how calculate the heat generated by a recirculating pump. 1

[gorkus]

I'd like to know if exist a formula to calculate the heat generated by a pump recirculating liquid in a short lenth of pipe.

Flow: 15 m3/h
Length pipe 7 m
diameter: 2"
Fluid: oil.

Thank you very much.

 

[btrueblood]

To a close approximation, find the input shaft or electrical power to the pump, and assume all of that energy is deposited as heat into the flow.

 

[gorkus]

YOU MEAN CONVERT FROM KW TO JULIOS....??

 

[DubMac]

Temperature rise in centrifugal at reduced flow:
T = H/778 * (1/e - 1)
T = Temperature rise in Deg.F
H = total head in feet
e = pump efficiency at capacity corresponding to H

 

[gorkus]

THIS FORMULA IS SUITABLE TO CALCULATE TEMPERATURE RISE IN POSITIVE DISPLACEMENT PUMPS.??

 

[DubMac]

Centrifugals.

 

[MortenA]

dubmac,

I dont think thats true for full recycle (i take it thats the question) - also i would think its only good for water.

In the case of full recycle the energy in the has but one place to go - into the fluid c.f. btrueblood above.

However, as the fluid becomes warmer heat losses from the pipe increases and thus eventually there will be an equlibrium. This will be true for both centrifugals and for PD pumps. You will also have to consider any cooling effect where the transported medium is used.

 

[DubMac]

MortenA,
Maybe I'm missing the point of the poster's question asking for a "formula to calculate the heat generated by a pump".

The equation determines the heat added to the system by the pump; it is based upon the differences in brake and hydraulic horsepowers. It is also as you say, based upon the specific heat of water (1 BTU/lb per degF). For another fluid, you would have to factor in difference in specific heats.

Maybe the poster was really asking for the total system's heat exchange properties; that's a Thermo deal and I hate Thermo.

I'm also thinking about the PD portion of the question and how the equation would change to adapt from centrifugals.....maybe just the constants?? What say you?

 

[chicopee]

Energy input from pump shaft minus heat loss from closed circuit system = internal energy rise in the closed circuit; mass is constant and there is a rate of temperature rise. you'll have to solve it via time step on a spread sheet.