Numerical study on charging characteristics of heat pipe-assisted cylindrical capsule for enhancing latent thermal energy storage

摘要

The charging characteristics of a cylindrical Encapsulated Phase Change Material (EPCM) capsule with embedded heat pipe (HP) is investigated numerically for latent heat storage. For the heat pipe-assisted capsule, called EPCM-HP unit, a 3-D transient thermal storage model is implemented combining Lumped Thermal Resistance Network (LTRN) as the heat pipe model with conventional enthalpy-porosity approach as phase change model. The effects of flow conditions (laminar and turbulent), heat pipe condenser length and types of HTFs (Therminol/VP-1 and air) on thermal characteristics of the EPCM-HP unit are simulated, respectively. Results show that embedding heat pipe can reduce the total charging time by 11.26%. The charging process under turbulent flow is more than 10 times faster than that under laminar flow. Increasing the condenser length of heat pipe cannot effectively reduce the charging time of ECPM-HP unit since the thermal resistance also increases and the starting time of convection is delayed. The results also reveal that Therminol/VP-1 (high Pr HTFs) can charge thermal energy faster than air (low Pr HTFs), while the enhancement effect of heat pipe is more significant when using air (low Pr HTFs).