Temp rise across chilled water pump

[SAK9]

Friends,

Could anyone please explain how is temperature rise across a chilled water pump calculated?

 

[TD2K]

I assume you mean the temperature rise due to mechanical inefficiencies within the pump. Basically, calculate the hydraulic Hp of the pump. Use the pump curve to determine the Hp required by the pump which includes inefficiencies. The difference is the amount of power being used to heat up the fluid's contents. Simply take that power, the flow rate through the pump and the liquid's heat capacity to calculate the temperature rise. The GPSA Engineering data book has a formula for that, unfortunately, I don't have it here in front of me.

 

[TD2K]

The equation in the GPSA data book (now that I'm in the office) is Tr = h(1/e - 1)/778*Cp

Tr is the dT across the pump in deg F
e is the efficiency as a fraction
Cp is the heat capacity of the liquid in BTU/lbF

 

[TD2K]

Just to be absolutely clear on the formula

Tr = h(1/e - 1)/(778*Cp)

 

[SAK9]

TD2K,

Thanks for the reply.What does 'h'stand for in the formula?Is it the power absorbed by the pump in hp?

 

[MNME]

I believe that 'h' in TDK's response is the Pump head in units of feet. The same equation, for temperature rise of fluid across a centrifugal pump, may be expressed as:

dT = H / (778*Cp*n)

dT = Temperature rise of fluid, deg-F
H = Pump head, Feet
Cp = Specific Heat of the liquid, Btu/(lb-deg F)
n = Pump efficiency, decimal value

This is the theoretical temperature rise of the liquid within the pump at steady state conditions assuming that all the heat generated remains in the fluid.