This can also be done via EES, but please show me how you arrive at the answers.

Question

This can also be done via EES, but please show me how you arrive at the answers.

A two-evaporator compression refrigeration system like that in system like that shown in the figure uses iefrigerant-134a as the working fluid. The system operates evaporator 1 at 30 psia, evaporator 2 at 15 psia, and the condenser at 140 psia. The cooling load for evaporator 1 is 3,000 Btu/h and that of evaporator 2 is 10,000 Btu/h. Determine the power required to operate the compressor and the COP of this system. The refrigerant is saturated liquid at the exit of the condenser and saturated vapor at the exit of each evaporator, and the compressor is isentropic.

Explanation / Answer

Power (W) of a compressor is the input power required to run the compressor motor at a specific operating point.this power is given by relation

W=QRejected_Qabsorbed

where Q represents the heat

also COP termed as coefficient of performance is defined as the ratio of heat absorbed to power .

let us analyse the give figure for flow of heat at different arkings

heat input to compressor is from markings 1,2,5,7 and ejection from .3,4,6

Now Qabsorbed =(1+5+7)-2

Qout =3-(4+6)

Qabsorbed=7000Btu/h

Qout=17000Bt/u

Therefore power=10.000

And COP=0.7

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