Theoretical Analysis And Experimental Study On R744/R32 Refrigerant In Refrigeration/Heat Pump System

Ozone depletion and greenhouse effect have become a global environmental problems and the situation is becoming more and more serious. One of the root causes is that so much synthetic refrigerants are used and discharged into the atmosphere. At present the most important work for us is to find the alternative environmental protection refrigerants. And the widespread use of natural working substance is the key to complete the traditional refrigerant replacement. In the natural working substance, CO 2 is valued for the second time and become the focus of attention because of its environmental protection security, non-toxic, low cost and excellent thermal properties. But the high operating pressure, low system efficiency and so on also limit its rapid use and promotion, and this become the focus of people study.In this subject, we mainly regard the mixed refrigerants of R744 and R32 as the study object and take advantage of their own strengths to improve the efficiency, reduce the discharge pressure and reduce the artificial refrigerant filling quantity of the carbon water-water heat pump system. The subject, which is based on the CO 2 water-water pump system test bench, is to research R744/R32 mixed refrigerant’s application performance in CO₂ water-water pump system with the method that combine the theoretical analysis and experimental research.Establish the model of heat pump system theory cycle, set calculation working conditions, and simulate the system operation process in different mixing ratio, to conclude the different mixing ratio influence for the system operation parameters. Compare with the heat pump system with internal heat exchanger and find the influence of internal heat exchanger to heat pump system.The best filling quantity experiment show that the best filling quantity in CO 2 water-water heat pump system with internal heat exchanger reduces about 11.11%. And the system of optimal COPc,COPh and high pressure increases 8.40% 、0.90% and 2.05%m,reapectively.In the experiment of optimal R744/R32 mixed quality ratio, setting the mass fraction of CO₂ in the mixed refrigerants are 50%、60%、70%、80%、90%、95% and 100%. The cooling water inlet and outlet temperature of gas coole r are 20℃/45℃、20℃/55℃ and 40℃/45℃, respectively.（1）The mass fraction of CO₂ in the mixed refrigerant is 0.6. For all test conditions, the COPc、COPh and η of the system increase by 10%³5%, compared with t he system, which uses the pure CO₂ refrigerant.（2）The mass fraction of CO₂ in the mixed refrigerant is 0.6. And place a internal heat exchanger in the system. For all test conditions, the COPc、COPh and η of the system increase by 10%³0%, compared with the system, which uses the pure CO₂ refrigerant.（3） The mass fraction of CO₂ in the mixed refrigerant is 0.6. Compare the test condition that the cooling water inlet and outlet temperature of gas cooler is 20℃/45℃ which can keep the “follow the temperature”feature well of the CO₂ refrigerant with the another two test conditions that the cooling water inlet and outlet temperature of gas cooler are 20℃/55℃ and 40℃/45℃ and we can find that the performance coeddcients are above 10%. So the test condition, which the cooling water inlet and outlet temperature of gas cooler is 20℃/45℃, has the highest performance coefficient. When we place the internal heat exchanger in the system, we can get the same conclusion.（4）The mass fraction of CO₂ in the mixed refrigerant is 0.6. Placing the internal heat exchanger in the system can be always beneficial to the CO₂ water-water heat pump system.