(c) In order to calculate the total entropy generation
S
gen
, the second law relation for
transient process can be used:
𝑄
𝑐𝑣
?
+ ?
𝑔𝑒𝑛
= ∑ 𝑚
𝑒
𝑠
𝑒
−
𝑒𝑥𝑖??
∑ 𝑚
𝑖
𝑠
𝑖
+
𝑖𝑛𝑙𝑒??
(𝑚
2
𝑢
2
− 𝑚
1
𝑢
1
)
𝑐𝑣
①
There is no water leaving the container, equation
①
can be simplified to:
T
Q
s
m
s
m
s
m
S
cv
cv
i
i
gen
)
(
1
1
2
2
②
The only term that needs to be found is
s
i
and
s
i
= s
sup
.
At P
i
= 400 kPa, use linear interpolation to find
s
i
. The relevant properties can be
found on table A-6.
h (kJ/kg)
s (kJ/kg·K)
3067.1
7.5677
3192.046984
s
i
3273.9
7.9003

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