Study On Material Properties And Dehumidification Regeneration Performance Of The Solid Desiccant Bed

Air conditioning season dive cold load (or wet load) accounting the total load of ventilation and air conditioning system for20%to45%, non-air-season dive cold load (or wet load) accounting the total load of system for nearly70%. Thus reducing air-conditioning system in the energy consumption of the dehumidification process, increase as solar and other renewable energy in the application of this process is important to reduce air conditioning energy consumption. Traditional solar reproduction method using the collector to collect heat, and then the heat is converted into the energy required for regeneration of the desiccant material, there is a second conversion and it will reduce the utilization of solar heat. This paper presents a solid desiccant bed of using solar direct to renew. Determine the density, porosity, thermal conductivity, and other basic performance parameters of the desiccant material through experimental tests. The establishment of an equivalent thermal conductivity fractal model, dehumidification performance and regeneration performance of the dehumidification bed were studied experimentally, aims to provide basic experimental basis for its engineering applications.According to the experimental test to desiccant material basic performance parameters: bulk density is1.034g/cm3; porosity is35.12%-41.36%; moisture content of0to75%of the state, the thermal conductivity of silica is0.21-0.66W/(m-K). Using fractal theory to establish fractal model of equivalent thermal conductivity of porous desiccant material, and through research found that the curved channel model is closer to the actual pore structure than the parallel channel model, and obtain the equivalent thermal conductivity of different pore model. Experimentally amend its equivalent thermal conductivity fractal model, the relative error between its theoretical and experimental test values is less than2.7%after corrected.Through experimental tests, and obtained the dehumidification performance of the dehumidifier bed, the test results are as follows:(1)Dehumidification rate:an amount of process air is594.27kg/h, the dehumidification rate of unit volume is44.928kg/(h·m3); as air handling capacity is620.75kg/h, the unit volume average dehumidification rate is41.037kg/(h·m3).(2) The maximum dehumidification capacity of unit volume Mc and inlet air dry bulb temperature t1, relative humidity φ of the multiple linear regression formula for Mc=3.1φ-0.84t1, determining the coefficient is0.979.(3)The maximum heat release of unit volume Q:and inlet air dry bulb temperature t1, relative humidity φ of the multiple linear regression formula for Q=136.15φ-177.24t1, determining the coefficient of0.933.Regeneration performance test results of dehumidifier bed are as follows:(1) Regeneration temperature:solar radiation intensity600W/m2,800W/m2,1000W/m2, the regeneration temperature of pure radiation conditions respectively are36.2℃,38.4℃,39.7℃.The multiple linear regression equation among regeneration temperature tc and solar radiation intensity I and ambient air temperature t2is tc=0.025I+0.934t2, the coefficient of determination R2=0.997; the regeneration temperature of dry air convection and radiation mixing regeneration conditions respectively are22.6℃,23.2℃,23.3℃, the formula between regeneration temperature th, and the temperature of the introduction of renewable air t3is th=0.973t3+0.285, the coefficient of determination R2=1; the regeneration temperature of pure radiation regeneration larger than mixing regeneration, respectively are32.1%,32.9%,40.2%.(2) Regeneration rate and regeneration time:solar radiation intensity of1000W/m2,800W/m2,600W/m2, regeneration average speed of pure radiation regeneration respectively are0.083kg/h,0.062kg/h,0.037kg/h, the regeneration time is8h; regeneration average speed of mixing regeneration respectively are0.119kg/h,0.098kg/h,0.091kg/h, effective regeneration time is3h.(3)Regeneration efficiency:solar radiation intensity of600W/m2,800W/m2,1000W/m2, the regeneration efficiency of pure radiation regeneration respectively are17.5%,26.5%,37.7%, a linear relation between regeneration efficiencyηc and solar radiation intensity I is ηc=10.1I+7.033, the coefficient of determination R2=0.996; regeneration efficiency of mixing regeneration respectively are40.0%,57.3%,62.2%, the multiple linear relationship among regeneration efficiencyηh and solar radiation intensity I, the temperature t3and moisture content d of introduction of regenerative air is ηh=0.0861I-3.12t3+9.6278d, the coefficient of determination R2=1.By analyzing the experimental results the following conclusions can be drawn:(1)The curved channel model is closer to the actual pore structure than the parallel channel model of the equivalent thermal conductivity fractal model of the porous desiccant material, and its (2)In the same inlet conditions, the flow rate of1.87m/s corresponding to the dehumidification rates is larger than the flow rate of1.96m/s, suggesting to use a smaller inlet air flow (such as1.87m/s)when the desiccant bed to dehumidify.(3)The larger relative humidity of the inlet air, the lower dry bulb temperature, the greater maximum dehumidification capacity and maximum heat release of unit volume of the dehumidifier bed.(4)The regeneration time of mixing regeneration is shorter than pure radiation5hours, and its regeneration efficiency greater. It is recommended to use the mode of dry air convection and radiation mixing reproduction to regenerate dehumidifying bed.