Design And Research On CO₂ Mobile Air Conditioning System

As a kind of natural working substances carbon dioxide has the most possibility to become the final substitute in automotive air conditioning system. In order to avoid our country automotive air conditioning industry facing the passive aspect again which the new refrigerant and the new technology import from overseas nearly completely in the R134a substitution process. We must accelerate the practical application research work on the mobile air conditioning system and develop a MAC system which performance can satisfy automotive air conditioning requirement and can be assembled in the real car.Our country researchers have already made some progresses in the CO₂ automotive air conditioning system, especially in the analysis of the system static and dynamic properties, as well as the part development. They have also carried on the massive research work on the performance optimization both in the parts and system. But until now, there are few papers on the researches in parts coordinate with the system in order to enable a good performance. Under this background, the automotive air conditioning system has been designed and the match researches have carried on in the thesis. The main contents and conclusions are included as the followings:1. The mathematical models of evaporator and gas cooler using copper tube and plain fin have been developed. Using the newly developed transfer coefficient and pressure drop correlations, the models can predict the performance of gas cooler and evaporator with a reasonable accuracy within±5% compared with the experimental data. Based on the mathematical models we carry on the optimization design on the view of refrigerant pass, tube arrangement and fin spacing.2. Based on the above two numerical models, a new simulations platform is built up for mobile air conditioning. The match analysis result indicated that the most suitable throttle area is 0.7mm2 while the best middle heat interchanger length is 1000mm in this design system. And refrigerant charge amount on the system performance have been also experimentally studied. Provide an analysis platform to determinate refrigerant charging quantity for the CO₂ air-conditioning system avoiding the massive experiments and the tedious theoretical calculation.3. The new generation CO₂ trans-critical automobile air conditioning system has been established which consists of heat exchangers, variable displacement compressor, accumulator, internal heat exchanger and short tube orifice. This is the first MAC sysytem assembled in a real auto mobile which contains short tube orifice. A trans-critical CO₂ automobile air conditioning system test bench has been built for this research. The temperature decrease curve and the parameters in and out for other parts have been experimentally studied. The test result indicated that when the ambient temperature is 25℃, the sunlight radiation is 300W/m², temperatures for each measuring points are approximately stable after 600s, the evaporator air outlet temperature can be stable in 12℃.