Numerical Crank-Nicolson transient thermal analysis of a single U-tube vertical ground battery borehole heat exchanger filled with the phase change material

Abstract

This paper investigates the transient thermal performance of a single u-tube vertical ground heat exchanger in which n-octadecane PCM material is considered as a backfill grout material. The analysis is performed based on the Crank-Nicolson finite difference numerical method which is a very stable numerical technique. Transient thermal characteristics of the battery borehole heat exchanger such as temperature variation of the PCM, soil, and the working fluid with respect to time and depth is presented in the analysis. Furthermore change in liquid fraction of the melting PCM with respect to time is expressed with the analysis. Finally it is concluded that the implicit numerical technique is suitable for long simulation time as the simulation is carried out for 3600 h of simulation.