Theoritcal And Experimental Study On The Novel Semi-decoupled Dehumidification Air Conditionging System

The integrated air conditioning system based on desiccant coated heat exchanger optimizes the treatment of both sensible and latent heat load and the COP of such system is much higher than other air conditioning systems.Both adsorption heat and sensible heat load are needed to be handled by a heat exchanger which is often switched between evaporator and condenser,hence,the sensible heat load handling capacity of such system is usually insufficient.Moreover,the stability and coordination of supply air are relatively poor.In order to solve these problems,a novel semi-decoupled dehumidification air conditioning system in which a desiccant coated evaporator and a conventional evaporator operate in series is proposed in this paper.The purpose of this paper is to reveal the thermodynamic mechanism of this novel air conditioning system and to obtain the performance of practical system.In order to achieve such targets,firstly,the thermodynamic performance of semi-decoupled dehumidification air conditioning system is analyzed theoretically in terms of air handling process and refrigerant cycle.Result shows that this novel air conditioning system can inherit the high COP of integrated air conditioning system and improve the sensible heat load handling capacity,the stability of the outlet air and the coordination between outlet air temperature and humidity.Secondly,a heat and mass transfer model of the combination of desiccant coated evaporator and conventional evaporator is established to predict the influences of main designed parameters.It is found that the adoption of silica gel as desiccant;0.25kg/m~2 as coating amount;50%as the ratio of the area of desiccant coated evaporator to total area of two evaporators is optimal for overall performance.Besides,the merit of the combination of desiccant coated evaporator and conventional evaporator is further verified under various inlet air conditions.Compared with single desiccant coated evaporator with same total area,the temperature drop is4.5~7?larger,and the fluctuating range of outlet air temperature can be reduced by about 85%.Moreover,the influence of inlet air condition on load handling capacity is analyzed.Finally,an experimental set up of semi-decoupled dehumidification air conditioning system is built and the dynamic characteristics of system under typical conditions are tested and analyzed.Result shows that semi-decoupled system can provide outlet air with high quality while maintaining high COP.For example,under typical ARI summer condition,COP can be up to 4.7,and secondary temperature drop can be up to 7.5?;the fluctuating range of outlet air temperature can be reduced by 63%;the temperature and humidity ratio of outlet air can be low simultaneously,as a result,supply air during whole cycle is satisfactory.In addition,the effects of the main operating parameters including the temperature of fresh air,the relative humidity of fresh air,the ratio of fresh air to process air and switching time on system performance are investigated experimentally.In sum,based on theoretical,modeling and experimental studies,novel semi-decoupled dehumidification air conditioning system can inherit the high COP of integrated air conditioning system and overcome the disadvantages of poor sensible heat load handling capacity,the instability of outlet air and the incongruity between outlet air temperature and humidity.