Performance Investigation of a Three Fluid Heat Exchanger Used in Domestic Heating Applications

Abstract

Recent work analytically investigates the heat transfer characteristics of a three fluid heat exchanger used for domestic heating applications with respect to different design parameters, i.e. flow rate, inlet temperature, tube diameter, coil diameter, and coil pitch. The present and previous results are compared with the literature. Overall agreement among these results are observed with little variation. Afterwards, the present temperature data was verified with prior experimental data and little deviation observed in these results vary from -4.28 % to +6.68 % and -6.17% to +5.92% in parallel and counter flow configuration, respectively. It is ensued that the coil side Nusselt number increases with the rise in coil side fluid flow rate and inlet temperature, coil outside fluid inlet temperature and coil diameter respectively. The increment in coil side flow rate and inlet temperature are identified as the major contributors, with 297% and 39.5% contributions. Similarly, growth in coil outside Nusselt number is observed with the rise in coil side fluid inlet temperature and flow rate, coil outside fluid flow rate and inlet temperature, and coil pitch respectively. The coil pitch and flow rate at the coil outside are identified as major contributors with 36% and 28.5% contribution repsectively. Distinct correlations for heat transfer in the present HEx are proposed for coil inside and outside fluid flow in a turbulent flow regime. The developed correlations results are compared with the present result, and reasonable agreement is observed within the data range of +13% to -14% and +10% to -11% for coil inside and outside Nusselt number, respectively.