水制冷剂及水蒸气压缩机研究现状和展望

水作为第4代制冷剂具有绿色环保（ODP=0，GWP<1）、原料易得、成本低廉、安全性好、稳定性高以及汽化潜热大等诸多优势，完全可以满足环保要求从而应用在热泵空调系统中；但是水蒸气分子量低、比容大以及绝热指数高也决定了水蒸气系统具有压差小、压比大、单位容积制冷量小、容积流量大、排气温度高等特点，对水蒸气制冷系统用的压缩机也提出了更高的要求。目前使用的水蒸气压缩机主要有离心式、螺杆式以及罗茨式，离心式压缩机虽然容积流量大，但是单级压比小，对液滴敏感，排气温升问题突出，叶片以及壳体材料要求高，经济成本高，适用于大流量，小压比的系统；螺杆式压缩机稳定性好，压比大，可以满足湿压缩要求，但是它容积流量有限，可用于小流量，大压比的系统；罗茨式压缩机振动小，结构简单，但是它的压比同样也比较小，适用于中小冷量，大温升系统。为了促进水制冷剂在生产生活领域的广泛使用，针对不同使用场合和供汽需求，研究开发与之适用的压缩机是未来制冷技术发展的一个重要方向。

A review on development and prospect of water refrigerant and water vapor compressor

As a representative of the fourth generation refrigerant, water has numerous advantages, such as non-pollution (ODP=0, GWP<1), accessible, low-cost, secure, stable and large latent heat of vaporization, which can completely satisfy the requirements of the environment as a refrigerant. However, low molecular weight, large specific volume and high adiabatic index of water vapor determine that the water vapor systems have the characteristics of small differential pressure, large compression ratio, small unit volume capacity, large volume flow and high discharge temperature. It also puts forward higher requirements for water vapor compressors, which seriously limit the use and promotion of water as a refrigerant. Currently, the water vapor compressors mainly are centrifugal, screw and roots compressor. Centrifugal water vapor compressor has the advantage of large volume flow rate, but it has small single stage compression ratio, high discharge temperature and droplet sensitivity. At the same time, the blade and shell material of the centrifugal water vapor compressor are severe and expensive. Therefore the centrifugal water vapor compressor is suitable for the largest volume flow rate and smallest compression ratio system. Screw water vapor compressor has the advantages of good stability, large compression ratio and wet compression; however the volume flow rate is smaller. It is more suitable for the refrigeration system with small volume flow rate and large compression ratio. Roots water vapor compressor has the advantages of less vibration components and simple structure, however it also has small compression ratio, so it is usually used in the medium heating capacity and large temperature rise systems. In order to promote water refrigerant to be wildly used in production and livelihood field, researching and developing practicable compressors for different usage occasions and steam requirements is an interesting and significant research project in future.