Experimental and numerical analysis of heat transfer enhancement inside concentric counter flow tube heat exchanger using different nanofluids

Abstract

The aim of this paper is to study experimentally and numerically heat transfer enhancement and friction factor inside a counter flow concentric tube heat exchanger using different volume fractions of CuO, Al2O3, and TiO2 nanofluids. Using nanofluids increases the thermal conductivity and conductive heat transfer coefficients compared to the base fluids. Increased heat transfer coefficients reduce the required tube length leading to reduced pressure drop in heat exchangers. Nanofluids have a high specific surface area, and therefore more heat transfer surface between particles and fluids is available. A standard k-ε turbulence model based on two equations was used in this investigation to solve the momentum and energy equations of nanofluids. The results were presented for Reynolds number range between 2000 and 12,000 and two different volume fractions of 0.05 and 0.2%, respectively. The numerical results illustrated that all the tested nanofluids exhibited better heat transfer coefficients compared with pure water. Particularly, CuO nanofluid illustrated the highest performance index for both concentrations. The performance index varied from 4.25, 3, and 2.5 to 1.5 for CuO, Al2O3, and TiO2 nanofluids, respectively, for the whole range of Reynold numbers. The results of this investigation may be used in designing heat exchangers-based nanofluids that can be used in many energy applications such as solar, energy production systems, and any industrial process.