Selection of cooling water pump
Thread Content
For the cooling water pump used in the cooling tower, the water flow rate of the cooling tower is 150 cubic meters per hour. The distributor on the outlet pipe of the cooling tower is located about 11 meters above the cooling water pump. The cooling water pipes have a diameter of 6 inches. It is a non-closed pipeline system between the pump and the cooling tower (tank --> pump --> cooling tower --> tank). Would a pump with 11 kilowatts of power, a head of 17 meters, and a flow rate of 167 cubic meters per hour be too powerful? What head does a pump need to have to be suitable?
For a 6-inch pipe, the flow resistance is less than 1 meter; a head of 15 meters is sufficient, which ensures that the motor power does not exceed the recommended level.
If the remaining energy from the water tank to the pump is not taken into account, the pipe resistance for a 11-meter long DN150 pipeline is approximately 1.22 mH2O; adding the head loss of 11 meters, and ignoring the remaining energy available in the cooling tower, the pump head required is 11 + 1.22 = 12.22 meters. Choosing a length of 17 meters is acceptable. The rated flow rate of 167 cubic meters still takes this remaining energy into consideration, so the selected parameters are quite good!
The suggestion regarding the bubble-patterned bamboo is correct; only when the pump efficiency reaches 85% can an 11kw motor meet the requirements for use. I don’t have the selection chart with me – can a small-sized single-stage double-suction pump achieve such a pump efficiency?
Thank you all for your advice. If the pump’s outlet is 4 inches in diameter and it is enlarged to 6 inches to connect to the cooling water pipe, will this have an impact on the head pressure? Motor efficiency IE3: 91.4%
It has no effect on the pump’s head; the change in diameter merely reduces the flow velocity and thus decreases the losses in the piping.
I have chosen a Grundfoss pump with a head of 14.6 meters, a flow rate of 160 cubic meters per hour, and a power output of 11 kilowatts. I would appreciate it if an expert could check whether this meets the requirements. Thank you!
At the outlet of the cooling tower, it is about 11 meters above the ground level of the pump – is the flow rate still too high?