t n.

Supply water temperatures t 1p and reverse t 2n pipelines for the adjusted schedule will be determined by formulas (27) and (28).

Yes, for t n \u003d -10 0 C we get

Let's do the calculations t 1p and t 2p and for other values t n. Let us determine using the calculated dependences (32) and (34) the temperature of the network water t 2v after heaters of ventilation systems for t n \u003d +8 0 C and t n \u003d -31 0 С (in the presence of recirculation). With a value tн = +8 0 С t 2v = 23 0 C.

Let's define the values Dt to and Dt to

;

Since the numerical values ​​of the left and right parts of the equation are close, the previously accepted value t 2v = 23 0 C, we will consider it final. Let us also define the values t 2v at t n = t 0 = -31 0 C. Let us preliminarily set the value t 2v = 47 0 C

Let us calculate the values ​​of D t to and

The obtained values ​​of the calculated values ​​are summarized in table 3.5

Table 5 - Calculation of the increased (adjusted) schedule for an open heat supply system.

Using the data in Table 5, we will build a heating and domestic, as well as elevated graphics supply water temperatures.

Fig. 5 Heating - domestic ( ) and elevated (----) graphs of network water temperatures for an open heat supply system

Hydraulic calculation main heat pipelines two-pipe water heating network of a closed heat supply system.

Design scheme The heating network from the heat source (HS) to city blocks (CV) is shown in Fig.6. For compensation temperature deformations provide gland compensators. Specific pressure losses along the main line should be taken in the amount of 30-80 Pa / m.

Fig.6. Calculation scheme of the main heat network.

Solution. The calculation is performed for the supply pipeline. We will take the most extended and loaded branch of the heating network from IT to KV 4 (sections 1,2,3) as the main highway and proceed to its calculation. According to the hydraulic calculation tables given in the literature, as well as in Appendix No. 12 study guide, based on the known flow rates of the coolant, focusing on the specific pressure loss R in the range from 30 to 80 Pa / m, we will determine the diameters of pipelines for sections 1, 2, 3 d n xS, mm, actual specific pressure loss R, Pa/m, water velocity V, m/s.

By known diameters on sections of the main highway, we determine the sum of the coefficients of local resistances S x and their equivalent lengths L e. So, in section 1 there is a head valve ( x= 0.5), tee per pass at flow separation ( x= 1.0), Number of expansion joints ( x= 0.3) on the section will be determined depending on the length of the section L and the maximum allowable distance between fixed supports l. According to Appendix No. 17 of the training manual for D y = 600 mm this distance is 160 meters. Therefore, in section 1, 400 m long, three gland expansion joints should be provided. The sum of local resistance coefficients S x in this area will be

S x= 0.5 + 1.0 + 3 × 0.3 = 2.4

According to Appendix No. 14 of the training manual (with TO e = 0.0005m) equivalent length l uh for x= 1.0 equals 32.9 m. L e will be

L e = l e × S x= 32.9 × 2.4 = 79 m

L n = L+ L e \u003d 400 + 79 \u003d 479 m

Then we determine the pressure loss DP in section 1

D P= R x L n = 42 × 479 = 20118 Pa

Similarly, we perform the hydraulic calculation of sections 2 and 3 of the main highway (see Table 6 and Table 7).

Next, we proceed to the calculation of the branches. According to the principle of linking the pressure loss D P from the point of division of flows to the end points (CV) for different branches of the system must be equal to each other. Therefore, in the hydraulic calculation of branches, it is necessary to strive to fulfill following conditions:

D P 4+5 = D P 2+3 ; D P 6=D P five ; D P 7=D P 3

Based on these conditions, we will find the approximate specific pressure losses for the branches. So, for a branch with sections 4 and 5, we get

Coefficient a, which takes into account the share of pressure losses due to local resistances, is determined by the formula

then Pa/m

Focusing on R= 69 Pa / m we determine the diameters of pipelines, specific pressure losses from the tables of hydraulic calculation R, speed V, pressure loss D R in sections 4 and 5. Similarly, we will calculate the branches 6 and 7, having previously determined the approximate values ​​for them R.

Pa/m

Pa/m

Table 6 - Calculation of equivalent lengths of local resistances

Table 7 - Hydraulic calculation main pipelines

Let us determine the discrepancy between pressure losses in the branches. The discrepancy on the branch with sections 4 and 5 will be:

The discrepancy on branch 6 will be:

The discrepancy on branch 7 will be.