自驱动柔性翅片实现储热单元相变强化的数值研究  

Simulation of PCM melting enhancement in heat storage units with self-driven flexible fins

作　　者：马骁婧 陈翰博 徐进良[1,2] MA XiaoJing;CHEN HanBo;XU JinLiang(Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy,North China Electric Power University,Beijing 102206,China;Key Laboratory of Power Station Energy Transfer Conversion and System,Ministry of Education,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学低品位能源多相流与传热北京市重点实验室,北京102206 [2]华北电力大学电站能量传递转化与系统教育部重点实验室,北京102206

出　　处：《中国科学：技术科学》2024年第9期1797-1808,共12页Scientia Sinica(Technologica)

基　　金：国家自然科学基金项目(编号:52206196);国家重点研发计划项目(编号:2023YFB4102400)。

摘　　要：相变材料储热技术是实现火电厂热电解耦和深度调峰最具潜力的实现途径之一,对于推动能源转型至关重要.相变材料(PCM)的低导热系数严重制约储热系统灵活调控与快速响应能力.采用翅片是提升相变材料储热系统热响应速度的有效方法.本文提出利用柔性翅片实现储热单元的固液相变强化,基于焓-孔隙率法和流固双向耦合模型,对于柔性翅片PCM储热单元的熔化过程及强化机理开展了数值研究和理论分析.结果表明,PCM储热单元熔化过程根据熔化速率分为初期、中期及末期三个阶段,柔性翅片储热单元相较刚性翅片储热单元可实现初期及中期的相变强化并有效缩短了蓄热时间,熔化速率最高提升20%.柔性翅片发生偏转储存弹性应变能,往复运动实现弹性应变能与流体动能的相互转化.翅片摆动提高液相流速并阻碍螺旋涡合并,通过增强PCM的对流换热强化固液相变.本文为相变材料储热单元的传热优化提供了新思路,提高了翅片储热单元的热响应能力,为热电联产灵活性改造技术的开发提供了理论基础.Heat storage technology of phase change materials(PCMs)is essential for thermoelectric decoupling and deep peak regulation in thermal power plants,playing a significant role in promoting energy transformation.However,the low thermal conductivity of PCMs poses a major challenge for the rapid response of heat storage systems.An effective solution to optimize PCM thermal storage systems is the use of fins.Herein,we propose a novel approach where flexible fins serve as a strengthening component to improve the melting process.We studied the melting process and strengthening mechanism of the flexible fin PCM heat storage unit both numerically and theoretically,using the enthalpy porosity method and a fluid–structure coupling model.Our findings revealed three distinct stages in the melting process:the initial melting state,mid-term melting stage,and final melting stage.These stages were differentiated based on the melting rate.The flexible fin enhanced the melting process during the initial and mid-term melting stages,significantly increasing the melting rate of the PCM.This effectively shortened the total heat storage time.The flexible fin was deflected to store elastic strain energy.This enabled energy conversion between the elastic strain energy of the fin and the kinetic energy of the fluid through reciprocating motion.The swinging motion of the flexible fin not only increased the flow rate of the liquid phase but also hindered the merging of the spiral vortex.As a result,the higher heat convection capacity of the PCM in the flexible fin heat storage unit enhanced the melting process.This paper presents a new perspective on enhancing the PCM heat storage unit.It improves the thermal response capacity of finned heat storage units,providing a theoretical foundation for the development of flexible modification technology in cogeneration.

关 键 词：柔性翅片 固液相变 相变强化 流固耦合 

分 类 号：TM621[电气工程—电力系统及自动化]