Study on thermal and humidity environment in large space with radiant cooling and displacement ventilation system

Radiant cooling and displacement ventilation system has certain application advantages in large space building where there has a distinct stratification of heat and mass. This paper focuses on the effects of variable temperature and variable air volume on the distributions of the temperature field, the humidity field, the flow field and the PMV-PPD under radiant cooling and displacement ventilation system in large space building with significant thermal stratification. By simplifying and dividing the building model according to waiting hall at certain railway station, a three-dimensional space model describing the characteristics of indoor temperature and humidity in large space with compound system was presented by considering both radiation heat transfer and convective heat transfer. The discrete ordinate radiation model and RNG equation were adopted to describe the indoor air flow and heat transfer characteristics. Cooling capacity of radiation floor, supply air temperature difference and the thermal and humidity environment were researched in detail, and the method of thermal and humidity control in working area was analysed numerically based on CFD simulation. The author has shown that the stratified phenomenon of temperature and humidity was more obvious in waiting area than that in walking area, and the distribution of temperature was more uniform than that of relative humidity in room, the cooling capacity proportion need to decrease when the total cooling loads of room were higher, and the appropriate range of cooling capacity ratio of radiation floor was 63%-88% relatively in this research model. Meanwhile, under the mode of variable air supply temperature difference, the cooling capacity of floor had dominant effects on humidity distribution, which can be considered to be a significant humidity control factor in practice in large space.