水蒸气热泵两相增压升温过程的热力学特性研究

Water vapor compression heat pump with water injection compressor as the key component is an energy saving and environmental benign method in industrial waste heat recovery. This kind of high temperature heat pump with water refrigerant can be widely applied to high temperature drying, chemical concentration, desalination of sea water and other industrial processes. Up to now, there are no guidelines for the design of water injection compressor and the corresponding water vapor compression heat pump system since the lack of studies of the thermodynamic investigation of water injection on the compression process and the heat pump system performance. Therefore, this project aims to study the distribution of water-injected and its movement, the mathematical leakage model between two adjacent base volume, the characteristics of heat and mass transfer between the steam compressed and water-injected. The variation of pressure and temperature in the base volume during working process will be also analyzed. And the mathematical models of the wet compression process of twin screw compressor will be developed. Experimental study also can be conducted to validate and modify the models based on the measured results. With the investigations above, the mechanism of water injection during the compression process can be revealed to clarify the compressor performance which changes with compressor structure, operating parameters, the mass and temperature of water-injected. Finally, the theoretical guidelines and research ideas will be provided for the twin screw water vapor compressor and high temperature heat pump system.

以蒸汽压缩机为核心部件的水蒸气高温热泵是一种绿色环保的工业余热回收技术，可以广泛应用到高温烘干，化工精馏，海水淡化等工业流程中。目前，国内外关于水蒸气高温热泵的研究才刚刚起步，为了研究具有喷水降温和气液两相压缩特性的水蒸气增压升温过程，本项目拟采用数值模拟与实验研究相结合的方法，探究双螺杆蒸汽压缩机的喷水液滴积聚及分布特性、基元容积内的非线性泄漏数学模型、气液两相间的传热与传质特性，分析两相压缩工作过程中基元容积内压力、温度随转子转角的变化规律，建立双螺杆蒸汽压缩机两相压缩工作过程的数学模型，结合实验研究结果对数学模型进行解耦分析和修正，从而阐明水蒸气压缩工作过程的喷水降温机理和热力学特性，揭示压缩过程中各性能参数随运行条件和喷水参数的变化规律，为喷水降温蒸汽压缩机的设计提供理论依据，并以此构建高效的闭式水蒸气热泵循环，为喷水降温水蒸气热泵循环的理论研究及设计方法提供新的研究思路。

水工质作为一种绿色环保，廉价易得的高温热泵工质，目前受到越来越多的关注。而以蒸汽压缩机为核心部件的水蒸气高温热泵是一种节能环保的工业余热回收技术，可以广泛应用到高温烘干，化工精馏，海水淡化等工业流程中，具有广阔的应用前景与潜能。本课题以水蒸气高温热泵的应用为目标，针对水蒸气压缩机内的气液两相压缩过程以及闭式水蒸气热泵系统性能进行了研究。分析了压缩腔内喷水液滴的运动分布特性，结果表明与直接喷水相比，雾化后的喷水更有利于双螺杆压缩机内部的降温与密封；模拟研究了水蒸气压缩过程中汽液两相间的传热与传质特性，结果表明在压缩过程中采用液体水滴喷射可以有效地降低压缩过程的排气温度，所建立的等压比多级压缩模型可以较好地体现水蒸气压缩的传热传质过程，具有较高的工业应用价值；模拟与实验研究了喷水参数对压缩过程喷水降温特性的影响，结果表明喷水可以有效地降低压缩机的排气过热度和功耗，同时喷水量的增加在一定程度上对性能的提升有利，但是喷水量有一个最优值，当超过这个数值时压缩机性能基本不变，而喷水温度对于压缩过程的影响可以忽略；最后搭建了闭式水蒸气热泵系统模型与样机，系统的研究了闭式水蒸气热泵循环特性，结果表明闭式水蒸气热泵循环具有优秀的高温供热性能，在蒸发温度为80℃，冷凝温度为120℃的工况下，系统的COP可以达到4.2，系统的最高供热温度高达155℃，优于目前已有的多种高温热泵系统，并且在温升一定的前提下，系统的COP还会随着冷凝温度的升高而升高，在高温工况下的系统性能优势更加明显。本研究的成果为以后水蒸气作为高温热泵工质应用在高温和超高温热泵领用进一步的指明了技术方向，有助于我国热泵行业的进步。