熔盐复合相变材料多尺度耦合的相变传热机理及过程优化研究

Guided by the great requirement of energy conservation and emission reduction, the researches on high efficiency thermal energy storage theory and its application will be performed to solve the non-steady-state problem of solar energy and industrial waste heat. The research includes three aspects: the preparation of high temperature multicomponent composite phase change materials (CPCM), the revealing of phase change heat transfer mechanism, and the process optimization of latent heat storage (LHS) system. In CPCM aspect, the preparation and characterization studies will be performed for salt/ceramic CPCM with carbon nanomaterials as additive, and the internal relation of the microscopic structure and macroscopic thermal performance parameters will be examined. In heat transfer mechanism aspect, the numerical simulation method for the multi-scale phase change heat transfer process in porous medium will be developed, then the interaction laws among the various components and phases in the CPCM will be investigated to reveal the effects of microscopic structure on phase change heat transfer performance. In process optimization aspect, the effects of CPCM thermal performance parameters and CPCM arrangement on the performance of cascade heat storage unit will be deeply investigated, and the multi-objective optimization for LHS process will be performed based on the process irreversibility, themal energy storage density and thermal energy storage rate. The objectives of the present project are to identify the influence mechanism of the CPCM microscopic structure on macroscopic thermal performance, to reveal the phase change heat transfer mechanism in porous CPCM under multi-scale coupling conditions, to propose the phase change material selection and matching principle for cascade LHS unit, to establish the multi-objective optimization theory and method for LHS process.

本项目以我国节能减排重大需求为导向，围绕太阳能及工业余热热源的波动性特征，从高温多元复合相变材料制备、相变传热机理揭示、相变储热过程优化三个层面，开展热量高效存储理论及应用研究。在储热材料方面，开展碳纳米高温复合相变材料制备及性能表征研究，分析微观结构和宏观热性能参数的内在联系。在储热机理方面，开发复合相变材料内多尺度下相变传热过程的模拟方法，研究复合相变材料各相、各组分之间的相互影响规律，探索微观结构对相变传热性能的影响机制。在过程优化方面，研究相变材料热力性质和布置方式对热量梯级存储单元储热性能的影响规律，从过程不可逆性、储热密度、储热速率等方面，开展相变储热过程的多目标优化研究。以期通过本项目的研究，查明复合相变材料微观结构对宏观储热性能的影响机制，揭示复合相变材料多尺度耦合下的相变传热机理，提出热量梯级存储系统相变材料筛选和匹配原则，建立相变储热过程的多目标优化理论及方法。

为了解决太阳能及工业余热热源的波动性问题，急需发展高效储热技术。本项目从高效复合相变储热材料制备及性能优化、相变储热机理揭示及过程强化、储热设备整体优化三个层面，开展相变储热系统的性能强化及优化理论研究。经过为期四年的研究，圆满地完成了预定研究任务，全面达到了预期研究目标。在材料制备及性能优化方面，制备了纳米材料-熔盐、金属泡沫-熔盐两大类复合相变储热材料，开展了热性能表征及优化研究，揭示了纳米材料微观结构对宏观储热性能的影响规律。在储热机理研究方面，实现了LBM和FVM的耦合，揭示了多孔材料的微观结构对储热密度和储热速率的影响机制，提出了改进的金属泡沫复合相变材料结构；查明了自然对流对相变储热过程的影响规律，开发了局部翅片管强化换热结构；开发了强化传热管和梯级储热相结合的复合强化方案，可以同时提升储热速率和储热密度。在系统强化和优化方面，将传热学领域的最新理论成果火积耗散极值原理推广到梯级相变储热系统的优化，构建了基于火积耗散极值原理的梯级相变储热系统优化理论和方法，提出了相变材料筛选和匹配准则。截止目前，研究成果已发表国际期刊论文11篇（SCI检索），其中2篇曾入选ESI高引论文。