Indian Journal of Science and Technology

Abstract

Background/Objectives: The common assumption made in basic heat exchanger design is that the fluid to be distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. But in actual practice it doesn’t happen. Thus the main objective of this paper is to reduce the non uniformity in the flow of fluid in compact heat exchanger form the header tube to the lateral tube. Methods/Statistical Analysis: In this work, the flow mal-distribution of heat exchanger at different cross-sectional headers like circular, rectangular, square and triangular header with various flow rates ranging from Re 1000 to 20000 is analyzed. Numerical models and boundary conditions used in the analyses are validated against experimental data. Following the validated procedure, three-dimensional CFD analyses are carried out to study the effect of geometrical variation of headers on flow distribution. For each geometrical variation, analysis is continued till the trend of behavior of flow distribution is completely understood. The results are analyzed to reach the optimum configuration with each variation. Findings: For all the four types of header cross section and for various inlet mass flow rates, the triangular header produces more uniform distribution. With low pressure drop in triangular cross section, the velocity distribution is uniform. Because of uniform velocity distribution in the header the flow maldistribution is minimum in heat exchanger with triangular cross sectional header. Triangular header shows 77%, 45%, and 70% less flow maldistribution when compared to circular, square and rectangular headers respectively. Application/Improvements: Development in the field of renewable energy had made a great revolution in the usage of solar flat plate water heater in each and every home. Implement of this triangular shaped header cross in the core tube of flat plate collector, would increase the efficiency of solar flat plate water heater, which would ultimately improve its usage among the people. 

Keywords: CFD, Fluent, Flow Maldistribution, Heat Exchanger