Numerical study on flow and heat transfer characteristics of a Tesla pipe-casing-type phase change heat storage device

Abstract

In the present study, five different Tesla pipes (T45A/T45C/D/GMF/TMW) are used to replace the straight pipes in the casing phase-change heat storage device (HSD) to improve the phase change speed of PCM, while giving the HSD pressure reduction capability. The unique structure of the Tesla pipe allows the HTF to form a local vortex zone during flow, which draws the surrounding HTF to increase the local effective thermal conductivity (ETC). In reverse flow, HTF reduces the pressure through multiple forward bifurcations and reverse confluences. The effect of the structure of Tesla pipes and HTF mass flow rate on the thermal performance and flow characteristics of HSD was analyzed by varying the mass flow rate of HTF at the inlet of different Tesla pipes. The numerical simulation results show that the HSD with Tesla pipes has a maximum increase of about 50 % in heat storage and release rate and a significant pressure reduction. In addition, the high local ETC during the heat storage process can compensate for the difference in the phase change rate of PCM caused by the smaller heat transfer area. This work can provide theoretical guidance for the design of heat storage devices with pressure reduction capability.