Study On Heat Transfer Performance Of Terminal Structure Of Radiation Air Conditioning System

The indoor terminal of the air conditioning system directly affects the indoor thermal comfort environment and the energy consumption of the air conditioning system.The terminal of the radiant air conditioning system has better comfort and energy saving than the terminal of the air conditioning system with forced convection.However,in order to prevent condensation,the temperature of the working fluid(or the surface temperature of the radiation heat transfer component)must be controlled above the dew point temperature,which limits the amount of cooling,resulting in insufficient radiation cooling.In order to solve the above problems,In this paper,a new type of suspended ceiling fin heat transfer panel with drain pan is used to carry out theoretical and experimental research on heat transfer performance.The main research contents and results are as follows:(1)The heat transfer analysis method is used to study the heat transfer structure,and the heat flux of the suspended ceiling fin heat transfer panel with drain pan is calculated.The results show that the average refrigerant temperature of fin heat transfer panel is stable at 6～7℃ under cooling condition and 48～50℃under heating condition.Because of the existence of the drain pan,the temperature difference between the fin heat transfer panel and the air temperature is large,which makes this kind of structure realize large temperature difference heating/cooling,and can provide sufficient cooling capacity and maintain good indoor comfort.Whether it is for cooling conditions or heating conditions,the natural convection heat flux of fin heat transfer panel accounts for 90%of the total heat flux.The heat transfer coefficient of the fin heat transfer panel increases with the temperature difference,and the natural convection heat transfer coefficient also increases.The temperature difference under heating conditions is large,resulting in heat flux under heating conditions greater than heat flux under cooling conditions.(2)The temperature test points at different heights in the room are arranged,and the thermal comfort of the end of the air conditioning system under heating and cooling conditions is analyzed,and the distribution law of the indoor temperature is obtained.The air temperature in the vertical direction of the room increases under the heating condition as the height increases.In the cooling condition,the temperature field in the vertical direction of the room is divided into upper,middle and lower layers.The upper and lower temperature layers are lower and the central temperature field is higher.Compared with the indoor vertical temperature distribution under heating conditions,the indoor vertical temperature distribution under cooling conditions is more uniform.(3)By controlling the outdoor temperature of the outdoor environment,the performance of the terminal of this kind of air conditioning system at different outdoor temperature is studied.The influence of outdoor ambient temperature on the terminal heat flux of air conditioning system is analyzed.Outdoor ambient temperature mainly affects the terminal heat flux by affecting the envelope temperature and fin temperature.In a variety of heating/cooling modes,the system can ensure the stability of the indoor temperature.(4)The uncertainty of the calculation results of the heat transfer model is analyzed,and the influence of each test variable on the heat flux of the heat transfer panel with a drain pan is analyzed.Air temperature has the greatest impact on the uncertainty of heat flux,followed by fin temperature,lower surface temperature of the drain pan,and maintenance structure temperature.The uncertainty of heat flux in both cooling and heating conditions is within±5W/m~2.The relative uncertainty under heating conditions is lower than the relative uncertainty of cooling conditions.(5)Comparing the heat transfer performance of the transfer panel with a drain pan studied in this paper with the heat transfer performance of other radiation terminals,the heat flux suspended ceiling radiant panels with different structures is analyzed.Suspended ceiling fin heat transfer panel with a drain pan can use a lower temperature refrigerant than the other two structures and have great potential for increasing heat flux.Its heat flux is twice that of other structural types,which can reduce the installation area of indoor radiant panels.The structure of the fin heat transfer panel is optimized.When the fin spacing of the fin heat transfer panel is 5.2mm,the cooling/heating capacity of the fin is 1.5 times,and the metal material is reduced to the original three-third.