1. T H enthalpy interval Hot Streams Cold Streams Section Stream j
Area Target T
Hot Streams
Cold Streams
Section Stream
Population j k H Qj
enthalpy interval

2. Townsend, D. W. and B. Linnhoff, “Surface Area Targets for Heat Exchanger Networks”, IChemE Annual Research Meeting, Bath, England (April, 1984)

3. T=100
T=90
CP = 0.5
CP = 2.5
CP = 1 T
CP = 1
Steam
CP = 6
T=80
T=75
CPH=7
T=100
T=90
T=80
T=75
CPC=14 CW H
Figure B.1 within each enthalpy interval it is possible to design a network in
(S - 1) matches. (From Ahmad and Simth, IChemE, ChERD, 67: 481, 1989;
reproduced by permission of the Institution of Chemical Engineers.)

4. Approach temperature = 10
Table 8.1-1
Approach temperature = 10
250
240
230
220
210
200
190
180
170
160
150
140
130
120
110
100 90
Hot
utility
Temperature, F 1 2 +
176 + + 2 1 + j + + + 2 2 +
Number of cold streams
in this interval 1 1 1 +
Cold
utility + +
Enthalpy, 1000 Btu/hr
= Hot = Cold
FIGURE 8.3-1
Tempreature-enthalpy diagram.

5. Hot composite Curve
T (F) H (BTU/hr)103
Cold composite Curve
T (F) H (103 BTU/hr)

6. MINIMUM HEAT TRANSFER AREA IN INTERVAL j
Stream No CP  qk,j  TS TT
and Type (BTU/hr.F) (BTU/hr) (F) (F)
1. Hot
2. Hot
3. Cold
4. Cold
Stream No CP  qk,j  TS TT
and Type (BTU/hr.F) (BTU/hr) (F) (F)
1. Hot
2. Hot /
31/
3. Cold
4. Cold 1 2 3

7. MINIMUM HEAT TRANSFER AREA IN INTERVAL j
where
Nj = total number of process streams in interval j
MIN

8. A Screening Procedure For Detection of “Bad” Matches
Thot-cold
(a)
PINCH
Tcold
A Screening Procedure For Detection of “Bad” Matches

9. A Screening Procedure For Detection of “Bad” Matches
A Good Match
(b)
Tcold
A Screening Procedure For Detection of “Bad” Matches

10. A Screening Procedure For Detection of “Bad” Matches
Two Bad
Matches
(c)
Tcold
A Screening Procedure For Detection of “Bad” Matches

11. Q =(UATLM)  FT FT = f (R,P)
Temperature
1-1 Exchanger
(b)
Temperature
1-2 Exchanger
TH1
TH1
TC2
TC2
TH2
TH2
TC1
TC1
Length
Length
TH1
partial cuntercurrent
partial cocurrent
countercurrent
TC1
TC2
TC2
TH1
TC1
TH2
TH2
Q = UATLM
Q =(UATLM)  FT FT = f (R,P)
Figure shells approach pure countercurrent flow, whereas 1-2 shells exhibit
partial countercurrent and partial cocurrent flow.

12. R=1
Figure 7.8

13. Figure 7.8 Designs with a temperature approach or small temperature cross can be accommodated in a single 1-2 shell, whereas designs with a large temperature cross become infeasible. (From Ahmad, Linnhoff, and Smith, Trans. ASME, J. Heat Transfer, 110: 340, 1988; reproduced by permission of the American Society of Mechanical Engineers.)

14. temperature
cross large
P large
(a) A single 1-2 shell is infeasible.
Figure A large overall temperature cross requires shells in series to reduce the cross in individual exchangers.(From Ahmad, Linnhoff, and Smith, Trans. ASME, J. Heat Transfer, 110: 340, 1988; reproduced by permission of the American Society of Mechanical Engineers.)

15. A B A B temperature crosses smaller
(b) Putting shells in series reduces the temperature cross
in individual exchangers. A
Figure A large overall temperature cross requires shells in series to reduce the cross in individual exchangers.(From Ahmad, Linnhoff, and Smith, Trans. ASME, J. Heat Transfer, 110: 340, 1988; reproduced by permission of the American Society of Mechanical Engineers.) B