ABSTRACT

Heat exchangers are widely used in industries to regulate, transfer heat from one medium to another. Several types of heat exchangers exist such as; Shell and tube heat exchanger, plate heat exchanger, double pipe heat exchangers. These different devices were designed for specific heating and cooling applications. Various enhancement methods for heat transfer exists such as; passive methods (tape inserts, fins, fluid type) and active methods (stirrers, jet impingement) etc.

In this numerical study, the heat transfer characteristics of various configurations of passive methods are presented for water and nanofluid which consists of 0.2vol% Al₂O₃ nanoparticles of 21nm size and water as basefluid. The analysis was carried out on three dimensional (3D) geometry of double pipe heat exchanger with extended surface (fins) and twisted tape insert under turbulent flow regime and the results where compared. Multiphase mixture model was used to simulate the nanofluid. ANSYS Fluent 19.0 Computational fluid dynamics (CFD) method was used to solve the governing equation of continuity, momentum, energy and volume fraction with residuals set up to 10-6 for each governing equations.

The increase in the coefficient of heat transfer for both water and nanofluid was higher in double pipe heat exchanger with extended surface (fins) compared to the other configurations. The results show that the heat transfer coefficient of nanofluid increases as compared to that of water in each of the heat exchangers. It is hoped that the results obtained from the analysis will influence the choice of application of different configurations of heat exchangers.