【作者】 汪城；

【导师】 张鹏；

【作者基本信息】 上海交通大学 ， 制冷与低温工程， 2010， 博士

【摘要】 随着世界经济的发展和能耗需求的增加,节约能源和保护环境目前已经成为世界范围所共同关注的一个热点问题。气固反应热变温器系统,是基于可逆气固反应构建的热力学循环,通过热能和化学能的相互转化,能够提升热量的温度,实现低品位余热资源的有效回收和利用。和其他形式的热量回收系统,如常规的蒸气压缩热泵系统相比,气固反应热变温器系统不依赖电力的消耗,无运动部件和噪音,具有广泛的应用前景。系统通常采用对环境无害的自然工质,因此受到了国内外越来越多的关注。在系统的工质对选型方面,相对于金属氢化物/氢和金属氧化物/二氧化碳等工质对,金属氯化物/氨的反应量较大,温度范围较适合于低温余热资源的利用。但是,系统在实际应用中存在几个主要的问题,一是金属氯化物的导热系数较低(如CaCl₂的导热系数仅0.1 0.3W·m·K^-1),无法有效的传递反应热,致使系统的功率较低;二是金属氯化物/氨工质对在多次的合成/分解反应后,金属氯化物发生结块的现象（agglomeration phenomenon）,导致反应性能衰减和传质恶化;三是系统的热力学性能(温度提升ΔT、系统COP和COP_ex)较低,经济性较差。此外,系统性能的研究主要是理论分析,实验系统的建立和性能测试较少。针对以上问题,本文对气固反应热变温器系统的传热传质和系统性能进行研究,所获得的研究成果对气固反应热变温器系统的设计和性能优化,以及相关的气固反应系统和复杂传热传质过程的研究,都具有一定的指导意义。本文的主要内容包括:（1）从温度提升ΔT、系统COP和COP_ex以及工质对的匹配等方面,对两种基本结构的气固反应热变温器系统（E/C + R系统和R + R系统）进行了对比分析,确定采用R + R系统作为本文的主要研究对象,并对该系统的热力学完善度进行了理论分析,确定了平衡温降和反应腔室的非充分回热是系统热力学不完善的主要影响因素。（2）气固反应热变温器系统通常由低温反应盐和高温反应盐组成,系统运行过程包含两种反应盐的合成和分解反应。气体腔室的存在将对系统中的反应盐的化学反应过程产生作用。结合系统的结构和运行过程,本文分析了气体腔室体积对系统功率SHP、系统COP和COP_ex的影响。在气体腔室体积较小时,两种反应盐的反应速率较趋于平衡。此时,系统的功率SHP、系统COP和COP_ex较大。（3）本文针对膨胀石墨压块基材的复合反应块,依据反应块的物理结构,结合所经历的物理和化学过程,对反应块在气固反应过程中的热导率和气体渗透率等物性进行了分析,并对传热、传质性能对气固反应过程和系统性能的影响进行了研究,提出了优化的性能参数区间,为系统的性能优化提供了重要的依据。（4）本文建立了单级气固反应热变温器的实验系统,对系统的性能进行了测试(ΔT = 30℃、SHP = 254W·kg^-1、COP = 0.19和COP_ex = 0.23),实验验证了系统的可行性,并探讨了系统内部的多步反应过程和系统操作模式对系统性能的影响,验证了闭阀操作对系统功率SHP、系统COP和COP_ex的提升作用。（5）本文提出了一种二级气固反应热变温器系统的热力学循环。此系统是基于单级系统进行改进,有效的提高系统温度提升ΔT,并且避免系统压力在系统改进过程中所受到的影响,改善系统运行的可靠性和系统操作的安全性。本文还建立了二级气固反应热变温器的实验系统,并对系统性能进行了测试和初步的实验,最大温度提升ΔTmax可达70℃。更多还原

【Abstract】 With the development of world economy and increment of energy demand,‘energy saving and environment protection’has become the common concern around the world. Solid-gas reaction heat transformer was the system based on reversible solid-gas reaction and natural material, and was able to effectively recycle and utilize low-temperature waste heat sources. Comparing with conventional vapor-compressed heat pump system, solid-gas reaction heat transformer system has the following advantages: 1) less consumption of electric power; 2) no reciprocate-motion device; and 3) less noise. As to solid-gas reaction heat transformer system, the working pair of metallic chloride and ammonia has large reaction heat and was the best choice available for recycle of wild-range waste heat. But there are several problems in the application of solid-gas reaction heat transformer system. Firstly, thermal conductivity of metallic chloride is very low (e.g. the thermal conductivity of CaCl₂ is only 0.1-0.3W·m^-1K^-1), so heat generation or consumption in solid-gas reaction can not be effective transferred, leading to low system power （SHP）. Secondly, serious agglomeration phenomenon was happened in repeating synthesis/decomposition process, and it significantly deteriorated mass transfer and reaction performance. Thirdly, low system performance (i.e. SHP, COP and COP_ex) led to minimal economic value. For solving all of above problems, investigation on‘heat and mass transfer in solid-gas reaction heat transformer and system performance’was conducted in this thesis. Based on this work, the main contents in this paper include as follows:（1） Two types of basic solid-gas reaction heat transformer system （i.e. E/C + R and R + R） were compared, with the concern of temperature upliftΔT, system COP and COP_ex, as well as option of working pairs. As a result, R + R system was taken as the subject of investigation in this paper. Equilibrium temperature drop and incomplete heat recovery were found as two major factors leading to thermodynamic irreversibility of solid-gas reaction heat transformer system.（2） Effect of gas volume in solid-gas reaction heat transformer system on reaction rate balance and system performance, mainly as system SHP, COP and COP_ex was discussed in this paper. It was concluded that gas volume has balance effect on reaction process of low-temperature salt and high-temperature salt in solid-gas reaction heat transformer system. In the case of small gas volume, system power SHP, system COP and COP_ex were improved.（3） Physical parameters, e.g. thermal conductivity and gas permeability, of composite reactive block based on expanded graphite matrix were investigated. The theoretical model took consideration of the physical structure of composite reactive block and the physical and chemical processes suffered. Theoretical results were compared with those experimental data from references; good agreement was concluded. The influences of heat and mass transfer performance and system structure on system performance were also conducted in this paper. It was concluded that system performance was mainly confined by heat transfer process. Optimistic thermal conductivityλand heat transfer coefficient U were also proposed.（4） Experimental set-up of single-stage solid-gas reaction heat transformer system was developed and its performance measured. The main system performance was:ΔT = 30℃, SHP = 254W·kg^-1, COP = 0.19 and COP_ex = 0.23. With the experimental set-up, feasibility of single-stage solid-gas reaction heat transformer system was proven; the effects of multi-step reaction and system operation mode on system performance were also investigated. It was confirmed that closed protocol on gas valve control was favored for system performance improvement, i.e. system power SHP, system COP and COP_ex.（5） To improve temperature uplift, novel two-stage solid-gas reaction heat transformer system was proposed and the experimental set-up was developed. Theoretical comparison between novel system and other two-stage solid-gas reaction heat transformer systems in references suggested that reliability, operation safety and system performances were better in the novel system. Preliminary experiments were conducted and system performance was measured, with significant improvement of temperature uplift, i.e. maximum temperature upliftΔTmax was approaching 70℃.更多还原