Abstract The calculation and analysis of the hydraulic balance of the heating network in the west district of China Architectural Design Institute were carried out. The hydraulic balance of the heating heating network was solved by hydraulic balance valve and other technical measures to solve the problem of hydraulic imbalance and achieve satisfactory results. Balance set accumulated some experience. Keywords heating network heat balance hydraulic balance valve 1. Issues raised Central and South Architectural Design Institute Western (living area) concentrated low-temperature hot water heating system in 1991 to complete the design and construction, and put into operation at the end of the year. System has been running for ten years, greatly improving the living conditions of our staff. However, the hot water heating system from the beginning of operation, there is the problem of thermal imbalance. With the increase of users, the radius of the pipe network increases. With the decrease of coal-fired steam boilers, steam-water heat exchangers and hot water circulation pumps, as well as the performance of valves and pipelines along the heating system Of the weakening of the heating system to reduce operating efficiency, thermal imbalances more serious problems, specifically in the network end of the user's heating effect is getting worse. To tie in with the development of our hospital along the street, the demolition of two multi-storey residential buildings facing the street in the west of the hospital district will be partially mitigated due to heating appliances (hereinafter referred to as single buildings or unit buildings) However, the problem of hydraulic imbalance in heat pipe network has not yet been solved. West hospital heating heating network layout status see "Figure I." Western heating area of ​​about 35000m2, the total heating load in winter 2230kw. Heating heat source for the West District boiler room and heat transfer station; 4t / h coal-fired steam boiler 1; Spiral plate steam - water heat exchanger 2; 1000m3 / h hot water circulating pump 2, 1 have a preparation, nameplate lift 3.2 Mpa; system is located in "Zhongnanhai 18 units" house and then high expansion tank constant pressure, heat exchange station system is given to the pump. The heating system is divided into three trees for water loop. The No. 1 loop is the central loop in the hospital. The original No. 1 to No. 3 units, No. 4 to No. 6 Units, Kindergarten, No. 29 to No. 32 Units (50 units), No. 18, No. 33 to No. 35 Unit (36 households) "and" 23 households "heating load, its water pipe for water pipe DN125, an increase of a user" North plate ", the total heat load of 1219kw. Due to the large number of users and long radius of action, the problem of thermal imbalance has been serious over the long term. The heating of users along the road is uneven. The most unfavorable "23" indoor heating system is in name only. The heating effect of "36" units is also poor. 2 # loop is the north loop in the hospital, which is responsible for heating load of "7 to 10 units", "11 to 14 units", "North board" and "40 households" Burden "in a single apartment" and "40" demolition, is only affordable "single apartment", the heat load of 115kw. 2. Hydraulic Calculation and Balance Analysis of Pipe Network For the above reasons, we have carried out hydraulic calculation and analysis on the heating heating network in the West District, and we intend to adopt hydraulic counterbalance valve and other technical measures to balance the heating network in order to improve the overall heating effect in the West Zone. 2.1 Calculation Conditions Known Conditions (1) The diameter of pipelines and the length of pipelines along the outer network, the heating design heating load and the total design heat load of each unit. The heat load of each loop user heating said "table 1 Table 1 user name 1 to 3 units 4 to 7 units North board 28 units 29 units kindergarten South kindergarten north unit unit heat load (kw) 126.1 126.1 160.0 51.0 33.6 44.1 38.0 70.7 70.7 78.2 Continuation of a user name 33 unit 34 unit 35 unit 23 households 7 to 10 units 11 to 14 unit Zhongnanhai 15 to 21 unit single heat load (kw) 55.7 60.9 60.9 155.8 184.7 184.7 527.6 115.0 (2) each loop user room The required pressure head for heating water system is obtained from the heating design drawings and materials of all the units, see the item "User required head pressure" in "Table 4" and "Table V." Assumptions: (1) Boiler and heat exchanger efficiency reduction, according to the system operation experience heating the maximum temperature of 80 ℃, the maximum temperature difference between supply and return 15 ~ 18 ℃. Heating and return water temperature to take 80/60 ℃. (2) As the system for many years Roughness of the inner wall of the outer pipe increases, and the roughness of the inner wall of the outer pipe is taken as K = 0.5mm. 2.2 Calculation of Friction Resistance of Loop External Loop The total heat load of loop # 1 is 1219kw and the circulating water is 52.8kg / h. Return pipe diameter DN125, Road outside the friction resistance calculation said "Table II" Table II pipe number flow (t / h) diameter (mm) flow rate (m / s) unit friction (Pa / m) pipe length (m) / m) Total friction (Pa / m) L1 52.8 125 1.25 171 154 26.30 26.3 L2 47.3 125 1.11 135 134 18.10 44.4 L3 41.9 125 0.99 107 124 13.30 57.7 L4 31.3 125 0.74 60 10 0.60 58.3 L5 26.3 125 0.62 42 26 1.10 59.4 L6 23.3 125 0.55 33 26 0.86 60.3 L7 18.1 100 0.67 66 54 3.56 63.8 L8 13.4 100 0.50 36 20 0.72 64.6 L9 10.8 100 0.41 25 20 0.50 65.1 L10 6.5 50 0.96 330 24 7.90 73.0 L11 10.5 65 0.90 157 20 3.14 60.9 L12 9.07 65 0.70 116 20 2.32 63.2 L13 6.93 65 0.62 80 50 4.00 67.2 2 # loop burden The total heat load is 897kw, the circulating water is 22.9kg / h, the supply and return water pipe diameter is DN125, loop outside the network friction Calculate the details in Table 3 Table 3 Pipe No. Pipe flow (t / h) Nominal diameter (mm) Pipe flow rate (m / s) Unit friction (Pa / m) Pipe length (m) Pipe friction (Pa / m) Total friction (Pa / m) L14 38.8 125 0. 92 92.4 200 18.48 18.5 L15 22.9 100 0.85 104.8 50 5.24 23.7 L16 22.9 80 1.26 300.4 200 60.0 83.7 L17 15.9 80 0.88 145.3 50 7.27 31.0 L18 7.94 80 0.44 36.4 130 4.73 35.7 The 3 # loop is currently supported on a single user with a design heat The load is 115kw, the circulating water volume is 4.95kg / h, the water supply and return water pipe diameter is DN100, the water supply and return pipe length is about 80m, the loop external network friction and local resistance are smaller, and the total resistance is about 5kpa. 2.3 Loop external network hydraulic balance analysis and balance measures 2.3.1 1 # loop external network hydraulic balance 1 loop the most disadvantaged users as "23 households", its external network friction along the way is 73.0kpa, Taking into account the local resistance along the path of friction is 10% that is 7.3 kpa, the total resistance is 80.3 kpa along the way, "23" capital pressure head is 30 kpa, therefore, 1 # loop capital required head pressure is 110.3 kpa ,, The value is 115 kpa. The user's home pipe diameter and the required capital pressure head range. 1 # loop hydraulic balance calculation details "Table IV." From the hydraulic balance calculation table "Table IV" can be seen that the user near the home water supply pipe are provided with digital lock balance valve, the valve diameter smaller than the corresponding diameter one, at the same time we can see that the opening of the balance valve are more Small, not yet reached the opening should be 60 ~ 90% of the ideal range. The most disadvantaged users "23" entrance does not set the balance valve. Table 4 user name user flow rate (t / h) loop provides pressure head (kpa) users required capital pressure head (kpa) balance valve pressure head (kpa) household diameter (mm) counterbalance valve diameter ) Balance valve opening (%) 4 to 6 units 5.42 83.7 30 53.7 50 40 30 1 to 3 units 5.42 65.6 30 35.6 50 40 38 kindergartens 1.90 52.3 20 32.3 40 32 25 30 units 3.04 52.3 25 27.3 50 32 35 31 units 30.4 51.7 25 26.7 50 32 37 Kindergarten North 1.64 50.6 20 30.6 40 32 23 32 Units 3.36 49.7 25 24.7 50 32 42 18 Household 2.75 46.2 25 21.2 40 32 38 33 Units 2.41 46.2 25 21.2 50 40 33 34 Units 2.64 45.4 25 20.4 50 40 38 35 unit 2.96 44.9 25 19.9 50 40 40 23 households 7.79 30.0 30 7.0 50 no valve 28 unit 1.44 49.1 25 24.1 50 32 23 29 unit 2.11 46.8 25 21.8 50 32 29 North plate 6.88 42.8 30 12.8 50 40 50 2.3. 2 2 # loop external network hydraulic balance 2 # loop is the most disadvantaged users "Zhongnanhai 15 to 21 units", its external network friction along the way is 83.7kpa, taking into account the partial resistance of the friction is 10% that 8.4 kpa , Along the way the total resistance of 91.7 kpa, the user pressure head of 30 kpa, therefore, 2 # loop required capital and head pressure of 1 21.7 kpa, the value is 125 kpa. The user's home pipe diameter and the required capital pressure head range. 2 # loop hydraulic balance calculation details "Table five." From the hydraulic balance calculation table "Table V" can be seen that the user near the end of the home water supply are provided with digital lock balance valve, the valve diameter smaller than the corresponding diameter one. The most disadvantaged users "Zhongnanhai 15 to 21 units," the units for the return pipe for the same level with the layout, so there is no balance valve. Table 5 user name user flow (t / h) loop to provide pressure (kpa) users required capital pressure (kpa) balance valve pressure head (kpa) Home diameter (mm) counterbalance valve diameter ) Balance valve opening (%) 7 to 10 units 7.95 83.7 30 90 50 40 30 11 to 14 units 7.956 65.6 30 85 50 40 38 Zhongnanhai 15 to 21 units 22.9 30 30 0 DN25 × 19DN20 × 6 No valves 2.3.3 3 # loop external network hydraulic balance 3 # loop along the total resistance of 5 kpa, user funding head 25 kpa, therefore, 3 # loop required capital head pressure of 30 kpa. Home diameter DN65, and the outer diameter of the loop pipe DN100 is relatively large, if only by adjusting the loop in the heat exchanger for the return pipe DN100 diameter of the valve opening is difficult to achieve the loop required lower capital pressure Therefore, it is proposed that DN40 digital lock balancing valve be installed at the inlet pipe of its user's "single apartment" and it is also prepared for the future development of such a loop in the hospital. The specific balance program is appropriate in the heat exchanger station closed 3 # loop back to the water supply manifold valve head opening loop capital pressure head is 50 kpa, users use DN40 digital lock balance valve consumption rich head pressure 20 kpa, the Balance valve opening is set to 42%. 3. Heat Supply Network Transformation and Effect Before the heating season in 2000, the central heating network of Central South School West District had been rebuilt according to the above-mentioned hydraulic balance plan. The specific approach is: (1) For the vast majority of heat users at the entrance of the thermal pipe are added SP-type digital lock balance valve, and set the balance valve in the calculation of the determined opening, the user back and forth on the original Manual stop valve or gate valve full open; (2) by adjusting the heat exchanger station set manifold at the loop for the main valve on the return pipe, so that 1 #, 2 #, 3 # loop pressure head respectively For 115 kpa, 125 kpa, 50 kpa. After the winter of 2000, the district central heating system was put into operation. The problem of thermal imbalance, which has long been trapped in our hospital, has been solved. For example, the "23" indoor heating system of the worst-performing 1 # loop original heating system is completely normal, the loop has achieved thermal balance, and its hydraulic balance has been reflected. 2 # loop In addition to "Zhongnanhai 15 to 16 units" individual indoor vertical pipe, the loop is also normal. "Zhongnanhai" heating system for each unit level with the same layout, the first few years of operation of the system is a normal unit, "15 to 16 units," the reason is not hot individual riser indoor analysis is that some households renovated in recent years When large changes to the indoor system led to poor water flow, part of the indoor riser can not open the backwash or blocked by debris, the current problem is rectification. 3 # loop "single apartment" slightly overheating phenomenon, after the fine-tuning system completely normal. 4. Summary (1) The heating and net after the transformation of the operating results prove that the above-mentioned hydraulic balance calculation and analysis results are correct and reliable, for the future balance of heat network has accumulated some experience. (2) balance valve is a powerful tool for heat pipe network balance, with the help of balance valve to quantify the hydraulic balance. (3) For the whole heat pipe network, the indoor pipe system of the single-room heating system is too large, which is particularly serious for the near-end users of the tree pipe network. It is worth our attention in the future design. References 1. Lu Yaoqing, editor in chief, heating and ventilation design manual, Beijing, China Building Industry Press, 1987 2. Zeng Zhicheng, editor in chief, city cold · warm · steam triple for brochures, Beijing, China Building Industry Press, 1995 3. Fu Yongzheng et al., Selection of Balancing Valves, HVAC, 1998 (3) Abstract Calculation and analysis of the hydraulic balance of the heating network in the west of China Architectural Design Institute was carried out. The hydraulic balance of the heating heating network was solved by hydraulic balance valve and other technical measures. Hydraulic imbalance problem, to achieve more satisfactory results, for heating heating network to accumulate a certain amount of hydraulic balance experience. Keywords heating network heat balance hydraulic balance valve 1. Issues raised Central and South Architectural Design Institute Western (living area) concentrated low-temperature hot water heating system in 1991 to complete the design and construction, and put into operation at the end of the year. System has been running for ten years, greatly improving the living conditions of our staff. However, the hot water heating system from the beginning of operation, there is the problem of thermal imbalance. With the increase of users, the radius of the pipe network increases. With the decrease of coal-fired steam boilers, steam-water heat exchangers and hot water circulation pumps, as well as the performance of valves and pipelines along the heating system Of the weakening of the heating system to reduce operating efficiency, thermal imbalances more serious problems, specifically in the network end of the user's heating effect is getting worse. To tie in with the development of our hospital along the street, the demolition of two multi-storey residential buildings facing the street in the west of the hospital district will be partially mitigated due to heating appliances (hereinafter referred to as single buildings or unit buildings) However, the problem of hydraulic imbalance in heat pipe network has not yet been solved. West hospital heating heating network layout status see "Figure I." Western heating area of ​​about 35000m2, the total heating load in winter 2230kw. Heating heat source for the West District boiler room and heat transfer station; 4t / h coal-fired steam boiler 1; Spiral plate steam - water heat exchanger 2; 1000m3 / h hot water circulating pump 2, 1 have a preparation, nameplate lift 3.2 Mpa; system is located in "Zhongnanhai 18 units" house and then high expansion tank constant pressure, heat exchange station system is given to the pump. The heating system is divided into three trees for water loop. The No. 1 loop is the central loop in the hospital. The original No. 1 to No. 3 units, No. 4 to No. 6 Units, Kindergarten, No. 29 to No. 32 Units (50 units), No. 18, No. 33 to No. 35 Unit (36 households) "and" 23 households "heating load, its water pipe for water pipe DN125, an increase of a user" North plate ", the total heat load of 1219kw. Due to the large number of users and long radius of action, the problem of thermal imbalance has been serious over the long term. The heating of users along the road is uneven. The most unfavorable "23" indoor heating system is in name only. The heating effect of "36" units is also poor. 2 # loop is the north loop in the hospital, which is responsible for heating load of "7 to 10 units", "11 to 14 units", "North board" and "40 households" Burden "in a single apartment" and "40" demolition, is only affordable "single apartment", the heat load of 115kw. 2. Hydraulic Calculation and Balance Analysis of Pipe Network For the above reasons, we have carried out hydraulic calculation and analysis on the heating heating network in the West District, and we intend to adopt hydraulic counterbalance valve and other technical measures to balance the heating network in order to improve the overall heating effect in the West Zone. 2.1 Calculation Conditions Known Conditions (1) The diameter of pipelines and the length of pipelines along the outer network, the heating design heating load and the total design heat load of each unit. The heat load of each loop user heating said "table 1 Table 1 user name 1 to 3 units 4 to 7 units North board 28 units 29 units kindergarten South kindergarten north unit unit heat load (kw) 126.1 126.1 160.0 51.0 33.6 44.1 38.0 70.7 70.7 78.2 Continuation of a user name 33 unit 34 unit 35 unit 23 households 7 to 10 units 11 to 14 unit Zhongnanhai 15 to 21 unit single heat load (kw) 55.7 60.9 60.9 155.8 184.7 184.7 527.6 115.0 (2) each loop user room The required pressure head for heating water system is obtained from the heating design drawings and materials of all the units, see the item "User required head pressure" in "Table 4" and "Table V." Assumptions: (1) Boiler and heat exchanger efficiency reduction, according to the system operation experience heating the maximum temperature of 80 ℃, the maximum temperature difference between supply and return 15 ~ 18 ℃. Heating and return water temperature to take 80/60 ℃. (2) As the system for many years Roughness of the inner wall of the outer pipe increases, and the roughness of the inner wall of the outer pipe is taken as K = 0.5mm. 2.2 Calculation of Friction Resistance of Loop External Loop The total heat load of loop # 1 is 1219kw and the circulating water is 52.8kg / h. Return pipe diameter DN125, Road outside the friction resistance calculation said "Table II" Table II pipe number flow (t / h) diameter (mm) flow rate (m / s) unit friction (Pa / m) pipe length (m) / m) Total friction (Pa / m) L1 52.8 125 1.25 171 154 26.30 26.3 L2 47.3 125 1.11 135 134 18.10 44.4 L3 41.9 125 0.99 107 124 13.30 57.7 L4 31.3 125 0.74 60 10 0.60 58.3 L5 26.3 125 0.62 42 26 1.10 59.4 L6 23.3 125 0.55 33 26 0.86 60.3 L7 18.1 100 0.67 66 54 3.56 63.8 L8 13.4 100 0.50 36 20 0.72 64.6 L9 10.8 100 0.41 25 20 0.50 65.1 L10 6.5 50 0.96 330 24 7.90 73.0 L11 10.5 65 0.90 157 20 3.14 60.9 L12 9.07 65 0.70 116 20 2.32 63.2 L13 6.93 65 0.62 80 50 4.00 67.2 2 # loop burden The total heat load is 897kw, the circulating water is 22.9kg / h, the supply and return water pipe diameter is DN125, loop outside the network friction Calculate the details in Table 3 Table 3 Pipe No. Pipe flow (t / h) Nominal diameter (mm) Pipe flow rate (m / s) Unit friction (Pa / m) Pipe length (m) Pipe friction (Pa / m) Total friction (Pa / m) L14 38.8 125 0. 92 92.4 200 18.48 18.5 L15 22.9 100 0.85 104.8 50 5.24 23.7 L16 22.9 80 1.26 300.4 200 60.0 83.7 L17 15.9 80 0.88 145.3 50 7.27 31.0 L18 7.94 80 0.44 36.4 130 4.73 35.7 The 3 # loop is currently supported on a single user with a design heat The load is 115kw, the circulating water volume is 4.95kg / h, the water supply and return water pipe diameter is DN100, the water supply and return pipe length is about 80m, the loop external network friction and local resistance are smaller, and the total resistance is about 5kpa. 2.3 Loop external network hydraulic balance analysis and balance measures 2.3.1 1 # loop external network hydraulic balance 1 loop the most disadvantaged users as "23 households", its external network friction along the way is 73.0kpa, Taking into account the local resistance along the path of friction is 10% that is 7.3 kpa, the total resistance is 80.3 kpa along the way, "23" capital pressure head is 30 kpa, therefore, 1 # loop capital required head pressure is 110.3 kpa ,, The value is 115 kpa. The user's home pipe diameter and the required capital pressure head range. 1 # loop hydraulic balance calculation details "Table IV." From the hydraulic balance calculation table "Table IV" can be seen that the user near the home water supply pipe are provided with digital lock balance valve, the valve diameter smaller than the corresponding diameter one, at the same time we can see that the opening of the balance valve are more Small, not yet reached the opening should be 60 ~ 90% of the ideal range. The most disadvantaged users "23" entrance does not set the balance valve. Table 4 user name user flow rate (t / h) loop provides pressure head (kpa) users required capital pressure head (kpa) balance valve pressure head (kpa) household diameter (mm) counterbalance valve diameter ) Balance valve opening (%) 4 to 6 units 5.42 83.7 30 53.7 50 40 30 1 to 3 units 5.42 65.6 30 35.6 50 40 38 kindergartens 1.90 52.3 20 32.3 40 32 25 30 units 3.04 52.3 25 27.3 50 32 35 31 units 30.4 51.7 25 26.7 50 32 37 Kindergarten North 1.64 50.6 20 30.6 40 32 23 32 Units 3.36 49.7 25 24.7 50 32 42 18 Household 2.75 46.2 25 21.2 40 32 38 33 Units 2.41 46.2 25 21.2 50 40 33 34 Units 2.64 45.4 25 20.4 50 40 38 35 unit 2.96 44.9 25 19.9 50 40 40 23 households 7.79 30.0 30 7.0 50 no valve 28 unit 1.44 49.1 25 24.1 50 32 23 29 unit 2.11 46.8 25 21.8 50 32 29 North plate 6.88 42.8 30 12.8 50 40 50 2.3. 2 2 # loop external network hydraulic balance 2 # loop is the most disadvantaged users "Zhongnanhai 15 to 21 units", its external network friction along the way is 83.7kpa, taking into account the partial resistance of the friction is 10% that 8.4 kpa , Along the way the total resistance of 91.7 kpa, the user pressure head of 30 kpa, therefore, 2 # loop required capital and head pressure of 1 21.7 kpa, the value is 125 kpa. The user's home pipe diameter and the required capital pressure head range. 2 # loop hydraulic balance calculation details "Table five." From the hydraulic balance calculation table "Table V" can be seen that the user near the end of the home water supply are provided with digital lock balance valve, the valve diameter smaller than the corresponding diameter one. The most disadvantaged users "Zhongnanhai 15 to 21 units," the units for the return pipe for the same level with the layout, so there is no balance valve. Table 5 user name user flow (t / h) loop to provide pressure (kpa) users required capital pressure (kpa) balance valve pressure head (kpa) Home diameter (mm) counterbalance valve diameter ) Balance valve opening (%) 7 to 10 units 7.95 83.7 30 90 50 40 30 11 to 14 units 7.956 65.6 30 85 50 40 38 Zhongnanhai 15 to 21 units 22.9 30 30 0 DN25 × 19DN20 × 6 No valves 2.3.3 3 # loop external network hydraulic balance 3 # loop along the total resistance of 5 kpa, user funding head 25 kpa, therefore, 3 # loop required capital head pressure of 30 kpa. Home diameter DN65, and the outer diameter of the loop pipe DN100 is relatively large, if only by adjusting the loop in the heat exchanger for the return pipe DN100 diameter of the valve opening is difficult to achieve the loop required lower capital pressure Therefore, it is proposed that DN40 digital lock balancing valve be installed at the inlet pipe of its user's "single apartment" and it is also prepared for the future development of such a loop in the hospital. The specific balance program is appropriate in the heat exchanger station closed 3 # loop back to the water supply manifold valve head opening loop capital pressure head is 50 kpa, users use DN40 digital lock balance valve consumption rich head pressure 20 kpa, the Balance valve opening is set to 42%. 3. Heat Supply Network Transformation and Effect Before the heating season in 2000, the central heating network of Central South School West District had been rebuilt according to the above-mentioned hydraulic balance plan. The specific approach is: (1) For the vast majority of heat users at the entrance of the thermal pipe are added SP-type digital lock balance valve, and set the balance valve in the calculation of the determined opening, the user back and forth on the original Manual stop valve or gate valve full open; (2) by adjusting the heat exchanger station set manifold at the loop for the main valve on the return pipe, so that 1 #, 2 #, 3 # loop pressure head respectively For 115 kpa, 125 kpa, 50 kpa. After the winter of 2000, the district central heating system was put into operation. The problem of thermal imbalance, which has long been trapped in our hospital, has been solved. For example, the "23" indoor heating system of the worst-performing 1 # loop original heating system is completely normal, the loop has achieved thermal balance, and its hydraulic balance has been reflected. 2 # loop In addition to "Zhongnanhai 15 to 16 units" individual indoor vertical pipe, the loop is also normal. "Zhongnanhai" heating system for each unit level with the same layout, the first few years of operation of the system is a normal unit, "15 to 16 units," the reason is not hot individual riser indoor analysis is that some households renovated in recent years When large changes to the indoor system led to poor water flow, part of the indoor riser can not open the backwash or blocked by debris, the current problem is rectification. 3 # loop "single apartment" slightly overheating phenomenon, after the fine-tuning system completely normal. 4. Summary (1) The heating and net after the transformation of the operating results prove that the above-mentioned hydraulic balance calculation and analysis results are correct and reliable, for the future balance of heat network has accumulated some experience. (2) balance valve is a powerful tool for heat pipe network balance, with the help of balance valve to quantify the hydraulic balance. (3) For the whole heat pipe network, the indoor pipe system of the single-room heating system is too large, which is particularly serious for the near-end users of the tree pipe network. It is worth our attention in the future design. References 1. Lu Yaoqing, editor in chief, heating and ventilation design manual, Beijing, China Building Industry Press, 1987 2. Zeng Zhicheng, editor in chief, city cold · warm · steam triple for brochures, Beijing, China Building Industry Press, 1995 3. Fu Yongzheng et al., Selection of balancing valve, HVAC, 1998 (3) User name 1 ~ 3 unit 4 ~ 7 unit North board 28 unit 29 unit kindergarten South kindergarten north unit unit heat load (kw) 126.1 126.1 160.0 51.0 33.6 44.1 38.0 70.7 70.7 78.2 User Name 33 Unit 34 Unit 35 Unit 23 Households 7 to 10 Units 11 to 14 Units Zhongnanhai 15 to 21 Unit Single Thermal Load (kw) 55.7 60.9 60.9 155.8 184.7 184.7 527.6 115.0 Pipe No. Flow Rate (t / h) Diameter (mm) Flow rate (m / s) Unit friction (Pa / m) Section length (m) Section friction (Pa / m) Total friction (Pa / m) L1 52.8 125 1.25 171 154 26.30 26.3 L2 47.3 125 1.11 135 134 18.10 44.4 L3 41.9 125 0.99 107 124 13.30 57.7 L4 31.3 125 0.74 60 10 0.60 58.3 L5 26.3 125 0.62 42 26 1.10 59.4 L6 23.3 125 0.55 33 26 0.86 60.3 L7 18.1 100 0.67 66 54 3.56 63.8 L8 13.4 100 0.50 36 20 0.72 64.6 L9 10.8 100 0.41 25 20 0.50 65.1 L10 6.5 50 0.96 330 24 7.90 73.0 L11 10.5 65 0.90 157 20 3.14 60.9 L12 9.07 65 0.70 116 20 2.32 63.2 L13 6.93 65 0.62 80 50 4.00 67.2 Pipe No. Pipe (T / h) Nominal diameter (mm) Pipe flow rate (m / s) Unit friction (Pa / m) Pipe length (m) Pipe friction (Pa / m) Total friction (Pa / m) L14 38.8 125 0.92 92.4 200 18.48 18.5 L15 22.9 100 0.85 104.8 50 5.24 23.7 L16 22.9 80 1.26 300.4 200 60.0 83.7 L17 15.9 80 0.88 145.3 50 7.27 31.0 L18 7.94 80 0.44 36.4 130 4.73 35.7 User Name User Flow (t / h) Loop Supplied Pressure Head kpa User required pressure head kpa Balance valve head pressure kpa Household diameter mm Balance valve diameter mm Balance valve opening% 53.7 50 40 30 1 to 3 units 5.42 65.6 30 35.6 50 40 38 Kindergarten South 1.90 52.3 20 32.3 40 32 25 30 units 3.04 52.3 25 27.3 50 32 35 31 units 30.4 51.7 25 26.7 50 32 37 Kindergarten North 1.64 50.6 20 30.6 40 32 23 32 units 3.36 49.7 25 24.7 50 32 42 18 households 2.75 46.2 25 21.2 40 32 38 33 units 2.41 46.2 25 21.2 50 40 33 34 units 2.64 45.4 25 20.4 50 40 38 35 units 2.96 44.9 25 19.9 50 40 40 23 households 7.79 30.0 30 7.0 50 Without Valve 28 Unit 1.44 49.1 25 24.1 50 32 23 29 Unit 2.11 46.8 25 21.8 50 32 29 North plate 6.88 42.8 30 12.8 50 40 50 User name User flow (t / h) Ring provided pressure (kpa) User required pressure head (kpa) Counterbalance valve head (kpa) (Mm) Balancing valve opening (mm) Balancing valve opening (%) 7 to 10 units 7.95 83.7 30 90 50 40 30 11 to 14 units 7.956 65.6 30 85 50 40 38 Zhongnanhai 15 to 21 units 22.9 30 30 0 DN25 × 19DN20 × 6 No valve