Study On The Heat And Mass Transfer Of Adsorbent Bed Under Alternating Boundary Conditions

In order to reduce the energy consumption of the indoor air purification process,the new fan system generally adopts a total heat exchange inner core for heat recovery.However,at the same time of heat recovery,it will certainly bring about the increase of fan resistance,noise and increase of equipment volume.Use for reference from the structure of the rotary heat exchanger,this paper proposes a flat-plate heat recovery device with total heat exchange function,in order to reduce the negative impact caused by the heat recovery of the new fan system,and realize the low power consumption,low noise and further miniaturization.Firstly,this paper set up the model of the heat storage,heat release,adsorption and desorption occurring simultaneously in the adsorbent bed.The corresponding numerical method solving algorithm and calculation program are compiled,which provides the necessary means for studying the heat and mass transfer process of heat exchange core under alternating boundary conditions.The thermophysical parameters,unit weight and porosity of the adsorbent bed materials were measured by experimental methods,which provided basic data for following research and selection of heat exchange inner cores.Referring to the actual fresh air volume,a flat-type adsorption bed heat exchange inner core experimental equipment was designed and built,using the porous diatomaceous earth plate adsorption bed as the heat exchange inner core.The experimental equipment can realize the alternating contact of the adsorption bed with the fresh air and the exhaust air,and can adjust the parameters of the fresh air and the exhaust air if needed,also can meet the needs of experimentally researching the heat and humidity exchange performance.The effects of operating parameters such as gas temperature,humidity and superficial gas velocity on the heat and mass transfer characteristics of the adsorbent bed were studied by experiments and numerical simulation methods.On the basis of the work above,the numerical method was used to simulate the heat and mass exchange process under different working conditions in order to get the details of the heat and mass exchange process in the adsorption bed.The results show that the temperature and moisture content distribution in the heat exchange core of the adsorption bed tends to be evidently inhomogeneous.The heat transfer and mass transfer are mainly concentrated in the thin layer near the interface.The variational range of temperature and moisture content in the adsorbent bed tend to be decreased with depth.Since the both ends are respectively the inlets of the front and rear half cycles,the temperature difference between the gas flow and the adsorbent bed medium is larger,and the temperature and moisture content change more obviously than in the middle of the adsorption bed.In addition,the variation of the average temperature and moisture content of the adsorbent bed media and inlet and outlet air with time under different thermal conductivity and water diffusion coefficient were obtained by numerical simulation.