Numerical study of heat transfer performance of nanofluids in a heat exchanger

This article presents a numerical study of natural convection heat transfer in a heat exchanger filled with nanofluid. Walls of the enclosure are insulated and constant temperature conditions are given for hot (T-h) and cold (T-c) pipes (T-h > T-c). The effects of pertinent parameters such as; Rayleigh number, temperature of the nanofluid, diameter and type of the nanoparticles on the heat transfer rate are examined. Moreover, the influence of design parameters such as; arrangement and orientation of the hot and cold pipes, location and number of the hot pipe, internal and external cooling and heating on the flow field, temperature distributions and the heat transfer rate are also investigated. The results show that, the total Nusselt number enhances with increasing the nanoparticle volume fraction up to an optimal particle loading at which the heat transfer rate within the enclosure has a maximum value. In addition, the results indicated that, the heat transfer rate and the optimal particle loading enhances by increasing the average temperature of the nanofluid. Finally, the numerical results demonstrate that, location, arrangement and number of the hot and cold pipes have a significant impact on the heat transfer rate across the heat exchanger. (C) 2016 Elsevier Ltd. All rights reserved.