R32涡旋压缩机排气温度控制方法研究

发布时间：2019-03-18 20:15

【摘要】：为了应对“臭氧层破坏”和“全球气候变暖”两大主要环境问题,根据《蒙特利尔议定书》要求,目前在空调/热泵领域广泛使用的HCFCs制冷剂正在加速淘汰。发展零ODP、低GWP的环保制冷剂是制冷和暖通空调行业面临的迫在眉睫的问题。R32的ODP为零,GWP相对较低,且具有热工性能优良、循环性能高、价格便宜等优点,是空调热泵领域一种重要的中长期替代制冷剂。然而,R32较高的排气温度是限制其大规模应用的主要问题之一。因此,研究R32涡旋压缩机排气温度控制方法对于推动R32的替代和应用有重要意义。本文对降低排气温度的三种主要方法,吸气两相、中间喷液和两相喷射进行了深入评价和研究。首先,建立了考虑涡旋壁温度分布的涡旋压缩机动态分布参数模型。在总结前人的热力学模型的基础上,进一步分析了压缩过程中涡旋壁导热的物理过程,通过时间尺度上的分析将周期边界条件转化为稳态边界条件,从而将该过程简化为具有对流换热边界条件的一维稳态导热过程。通过实验数据修正和验证了该模型,结果表明该模型具备较高的精度。其次,基于验证的模型,深入分析了三种方法对压缩过程内部参数、排气温度、性能和压缩机运行范围的影响,并进一步探讨了三种方法的系统实现方式。结果表明三种方法均能有效降低R32涡旋压缩机排气温度,但对压缩机的性能影响有所不同。两相喷射能在降低排气温度的同时,能显著提升压缩机的制冷量和COP,提出了单喷射支路和双喷射支路两种两相喷射实现方式。然后,建立了可用于三种排气温度控制方法的R32涡旋压缩机实验台。通过实验进一步研究了三种方法在压缩机和系统工况下的性能。结果表明,低压腔压缩机吸气两相时存在最低的实际吸气干度;中间喷液时应选用合适直径的喷射通道避免液体被加热汽化;两相喷射在制冷和制热工况下都展现了较大的性能优势;采用三种技术后,系统的蒸发温度和冷凝温度发生了偏移,具体到两相喷射,其蒸发温度下降,冷凝温度升高,且存在最优喷射比。最后,通过模拟仿真研究了单喷射支路两相喷射系统的设计和控制方法。从压缩机的角度指出了理想喷射点,并通过优化中间换热器的大小和中间压力的控制使得实际喷射点趋近理想喷射点。结果表明,两相制冷剂喷射系统的中间换热器面积存在合理范围,而中间压力可以根据排气温度来优化控制。
[Abstract]:In order to deal with the two major environmental problems of "ozone layer destruction" and "global warming", HCFCs refrigerant, which is widely used in air conditioning / heat pump field, is being accelerated in accordance with the requirements of the Montreal Protocol. Developing zero GWP, low GWP environmental friendly refrigerant is an urgent problem faced by refrigeration and HVAC industry. R32 has the advantages of zero ODP, relatively low GWP, excellent thermal performance, high cycle performance and low price, and so on. It is an important medium-and long-term alternative refrigerant in the field of air-conditioning and heat pump. However, the high exhaust temperature of R 32 is one of the main problems limiting its large-scale application. Therefore, it is of great significance to study the exhaust temperature control method of R32 scroll compressor in order to promote the replacement and application of R32. In this paper, three main methods of reducing exhaust temperature, suction two-phase, intermediate liquid injection and two-phase injection, have been deeply evaluated and studied. Firstly, the dynamic distribution parameter model of scroll compressor considering the temperature distribution of vortex wall is established. On the basis of summarizing the previous thermodynamic model, the physical process of heat conduction of vortex wall in compression process is further analyzed, and the periodic boundary condition is transformed into steady state boundary condition by time scale analysis. Thus, the process is simplified to a one-dimensional steady-state heat conduction process with convective heat transfer boundary conditions. The model is modified and verified by experimental data. The results show that the model has high accuracy. Secondly, based on the verification model, the effects of the three methods on the internal parameters, exhaust temperature, performance and operating range of the compressor are deeply analyzed, and the system implementation methods of the three methods are further discussed. The results show that all the three methods can effectively reduce the exhaust temperature of the R32 scroll compressor, but have different effects on the performance of the compressor. The two-phase injection can not only reduce the exhaust temperature, but also significantly increase the cooling capacity of the compressor. COP, proposed two kinds of two-phase injection modes: single injection branch and double injection branch. Then, the R32 scroll compressor experimental bench, which can be used in three exhaust temperature control methods, is set up. The performance of the three methods under compressor and system conditions is further studied by experiments. The results show that the low pressure cavity compressor has the lowest actual suction dryness when the two phases are aspirated, and the proper diameter injection channel should be chosen to avoid the liquid vaporization when the liquid is injected in the middle of the compressor. The two-phase injection shows great performance advantage under both cooling and heating conditions. The evaporation temperature and condensation temperature of the system are shifted after three kinds of techniques. When two-phase injection is used, the evaporation temperature decreases, the condensation temperature increases, and there is an optimal injection ratio. Finally, the design and control method of two-phase injection system with single injection branch is studied by simulation. The ideal injection point is pointed out from the angle of compressor. By optimizing the size of the intermediate heat exchanger and the control of the intermediate pressure, the actual injection point approaches the ideal injection point. The results show that the area of the intermediate heat exchanger in the two-phase refrigerant injection system has a reasonable range, and the intermediate pressure can be optimized according to the exhaust temperature.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU83

【相似文献】