Selection of cold water pump
DATE:2024-10-15
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Selection of cold water pump
Usually choose the centrifugal water pump with a rotational speed of 30~150 revolutions per second, and the flow rate of the pump should be 1.1~1.2 times of the rated flow rate of the chiller (1.1 for a single unit and 1.2 for two units working in parallel). The head of the pump should be 1.1~1.2 times of the total water pressure drop of the most unfavorable loop of the supply and return water pipe network that it bears. The most unfavorable loop of the total water pressure drop, including chiller evaporator water pressure drop Δp1, the loop in parallel with the various air conditioning end device water pressure loss of the largest one of the water pressure drop Δp2, the loop in a variety of fittings of the water pressure drop and the sum of the pressure drop along the way. Chiller evaporator and air-conditioning end device water pressure drop, according to the design conditions from the product samples; loop fittings of the local loss and the loop along the loss should be calculated hydraulically, in the estimation, it can be roughly take every 100m pipe length along the loss of 5mH2O. so that, if the most unfavorable loop length (i.e., the sum of supply and return piping pipe length) for the L, then the chilled water pump head H (mH2O) can be estimated according to the following formula.
Hmax = Δp1 + Δp2 + 0.05L (1 + K)
Where K is the most unfavorable loop in the local resistance equivalent length of the sum and the ratio of the total length of the straight pipe. When the most unfavorable loop longer K take 0.2 ~ 0.3; the most unfavorable loop shorter K take 0.4 ~ 0.6.
Cooling water pump selection
(1) The flow rate of the cooling water pump should be 1.1 times of the cooling water volume of the chiller.
(2) the head of the pump for the chiller condenser water pressure drop Δp1, cooling tower open section height Z, pipeline along the loss and pipe fittings local loss of the sum of four 1.1 ~ 1.2 times. Δp1 and Z can be found from the relevant product samples; along the loss and the local loss should be derived from the hydraulic calculations, for the estimation of the pipeline fittings can be taken as a local loss of 5mH2O, along the loss of about 5 mH2O can be taken for each 100m pipe length. If the cooling water system back and forth pipe length is L, the estimated value of cooling water pump head required H (mH2O) is about
H = Δp1 + Z + 5 + 0.05L
3) Based on the cooling water pump flow and head, refer to the pump performance parameters selection of cooling water pump.
Water flow calculation
1.. Cooling cooling water flow water flow: generally in accordance with the product samples to provide the value of the selection, or in accordance with the following formula for calculation, the formula Q for the refrigeration host cooling capacity
L (m ³ / h) = [Q (kW) / (4.5 ~ 5) ℃ x 1.163] X (1.15 ~ 1.2)
2、Chilled water flow rate: the unit selected without considering the simultaneous utilization rate can be selected according to the values provided in the product samples or calculated according to the following formula. If the simultaneous utilization rate is considered, it is recommended to use the following formula for calculation. Q in the formula is the total cooling load of the building without considering the simultaneous utilization rate.
L(m3³/h)=Q(kW)/(4.5~5)℃x1.1635
3, the cooling water make-up water volume is generally 1 for the cooling water circulating water volume of 1~1.6%
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Usually choose the centrifugal water pump with a rotational speed of 30~150 revolutions per second, and the flow rate of the pump should be 1.1~1.2 times of the rated flow rate of the chiller (1.1 for a single unit and 1.2 for two units working in parallel). The head of the pump should be 1.1~1.2 times of the total water pressure drop of the most unfavorable loop of the supply and return water pipe network that it bears. The most unfavorable loop of the total water pressure drop, including chiller evaporator water pressure drop Δp1, the loop in parallel with the various air conditioning end device water pressure loss of the largest one of the water pressure drop Δp2, the loop in a variety of fittings of the water pressure drop and the sum of the pressure drop along the way. Chiller evaporator and air-conditioning end device water pressure drop, according to the design conditions from the product samples; loop fittings of the local loss and the loop along the loss should be calculated hydraulically, in the estimation, it can be roughly take every 100m pipe length along the loss of 5mH2O. so that, if the most unfavorable loop length (i.e., the sum of supply and return piping pipe length) for the L, then the chilled water pump head H (mH2O) can be estimated according to the following formula.
Hmax = Δp1 + Δp2 + 0.05L (1 + K)
Where K is the most unfavorable loop in the local resistance equivalent length of the sum and the ratio of the total length of the straight pipe. When the most unfavorable loop longer K take 0.2 ~ 0.3; the most unfavorable loop shorter K take 0.4 ~ 0.6.
Cooling water pump selection
(1) The flow rate of the cooling water pump should be 1.1 times of the cooling water volume of the chiller.
(2) the head of the pump for the chiller condenser water pressure drop Δp1, cooling tower open section height Z, pipeline along the loss and pipe fittings local loss of the sum of four 1.1 ~ 1.2 times. Δp1 and Z can be found from the relevant product samples; along the loss and the local loss should be derived from the hydraulic calculations, for the estimation of the pipeline fittings can be taken as a local loss of 5mH2O, along the loss of about 5 mH2O can be taken for each 100m pipe length. If the cooling water system back and forth pipe length is L, the estimated value of cooling water pump head required H (mH2O) is about
H = Δp1 + Z + 5 + 0.05L
3) Based on the cooling water pump flow and head, refer to the pump performance parameters selection of cooling water pump.
Water flow calculation
1.. Cooling cooling water flow water flow: generally in accordance with the product samples to provide the value of the selection, or in accordance with the following formula for calculation, the formula Q for the refrigeration host cooling capacity
L (m ³ / h) = [Q (kW) / (4.5 ~ 5) ℃ x 1.163] X (1.15 ~ 1.2)
2、Chilled water flow rate: the unit selected without considering the simultaneous utilization rate can be selected according to the values provided in the product samples or calculated according to the following formula. If the simultaneous utilization rate is considered, it is recommended to use the following formula for calculation. Q in the formula is the total cooling load of the building without considering the simultaneous utilization rate.
L(m3³/h)=Q(kW)/(4.5~5)℃x1.1635
3, the cooling water make-up water volume is generally 1 for the cooling water circulating water volume of 1~1.6%