Flow maldistribution in heat exchangers

Based on the study of gross flow maldistribution in an experimental electri cal heater, this paper presents the effect of flow nonuniformity on the per formance of heat exchangers. First, it is shown that it is much more import ant to understand maldistributions for electrical heaters than for two-flui d heat exchangers. The study of the flow distribution in a particular heate r shows that reverse flows may occur for poor inlet header design. Suggeste d here is a simple way to homogenize the flow distribution and a simple law to calculate, with good accuracy, the velocity ratio (ratio of the highest velocity in the tubes to the lowest velocity). The original fluid distribu tion is applied to heat exchangers (condensers, counterflow and crossflow h eat exchangers), and it is shown that gross flow maldistribution leads to a loss of effectiveness of about 7% for condensers and counterflow heat exch angers, and up to 25% for crossflow exchangers, for velocity ratios up to 1 5. (C) 1999 Elsevier Science Ltd. All rights reserved.