Environmental Engineering Reference
In-Depth Information
Ff
=
1 ( , cc, ch)
c
( 2)
h
where c is the thickness of the core unit of the heat exchanger, cc is the dimension
of the fi n unit on the airside, and ch is the fi n unit dimension on the liquid side.
From eqns (1) and (2), the core unit thickness is obtained as
cf
=
(
Qk t
,
,
Δ
, cc, ch)
( 3)
2
h
m
From the known condition:
Qf
=
(
v
)
( 4)
3 ,in
Total heat transfer coeffi cient:
kf
=
(,
aa
,
hh
,
FF
,
)
( 5)
h
4
c
h
0,c
0,h
c
h
Heat transfer coeffi cient on the airside:
a
=
fv
(
, )
( 6)
c
5
c,in
Heat transfer coeffi cient on the liquid side:
a
=
fv
(,c )
(7)
h
6
Flow velocity of the fl uid:
vf
=
7 ( , cc, ch)
c
(8 )
h
Fin effi ciency on the air side:
h
=
f
(cc,
a
)
( 9)
0,c
8
c
Fin effi ciency on the liquid side:
h
=
f
(ch,
a
)
( 10)
0,h
9
h
Total heat transfer area on the airside:
Ff
=
10 ( , cc, ch)
c
(11)
From eqns (2), (5) and (11), the total heat transfer coeffi cient based on the total
heat transfer area on liquid side can be expressed as
c
kf
=
( , cc, ch,
c
v
)
( 12 )
h
11
c,in
Heat transfer mean temperature difference,
Δ= ( 13)
where t c,in and t c,out represent the inlet and outlet temperature of the air, t h,in and
t h,out are inlet and outlet temperatures of the ethylene glycol aqueous solution
respectively, in which t c,in and t h,out are known quantities.
t
f
(
t
,
t
,
t
,
t
)
m
12
c,in
c,out
h,in
h,out
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