Page 113 - Design and Operation of Heat Exchangers and their Networks

Steady-state characteristics of heat exchangers 101

Example BA1,6 2 2
B A
1 1
ð
ð
ν ∗ a A , b A Þν ∗ a B , b B Þ
ϕ 6¼ 1 : ε 1 ¼ 1 (3.181)
ν ∗ a B , b B Þ ν ∗ a A , b A Þ
ð
ð
ðÞKb B
1 b B Kb A ðÞ
ðÞ
ðÞ
Kb A ϕKb B
ν ∗ 2 ð a, bÞ
ϕ ¼ 1 : ε 1 ¼ 1 2 (3.182)
1 abK bðÞν ∗ a, bð Þ
Since ϕ¼1.5, we have
0:7593 0:7051
ε 1 ¼ 1 ¼ 0:3768
0:7051 0:7593
1 1:2 0:6883 0:5823
0:6883 1:5 0:5823
Example BA2,5 2 2
B A
1 1
ð
ν a A , b A Þ
ε 1 ¼ 1
½
ðފ
1+ hb A , a A , ϕKb B
(3.183)
0:7579
¼ 1 ¼ 0:3758
1+ 0:2141

Example BA2,6 2 2
B A
1 1

ð
ν a A , b A Þν ∗ a B , b B Þ
ð
ε 1 ¼ 1
½
ðފ
ð
ν ∗ a B , b B Þ hb A , a A , ϕKb B
(3.184)
0:7579 0:7051
¼ 1 ¼ 0:3774
ð
0:7051 0:1532Þ