Fundamental Flow Characteristics in a Small Columnar Latent Heat Storage Bath

抄録

Latent heat storage is one of the key technologies to utilize waste heat because this technology enables to store thermal energy in high density and for long time. This study focuses on flow characteristics in heat storage bath in form of direct contact since it has great effects on operation limit or thermal efficiency. The two-phase flow behavior of immiscible fluids was measured in a small cylindrical heat storage bath which had a nozzle at the center of the bottom and was settled in a rectangular transparent tank. A heating medium oil was fed from the nozzle to the bath half filled with a phase change material (PCM). Two series of the experiments were carried out. One was cold isothermal experiment which used water as model PCM, and the other was heat storage experiment which used sodium acetate trihydrate as the PCM. The formation behavior of the heating medium droplet changed from single droplet at nozzle outlet, single droplet from liquid column, multiple droplet from liquid column to atomization at the nozzle with increase in inflow velocity of heating medium. At the interface between the PCM and the heating medium, the heating medium droplets accumulated, coalesced, enlarged and disrupted, then the heating medium was released from the PCM layer. Furthermore the variation of flow behavior in the heat storage bath with progress in phase change of the PCM was elucidated.