Page 567 - Mechanical Engineers' Handbook (Volume 4)

556 Thermal Systems Optimization

Pa
Pa 6 6 6 6
Ambient Pressurere
ha ha A m b i en P r es s u
6 6 •
•
a
a
ma in in Ha in in
Cons t . Vol t a ge Sou r c e Cf Cf Cf Cf
Const. Voltage Source
Condens e r Fan
Condenser Fan
•
9 • out t • ou t
9 W
ou
out
a
a
Cf Cf ma Cf Cf Ha Cf Cf
Pa
Pa 7 7
ha ha 7 7 7 7 in in • in in
•
ma Cd Ha Cd
a
a
Cd
Cd
•
out
out
in in
m • out H • out m H in in
P P 3 3 Cd Cd Cd Cd P P 2 2
Cd
Cd
Cd
Cd
e
Condens
h h 3 3 Condenser r h h
3 3 2 2 2 2
•
•
ou
ou
out
out
a
ma Cd t Ha Cd t • out t • out
a
out
ou
Cd
Cd
•
in in
Pa
m • in in Ex H Ex Pa 8 8 m H C C
C C
Ex
Ex
ha ha 8 8 Ambient Pressure
b
m
A
es
re
P
t
u
s
i
en
r
8 8
Sou
e
c
ge
r
t
.
Vol
Cons
a
Const. Voltage Source
t
lve
x
E
nsi
pa
a
Expansion Valve Com p r e ss or
Compressor
on V
•
W 5 5
C C
Pa
Pa 12 12
12
• 12 Ambient Pressure
e
s
Am
b
P
e
n
r
u
r
t
i
e
s
out
out
m • out H out ha ha • in • in in
Ex Ex 12 12 • m C H C C
Ex
Ex
•
ou
ou
a
ma out t Ha out t
a
E E E E
P P 4 4 4 4 Evaporator r 1 1 P P 1 1
r
a
t
o
Ev
a
p
o
h h • in in • inin • outout • ou t h h
out
4 4 m H EE m EE H E E 1 1
E E
•
•
a
ma in in Ha in in
a
Pa
Pa 11 11 E E E E
11
ha ha 11
11 11 • ou t • out t
out
ou
a
ma Ha
a
Const. Voltage Source
Cons t . Vol t a ge Sou r c e Ef Ef Ef Ef
Evaporator Fan
E v a p or ato r Fan
•
13 W
13 • • in in • in in
Ef Ef ma Ef Ef Ha Ef Ef
a
a
Pa 10 10
Pa
u
s
re
b
i
A
m
en
r
es
t
P
ha ha Ambient Pressure
10 10
10
10
Figure 1 Network representation of vapor compression system with air fans.
and the choice of the appropriate formulation can have a significant influence on the con-
vergence of the simulation.
The convergence of numerical equation solvers typically depends on the quality of the
initial guess values. Special care must be given to provide good guess values to the equation
solver. Other sources of divergence are invalid inputs to thermophysical property functions
and invalid inputs to component models. Both instances can occur during the course of the
Table 1 Residual Equations for Vapor Compression System
out in
4
C
R ˙m C ˙m Cd R M System M M Cd M Ex M E
1
out in out in
5
2
R ˙m Cd ˙m Ex R ˙m Cf ˙ma Cd
out in out in
3
R ˙m Ex ˙m E R ˙m Ef ˙ma E
6
out in
R ˙m E ˙m C
4