Working Pairs Analysis And Study Of Key Process Of GAX Absorption Cycle

Under the condition of the society who focuses on energy saving,the technology of absorption cycle has been greatly paid attention in recent years.GAX absorption cycle is one of the new absorption cycle with high efficiency.Absorber and evaporator of GAX absorption cycle are important elements of the energy coupling equipment,which play a key role on a total performance of the refrigeration or heat pump system.This paper studies on the crucial subjects:new working pairs,simulation of the absorption cycle and performance anylasis of the key process of GAX absorption cycle.By summarizing and analysis the recent research on the working pairs of the absorption cycle,the paper introduced ionic liquid as a new working fluid.The Ionic Liquid has several special characteristic used in absorption cycle as environmentally benign medium,such as excellent solubility,high boiling point and low vapor pressure.The heat capacities of ionic liquids [Emim]BF₄ and its aqueous solution were measured by Calvet microcalorimeter.The relationship between the heat capacity and its temperature as well as concentration has also been built.Set up the thermal property models of the ionic liquid and the calculation program of the absorption heat transforme(AHT)cycle based on the models.The performance of the absorption heat transformer with the working pair TFE-[Bmim]Br was studied.Compared with the H₂O-LiBr AHT system, the TFE-[BMIm]Br AHT cycle could be used in a broad working condition and has high temperature output.Taking the technologies of falling film and climbing film as the background,a device has been set up which contains a falling film process inside and a forced climbing film outside.This device is 3000mm high and with a heat-transfer-length of 2000mm long.The diameter of the falling film is 16mm,and the thick of the climbing film is 1mm.The device could bear the pressure of 1MPa,and contains a temperature data acquisition system.Carried out the cold model experiment and got the different heat-transfer performances of the double-film device with different water flow rates. On-site experimental operation shows that the proposed system is stable, the relationship of the simulation data and experiment data has a certain consistency that the average deviation is lower than 2%.According to the simulation result,there is a 25%performance improvement compared with the ordinary falling film process.Based on the transfer property of the double-film device got from the cold model experiment,the hot model experiment was carried out and simulated.A hot model experiment was carried out at the condition:flow of the falling film,1.50 L·min^-1;inlet temperature of the falling film,21.5℃;inlet temperature of the forced climbing film,21.5℃;pressure of the NH₃, 0.2MPa.A qualitative temperature distribution curve was observed.A model for the coupling of falling film absorption process inside and forced climbing film heat-mass-transfer process was presented based on the properties of the ammonia solution and the heat-transfer model of the cold model experiment.The author simulated the double-film process with the working pair of NH₃-H₂O,and analyzed the heat and mass changes inside of the system.These elements were analyzed:absorption heat change,dQ_x; cooling load change,dQ_c;flow of the NH₃ absorbed by H₂O,dq_m; concentration of NH₃ in the vapor phase,y^e.This paper offers the basic data and provides reference for the absorption cycle with the working pairs of[Emim]BF₄-H₂O or TFE-[Bmim]Br.The technique of double-film,the double-film device and the double-film model coupling the heat and mass transfor set up a foundation for the following experiment and the principle analysis in the research area of the GAX cycle.