Solution Homework 9
1.
A cylinder is initially filled with R134a at a specified state. The refrigerant is cooled at
constant pressure. The amount of heat loss is to be determined, and the process is to be
shown on a
Tv
diagram.
Assumptions
1
The cylinder is stationary and thus the kinetic and potential energy changes are zero.
2
There are no work interactions involved other than the boundary work.
3
The thermal energy stored in
the cylinder itself is negligible.
4
The compression or expansion process is quasiequilibrium.
Analysis
We take the contents of the cylinder as the system. This is a closed system since no mass
enters or leaves. The energy balance for this stationary closed system can be expressed as
)
(
0)
=
PE
=
KE
(since
)
(
1
2
out
1
2
ou
,
out
energies
etc.
potential,
kinetic,
internal,
in
Change
system
mass
and
work,
heat,
by
nsfer
energy tra
Net
out
in
h
h
m
Q
u
u
m
U
W
Q
E
E
E
t
b
since
U
+
W
b
=
H
during a constant pressure quasiequilibrium
process. The properties of R134a are
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 Summer '07
 RAMUSSEN
 Thermodynamics, Energy, Heat, Net energy tran, energy tran sfer

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