A R-12 plant is to develop 5 tons of refrigeration. the condenser and evaporator

ID: 1857737 • Letter: A

Question

A R-12 plant is to develop 5 tons of refrigeration. the condenser and evaporator temperature are to be 40c and -10 c respectively. determine

a) the referigeration flow rate in kg per second

b) the volume flow rate handled by the compressor in cubic meters per second

c) the compressor discharge temperature

d) the pressure ratio

e) the heat reject ed to the condensor in kilowatts

f) the flash gas percentage after throttling

g) the cop

h) the power required to drive the compressor

i) how does this cop compare with that of a carnot refrigerator operating between 40 c and -10 c.

at -10 degree c

hf=29.94 kj/kg

hg=184.22kj/kg

p=2.193bar

at 40 degree c

hg=204.75kj/kg

vg=.0183m^3/kg

p=9.634

5TR=5*3.5167=17.583kj

Q=m(hg-hf)

m=17.583/(184.22-29.94)=.1139kg

v=m*vg=2.08*10^-3 m^3

pressure ratio=9.634/2.193=4.393

cop=T2/(T1-T2)=5.26

Q/W=5.26

w=3.3427 kj

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