Study On The Performance Of Solar Driven Two-stage Desiccant Air Conditioning System

While the society is developing constantly, people have more and more high requirement in the air quality of our living environment, which means that we not only need air conditioning to provide appropriate temperature and relative humidity supply air, but also need air conditioning to ensure enough fresh air. However, this will inevitably increase the energy consumption of air conditioning system. The solar driven two-stage desiccant air conditioning system combines rotary-wheel dehumidification with evaporative cooling to adjust temperature and humidity of supply air separately. So it can precisely control air temperature and humidity. In addition, it is environmentally friendly and nonpolluting that the air conditioning system use abundant solar energy as regeneration heat source and water as the refrigerant.Based the existing test bed, this paper has made experimental study on performance of solar driven two-stage desiccant air conditioning system, whose rotary wheels are made from composite desiccant material, of which regeneration temperature is low. After analyzing these operating parameters, the orthogonal experiment with 7 factors and 3 levels is designed to study how the main operating parameters including process air inlet temperature, regeneration air inlet temperature etc. impact on performance of the system. The effect weight and the optimal combination of seven operating parameters on 5 evaluation indexes in the experimental conditions are achieved by range and variance analysis method, as well as effect curves. Next, the text experiment of return air is carried out to analysis refrigeration capacity in the traditional operating mode. Finally, system simulation model is established to calculate supply air temperature in a wide range of conditions. Through theoretical and experimental analysis, conclusions are as follows:(1) Process air inlet temperature has the greatest impact on performance of solar driven two-stage desiccant air conditioning system. The higher process air inlet temperature, the greater supply air temperature, cooling capacity, dehumidification capacity, thermal COP and electric COP. When process air inlet relative humidity raises, supply air temperature and dehumidification capacity increase, cooling capacity and electric COP decrease first and then increase, thermal COP increases first and then mostly remains the same.(2) When regeneration temperature is at around 65℃, the minimum supply air temperature is achieved. With process air capacity increasing, cooling capacity, dehumidification capacity, and electric COP decrease, supply air temperature increases, and thermal COP increases first and then decreases. If solar radiation energy is sufficient and thermal COP is not considered, the maximum regeneration air capacity of 1350m3/h can make the best performance of system.(3) Rotary wheel I at smaller rotational speed will help improve the overall performance of air conditioning system, while the maximum rotational speed of 8r/h is suitable for rotary wheel II.(4) When all of supply air is from the return air, supply air temperature can reach 20-22℃, cooling capacity and electric COP can respectively maintain around 8k W and 0.9, and indoor temperature can be lowered to 27.1 ℃ with a slower rate than conventional air conditioning.