同时供冷供热二氧化碳双级压缩制冷热泵循环（火用）分析

发布时间：2018-04-19 19:05

本文选题：热回收 + CO_2双级压缩　；参考：《西安建筑科技大学》2017年硕士论文

【摘要】：本文提出了一种同时供冷供热的二氧化碳双级压缩制冷热泵循环,并详细叙述了其作为空调热泵热水器时的工作原理、构成以及其运行模式和控制方案。该系统以二氧化碳为工质,在夏季工况时,能够同时生产空调冷冻水和生活热水,并可以克服现有冷凝热回收空调系统效率低和设备使用率低的缺陷。为了进一步发掘其节能潜力,改进系统、优化系统运行方案,理论分析了系统在制冷情况下不同制冷剂质量流量系数、不同中间压力以及不同高压压缩机排气压力下循环的（火用）效率。结果表明,系统在高压压缩机出口压力8.5MPa~12MPa区间变化时,系统（火用）效率随着流量系数的升高而降低,在高压压缩机出口压力超过10MPa时,系统的（火用）效率会有较为明显的下降,而且统（火用）效率下降率会在流量系数0.3时突降。系统在中间压力5MPa~7MPa区间变化时,系统（火用）效率随着高压压缩机出口压力的升高先升高后降低,且都在高压压缩机出口压力为9MPa时系统（火用）效率取得最大值。系统在流量系数0~1区间变化时,系统（火用）效率随着中间压力的升高而升高,且流量系数越大,在中间压力的变化时系统（火用）效率的增长率就越大。该系统虽然可以调节回收的热量,但是随着回收热量的增加该系统的（火用）效率会有所下降。高压压缩机出口压力在持续增大时,（火用）损率最大的部件由第一节流阀变为热水加热器,中间压力在持续降低时,（火用）损率最大的部件由第二节流阀变为第一节流阀,而（火用）效率最低的部件是热源侧换热器,仅有57.3%,但是热源侧换热器只有在热需求量较大时才会对系统产生较大的影响,因此,低压时的第一节流阀与高压时的热水加热器和热源换热器是整个系统改进的主要对象。同时也发现,随着压力、制冷剂质量流量系数的变化热源测换热器的（火用）效率和（火用）损率变化不大,而热水加热器随压力的上升（火用）效率变化较大,从94.7%下降到62.0%。
[Abstract]:This paper presents a carbon dioxide two-stage compression refrigeration heat pump cycle for cooling and heating at the same time, and describes in detail its working principle, composition, operation mode and control scheme when it is used as an air-conditioned heat pump water heater. Using carbon dioxide as the working medium, the system can produce air conditioning chilled water and domestic hot water simultaneously in summer working conditions, and can overcome the shortcomings of low efficiency and low utilization rate of the existing condensate heat recovery air conditioning system. In order to further explore the potential of energy saving, improve the system and optimize the system operation scheme, the mass flow coefficient of different refrigerants in the system under the condition of refrigeration is analyzed theoretically. Exergy efficiency under different intermediate pressure and different pressure compressor exhaust pressure. The results show that the exergy efficiency of the system decreases with the increase of the flow coefficient when the outlet pressure of the high pressure compressor changes in the 8.5MPa~12MPa region, and when the outlet pressure of the high pressure compressor exceeds 10MPa, the system exergy efficiency decreases with the increase of the flow coefficient. The exergy efficiency of the system will decrease obviously, and the decline rate of exergy efficiency will drop suddenly when the flow coefficient is 0.3. The exergy efficiency of the system increases first and then decreases with the increase of the outlet pressure of the high pressure compressor when the intermediate pressure 5MPa~7MPa interval changes, and the exergy efficiency reaches the maximum when the outlet pressure of the high pressure compressor is 9MPa. The exergy efficiency of the system increases with the increase of the intermediate pressure, and the greater the flow coefficient, the greater the rate of increase of the exergy efficiency of the system with the change of the intermediate pressure. Although the system can adjust the heat recovery, the exergy efficiency of the system will decrease with the increase of heat recovery. When the outlet pressure of a high pressure compressor continues to increase, the components with the greatest exergy loss rate change from the first throttle valve to the hot water heater, and the component with the highest exergy loss rate when the intermediate pressure continues to decrease, from the second throttle valve to the first throttle valve, The lowest exergy component is the heat source side heat exchanger, which is only 57.3%, but the heat source side heat exchanger will have a great impact on the system only when the heat demand is high. The first throttle valve at low pressure and the hot water heater and heat source heat exchanger at high pressure are the main objects for the improvement of the whole system. It is also found that the exergy efficiency and exergy loss rate of the heat exchanger vary little with the change of the refrigerant mass flow coefficient, while the exergy efficiency of the hot water heater changes greatly with the increase of the pressure, from 94.7% to 62.0%.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU83

【参考文献】