Theoretical And Experimental Study On Technology Of Fluidization Adsorption Refrigeration

The severity of the ozone layer destruction problem due to CFCs and HCFCs has been calling for rapid development in environment friendly refrigerant technologies. From 1990s, because of not using CFCs refrigerant and allowing to use waste heat, solid adsorption refrigeration technique has been studying extensively. But up to now, there are still some problems of it, for example, the coeffiecents of heat and mass transfer in a fixed bed adsorber are very low, the working pairs used in the system have some problems, which limits the wide use of adsorption systems.In view of the facts that many problems caused by a fixed bed adsorption system, a novel one is put forward, in which a fluidized bed is used as the adsorber. In the process of adsorption, the granules of adsorbent are blown by the vapor refrigerant, at the same time, the mass transfer between the adsorbent and the refrigerant, and the heat transfer between the adsorbent and the heat exchanger tubes are being enhanced; in the process of desorption, with the granules' movement around the heat exchanger tubes, heat and mass transfer will be accomplished very quickly.In order to choose the available working pair for the system, HFCs and natural working fluids are analyzed. The adsorption experiments are carried out. The candidate working fluids and activiated carbon are selected as the working pairs. According to the results of theoretical analysis and experiments, R134a-activiated carbon is chosen as the working pair in the fluidization adsorption system.A pressurized thermal balance is used to measure the adsorption and desorption characteristics of R134a-activiated carbon. Based on the experimental data, theoretical analyses were carried out including: the D-A equation is obtained by fitting the experimental data; using the Kelvin equation to analyze the relation of adsorption quantity and its impacting factors, the influence of the parameters to the adsorption characteristic is obtained; using the experimental data to analyze the relation of the refrigerating capacity and the COP of the adsorption refrigeration system and the working parameters, the relationship of them is obtained.Heat transfer model of the fluidized bed adsorber is built. The probability theory is introduced to analyze the granules' flowing state around the heat exchanger tubes. The gamma distribution is chosen to simulate the granules' flowing state. After analyzing the influence of the parameters to the heat transfer coefficient, a simplified heat transfer equation is put forward.A fluidization adsorption experiment rig was designed and set up. The adsorption and desorption experiments for a non-fluidized bed adsorption system and a fluidized bed system are measured. Through analyzing the experimental results of the non-fluidized bed system and the fluidized bed system, the following conclusions are drawn: firstly, the coefficients of heat and mass transfer in the fluidized system is much higher than the non-fluidized one; secondly, the SCP of the fluidized system is much higher than that of the fixed bed; thirdly, although there are some errors in the coefficient of heat transfer between the heat transfer model and the experimental results, the model can still be used to simulate or predict the coefficient of heat transfer of the fluidization system; lastly, the fluidization technique is more suitable for a large system, for example, central air conditioning system, etc.