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1、Computers them. Engng Vol. 19, Suppl., pp. S137S142.1995 Cotwrinht 8 1995 Elsevier Science Ltd Pergamon 009%1354(95)00165-4 Printed in &eat Britain. All rights reserved 0098-1354/95 $9.50 t 0.00 A NEW DESIGN METHOD FOR SEGMENTALLY BAFFLED HEAT EXCHANGERS M. REPPICH and S. ZAGERMANNt * F. Ambs GmbH &
2、 Co. KG, Postfach 1560, D-79305 Emmendingen. t Rohrleitungs- und Anlagenbau GmbH, Leipziger StraSe 2, D-04439 Engelsdorf. ABSTRACT The optimization of shell-and-tube heat exchangers from an economic viewpoint gains in importance because of the current and future share of the market of this heat exch
3、an- ger type in various industries. The developed computer-based design concept assuming from the calculation of optimum tubeside and shellside pressure drops allows to deter- mine the optimum dimensions of segmentally baffled shell-and-tube heat exchangers. As the objective function that is minimiz
4、ed are chosen the total annual costs of the heating or cooling system consisting of the heat exchanger and pumps or compressors. The dis- cussed design method can be used for single-phase liquid or gaseous stream applications. KEYWORDS Shell-and-Tube Heat Exchanger, Optimization, Heat Transfer, Pres
5、sure Drop. INTRODUCTION The market of heat exchangers is increasing continuously because of the necessity of energy saving, their multiple using and the current overcoming of the economic crisis in the chemical industry in Europe. The shell-and-tube heat exchanger is the most com- monly used basic h
6、eat exchanger type in process industries. In the past few years there were realized several developments to improve the thermal effectiveness of shell-and-tube heat exchangers. New types of tubeside turbulence pro- moters (e. g. tube inserts, corrugated tubes) and tube supports (e. g. helical baffle
7、s) have been successfully introduced. At present several commercial programs are available to design and rate shell-and-tube heat exchangers, however, this tools do not offer any optimization strategies from eco- nomic viewpoint. In the field of heat exchanger design methods several works dealed amo
8、ng others with the determination of optimum allowable tubeside and shellside pressure drops from economic viewpoint that are in design algorithms usually treated as constraints. The optimum heat exchanger will be the one which makes full use of both optimum pressure drops. On the basis of simplified
9、 expressions describing the interaction between heat transfer and pressure drop are calculated tubeside and shellside pressure drops so that the total annual costs of a heating or cooling system consisting of capital, operating and main- tenance costs are minimized. The pressure drop equations publi
10、shed in a recent paper (Reppich, 1994) are now modified to allow the suggestion of geometric dimensions of such heat exchanger that has under given economic and process conditions minimum total annual costs. s137 S138 European Symposium on Computer Aided Process Engineering-S PRESSURE DROPS Reppich
11、(1994) published the following simplified equations to determine the tubeside and shellside pressure drop of segmentally baffled shell-and-tube heat exchangers. The tubeside pressure drop is given by dp, = a 1 2 (c, ,“,)“” (2)” ; $+W . The shellside pressure drop can be expressed as (1) In deriving
12、the relationship for shellside pressure drop by eq. (2) it is assumed that bundle crossflow and baffle window flow aress resp. velocities are equal to achieve the best possible use of available pressure drop in the promotion of heat transfer. A Figure 1. Schematic flow distribution for baffled shell
13、side flow. Based on Tinker (1958), Palen and Taborek (1969). Unfortunately, eq. (2) does not cover the influence of leakage and bypass streams shown in Fig. 1 on shellside heat transfer and pressure drop. In recommended design methods there are introduced correction coefficients td cover the effects
14、 of bypass and leakage streams (see VDI-U%rmeatZas, 1994). Considering these correction coefficients eq. (2) was modified as follows where zl, z2, q and z2 are complex terms corresponding to the coefficients in eq. (2). The correction coefficients (pl and cp2 are depending on geometric parameters of
15、 apparatus and they are determined according to the calculation method described in VDI-W&me- atlas (1994). The pressure drops calculated using eqs. (1) and (3) corresponds very well to the results obtained with mentioned method. The eqs. (1) and (3) are suitable for optimum design of heat exchanger
16、s since the only unknown variables they contain are the tubeside and shellside heat transfer coefficients a1 and a2_ The correction coefficients Q and cp2 are determined iteratively during optimization because of their dependence on the heat exchanger geometry. European Symposium on ComputerAided Process Engineering-5 s139 OVERALL OPTIMIZATION OF A HEAT EXCHANGER SYSTEM Using of economic criteria allows the optimum design of heat exchanger system consisting of heat exchanger, pumps and/or compre
