INFLUENCE OF A FINITE NUMBER OF BAFFLES ON SHELL-AND-TUBE HEAT-EXCHANGER PERFORMANCE

In single-phase shell-and-tube heat exchangers, thermal performance pr ediction is customarily accomplished with an idealization that the num ber of baffles used Is very large and can be assumed to approach infin ity. Under this idealization, the temperature change within each baffl e compartment is very small in comparison with the total temperature c hange of the shell fluid through the heat exchanger. Thus the shell fl uid can be considered as uniform (perfectly mixed) at every cross sect ion (in a direction normal to the shell axis). It is with this model t hat the mean temperature difference correction factor is normally deri ved for single-phase exchangers. In reality, a finite number of baffle s are used, and the condition stated above can be achieved only partia lly. In this article, a comprehensive review is made and new results a re derived where needed to assess the influence of a finite number of baffles on heat transfer performance for 1-1, 1-2 and 1-N TEMA E, 1-2 TEMA J, and 1-2 TEMA G and H single-phase shell-and-tube exchangers. I t is shown that the number of baffles required to achieve the performa nce within about 2% of an exchanger with an infinite number of baffles varies with the type of exchanger and the performance parameters. The new results are presented in tabular form.