【作者】 郑彬；

【导师】 翁一武；

【作者基本信息】 上海交通大学 ， 动力工程及工程热物理， 2011， 博士

【摘要】 太阳能、地热能以及工业余热等低温热源(<200℃)具有储量大、种类多、品质低等特点,很难被传统的能量转化设备集中高效利用。在能量转化过程中,大量低品位热能被直接排放,造成了能源的巨大浪费。近年来,伴随着社会经济发展与能源供给矛盾的日益显现,低温热源引起了国内外学者的广泛关注。低品位热能利用是节能领域研究中的热点问题。近期,国内外诸多学者针对低温热源(<200℃),相继提出一些发电制冷复合循环。这些循环可以将低品位热能转化为电量和冷量输出,为低温热源的有效利用开辟了新的途径。根据工作原理不同,目前这些发电制冷复合循环可以分为如下两类:(1)吸收式发电制冷复合循环;(2)喷射式发电制冷复合循环。这两类循环在发电制冷过程中各具特点。本文以低温热源热利用为背景,针对喷射式发电制冷复合循环进行了深入的理论和实验研究。主要的研究内容包括:(1)以低品位热能利用为背景,提出一种低温热源喷射式发电制冷复合循环。该循环采用安全环保的有机物工质,将朗肯循环与喷射式制冷循环相结合,可以将低品位热能转化为电量和冷量输出。从热力学第一定律和热力学第二定律角度,对循环的热力过程进行理论分析,得到该复合循环在能量转化过程中的工作特点。在此基础上,对低温热源发电制冷复合循环效率评价体系进行讨论。(2)以涡旋式膨胀机和喷射器为核心部件,建立喷射式发电制冷复合循环热力学模型。着重对涡旋式膨胀机和“定压混合”喷射器的建模过程进行了分析讨论。利用Matlab和Refprop软件编写系统仿真程序,并建立系统仿真方法。(3)运用仿真程序对喷射式发电制冷复合循环的工作性能进行分析计算。分析了循环各主要设计参数,关键部件设计参数,热源条件对循环工作性能的影响。结果表明,喷射式发电制冷复合循环可以有效的将低品位热能转化为电量和冷量,且与吸收式发电制冷复合循环相比具有制冷量较大的特点。(4)运用仿真程序对喷射式发电制冷复合循环工质选择问题进行讨论分析。以太阳能热利用为背景,从循环效率、工作压力范围、对关键部件影响、环保特性等方面对20种工质的工作性能进行了分析比较。指出了R123,R600a,R245fa等一些临界温度相对较高的有机物工质比较适于在该复合循环中使用。(5)首次建立kW级低温热源喷射式发电制冷实验装置,初步验证了该复合循环运行原理的可行性。应用一维“定压混合”喷射器设计理论设计加工喷射器。以R600a为工质,对实验装置单独发电、单独制冷、同时发电制冷三种模式下的工作性能进行了实验研究,为低品位热能利用积累了实验数据。在实验过程中,分别考察了热源温度、蒸汽发生器工作压力、变频器频率以及负载对系统工作性能的影响。(6)在总结全文的基础上,对低温热源喷射式发电制冷复合循环理论与实验研究中存在的问题进行了总结,并对今后相关研究工作的进一步开展提出建议,为今后该技术的推广和应用奠定了相应的基础。更多还原

【Abstract】 Low temperature heat sources (<200℃), such as solar energy, geothermal energy and low temperature waste heat, exist in the world extensively with different forms. Most of them can’t be utilized by the conventional power machines efficiently, so larger capacity of low grade waste heat is rejected to the environment directly, which results in large-scale energy waste. Recently, low temperature heat sources have caught much attention of the world due to the contradiction between the blooming economic development and the energy requirement.Low-grade heat utilization technology has become the hot question in the energy saving research area. In recent years, many combined power and refrigeration cycles have been proposed to give effective solutions for low temperature heat sources. The proposed combined cycles can supply both power and refrigeration outputs simultaneously. According to the different principles of work, the proposed combined cycles can be classified into two categories including: (1) the combined power and absorption refrigeration cycle (2) the combined power and ejector refrigeration cycle. Each of the combined cycle has its own characteristic. Based on the low-grade heat utilization background, both theoretical and experimental research works are under investigated on the combined power and ejector refrigeration cycle. Main research contents are included as follow:(1) A combined power and refrigeration cycle is proposed for low temperature heat sources. The proposed cycle combines the Rankine cycle and the ejector refrigeration cycle using safe and friendly working fluids. The proposed cycle can convert the low-grade heat into power output and refrigeration output. A theoretical investigation was conducted on the combined power and ejector refrigeration based on the first and second law of thermodynamics. The characteristics of the combined cycle in power and refrigeration generating process were analyzed. Besides, the efficiency definition is discussed to evaluate the cycle performance properly.(2) The thermal model of the combined power and ejector refrigeration cycle is established based on scroll expander and ejector. The mathematic models of scroll expander and“constant-pressure mixing”ejector are discussed especially. Besides, the simulation program are developed using Matlab and Refprop softwares.(3) Based on the simulation model, parametric study is conducted to simulate the cycle performance. Some contents are analyzed including the effects of key cycle design parameters, key componets design parameters, heat sources parameters on cycle performance.(4)Based on the simulation model, working fluids selection of the combined power and ejector refrigeration cycle is discussed. Based on the solar thermal utilization background, 20 kinds of working fluid are analyzed and compared from several aspects including cycle efficiency, working pressre range, effects on key components, safety and environmental problem. Results show that working fluids with comparative higher critical temperature, such as R123, R600a, R245fa, are suitable for the proposed cycle.(5) A kW class experimental prototype is developed to validate the feasibility of the combined power and ejector refrigeration cycle. Experimental research is investigated using R600a as working fluids. The system performances are tesed under three different modes: power output mode, refrigeration output mode, power and refrigeration mode. The effects of heat source temperature, generating pressure, frequency of the convertor as well as loads on cycle performance are analyzed.(6) All research work was summarized and the future problems in the research process are discussed and the prospects of the combined power and refrigeration cycle for low temperature heat sources are presented.更多还原