Research Of Air Conditioning System Based On Solution Dehumidification Method Of Low Grade Heat Source Regeneration

It is increasingly important that air conditioning system should meet requirements of comfort and energy-decreasing. And it challenges to the traditional refrigeration air conditioning system. In order to dehumidify, the traditional system decreases air temperature to its dew point, increasing the power of compressor and down the comfort of air, which can not completely adapt to the requirement of the society for air conditioning system. Therefore, the researchers proposed some new air conditioning ways and systems by taking moisture control into consideration.In this paper, the solution dehumidification process is discussed from the point of view of the driving force of mass transfer theoretically. The dehumidification and regeneration characteristics of LiCl solution are studied experimentally. The characteristics of the frozen dehumidification unit under variable condition are studied experimentally too. Based on the above theoretical and experimental results, the liquid desiccant air conditioning system of low grade heat source regeneration is designed and the power consumption is analyzed.In theory, the equilibrium curves of isothermal dehumidification process are calculated based on the analysis of the driving force of mass transfer and the physical properties of the LiCl solution and wet air. The equilibrium curves of temperature-rising dehumidification process are calculated too given that all condensation heat of water vapor is absorbed by LiCl solution. And the two kinds of equilibrium curves are compared when the inlet temperatures of solution and air are25℃,30℃and35℃separately. The gap of the two kinds of curves reduces with the decreasing solution mass concentration. Moreover, the gap is obvious with inlet temperature rising.The LiCl solution dehumidification experiments are carried out. The experimental results show that the condensation heat causes mainly the rising of solution temperature. The water condensation rate increases with air flow rate, but not with solution flow rate completely. Under the condition of air and solution contacting well, the dehumidification efficiency goes down with the air flow rate increasing. The change trend of dehumidification efficiency with solution flow rate is similar to that of water condensation rate. The dehumidification performances of the packing with two kinds of height are compared. The water condensation rate increases with the increase of packing height. But the total volumetric mass transfer coefficient is lower with the increase of packing height. And it shows that the effect of entry section exists in dehumidification process, which is similar to heat transfer process. The LiCl solution regeneration experiment results show that the regenerative effect goes down with increasing solution concentration. The regeneration amount increases with inlet solution temperature going up. The regenerative effect is poorer when the inlet temperature is lower than50℃.In order to analyze the energy efficiency of the heat pump unit under variable conditions in composite air conditioning system, experimental investigation of the traditional refrigeration unit has been made under different conditions. And the correction coefficients of COP with the evaporation temperature and condensation temperature are studied. The experimental results show that the impacts of indoor environmental parameters are obvious on capacity and water condensation rate. The power consumption of per water condensation rate changes with air flow rate in the quadratic curve form. It has a minimum in a certain environment. The minimum value is smaller in wetter environment. And it moves to the larger airflow direction.The scheme of secondary returned air and two-stage solution dehumidification is put forward based on the controlling principle of temperature and humidity independently and the above theoretical and experimental results. And a small composite air conditioning system is designed. The parameters of outlet air are met firstly. And the regeneration temperature and heat required of solution regeneration are met too. To cool both air and solution, two small heat pump units are designed which provides the chilled water with17℃. The flow rate of chilled water is adjusted to get the max value of comprehensive COP of two units.Finally, the models of power consumption analysis are built of a three-floor villa in Shanghai city. It includes air cooled heat pump system independently, ground source heat pump system and the composite system above. The units are chosen on the max loads of the building between July and August. The outlet air parameters, dehumidification performance and power consumption of different systems are compared based on the equal water condensation rate. The results show that the relative humidity of outlet air of the composite air conditioning system is lower than other systems in a certain outlet air temperature condition, which improves the indoor comfort largely. The energy-saving of the composite system is not obvious when the temperature of inlet solution of regenerator is52℃and the efficiency of heat exchangers is0.7. But the comprehensive COP of the composite system increases by0.22when the efficiency of heat exchangers is0.8. And it is energy-saving to some extend.