跨临界二氧化碳增压系统性能对比分析研究

发布时间：2018-10-26 07:00

【摘要】：随着全球的ODS的全面淘汰,臭氧层保护工作取得阶段性的成果,全球的环境保护形势发生了深刻的变化,温室气体排放、全球变暖取代臭氧层破坏上升为现阶段世界范围内环境保护的首要任务与课题。为了应对全球气候变暖给人类经济和社会发展带来的不利影响,当前国际社会限制和削减HFCs使用和消费的呼声日益高涨。在全球淘汰含氟温室气体的大环境下,二氧化碳作为传统制冷剂的替代冷媒,凭借其独特优势在制冷领域得到了越来越多的应用,在多种复杂的场合发挥着重要的作用,其应用系统型式多样,主要包括:复叠系统、载冷系统和跨临界系统。其中跨临界制冷系统以CO_2作单一制冷剂,该系统的应用在降低制冷系统对环境的不利影响方面具有独特的优势,其能效表现的好坏直接影响其发展和推广应用。本文对基本的增压系统、带并行压缩的增压系统和带机械过冷的增压系统三种跨临界二氧化碳系统进行理论分析。通过了解国外相关课题的研究现状以及热力循环理论分析得出以下结论:(1)基本增压系统随气体冷却器出口温度的不同,存在最优排气压,使力得系统COP最大,且出口温度越低,最优排气压力越低;随中间压力的增加,基本增压系统制冷量、COP呈逐渐降低的变化趋势,但变化趋势较为平缓;随蒸发压力降低,基本增压系统的COP逐渐减小,且气体冷却器出口温度越低,系统COP下降越明显。(2)带并行压缩的增压系统中气体冷却器出口温度高于临界温度时,系统存在最优排气压力和中间压力使得系统COP最大。气冷器出口温度为32℃时,最优排气压力和中间压力分别为80bar和35bar;气冷器出口温度为37℃时,最优排气压力和中间压力分别为90bar和40bar。(3)机械过冷系统能提升增压系统的COP:过冷度分别为2.5℃、5℃、7℃、10℃时,系统最大COP分别提升4.8%、9.3%、12.4%、14.5%。(4)通过对三种系统的分析对比发现带有并行压缩的系统和机械过冷系统相比基本的增压系统,在相同工况下COP均有所提高,而且机械过冷系统的COP要高于带并行压缩的系统。在计算的工况范围内,带并行压缩的增压系统最大COP比基本的增压系统最大COP高7.8%;机械过冷度为5℃的系统的最大COP比基本的增压系统最大COP高30.7%;机械过冷度为10℃的系统的最大COP比基本的增压系统的最大COP高38.2%。而且相比基本的增压系统带并行压缩的增压系统和机械过冷系统最优气体冷却器压力要低。(5)通过理论分析和选型计算,搭建了增压系统实验台。
[Abstract]:With the total elimination of ODS in the world, the ozone layer protection has made a phased achievement, the global environmental protection situation has undergone profound changes, greenhouse gas emissions, Global warming, instead of ozone layer destruction, is the most important task of environmental protection all over the world. In order to cope with the adverse effects of global warming on human economic and social development, the international community is increasingly clamoring to limit and reduce the use and consumption of HFCs. In the global environment of eliminating fluorine-containing greenhouse gases, carbon dioxide, as the alternative refrigerant of the traditional refrigerant, has been applied more and more in the field of refrigeration with its unique advantages, and plays an important role in many complex situations. Its application system is diverse, including: overlay system, carrier cooling system and transcritical system. CO_2 is used as a single refrigerant in the transcritical refrigeration system. The application of the system has a unique advantage in reducing the adverse impact of the refrigeration system on the environment. The performance of its energy efficiency directly affects its development and application. In this paper, three kinds of transcritical carbon dioxide systems, namely, the basic supercharging system, the supercharging system with parallel compression and the supercharging system with mechanical undercooling, are theoretically analyzed. The following conclusions are drawn by understanding the current research situation of foreign related subjects and the theoretical analysis of thermodynamic cycle: (1) the optimal exhaust pressure exists in the basic pressurized system with different outlet temperature of the gas cooler, which makes the COP of the system maximum. The lower the outlet temperature, the lower the optimal exhaust pressure. With the increase of the intermediate pressure, the refrigerating capacity of the basic supercharging system, COP decreased gradually, but the change trend was relatively gentle. With the decrease of evaporation pressure, the COP of the basic booster system decreases gradually, and the lower the outlet temperature of the gas cooler, the more obvious the decrease of the system COP. (2) when the outlet temperature of the gas cooler in the supercharged system with parallel compression is higher than the critical temperature, The optimal exhaust pressure and intermediate pressure make the system COP maximum. When the outlet temperature of the air cooler is 32 鈩，

本文编号：2294934