Compressor power requirement

[claver]

Hi,

Can anyone help with the correct formula for estimating the power requirement of powering a fridge compressor. We have a compressor which normally would be powered by a large diesel engine. The customer wants us to power the fridge using only DC power (or AC via an inverter). I am familiar with calculating power for hydraulic systems with incompressible fluids… This is a different ball game. My understand is that we have the following parameters to juggle :

1 - Compressor RPM
2 - Compressor size in cc
3 – Pressure on the inlet of the compressor in Bar
4 – Pressure on the outlet of the pump in Bar
5 – The amount of gas in the system in kg

The pressure on the inlet and outlet of the pump is a function of the “box temperature” and the “outside air temperature”

I am happy to work with imperial measurements if anyone can give me a hand here.

Best regards

Ian

 

[dcasto]

typically the unit will have how many tons of cooling. A typical room AC uses about 1200 watts per ton. a ton = 12,000 BTU/hr. If you are running a refrigerator, the energy will jump to 1500, and a freezer to 2000 watts per ton.

To try and led through displacement, volumetric efficency, ratios, ect..... Google the term "refrigeration horsepower per ton".

 

[MintJulep]

The compressor manufacturer can provide you with curves of capacity and power draw of the compressor at various suction and discharge conditions.

But the power required will not change just because you change the prime mover from diesel to electric. If you know the power produced by your diesel at the conditions of interest, you have your answer. If not, it's relatively simple to install a torque cell in the coupling, and you'll have your answer.