2006-09-18 12:25:48 · 3 answers · asked by Optimus Prime 2 in Science & Mathematics ➔ Engineering
Pump and Fan effinity laws give you a rough estimate of the performance of a pump or a fan when the speed varies (keeping other things like geometry of pump, impeller size and piping size etc. constant) or performance of a pump or a fan when the diameter of impeller varies (keeping other things like speed of the pump etc constant).
For example, you have a pump running at 2900 rpm and with a flow rate of 100 gpm and a differential pressure(between discharge and suction) of 100 ft with an impeller diameter of 10", if you reduce the speed of the pump by half, then
Q & N i.e new flowrate will be 50 gpm (since Q1/Q2 = N1/N2)
H & N^2 i.e new dp will be 25 ft (since H1/H2 = (N1/N2)^2)
P & N^3
The initial water HP can be calculated by HP = GPM x TDH/3960 = 100 x 100/3960 = 2.52
Therefore new power consumption will be 2.52/8 = 0.315 HP
Care should be taken to include actual efficiencies of the pump from its performance curve while calculating BHP of the pump.
The formulae are similar for diameter changes when you keep the speed constant.
2006-09-18 16:52:14 · answer #1 · answered by absolutezero 2 · 1⤊ 0⤋
Interesting stuff. I had never heard of these laws thats why I went looking. Hope this is helpful.
Explanation from: http://www.engineeringtoolbox.com/affinity-laws-d_408.html
This site has built in calculators if you want to try rpm, pipe or impeler size variables.
Affinity Laws
Turbo machines affinity laws are commonly used within pumps and fans to calculate volume capacity, head or power consumption when speed - rpm, or wheel diameters are changed
Example - Pump Affinity Laws - Changing Pump Speed
The pump speed is changed when the impeller size is constant. The initial flow is 100 gpm, the initial head is 100 ft, the initial power is 5 bhp, the initial speed is 1750 rpm and the final speed 3500 rpm.
Example - Pump Affinity Laws - Changing Impeller Diameter
The diameter of the pump impeller is reduced when the pump speed is constant. The diameter is changed from 8 to 6 inches.
My Simplification. Affinity Laws
volume capacity----head or power consumption---- rpm, or wheel diameters are changed (LESS rpm, or smaller wheel = Less volume capacity LESS power consumption.
2006-09-18 13:02:48 · answer #2 · answered by 1rhino 2 · 2⤊ 0⤋
Fan Affinity
2016-12-10 20:32:07 · answer #3 · answered by ? 4 · 0⤊ 0⤋