Study On Heat And Mass Transfer Characteristics Of The Desiccant Wheel

Solid adsorption cooling system using ambient air as the working medium and water as the refrigerant has received widespread attention because of its advantages of energy conservation and environmental protection.As the key component in a rotational solid adsorption cooling system,the performance of the desiccant wheel directly affects the dehumidification and cooling capacity,while the performance of the desiccant wheel mainly depends on the adsorbent material,the matrix structure,the process air inlet parameters and regeneration air inlet parameters.Therefore,studying the influence of operating parameters and structural parameters on the performance of the desiccant wheel is beneficial to optimize the design of the desiccant wheel and improve the operation level of the rotational solid adsorption cooling system.The effects of four important operating parameters of the process air inlet temperature,the process air inlet humidity ratio,the process air inlet velocity and regeneration air inlet temperature on the process air outlet humidity ratio and outlet temperature were studied experimentally,and the performance of the desiccant wheel was evaluated by moisture removal capacity,dehumidification efficiency,sensible heat capacity,sensible energy ratio and dehumidification coefficient of performance.Based on the heat and mass transfer theory of unsaturated porous media,a three-dimensional unsteady heat and mass transfer model of a corrugated channel is established,which is used to analyze the effects of seven parameters that are the process air inlet temperature,the process air inlet humidity ratio,the process air inlet velocity,the regeneration air inlet temperature,the matrix rotational speed,the regeneration angle and airflow direction on the heat and mass transfer of a corrugated channel.The results show that the optimal matrix rotational speed is 12r/h;the larger the regeneration angle,the smaller the process air outlet humidity ratio,but the process air outlet temperature increases;the dehumidification capacity of counter flow is significantly better than that of parallel flow,but the process air outlet temperature of counter flow is higher than that of parallel flow.Based on the analysis of corrugated channel simulation results,when the corrugated channel enters the dehumidification zone from the regeneration zone,the process air outlet humidity ratio is not reduced,but instead increases,and the process air outlet temperature is obviously affected by the matrix heat,so the desiccant wheel is provided with the pre-cooling zone to optimize the outlet humidity ratio and outlet temperature.The optimal angle of pre-cooling zone is selected according to the maximum dehumidification optimization ratio.The results show that the optimal pre-cooling zone angle of the desiccant wheel with a regeneration angle of 90° is 30°,and compared with the desiccant wheel without pre-cooling zone under the same conditions.,the moisture removal capacity increased by 6.0%,the sensible heat capacity decreased by 29.3%and the regeneration air heating capacity decreased by 26.8%;the optimal pre-cooling zone angle of the desiccant wheel with a regeneration angle of 135° is 21°,and compared with the desiccant wheel without pre-cooling zone under the same conditions.,the moisture removal capacity increased by 4.9%,the sensible heat capacity decreased by 26.1%and the regeneration air heating capacity decreased by 14.3%;the optimal pre-cooling zone angle of the desiccant wheel with a regeneration angle of 180° is 18°,and compared with the desiccant wheel without pre-cooling zone under the same conditions,the moisture removal capacity increased by 1.4%,the sensible heat capacity decreased by 20.4%and the regeneration air heating capacity decreased by 9.9%.