Latent-heat thermal-energy storage in heat exchanger with plain and finned tube

Abstract

Two design solutions of the heat exchanger containing a material for latent-heat storage are presented. The devices are exposed to controlled energy-charging and-discharging process by virtue of internal water flow. Temperature variations at several monitoring locations are recorded in order to estimate the performance of energy storage and recovery. The experiment confirms that the heat transfer rate in the heat exchanger with fins is significantly larger than in the case of smooth plain tube, which contributes to better storage performance. The unit with plain tube reveals strong temperature gradient in radial direction. In the setup with finned tube, higher temperatures in the storage material as well as shorter charging and discharging times are achieved. Vertical temperature gradient arising during the heating after the phase change indicates development of convective heat transfer in the liquid phase. Melting of the phase-change material, however, turns out to be inhomogeneous yielding remaining solid parts as well as entrapped air bubbles.