Study On Indoor Thermal Safety Of Low Temperature Air Supply Ceiling Radiant Cooling Air Conditioning System

The low temperature air supply combine with ceiling radiant cooling technology can realize building energy-saving while solving the problems of condensation,cold air shortage and limited cooling capacity of ceiling radiant cooling.The composite air conditioning system can use low-temperature air supply to bear part of the indoor cooling load so as to improve the cooling temperature of the ceiling radiant panel.At the same time,because the air supply temperature is low and the dehumidification capacity is strengthened,the indoor relative humidity can be kept in a low range,so the risk of condensation of the cold radiant ceiling can be reduced.However,the air supply temperature of the low-temperature air-cooled radiant ceiling air-conditioning system is low,and the indoor air pressure is poorly generated due to the "cold wind" falling too fast,and the temperature gradient is large,so that the indoor thermal comfort is low.In this paper,the temperature distribution and air flow field in an office in Shanghai are simulated by CFD software.The temperature field and velocity field of four different top supply angles(30°,45°,60° and 75°)at 11℃ and 13℃ are simulated,and the thermal comfort of radiation cooling room is analyzed Influence.At the same time,the simulation results are verified by experiments.According to the room conditions,the measuring points are arranged,the air temperature and wind speed of each measuring point are measured by instruments,and the thermal comfort of EDT and ADPI indexes is calculated by the experimental data.The experimental results are consistent with the simulation analysis,and the simulation results are true and reliable.At the same time,through the way of questionnaire,the subjective heat feeling,subjective wet feeling and subjective wind feeling of the personnel in the room using the low-temperature air-cooled radiant ceiling air conditioning technology are analyzed according to the evaluation scale.The analysis results also verify the effectiveness of the numerical simulation,which shows that the indoor thermal security is the best when the air temperature is 13℃ and the air angle is 75°.Finally,according to the results of the investigation of the subjective thermal feeling of all the personnel,the indoor thermal neutral temperature of the composite air conditioning system is 27.1℃;the range of the thermal acceptability is: the lower limit of the temperature under 80% thermal acceptability is 26.8℃,the upper limit is 27.2℃,the lower limit of the temperature under 90% thermal acceptability is 26.9℃,and the upper limit is 27.1℃.