采用纳米颗粒复合相变材料能够有效提升相变储热系统的传热性能,但由于纳米颗粒对于储热系统热力学特性的影响机理尚不清晰,因而限制了储热系统的性能优化设计。构建了基于石蜡-氧化铝纳米复合相变材料的管壳式相变储热系统,并开展了相变储热系统热力学特性研究。研究结果表明:换热流体流量的提升一方面增强了系统内的对流换热,使平均储热功率、储热效率均得以提高,另一方面也引发了系统热力学损失的增加,进而导致㶲效率降低。相变材料初始温度的增加缩短了固体显热储热阶段,从而加速了储热过程,减少了在升温过程中因热传导和对流造成的热损失。纳米颗粒含量的增加缩短了储热时间,使得系统的平均储热功率也随之增加,纳米颗粒质量分数从2%增加到10%时,平均储热功率从11.5W提高到12.4W。但当纳米颗粒含量过高时,系统的热力学损失增加,从而降低了系统的㶲效率,纳米颗粒质量分数为5%时,㶲效率最高为72.3%,而当纳米颗粒质量分数提升至10%时,㶲效率降低至62.5%。
The use of nanoparticle-enhanced composite phase-change materials can effectively improve the heat transfer performance of latent heat storage systems.However,the underlying mechanisms of the effect of nanoparticles on the thermodynamic characteristics of latent heat systems remain unclear,limiting the performance optimization design of these systems.This study constructed a shell-and-tube latent heat storage system using paraffin-alumina nanoparticle composite phase-change materials and experimentally investigated its thermodynamic properties.The results demonstrated that increasing the flowrate of the heat transfer fluid enhanced convective heat transfer,thereby raising the average thermal storage power,thermal storage efficiency,and overall system efficiency.However,it also amplified thermodynamic losses,leading to reduced exergy efficiency.Higher initial system temperatures shortened the solid sensible heat storage stage,accelerating the thermal storage process and reducing heat losses caused by conduction and convection during temperature rise.Increases in nanoparticle concentration significantly reduced thermal storage time while increasing average thermal storage power and energy density.When nanoparticle concentration rose from 2wt% to 10wt%,average thermal storage power increased from 11.5W to 12.4W.Excessive nanoparticle concentrations increased thermodynamic losses,thereby decreasing system exergy efficiency.The highest exergy efficiency reached 72.3% at 5wt% nanoparticle concentration,whereas increasing concentration to 10wt% reduced exergy efficiency to 62.5%.
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基金资助
国家自然科学基金项目(52006187)
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