Numerical Analysis of Cooling System to Enhance Heat Exchange in Different Environmental Conditions

Abstract

Heat exchangers find their application in many engineering and industrial applications. They provide means to maintain the temperature of a system at its desired level. In this thesis, numerical simulations of a heat exchanger with staggered arrangement of elliptical shaped tubes are performed with Reynolds number ranging from 5000 to 20000. Relative humidity is varied from 0% to 80% in each case. Numerical results are validated with the existing results available in the literature. Besides the Reynolds number, heat exchange also depends on the water content in the cooling air. Thermo-physical properties of desiccated and moist air are employed to investigate the effect of relative humidity on the heat exchanger. Relative humidity is modeled as the mass fraction of water vapours in dry air. Impact of relative humidity on the forced convection and the average Nusselt number of the heat exchanger is analyzed for a typical radiator cross-section. Variance in pressure drop is also calculated with the changing moisture content in the air. Numerical results indicate an escalating trend of Nusselt number upto 4.5% and a receding trend of pressure loss up to 5.5% with the range of specified relative humidity. This variation becomes more pronounced when the capacity of air to absorb water increases with the same relative humidity but at higher temperatures. This paper provides a tool to analyse the average Nusselt number and pressure drop of the heat exchanger with the specific tubes for moist air using its thermo-physical properties.