Thermal analysis and performance evaluation of triple concentric tube heat exchanger

Abstract

Triple concentric-tube exchanger (TCTHE) is an improved version of double concentric tube heat exchanger (DCTHE). Introducing an intermediate tube to a DCTHE provides TCTHE and enhances the heat transfer performance. Recognizing the need of experimental results, extremely scarce in the literature and essential to validate theoretical analyses, the aim of this work is to investigate thermal behavior of TCTHE. The present study includes design, development and experimental analysis of TCTHE for oil (ISO VG 22) cooling application required for industrial purposes. It comprises of water (cooling fluid) flowing through innermost tube as well as outer annulus and oil (hot fluid) flows through inner annulus. The experimental studies of the temperature distribution for three fluids along the length and heat transfer characteristics for TCTHE under insulated condition for counter current flow mode are carried out and discussed. The effect of change in oil (hot fluid) temperatures is analyzed keeping water inlet temperatures same at various operating conditions. The experiments have been conducted by varying flow rate of one of the fluids at a time and keeping other two fluid flow rates constant. The results are expressed in terms of temperature variation for all three fluids along the length. The effect of change in hot fluid inlet temperature is expressed in terms of heat transfer rate variation with respect to Reynolds number. The variation of non-dimensional parameters as temperature effectiveness and thermal conductance with respect to Reynolds number is also presented in this paper. Theoretical studies are carried out for evaluation of heat transfer rate using empirical correlations. Experimental validation is carried out for degree of cooling at different Reynolds numbers with theoretical analysis.