Heat loss in hot water supply pipelines calculation method. Calculation of temperature loss in hot water pipelines

2.2 Determination of heat loss and circulation flow rates in the supply pipelines of the hot water supply system

Circulation flow hot water in the system, l/s:

,(2.14)

where> is the total heat loss from the supply pipelines DHW systems, kW;

The temperature difference in the supply pipelines of the system to the most remote water collection point, , is assumed to be 10;

Circulation misregulation coefficient, accepted 1

For a system with variable resistance of circulation risers, the value is determined from the supply pipelines and water risers at = 10 and = 1

Heat loss in areas, kW, are determined by the formula

Where: q is the heat loss of 1 m of pipeline, W/m, taken according to Appendix 7 AAAAAAAAAAAAAAAAAAAAAAAAAAA

l - length of the pipeline section, m, taken according to the drawing

When calculating the heat loss of sections of water risers, the heat loss of a heated towel rail is taken to be 100 W, while its length is excluded from the length of the floor riser. For convenience, the calculation of heat loss is summarized in one table 2 with hydraulic calculation networks.

Let us determine the heat loss for the entire system as a whole. For convenience, it is assumed that the risers located on the plan in a mirror image are equal to each other. Then the heat loss of the risers located to the left of the input will be equal to:

1.328*2+0.509+1.303*2+2.39*2+2.432*2+2.244=15.659 kW

And the risers located on the right:

1.328*2+(0.509-0.144) +2.39*2+(0.244-0.155) =7.89 kW

The total heat loss per house will be 23.55 kW.

Let's determine the circulation flow:

l/s

Let us determine the calculated second consumption of hot water, l/s, in sections 45 and 44. To do this, we determine the ratio qh/qcir; for sections 44 and 45 it is equal to 4.5 and 5.5, respectively. According to Appendix 5, the coefficient Kcir = 0 in both cases, therefore, the preliminary calculation is final.

Provided for circulation circulation pump brand WILO Star-RS 30/7

2.3 Selection of water meter

acc. from clause a) clause 3.4, we check the condition 1.36m<5м, условие выполняется, принимаем крыльчатый водомер METRON Ду 50 мм.

3. Calculation and design of the sewerage system

The sewerage system is designed to remove from the building contaminants generated during sanitary and hygienic procedures, economic activities, as well as atmospheric and melt water. The internal sewer network consists of outlet pipelines, risers, outlets, exhaust parts, and cleaning devices. Discharge pipes are used to drain wastewater from sanitary fixtures and transfer it to the riser. The outlet pipes are connected to the water seals of sanitary fixtures and laid with a slope towards the riser. Risers are designed to transport wastewater to the sewer outlet. They collect wastewater from outlet pipes and their diameter must be no less than the largest diameter of the outlet pipe or the outlet of the device connected to the riser.

In this project, the intra-apartment wiring is made of socketed PVC pipes with a diameter of 50 mm, risers with a diameter of 100 mm are made of cast iron, also connected by sockets. Connection to risers is made using crosses and tees. The network is subject to inspections and cleaning to remove blockages.

3.1 Determination of estimated sewerage costs

Total maximum design water flow:

Where: - water consumption by the device is assumed to be 0.3 l/s, respectively. from app. 4; - coefficient depending on the total number of devices and the probability of their use Рtot

, (7)

Where: - the total rate of consumption per hour of greatest water consumption, l, is taken in accordance with Appendix 4 to be equal to 20

Number of water consumers equal to 104 * 4.2 people

Number of sanitary fixtures, accepted 416 as ordered

Then, the product N*=416*0.019=7.9, therefore =3.493

The resulting value is less than 8 l/s, therefore, the maximum second wastewater flow:

Where: - flow rate from the sanitary-technical device with the greatest drainage, l/s, taken according to Appendix 2 for a toilet with a flush tank equal to 1.6

3.2 Calculation of risers

The water consumption for risers K1-1, K1-2, K1-5, K1-6 will be the same, since an equal number of devices are connected to these risers, each with 52 devices.

We assume the diameter of the riser is 100 mm, the diameter of the floor outlet is 100 mm, the angle of the floor outlet is 90°. Maximum throughput 3.2 l/s. Estimated flow rate 2.95 l/s. Consequently, the riser operates in normal hydraulic mode.

The water consumption for risers K1-3, K1-4 will be the same, since an equal number of devices are connected to these risers, each with 104 devices.

Heat losses DQ, (W), in the calculated section of the supply pipeline or riser are determined by standard specific heat losses or by calculation using the formula:

Where TO - heat transfer coefficient of an insulated pipeline, K=11.6 W/(m 2 -°C); t g av - average water temperature in the system, t g avg,=(t n +t k)/2,°C; t n, - temperature at the outlet of the heater (temperature of hot water at the entrance to the building), °C; t to - temperature at the most distant water tap, °C; h- Thermal insulation efficiency (0.6); / - length of the pipeline section, m; d H - outer diameter of the pipeline, m; t 0 - ambient temperature, °C.

Water temperature at the most distant water tap t to should be taken 5 °C below the water temperature at the entrance to the building or at the outlet of the heater.

Ambient temperature t 0 when laying pipelines in furrows, vertical channels, communication shafts and shafts of sanitary cabins, it should be taken equal to 23 ° C, in bathrooms - 25 ° C, in kitchens and toilet rooms of residential buildings, dormitories and hotels - 21 ° C.

Bathrooms are heated by heated towel rails, so heat losses from heated towel rails are added to the heat loss of the riser in the amount 100p(W), where 100 W is the average heat transfer from one heated towel rail, P - number of heated towel rails connected to the riser.

When determining circulation water flow rates, heat losses through circulation pipelines are not taken into account. However, when calculating hot water supply systems with heated towel rails on circulation risers, it is advisable to add the heat transfer of heated towel rails to the amount of heat loss by the supply heat pipes. This increases the circulation flow of water, improves the heating of heated towel rails and heating of bathrooms. The calculation results are entered into the table.

åQп=5591.598 W

Hydraulic calculation of circulation pipelines

The circulating water flow rate in the hot water supply system G c (kg/h) is distributed proportionally to the total heat losses:

where åQ c is the total heat loss by all supply pipelines, W; Dt is the difference in water temperature in the supply pipelines of the hot water supply system, Dt=t g -t to =5°C; c is the heat capacity of water, J/(kg°C).

The circulation flow rates of water in the main sections of the hot water supply system consist of the circulation flow rates of the sections and risers that are located in front of the water movement.

Riser 1:

Section 2

Riser 2:

Section 3:

Riser 3:

Section 4:

Hydraulic calculation of circulation pipelines of an open hot water supply system.

We determine the discrepancy of pressure losses in two directions through the near and far risers using the formula: DH ch - pressure loss in the water meter, m; H St - available free pressure at the bath mixer (3m); DH cm - losses in the mixer (5 m); N g - geometric height of water rise from the axis of the pipeline at the inlet to the axis of the highest located water tap (24.2 m).

The water meter is selected based on water flow at the inlet G and nominal diameter Dy By . Pressure loss in the water meter DH mid(m), are determined by the formula:

where S is the hydraulic resistance of the water meter, taken according to (0.32 m/(l/s 2)). We accept the VK-20 water meter.

Excessive inlet pressure:

Bibliography.

1. Building codes and regulations. SNiP 3.05.01-85. Internal sanitary systems. M: Stroyizdat, 1986.

2. Building codes and regulations. SNiP 2.04.01-85. Internal water supply and sewerage of buildings. M.: Stroyizdat, 1986.

3. Building codes and regulations. SNiP II-34-76. Hot water supply. M.: Stroyizdat, 1976.

4. Designer's Handbook. Heating, water supply, sewerage / Ed. I. G. Staroverova. - M.: Stroyizdat, 1976. Part 1.

5. Handbook of heat supply and ventilation / R.V. Shchekin, S.M. Korenevsky, G.E. Bem, etc. - Kyiv: Budivelnik, 1976. Part 1.

6. Heat supply: Textbook for universities / A. A. Ionin, B. M. Khlybov, etc.; Ed. A. A. Ionina. M.: Stroyizdat, 1982.

7. Heat supply (course design): Textbook for universities on special topics. “Heat and gas supply and ventilation” / V. M. Kopko, N. K. Zaitseva and others; Ed. V. M. Kopko. - Mn.: Higher. school, 1985.

8. Heat supply: A textbook for university students / V. E. Kozin, T. A. Levina, A. P. Markov, etc. - M.: Vyssh. school, 1980.

9. Zinger N. M. Hydraulic and thermal regimes of heating systems. - M.: Energoatomizdat, 1986.

10. Sokolov E.Ya. District heating and heating networks. - M.: MPEI Publishing House, 2001.

11. Setup and operation of water heating networks: Directory / V. I. Manyuk, Ya. I. Kaplinsky, E. B. Khizh and others - M.: Stroyizdat, 1988.

We determine the discrepancy of pressure loss in two directions through the near and far risers using the formula:

where ΣΔp1, ΣΔp2 are, respectively, pressure losses when calculating directions through the far and near risers.

5. Calculation of heat losses by pipelines of the hot water supply system

Heat losses DQ, (W), in the calculated section of the supply pipeline or riser are determined by standard specific heat losses or by calculation using the formula:

where K is the heat transfer coefficient of the insulated pipeline, K=11.6 W/(m2-°C); tгср - average water temperature in the system, tгср,=(tн +tк)/2, °С; tн, - temperature at the outlet of the heater (temperature of hot water at the entrance to the building), °C; tk is the temperature at the most distant water tap, °C; h - thermal insulation efficiency (0.6); / - length of the pipeline section, m; dH - outer diameter of the pipeline, m; t0 - ambient temperature, °C.

The water temperature at the most remote water tap tk should be taken 5 °C lower than the water temperature at the entrance to the building or at the outlet of the heater.

The ambient temperature t0 when laying pipelines in furrows, vertical channels, communication shafts and sanitary cabin shafts should be taken equal to 23 ° C, in bathrooms - 25 ° C, in kitchens and toilet rooms of residential buildings, dormitories and hotels - 21 ° WITH .

Heating of bathrooms is carried out by heated towel rails, therefore, to the heat loss of the riser, heat loss from heated towel rails is added in the amount of 100p (W), where 100 W is the average heat transfer by one heated towel rail, n is the number of heated towel rails connected to the riser.

When determining circulation water flow rates, heat losses through circulation pipelines are not taken into account. However, when calculating hot water supply systems with heated towel rails on circulation risers, it is advisable to add the heat transfer of heated towel rails to the amount of heat loss by the supply heat pipes. This increases the circulation flow of water, improves the heating of heated towel rails and heating of bathrooms. The calculation results are entered into the table.

A new column has appeared in receipts for utility services - hot water supply. It caused confusion among users, since not everyone understands what it is and why it is necessary to make payments on this line. There are also apartment owners who cross out the box. This entails the accumulation of debt, penalties, fines and even litigation. In order not to take matters to extreme measures, you need to know what DHW is, DHW heat energy and why you need to pay for these indicators.

What is DHW on the receipt?

DHW - this designation stands for hot water supply. Its goal is to provide apartments in apartment buildings and other residential premises with hot water at an acceptable temperature, but hot water supply is not the hot water itself, but the thermal energy that is spent on heating the water to an acceptable temperature.

Experts divide hot water supply systems into two types:

• Central system. Here the water is heated at a heating station. After this, it is distributed to apartments in multi-apartment buildings.
• Autonomous system. It is usually used in private homes. The principle of operation is the same as in the central system, but here the water is heated in a boiler or boiler and is used only for the needs of one specific room.

Both systems have the same goal - to provide home owners with hot water. In apartment buildings, a central system is usually used, but many users install a boiler in case the hot water is turned off, as has happened more than once in practice. An autonomous system is installed where it is not possible to connect to the central water supply. Only those consumers who use the central heating system pay for hot water supply. Users of an autonomous circuit pay for utility resources that are spent to heat the coolant - gas or electricity.

Important! Another column in the receipt related to DHW is DHW at one unit. Decoding ODN - general house needs. This means that the DHW column on one unit is the expenditure of energy on heating water used for the general needs of all residents of an apartment building.

These include:

• technical work that is performed before the heating season;
• pressure testing of the heating system carried out after repair;
• repair work;
• heating of common areas.

Hot water law

The law on hot water supply was adopted in 2013. Government Decree No. 406 states that users of a central heating system are required to pay a two-part tariff. This suggests that the tariff was divided into two elements:

• thermal energy;
• cold water.

This is how DHW appeared on the receipt, that is, the thermal energy spent on heating cold water. Housing and communal services specialists came to the conclusion that risers and heated towel rails, which are connected to the hot water supply circuit, consume thermal energy to heat non-residential premises. Until 2013, this energy was not taken into account in receipts, and consumers used it free of charge for decades, since the air in the bathroom continued to be heated outside the heating season. Based on this, officials divided the tariff into two components, and now citizens have to pay for hot water.

Water heating equipment

The equipment that heats the liquid is a water heater. Its breakdown does not affect the hot water tariff, but users are required to pay the cost of repairing the equipment, since water heaters are part of the property of homeowners in an apartment building. The corresponding amount will appear in the receipt for the maintenance and repair of the property.

Important! This payment should be carefully considered by the owners of those apartments that do not use hot water, since their housing has an autonomous heating system installed. Housing and communal services specialists do not always pay attention to this, simply distributing the amount for water heater repairs among all citizens.

As a result, these apartment owners have to pay for equipment they did not use. If you discover an increase in the tariff for repairs and maintenance of property, you need to find out what this is connected with and contact the management company for recalculation if the payment was calculated incorrectly.

Thermal energy component

What is this - a coolant component? This is heating cold water. The thermal energy component does not have a meter installed, unlike hot water. For this reason, it is impossible to calculate this indicator using a counter. How, in this case, is the thermal energy for hot water calculated? When calculating the payment, the following points are taken into account:

• tariff set for hot water supply;
• expenses spent on maintaining the system;
• cost of heat loss in the circuit;
• costs spent on coolant transfer.

Important! The cost of hot water is calculated taking into account the volume of water consumed, which is measured in 1 cubic meter.

The size of the energy fee is usually calculated based on the readings of the common hot water meter and the amount of energy in the hot water. Energy is also calculated for each individual apartment. To do this, water consumption data is taken, which is learned from the meter readings, and multiplied by the specific heat energy consumption. The received data is multiplied by the tariff. This figure is the required contribution, which is indicated on the receipt.

How to make your own calculation

Not all users trust the payment center, which is why the question arises of how to calculate the cost of hot water supply yourself. The resulting figure is compared with the amount on the receipt and on the basis of this a conclusion is made about the correctness of the charges.

To calculate the cost of hot water supply, you need to know the tariff for thermal energy. The amount is also affected by the presence or absence of a meter. If there is one, then readings are taken from the meter. In the absence of a meter, the standard for the consumption of thermal energy used to heat water is taken. This standard indicator is established by an energy saving organization.

If an energy consumption meter is installed in a multi-storey building and the housing has a hot water meter, then the amount for hot water supply is calculated based on general building metering data and the subsequent proportional distribution of the coolant among apartments. If there is no meter, the rate of energy consumption per 1 cubic meter of water and the readings of individual meters are taken.

Complaint due to incorrect calculation of receipt

If, after independently calculating the amount of contributions for hot water supply, a difference is identified, you must contact the management company for clarification. If the organization's employees refuse to provide explanations on this matter, a written complaint must be submitted. Company employees have no right to ignore it. The response must be received within 13 working days.

Important! If no response is received or it is not clear from it why this situation arose, then the citizen has the right to file a claim with the prosecutor’s office or a statement of claim in court. The authority will consider the case and make an appropriate objective decision. You can also contact the organizations that control the activities of the management company. Here the subscriber's complaint will be considered and an appropriate decision will be made.

Electricity used to heat water is not a free service. Payment for it is charged on the basis of the Housing Code of the Russian Federation. Each citizen can independently calculate the amount of this payment and compare the data obtained with the amount on the receipt. If any inaccuracy occurs, you should contact the management company. In this case, the difference will be compensated if the error is recognized.