Study On Liquid Desiccant Dehumidification Technique For Fresh Air Handling In The Hot And Humid Area

The fresh air cooling load in hot and humid area is analyzed. The results show that about 87.9 percent of fresh air cooling load is latent load, and energy consumption for dehumidifying is more than that for cooling in fresh air handling. Therefore, the fresh air dehumidification technique plays an important part in the energy consumption for fresh air handling. Liquid desiccant dehumidification is a rising, energy-efficient and environmental protective air dehumidification technique. Theoretical analysis and experimental study on the performance of liquid desiccant dehumidification technique for handling fresh air in hot and humid area has been investigated in this thesis. Liquid desiccant physical properties, dehumidifier performance and dehumidifier thermodynamics analysis are studied.Based on the dynamic method, experimental setup for measuring vapor pressure of liquid desiccant is set up, and vapor pressure of CaCl₂ and LiCl mixed solution in different proportion is measured. By synthetically analyzing vapor pressure and cost of mixed solution, a 50%CaCl₂+50%LiCl mixed solution is found to be a both good performance and low price liquid desiccant. The performance of fin-tube form internally-cooled dehumidifier in hot and humid conditions is tested using this mixed solution as liquid desiccant. The results show that it can satisfy fresh air handling in hot and humid area. For example, when solution and air mass flow ratio is more than 1.66, the outlet air humidity content can reach the designing value 9.58 g/kg, in the condition that fresh air loads the indoor humid load.The exergy analysis model of liquid desiccant dehumidifier is developed and the exergy efficiency of dehumidifier under different states is analyzed. The results show that the more the impulsion of heat and mass transfer is, the more exergy loss is caused and the smaller the exergy efficiency is. To optimize the system exergy efficiency, the NTUa and NTUw are analyzed. Maximum of system exergy efficiency is 66% when NTUa and NTUw are 0.8 and 3 respectively.By theoretical and experimental study, it is concluded that the liquid desiccant dehumidification technique can load the fresh air humid load, and can be used for fresh air dehumidification in hot and humid area.