Analysis Of A New Hybrid Air-Conditioning System Dehumidified By Liquid Desiccant With Special Temperature Range

In order to adapt to the divers functions of buildings and the increase of occupant density, building energy consumption will account for 30% of the total social energy consumption, meanwhile over half of the building energy consumption is related to the air-conditioning systems. Thus, air-conditioning energy-saving is impotent for the improvement of society energy efficiency. Conventional air-conditioning system dominated significant energy consumption and caused serious environmental problems, due to some deficiencies existed in its structure and the air temperature and humidity control process. Therefore, air-conditioning energy conservation has come to a critical state and becomes very useful. This paper proposes a novel heat pump driven liquid desiccant self-regeneration (HPLD-SR) air-conditioning system, which based on low-temperature liquid desiccant air dehumidification. In this study, the heat and mass transfer characteristics of the dehumidification and regeneration processes are studied by experimental researches and theoretic analyses, and the overall performance of the system is discussed in-depth.At first, on the basis of system designment, the experimental platform of the HPLD-SR system is constructed. The HPLD-SR system is consist of a liquid desiccant cycle and a heat pump cycle, liquid desiccant with low-temperature and low-concentration is used for air dehumidification, and condensation heat is applied for solution regeneration. The character of the liquid desiccant cycle is that, dehumidification and regeneration self-cycles as well as an interstage cycle is designed, and concentration cascade utilization is then achieved by this model. The character of the heat pump cycle is that, to hand the condensation heat, two condensers are installed in series. Therefore, the condensation heat can be taken away by both desiccant solution and ambient air, and the condensation heat can be used effectively.Secondly, the experimental and theoretical analysis of the air dehumidification process with low-temperature and low-concentration desiccant solution is carried out The effects of the inlet thermophysical properties of air and desiccant solution on the performance of the dehumidification process are investigated by experiment. And the heat and mass transfer coefficients between air and desiccant solution for this special process are developed. The contents of the theoretical research are that:the NTU-Le model which is used to describe the heat and mass transfer process of direct contact of air and liquid desiccant is derived and modified, and a new method for determining the coupled heat and mass transfer coefficients between air and desiccant solution is developed.Then, theoretical and experimental studies on the regeneration process using condensation heat are performed. The character of using both hot air and hot solution for desiccant solution regeneration is investigated experimentally, and the heat and mass transfer coefficients for this process is derived, which lays a theoretical foundation for the following study. In this paper, the concept of the condensation heat regeneration use ratio is proposed, and its value for the HPLD-SR system is calculated. Based on the studies of the condensation heat regeneration use ratio, the average mass transfer driving force and the accessible operation area of the regeneration process, three different types of condensation heat regeneration utilization model are compared. As a result, the optimal principle of condensation heat distribution is summarized. In addition, in the view of regeneration energy level, the advantage of using liquid desiccant with low-concentration for the system performance is analyzed.In the last, performance and thermophysical properties of the HPLD-SR system are studied experimentally and theoretically. In the experimental process, the influences of system parameters and environment condition on all the system performance indexes are investigated, and the ambient adaptability of the system is also proved. A numerical model for system simulation is established which provides a theoretical analysis foundation for the following study. Then, by combining of theories with experimental researches, the capacity match between the concentration balance of the desiccant solution and the energy changes of the system is revealed. The energy-saving features of the HPLD-SR system is proved by compare its performance with the conventional air-conditioning system and the national standard. On this basis, a novel exergy calculation method for desiccant solution is proposed, and the exergy analysis mathematical model for the system is created. Subsequently, the flow path of the air handing and solution regeneration processes together with the system forms are optimized by using the exergy analysis method. In addition, the energy efficiency potentials of the various components in the HPLD-SR system are discussed.