Study On Packing Characteristics And Capacity Matching Of A Heat Pump Driven Liquid Desiccant Outdoor Air Handler

With the improvement of people's comfortable living environment and the deepening of building energy efficiency,the heat pump driven liquid desiccant outdoor handler has unique advantages in improving air quality,using heat of condensation and achieving thermal and humidity independent control,which has attracted wide attention of the market.In order to explore the effect of packing characteristics on the heat and mass transfer processes of air and solution,and to optimize the capacity matching between the heat pump system and the air conditioning/solution regeneration system,the following studies have been conducted.Firstly,we performed dehumidification experiments on wet curtain packing,orifice corrugated packing,non-woven packing on the unit performance test platform.The experimental results show that the comprehensive performance of the non-woven filler with better wettability is optimal,which indicates that the wettability of the packing material has an important influence on the heat and mass transfer processes of air and solution.In addition,when the flow rate of the solution is small,the orifice corrugated packing with fine corrugated surface have the best performance,which indicates that the detail structure of the packing surface is also an important factor affecting the heat and mass transfer processes of air and solution.Secondly,a three-dimensional gas and liquid two-phase countercurrent model of the corrugated packing was established by CFD numerical simulation method.The effect of surface tension and interface stress shear on the solution flow was considered in the model.The model described the flow process of LiBr solution on the corrugated packing surface with different wettability(solid-liquid contact angle 0°~60°)and with or without fine corrugations,and explored the mechanism of LiBr solution spreading on the surface of corrugated packing.The simulation results show that even if the surface wettability of the packing reaches an ideal state,the solution still cannot wet the entire packing surface,and due to the influence of gravity,the upper half of the packing surface has poor wetting effect.Selecting wettable material or adding fine corrugations on the surface of the packing sheet can effectively increase the wetting area of the packing surface.Finally,on the basis of unit operation data from the aspect of analysis of energy flows,the unit adopting the capacity matching method control system solution concentration and the water supplementation method were compared in the annualconditions.The analysis results show that the unit is unsuited for using the outdoor air regeneration in the winter condition.Comparing with the outdoor air regeneration,the effect of the return air regeneration is as follow: the heating performance coefficient of the unit increases by 9.2%,the humidification increases by 12.1%.Comparing with the water supplementation method,the effect of unit solution concentration control adopting the capacity matching method as follow: in the summer condition,the comprehensive performance of the unit is significantly improved,the refrigeration performance coefficient of the unit increases by 9.7%,the dehumidification increases by 14.2%.in the winter condition,the humidification reduces by 27.7%,but the normal humidification capacity of the unit can be guaranteed.At the same time,the unit omits an external water supply device to achieve the optimization of the unit's overall structure.Therefore,unit solution concentration control adopting the capacity matching method has certain advantages over the water supplementation method.