Development of a Validated CFD Model For Simulation of Tube Heat Exchangers: A Comparison of Methods and Models

Abstract

Thermal management is an increasingly relevant topic within a range of engineering fields and industries. From cooling of batteries in electric cars and trucks to higher efficiency turbofan engines, the demand for well performing and lightweight compact heat exchanger designs is high. Having the ability to measure the performance of a heat exchanger geometry using numerical methods with good confidence in the results is of great benefit as it can save time and money compared to experimental methods. In this thesis, two tube heat exchanger geometries have been modelled and simulated in Siemens Star-CCM+, a commercial CFD software. The heat exchanger geometries are taken from the book Compact Heat Exchangers (1984) by William M. Kays and Alexander L. London. This book contains experimental data for a wide range of heat exchanger designs. The simulation models are validated by comparing two key performance parameters for heat exchangers to experimental data; the Fanning friction factor and the Colburn j-factor. Two modelling approaches have been investigated; a ”single channel” approach and a ”unit cell” approach. Using a ”single channel” approach with a steady coupled solver, friction factor values within 5% error to experimental values are achieved across most Reynolds numbers for both heat exchangers. Colburn j-factor values within 10-12% error to experimental values are achieved for the tube heat exchanger and within 23-28% for the finned tube heat exchanger. Results show that the SST k-omega turbulence model together with the Gamma-ReTheta transition model show the best ability to match experimental results and trends for both geometries.