Effect of flow maldistribution on the optimal design of a cross flow heat exchanger

Abstract

In this study, a cross flow heat exchanger is optimized based on multi objective optimization algorithm by considering the effects of flow maldistribution for both cold and hot sides. For this purpose, total annual cost (TAC) and effectiveness of exchanger are selected as fitness functions and six decision variables including the heat exchanger and fin geometries are considered as decision variables. The optimization is performed for the three non-uniform velocity inlet profiles including linear, parabolic and power law and their optimum results are compared with the uniform (constant) profile. It is observed that, the Percentages of reduction in effectiveness for the final optimum solution are in the range of 2.93–4.88%, 1.50–3.38% and 0.79–1.24% respectively in the cases of linear, parabolic and power law profiles compared with constant inlet profiles. Moreover, Percentages of growth in the TAC for the final optimum solution are in the range of 13.00–16.49%, 6.97–10.49% and 0.77–1.63% respectively in the cases of linear, parabolic and power law profiles compared with constant inlet profiles. In addition, the higher hot and cold stream flow lengths and lower fin height and fin spacing are needed in the cases of linear, parabolic and power law profiles compared with the constant velocity profile for the fixed value of effectiveness.