Numerical analysis the thermal performance of slinky-type of horizontal geothermal heat exchanger equipped with turbulator

Abstract

Among several kinds of heat exchangers, borehole (ground) heat exchangers have a prominent place in application of renewable energy systems to supply energy. Recently, there has been noteworthy improvement in new methods of modeling and analyzing such systems. This development is the outcome of several empirical and theoretical researches in the thermal performance enhancement of ground heat exchangers (GHEs). Various methods have been employed to arrange the pipes of GHEs, both horizontally and vertically. Among these methods, the horizontal arrangement has proven to be the most cost-efficient option for the project. Slinky-type GHEs have become very common because they require a smaller footprint compared to conventional GHEs. One effective method to improve heat transfer in heat exchangers is to use a turbulator as an efficient passive method. By creating swirling flows in the heat exchanger, the amount of heat transfer increases. In the present work, the thermal performance of a Slinky-type GHE equipped with twisted tape as swirl generator or turbulator is numerically evaluated. The studied range of the inlet flowrate is 0.25-1 kg/s. Numerical simulation was performed using commercial finite volume method (FVM) code, ANSYS Fluent 18.2. The variable parameters in the present work are the pitch of the twisted tape, P, varied from 200 to 400 mm, as well as the mass flowrate varied from 0.25 to 1 kg/s. The numerical results indicate that, for all considered mass flowrates, the case with a pressure of 200 mm achieves the highest thermal performance. Additionally, it is worth noting that the maximum thermal performance is achieved at a mass flowrate of 0.5 kg/s in all the cases studied.