Study On The Effect Of The Coupling Of Air Supply Mode And Air Temperature On Human Thermal Comfort

From 2019 to 2020,a global epidemic of new crown pneumonia virus has break out.It is necessary to have good ventilation and air environment indoor.This topic combines numerical simulation and experimental method to study the influence of the coupling effect of air supply mode and air temperature on human thermal comfort.Among them,the simulation study set up three ventilation systems:displacement ventilation,stratum ventilation and underfloor air distribution.The ANSYS Fluent software was used to simulate the airflow organization,temperature distribution and CO₂ concentration distribution under these ventilation systems.There are four systems in the experimental study including displacement ventilation,stratum ventilation,underfloor air distribution and combined ventilation system composed of displacement ventilation and underfloor air distribution.Comparative studies were conducted on the indoor temperature field,the airflow temperature of the inlet,the human thermal comfort and the energy utilization coefficient under various experimental conditions.In addition,the simulation results are in a good agreement with the experimental results and the conclusions are as follows:?1?It could be found that different supply air temperatures could cause the different air velocity patterns,temperature distributions,and CO₂ concentration distributions under the displacement ventilation system in the numerical results.The experimental results indicated that,the temperature distributions showed a layered structure of higher temperature in the upper room than that in the lower room.The value of mean temperature difference between the head?Z=1.2m?and the ankle?Z=0.3m?around the human body?columns of I and H?was about 0.7°C.The air jet length of the inlet was short,and there was a water imbalance phenomenon in the inlet of“a”and“c”.The human thermal comfort was more suitable as the air-supplied temperatures were 20.86?,22.43?,23.26?and 24.19?.?2?It could be concluded that different supply air temperatures could cause the different air velocity patterns,temperature distributions,and CO₂ concentration distributions under the stratum ventilation system in the numerical results.The experimental results showed that the indoor temperature distribution was slightly different in the E,F,G,and M columns.The value of mean temperature difference between the head?Z=1.2m?and the ankle?Z=0.3m?around the human body?columns of I and H?was about 0.35°C.The air jet length of the inlet was long,and there was a water imbalance phenomenon in the inlet of“A”and“B”.The human thermal comfort was more suitable as the air-supplied temperatures were21.15°C,21.96°C,22.80°C,and 23.78°C.?3?It could be found that different supply air temperatures could cause the different air velocity patterns,temperature distributions,and CO₂ concentration distributions under the underfloor air distribution system in the numerical results.The experimental results showed that the indoor temperature distribution has the largest fluctuation at the height of Z=1.8m.The value of mean temperature difference between the head?Z=1.2m?and the ankle?Z=0.3m?around the human body?columns of I and H?was about 0.6°C.The air jet length of the inlet was short,and the water imbalance phenomenon at the inlets was less obvious.The human thermal comfort was more suitable as the air-supplied temperatures were 21.16?,21.70?,and 22.82?.?4?The results of the air-supplied temperature of 18°C of simulation were set as the examples to compare the systems of displacement ventilation,stratum ventilation and underfloor air distribution.It was found that in the underfloor air distribution system,the airflow velocity was uniform,and the air velocity around the human body was the smallest,which in the range of 0-0.32 m/s.The best cooling performance near the human body was provided by stratum ventilation system,followed by displacement ventilation system and underfloor air distribution system.The discharge effect of CO₂ was the best in the stratum ventilation system,followed by the underfloor air distribution system and the displacement ventilation system.?5?The results of the air-supplied temperature of 18²4°C of experiment were set as the examples to compare the systems of displacement ventilation,stratum ventilation and underfloor air distribution.The results indicated that the three air supply systems exhibited different temperature distributions.In other words,different supply air systems produced different airflow patterns at different supply air temperatures.In terms of human thermal comfort,when the supply air temperature is about 18°C,an underfloor air distribution system is recommended.When the supply air temperature is 21²3°C,a stratum ventilation system is recommended.When the supply air temperature is 19²0?and 24°C,a displacement ventilation system is recommended.From the perspective of energy saving effects,when the supply air temperature is about 18°C and 22°C,it is recommended to use an underfloor air distribution system or a displacement ventilation system.When the supply air temperature is about 19°C,21°C and 24°C,it is recommended to use a displacement ventilation system.When the supply air temperature is about 20?and 23?,an underfloor air distribution system is recommended.?6?The experimental results showed that in the combined air supply system,the temperature values of column I around the human body were higher than that far away from the human body at most heights.The value of mean temperature difference between the head?Z=1.2m?and the ankle?Z=0.3m?around the human body?columns I and H?was about0.6°C.