CFD study on the effect of nanofluids in natural circulation loop

Abstract

A vertically placed natural circulation loop consists of a heater in the riser pipe and a heat exchanger at the top end for heating and cooling the working fluid. In this investigation, the heat source is placed in the side pipe of the loop called riser. The performance of natural circulation loop is investigated with water, Alumina nanofluid and Copper Oxide (CuO) nanofluid of 0.5%, 1% and 1.5% (by wt) concentration. The behaviour of the loop for various heat inputs at the heat source is investigated with water and then with Alumina and CuO nanofluids.It is found that the performance of the loop is high when the working fluid used is copper oxide nanofluid compared to alumina nanofluid and water. The mass flow rate is highest for 1.5% CuO nanofluid which is 4.58 g/s. Heat transfer coefficient of the loop fluid at the heat source increases with an increase in the heat input at the heat source. There is also a significant difference for heat transfer coefficients of water and the nanofluids of CuO and alumina in the natural circulation loop for various amounts of heat supplied in the heat source.