Page 403 - Design and Operation of Heat Exchangers and their Networks

386 Design and operation of heat exchangers and their networks

Table 7.4 Comparison of predicted steady-state outlet fluid temperatures with the
experimental data of a four-stream plate-fin heat exchanger.

2
00
0
C (W/K)
Stream ^ _ α (W/m K) ^ t (°C) ^ t (°C) ^ t 00 exp (°C)
1 338.5 1644 41.93 32.63 32.43
2 240.1 1791 34.93 38.97 39.40
3 147.55 1465 31.06 39.49 39.62
4 200.375 818.9 21.98 26.63 27.23

33.0 40.0

32.8 39.8

32.6 39.6
t 1 ² (°C) t 3 ² (°C)
32.4 39.4

32.2 39.2
39.0
32.0 0 50 100 150 200
0 50 100 150 200 (s)
(s)
39.8 27.0
39.6 26.8

t 2 ² (°C) 39.4 t 4 ² (°C) 26.6
39.2 26.4
26.2
39.0
26.0
38.8 0 50 100 150 200
0 50 100 150 200
(s) (s)
Fig. 7.15 Exit stream temperature responses to a step change in the mass flow rate of
stream 2 (σ ¼ 0.2).

Δt 1 ¼9.975 K. The exit temperatures at the new steady state (τ!∞) are
0
also shown in Fig. 7.14. The exit stream temperature responses to a step
change in the mass flow rate of stream 2 are shown in Fig. 7.15. The
dotted lines are the temperature responses calculated with the modified
Pingaud’s model. They coincide with the exact model very well.