Thermal analysis of nanofluids flow in a double pipe heat exchanger with twisted tapes insert in both sides

Abstract

In this paper, heat transfer enhancement in a double pipe heat exchanger with a twisted tape as a swirl generator in both sides is investigated numerically. The three-dimensional numerical simulations have been done by finite volume method using a commercial CFD code. The spatial discretization of mass, momentum, turbulence dissipation rate, and turbulence kinetic energy equations has been achieved by a second-order upwind scheme. A SIMPLE algorithm has been used for velocity–pressure coupling. To calculate gradients, Green–Gauss cell-based method has been utilized. The swirl generator is considered in both channels of the heat exchanger (hot and cold streams). Three types of nanofluids containing Al2O3, CuO, and SiO2 are considered as heat transfer fluid in the inner channel (hot fluid flow). Results showed that the maximum thermal performance belongs to CuO/water nanofluid at Re = 5492 by 7% enhancement in thermal performance in comparison with net water. Also, the SiO2/water nanofluid at Re = 3343 has the minimum enhancement in thermal performance by 2.5% in comparison with the net water. In a lower Reynolds number (Re = 3343), the greatest thermal performance is obtained for a case with ϕ = 4% by 1% improvement in thermal performance compared to pure water. However, the case with ϕ = 5% presents a lower thermal performance by 3.7% compared to pure water. However, in higher Reynolds number (Re = 5492), the highest thermal performance is achieved for the case with ϕ = 4% by 6.4% improvement in thermal performance compared to pure water and the lowest improvement belongs to the case with ϕ = 3% by 1.3% enhancement in thermal performance compared to pure water.