# Homework Help: Efficiencies of compressor in industrial chiller system.

1. Dec 2, 2012

### chonvlc

1. The problem statement, all variables and given/known data
Data: http://postimage.org/image/4bb6y6jrd/
Variables: http://postimage.org/image/sk8xnrru5/

Question asks to find mechanical, volumetric and isentropic efficiencies.

The test facility is based around a chiller of nominal cooling capacity of 25 kW. The chiller is equipped with shell and tube heat exchangers, an externally equalised thermostatic expansion valve, a 4 cylinder hermetic compressor designed for use with R404A and appropriate controls. The compressor displacement is 33.07 m3/hr at 1450 rpm.

2. Relevant equations

n(isentropic)=isnetropic work per unit mass of compressed fluid/actual work per unit mass of compressed fluid.

n(volumetric)=actual vol of fresh gas infuced/compressor swept volume.

n(mechanical)=work on gas/work delivered to shaft.

work on gas=massflowrate (h2-h1) where h2 is enthalpy after comrpession and 1 is before compression.

If you could just show me how to do the first one, or explain the method that'd be great.
e-mail chonssdw@gmail.com for steam tables, or assume random values just to show the point.

Last edited: Dec 2, 2012