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Pump head

Date: November 8, 2015 popularity: 177
Head usually refers to the maximum height that the pump can lift water, expressed by H. The most commonly used calculation formula of pump head is h = (p2-p1) / ρ G + (c2-c1) / 2G + z2-z1.
Among them, h -- head, m; P1, P2 -- pressure of liquid at pump inlet and outlet, PA; C1, C2 -- velocity of fluid at pump inlet and outlet, M / S; Z1, Z2 -- inlet and outlet height, m; ρ -- liquid density, kg / m3; G -- gravity acceleration, M / S2.
The centrifugal clean water pump with specific speed of 130-150 ns is usually selected, and the flow rate of the pump should be 1.1-1.2 times of the rated flow of the chiller (1.1 for a single pump and 1.2 for two parallel pumps).
According to the estimation, it can be roughly taken as 5mh2o per 100m pipe length. The calculation formula of pump head (mh2o) is as follows:
Hmax=△P1+△P2+0.05L (1+K)
Δ P1 is the water pressure drop of the evaporator of the chiller.
Δ P2 is the water pressure drop of the air conditioning unit with the largest water pressure loss in parallel in the loop.
L is the length of the most unfavorable loop
K is the ratio of the sum of the local resistance equivalent length in the most unfavorable loop to the total length of the straight pipe. When the most unfavorable loop is long, the value of K is 0.2-0.3, and the value of K is 0.4-0.6 when the most unfavorable loop is short.
After reading the calculation formula of pump head, I believe that we have a more comprehensive understanding of how to calculate the pump head. Generally speaking, the pump head is calculated by Bernoulli equation.

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