Heat storage in direct-contact heat exchanger with phase change material

This paper describes the development and performance of a direct-contact heat exchanger using erythritol (melting point: 391 K) as a phase change material (PCM) and a heat transfer oil (HTO) for accelerating heat storage. A vertical cylinder with 200-mm inner diameter and 1000-mm height was used as the heat storage unit (HSU). A nozzle facing vertically downward was placed at the bottom of the HSU. We examined the effects of flowrate and inlet temperature of the HTO using three characteristic parameters of heat storage – difference between inlet and outlet HTO temperatures, temperature effectiveness, and heat storage rate. The temperature history of latent heat storage (LHS) showed three stages: sensible heat of solid PCM, latent heat of PCM, and sensible heat of liquid PCM. Further, the operating mechanism of the DCHEX was proposed to explain the results. The average heat storage rate during LHS was proportional to the increase in flowrate and inlet temperature of HTO. Thus, latent heat can be rapidly stored under large HTO flowrate and high inlet temperature in the DCHEX.

► Direct-contact heat exchanger with a phase change material and heat transfer oil.
►  We examined the effects of operating conditions on latent heat storage.
► The rate of heat storage increased with the flowrate of heat transfer oil.
► The rate of heat storage increased with the temperature of heat transfer oil.
► We proposed the mechanism of latent heat storage from the observations.