November 25, 2024, 03:27:24 AM
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Topic: a heat transfer- energy balance question- am i doing it correctly?  (Read 4239 times)

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Offline b0mb3rz

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ive tried the following question which is as follows
the cycle belo is a commercial refrigeration system . a refrigerant passes continuously at steady state rate, m, through the process. energy transformations at different pressures are used to absorb heat in the evaporator ( allowing cooling to take place) and dissipate it at the condenser. determine the:
a) mass flow rate of the refridgerent around the cycle
b) heat transfer to the evaporator
c) enthalpy of the refrigerant entering the evaporator

for a)
assuming change in KE and PE are 0
i got the energy balance equation for open steady state to be
m(h2-h1)+Q=0
m(200-65)-1500=0
m=11.1kg/s

b)
i used the formula 0=Qin+Qout+Win
so subbing in values i got
Qin=1500-310=1190W

c) using the energy balance equation
m(h4-3)=0 with change in KE and PE being 0
here would i then do
h4-h3=∫Cpdt
and then sub in all the values to find h4?

or is the answer just 65kj

any help would be appreciated

thanks for your time

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