| In recent years,radiant cooling technology has developed rapidly,and the research results are quite abundant.However,as a kind of air conditioning system with great advantages and potential,there are still many problems in its design and use.In this paper,the characteristics and operating conditions of the cooling radiant ceiling panel system and the all-air system are analyzed and compared by the experiments conducted at the Lawrence Berkeley National Laboratory.The indoor air temperature,indoor wall temperature,wall heat flux,operative temperature and cooling capacity are analyzed emphatically.During daytime,two rooms maintain a consistent operative temperature,the air temperature of the room conditioned by radiant cooling air conditioning can be maintained at a higher level.In the night ventilation period,the operative temperature of the room conditioned by all-air system than that of the room conditioned by radiation cooling system operative temperature of about 0.9-1.1?,indicating that the radiation cooling system room enclosure structure more cold storage,resulting in the night to release more cold,so that the room operative temperature lower.Radiation cooling system room wall and floor interior surface temperature is lower than the all-air system room,the overall radiation temperature of the enclosure is lower than the latter,which strengthens the body and the envelope between the radiation heat transfer intensity,so that the human body comfortable feeling enhanced.Integrating radiation heat transfer and convective heat transfer,the surface heat transfer intensity of room wall in radiant cooling system is lower than that of all-air system.The average cooling capacity of the radiant roof system is 2.1% higher than the average cooling capacity of the all-air system.Afterwards,based on the two test chambers and the systems,the EnergyPlus software was used to establish the simulation model.The results show that the simulation results are in agreement with the experimental results,which indicates that the model is reliable,and this model provides the basis for the follow-up research.The operation of two kinds of systems under different weather conditions is simulated in this paper.Under the weather conditions of Xi'an and Beijing,there is no condensation risk in the cooling radiant system,and the average cooling capacity is 56.42% and 53.15% higher than that of the air system,respectively.Under the weather conditions of Wuhan,Shanghai and Guangzhou,the cooling radiant system shows different degree of condensation phenomenon,the indoor operating temperature is out of control,and it needs to be combined with fresh air dehumidification system to meet the air conditioning needs.Adding the wet source in the above model,the condensation condition of the radiant cooling system is simulated and analyzed.The operating conditions of radiant cooling system with 0 person,1 person,2 persons and 3persons in room in Berkeley and Xi'an are analyzed.As the number of people increased,the risk of condensation increased,the more the system radiant plate closed,the cooling volume decreased,the more serious indoor temperature control.Compared with the radiation cooling system of roof under two weather conditions,under the same number of people,the dew risk in Xi'an was greater than that in Berkeley weather conditions,and the indoor temperature was more difficult to control.With 0 person,1 person,2 persons and 3persons in room,the average cooling capacity of roof radiant cooling system was higher than that of 18.58%,18.28%,16.62% and 18.83% respectively.Afterwards,for the model with condensation risk,adding the ventilation system and controlling the ventilation amount can effectively eliminate the risk of condensation,and control the indoor operative temperature well.Finally,the relationship between the ventilation volume and the maximum internal heat source in two kinds of weather conditions is studied. |
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