Composition Optimization And Experimental Study On Single-stage Refrigeration Cycle Using Mixed Refrigerants

The mixed refrigerator has a simple structure and can be used to obtain low temperature.What's more,it has higher thermodynamic efficiency than traditional method when the refrigerator operates in a wide temperature range of 120~ 240 K.It has great application prospects in Cryotherapy Technology,low temperature cold chain,bioengineering and gas liquefaction,and has significant advantages in micro or small cryogenic equipment.The ability to achieve cryogenic realized by using single-stage refrigerator with mixed refrigerants is determined by both external and internal reasons: the former is that the refrigeration system can realize the regenerative heat transfer in a large temperature range;And the latter is the unique thermophysical properties of mixed refrigerants.The purpose of this paper is to analyze the influence of mixed refrigerants on the thermodynamic performance of the refrigeration cycle by theoretical and experimental research,and explore the internal mechanism of the single stage refrigeration using mixed refrigerants,design a more efficient and reliable refrigeration system and obtain optimal mixed refrigerants composition provides guidance.Based on the above purposes,this paper mainly carried out the following work and obtain some useful conclusions:1.The MATLAB is used to invork Refprop to calculate the thermal property parameters of the mixed refrigerants,and the interpolation method is used to optimize this thermal property parameters calculation method.Compared with calculated directly,the operation speed can be improved by 78% and the calculation stability is improved.2.The thermodynamic analysis of the optimization results was carried out by combining the isothermal throttling effect and the integral throttling effect of the mixed refrigerants,and the internal mechanism of the mixed refrigerants optimization was theoretically explained.3.Designed a set of high-precision mixed refrigerants preparation and filling system,which can ensure the mixing ratio of mixed refrigerants according to design requirements;4.The ternary mixed refrigerants R14/R170/R600 a and R14/R23/R600 a were separately optimized and then subjected to throttling refrigeration test.The lowest temperature of the system reached 208 K,and the latter used a shorter time,the COP reached 0.106,showing a better throttling capacity.The TEWI evaluation method was used to evaluate the impact of the two on the environment.It was found that although the latter had a higher direct impact on the environment,the indirect effect was much smaller than the former;5.The quaternary mixed refrigerant R14/R23/R22/R600 a and R14/R23/R134a/R600 a were separately optimized and then subjected to throttling refrigeration test.The results show that the two have similar throttling and cooling capacity,the lowest temperature is lower than 200 K,and the latter has a COP of 0.095 ? at 208 K.Compared with the test results of the ternary mixed working fluid R14/R23/R600 a,its operating parameters are more stable.The TEWI evaluation results show that the environmental protection of the latter is slightly better than the former.