Research On Air Conditioning Terminalsfor Chilled Water With Large Temperature Difference

With the development of economy and the advancement of urbanization,the proportion of building energy consumption in the total energy consumption of major economies in the world is increasing,and it has reached about 33%of the total energy consumption at present.The energy consumption of the air conditioning system accounts for about 55%of the total energy consumption of the building,so it is of great significance to improve the energy efficiency of the air conditioning system and reduce the energy consumption of the air conditioning system for energy saving and emission reduction.From the point of view of heat transfer and thermodynamics,the temperature difference between supply and return water of chilled air conditioning can be between 6℃and 21℃to meet the requirements of dehumidification and cooling in general comfortable air conditioning.Compared with the conventional 7℃～12℃temperature difference system,the temperature difference of chilled water supply and return water is greatly increased,which can create conditions for reducing the circulation flow of chilled water,reducing the power consumption of pumping,using natural cooling sources,improving the energy efficiency of chillers,and improving the density and efficiency of cold storage equipment in water storage and ice storage air conditioning systems.Because most of the current terminal equipment is designed and developed based on the temperature difference between supply and return water of 7℃～12℃,it is difficult to match the operation of15℃cold water large temperature difference air conditioning system.Therefore,it is necessary to carry out the research on the end of 15℃cold water large temperature difference air conditioning system in order to provide technical support for building energy saving.In this paper,the feasibility analysis of the independent temperature and humidity control air conditioning system based on the large temperature difference of chilled water is carried out in different areas and different design conditions.The results show that the system is suitable for buildings with a personnel density of about 0.3 persons/m~2 and a fresh air volume of more than 30 m~3/h per capita.Due to the differences in adaptability in different cities,the actual situation of buildings should be considered;The indoor design humidity has a great influence on the system.In addition,the convection-radiation combination of large temperature difference terminal scheme for coil dehumidification in low temperature section and radiation cooling in high temperature section is also studied.In this paper,a series of dehumidification coils are obtained by using the orthogonal design method to optimize the design of fan coil units.The large temperature difference terminal scheme of dehumidifying coil in series with radiant floor,radiant wall and radiant ceiling is studied,and the cooling capacity and power consumption of the conventional fan coil unit are compared,and the feasibility of the series scheme is proved.The results show that the series scheme can reduce the water flow,reduce the total power consumption of the reduced terminal,and meet the requirements of normal operation.In order to study the influence of different arrangement forms in convection-radiation combination scheme on indoor air distribution,including temperature field,velocity field and humidity field,CFD simulation software was used to model an air-conditioned room,and the comfort situation of the room and the risk of condensation at the radiation end were analyzed and simulated.