Numerical Analysis on Charging Performance of the Macro-Encapsulating Combined Sensible-Latent Heat Storage System with Structural Parameters

For combined sensible-latent heat storage system(CSLHS)(termed as the hybrid configuration),macro encapsulation can effectively solve the leakage problem of PCMs.However,due to the poor thermal conductivity of PCMs,the charging performance of the hybrid configuration slightly increases compared to the solid structure(with only sensible materials).Meanwhile,the natural convection in the PCMs zone could improve the charging performance.So,how to improve natural convection intensity is a key issue for the CSLHS by macro encapsulating.It is found that adding fins can significantly enhance natural convection and accelerate the melting of PCM.In this paper,we proposed the hybrid configuration with fins built-in by macro encapsulation,and analyzed its charging performance with different fin structural parameters in the PCM zone by CFD simulation.In the case,the sensible heat storage material is high-temperature concrete and the PCM is a low-melting-point mixed molten salt.We analyzed the effects of fin number,fin length and fin thickness on the charging performance of the hybrid configuration respectively.From the result,the charging performance increases with the fin number,but the increase rate gradually decreases.When the fin number is 6,the charging performance increases by 20.18%compared to the situation without fin.The charging performance increases gradually with the fin length.Compared with the hybrid configuration without fin,for each 10 mm increase in fin length,its charging performances increase by 4.09%,5.26%,7.02%,8.77%,11.70%,and 15.79%,respectively.Different from number and length of fins,the effect of thickness on the charging performance is very small.When the fin thickness increased from 1 mm to 4 mm,the charging performance only increased by 2.3%.It indicates that the main reason for the improving the charging performance is to increase the natural convection intensity by dividing the PCM zone through fins.These results show that the charging performance of the CSLHS with macro encapsulation can be improved by optimizing fin structural parameters.

3D shape-stable temperature-regulated macro-encapsulated phase change material:KAl(SO_(4))_(2)·12H_(2)O-C_(2)H_(2)O_(4)·2H_(2)O-CO(NH_(2))_(2) eutectic/polyurethane foam as core and carbon modified silicone resin as shell

Micro-encapsulated phase change materials(PCMs)have been confirmed a high-efficiency way to store latent heat,but their poor mechanical properties,expensive and complicated synthesis block their industrial application.Herein,borrowing from this structure and magnifying it,we prepared a novel 3D shape-stable temperature-regulated macro-encapsulated PCMs.The KAl(SO_(4))_(2)·12H_(2)O-C_(2)H_(2)O_(4)·2H_(2)O-CO(NH_(2))_(2)(APSD-OAD-Urea)was configured as PCM to composite with light-weight porous polyurethane foam(PUF)framework,and the enthalpy reduction of PCM@PUF(core)was only 1.70%.Subsequent,carbon modified silicone resin(CMS,shell)was introduced to macro-encapsulate PCM@PUF.The results showed that with the optimized mass ratio of 75%APSD-25%OAD and extra addition of 10% Urea,the obtained PCM had a relatively high enthalpy(194.6 J/g),appropriate phase transition temperature(42.17℃)and suppressed supercooling(0.504℃).CMS thin-layer with 2.0 mm thickness increased resistance to deformation,impressions,scratches,and possessed a brilliant sealing effect on PCM@PUF to achieve leak-free and operation steady of PCM.PCM@PUF@CMS with low thermal conductivity from inside out displayed an outstanding thermal insulation performance.Moreover,the fluctuation of the thermodynamic property after 150 thermal cycles is relatively small.All these above enable the application of PCM@PUF@CMS in the thermal energy storage system and provide a novel strategy for the preparation of macro-encapsulated PCMs.