Numerical Study Of Rotary Dehumidification System

The rotary desiccant wheel dehumidification system is the main dehumidification system in the field of air conditioning.The performance of the desiccant wheel directly affects the dehumidification efficiency and energy saving index.In order to study the adsorption and desorption performance of the silica gel desiccant wheel during the dehumidification and regeneration stages,a single channel unit was studied in this paper.Aiming at the coupled heat and mass transfer phenomenon in the process of adsorption and desorption.On the one hand,a one-dimensional(1D)model was established in the axial direction,while the solution with finite difference method(FDM)was implemented in Python language.On the other hand,a three-dimensional(3D)model was established to describe both the axial and circumferential parameters,while the solution with finite volume method(FVM)is carried out by using Fluent’s user-defined scalar equation(UDS).In addition,the microstructure and adsorption characteristics of the adsorbent material in desiccant wheel were tested by electron microscopy and nitrogen adsorption.The results of the measurements,such as pore radius,porosity,specific surface area and adsorption isotherm were used to verify the parameters of the mathematical model.Finally,a dehumidification system platform was set up to qualitatively analyze the main factors of the performance under different conditions.Through the above research,the following conclusions are drawn:(1)3D model can obtain the radial and circumferential gradient temperature and humidity fields whose accuracy is higher than that of the 1D model,but the calculation is larger.Compared with the experimental results in references,the error of 1D model is less than 10%.The simulation results show that when the thickness,velocity and supply regeneration ratio increase,the humidity of the dehumidification outlet and the pressure drop on both sides increase.(2)Scanning electron microscopy(SEM)results show that the pore diameter of the material is much smaller than 200 nm.The results of nitrogen adsorption pore size analysis show that the average pore diameter,pore volume and specific surface area are 2.2952 nm,0.3424 ml/g and 595.84 m2/g,respectively.The isothermal curve of water vapor measured by the static volumetric method indicates that there is a strong capillary aggregation at 30 ℃.Furthermore,30 ℃ can be used as dehumidification temperature,while 120 can be used as desorption temperature because of its low adsorption capacity.Finally,the isothermal adsorption curve at 30 ℃ is in good agreement with the isothermal adsorption curve of references.(3)The experimental results of the dehumidification system platform show that when the regeneration temperature,rotation speed,SR,and velocity increase,the dehumidification coefficient(DCOP)increases with the increase of regeneration temperature,the increase of rotation speed,the increase of SR and the increase of wind speed.when the regeneration temperature,rotation speed,SR,and speed increase,the dehumidification coefficient of resistance DCOP increases,which is consistent with the trend of numerical simulation results.