Theoretical And Experimental Study On Absorption Refrigeration In Low Temperatures

Absorption refrigeration cycle can be driven by low grade energy, such as waste heat, solar energy and geothermal energy. However, traditional absorption refrigeration cycles have a lot of limitations, especially it can not achieve low refrigeration temperatures, therefore, their application fields are restricted. Based on reviews on recent developments and innovations in absorption refrigeration technology, a new cycle, called as auto-cascade absorption refrigeration cycle - ACAR cycle, is proposed to achieve low refrigeration temperatures by utilizing low grade thermal energy and extend application fields for absorption refrigeration technology. In addition, systematic researches on this new cycle are carried out both theoretically and experimentally with different refrigerants/DMF (absorbent) as working fluids.The refrigeration mechanism is discussed on ACAR cycle and the concept is proposed on lowest refrigeration temperature for absorption refrigeration cycle. The characteristics of ACAR cycle under different working conditions are calculated and analyzed based on mathematical and physical model. Besides, the characteristics of traditional single-effect absorption refrigeration cycle are also calculated for comparison under the same conditions. The results show that the proportion among refrigerant components has key effect on its performances. The component, thermodynamic state after condensing at condenser-evaporator and J-T refrigeration effect of vapor refrigerant separated at the separator is basically affected by the proportion amongrefrigerants. In addition, there is an optimal absorption pressure between two absorbers on double-absorber ACAR cycle and its COP can achieve 20% higher than that of basic ACAR cycle. Finally, the distillation ACAR cycle can achieve lowest refrigeration temperature among ACAR cycles under the same working conditions.In order to investigate the performance of ACAR cycle, an experimental setup is designed and built. A series of experiments, using R134a/DMF, R32+R134a/DMF, R23+R134a/DMF and R23+R32+R134a/DMF as working fluids, are respectively carried out on ACAR cycle and traditional absorption refrigeration cycle. The experimental results show that the traditional absorption refrigeration cycle can only achieve -24.7 lowest refrigeration temperature, while the ACAR cycle successfully achieves -47.3 refrigeration temperature under 160 generation temperature, which is the lowest refrigeration temperature achieved by absorption refrigeration system up to now by literatures. In these experiments, the ACAR cycle shows not only its ability to achieve low refrigeration temperature but also its great potential in utilizing low grade thermal energy as driving power.The theoretical and experimental studies proved the refrigeration mechanism of ACAR cycle and that it can achieve much lower refrigeration temperature than that of traditional one and excellent performances. Finally, some helpful suggestions and advices are proposed to improve the performances of ACAR cycle in the future researches.