CFD analysis of heat transfer enhancement in a concentric tube counter flow heat exchanger using nanofluids (SiO2/H2O, Al2O3/H2O, CNTs/H2O) and twisted tape turbulators

Abstract

A concentric tube, counter flow heat exchanger with nanofluids under turbulent flow conditions has been examined using a computational fluid dynamics model. The proposed model consists of Twisted Tape Turbulators (TTT) on the annular side and inside the tube along with different nanofluids. Twisted Tape Turbulators produce a swirl motion within the fluids to increase heat transfer. Al2O3/H2O, SiO2/ H2O, and CNTS/ H2O nanofluids (with varying volume concentrations of 1 %, 2 %, and 3 %) with the turbulent flow (Reynold number Re = 2000 to 10000) were considered to determine three major parameters i.e., heat transfer rate (Q), overall heat transfer coefficient (U) and Nusselt number (Nu). This study resulted in 6.03 %, 16.74 %, and 6.74 % enhancement of overall heat transfer coefficient (U) with a 3 % volume concentration of CNTS/H2O nanofluid, Al2O3/H2O nanofluid, and SiO2/H2O nanofluid, respectively, when equated to without twisted tape tabulators. This analysis shows the maximum value of Nusselt number as 143,136.68 and 140.12 for CNTS/H2O, Al2O3/H2O, and SiO2/H2O, respectively, for the twisted tape tubular arrangement. It is concluded that when using twisted tape turbulator, the heat transfer rate (Q), overall heat transfer coefficient (U), and Nusselt Number (Nu) increase with increasing Reynolds number (turbulent flow conditions) and volume concentrations of nanofluid.Novelty statement: Twisted Tape Turbulators (TTT) arrangement with different concentrations and types of nanofluids combined are infrequent in the study of concentric tube heat exchanger with turbulent flow to obtain enhanced heat transfer.