Multidisciplinary Optimization in Helical Grooved Tubes for Heat Transfer Enhancement

Abstract

Optimization in engineering is a significant tool for selecting the best fit when several design variables are present. It helps in determining the optimum through a combination of a set of design variables with objective functions subject to certain constraints. In the design of heat exchangers too, where tremendous research is going on to optimize its effectiveness, certain efforts are being done to improve the quality of the inner tube, shell, or plate design. In this respect, surface enhancement has been actively researched in recent decades. This sort of augmentation is usually dominant on the tube side. It has been seen that the study is greatly conducted in the past experimentally, but numerical studies are limited to determine friction factor or Nusselt number. Only a few discussed an important factor called entropy generation minimization. In this paper, with the optimization in view, the design is based on multiple disciplines. That is, first a numerical study is performed on the helically grooved tubes to examine the thermal enhancement factor. Numerical results are initially validated with published experimental results. The optimized tube is then selected based on the D-optimal design for the thermal enhancement factor and finally, the entropy minimization study concerning the Reynolds number is conducted on the optimized tube. It is observed that the tube with the greatest number of grooves, the maximum depth, and the least pitch performs the best. However, the optimum Reynolds number is at the point where the tube has the least entropy generated as compared to the smooth tube.