How to convert the pump’s head and outlet pressure

There is no conversion relationship between the pump’s head and the outlet pressure. Head is related to the pressure difference between the inlet and outlet; head = pressure difference / (fluid density x acceleration due to gravity). Attention must be paid to the units of each parameter when making conversions.

Backflow: P=Outlet-Inlet； Suction side: P=exit+inlet

1. The centrifugal pump category: The performance of these pumps is generally indicated by head. Assuming there is no pressure at the pump inlet, the value on the pump’s performance curve is 100 meters. When transporting water, the outlet pressure is approximately 1 MPa; when transporting 98% concentrated sulfuric acid, the outlet pressure is about 1.84 MPa. 2. The volumetric pump category: The performance of such pumps is generally expressed in terms of pressure. Assuming there is no pressure at the pump inlet, the value on the pump’s performance curve is 1 MPa; when transporting water, the head generated is approximately 100 meters, while when transporting 98% concentrated sulfuric acid, the head is about 54 meters. This is related to the type of pump; some types of pumps have high pipe losses, so it is only meaningful in practical applications to calculate the relationship between pressure and head by taking external conditions into account.

1. Head usually refers to the maximum height that a water pump can lift water to, denoted by H. The most commonly used formula for calculating the head of a water pump is H=(p2-p1)/ρg+(c2-c1)/2g+z2-z1. 2. Here, H is the head, in meters; p1 and p2 are the pressures of the liquid at the inlet and outlet of the pump, in Pa; c1 and c2 are the flow velocities of the fluid at the inlet and outlet of the pump, in m/s; z1 and z2 are the heights at the inlet and outlet, in meters; ρ is the density of the liquid, in kg/m3; g is the acceleration due to gravity, in m/s2. 3. Centrifugal water pumps with a specific speed of ns between 130 and 150 are generally selected. The flow rate of such pumps should be 1.1 to 1.2 times the rated flow rate of the chiller unit (1.1 for a single pump, and 1.2 when two pumps are used in parallel). 4. It can be estimated that the friction loss per 100 meters of pipe length is approximately 5 mH2O. The formula for calculating the pump head in mH2O is as follows: 5. Hmax = △P1 + △P2 + 0.05L(1+K). 6. △P1 represents the water pressure drop across the evaporator of the chiller. 7. △P2 is the pressure drop of the air-conditioning terminal unit with the greatest water pressure loss among those connected in parallel within that loop. 8. L is the length of the most unfavorable loop. 9. K is the ratio of the sum of the equivalent lengths of local resistance in the most unfavorable loop to the total length of the straight sections; when the most unfavorable loop is long, K takes a value between 0.2 and 0.3, while when it is short, K ranges from 0.4 to 0.6. I’m a beginner and not sure if I’m saying the right things. Regarding head, please check if this is correct: http://www.llzypump.com/daogou/cb/131.html

Based on the inlet and outlet diameters of the pump, the principle of energy conservation in Bernoulli’s equation, as well as the properties of the fluid, it is possible to calculate the head of the pump; this head can then be used to determine the pressure at the outlet.

This post was last edited by 156026692 on 2018-12-25 at 14:53, using simulation software to calculate the head of the pump. Video viewing address: https://v.youku.com/v_show/id_XMTYzNDA2MzgwOA==.html

This post was last edited by 156026692 on 2018-12-25 at 14:54. It’s good; it’s a quite long video

My friend, why do the design institutes specify the operating pressure for the pump outlet pipeline based on the values for clean water, rather than multiplying that value by an appropriate coefficient due to the change in medium density?