Experimental evaluation of the effect of supply air direction on air current and temperature in a room with underfloor air distribution system

One of the concerns about the operation of underfloor air distribution systems is the occurrence of local thermal discomfort such as draught and vertical air temperature difference. In the present study, to investigate these discomfort parameters in a room with the mentioned system, the temperature, mean velocity and turbulence intensity for vertical and horizontal supply air diffuser with 16 and 20°C inlet temperatures were evaluated. These parameters were measured at 0, 30 and 60cm distances from the center of diffuser of the underfloor air distribution system at 8 different heights from the floor. Also, by using the Fanger model, thermal sensation, percentage of thermal discomfort and the percentage of thermal discomfort caused by the draught were determined. The results indicated that the amount of thermal discomfort in a room with an underfloor air distribution system is significantly dependent on supply air direction (horizontal/vertical) and, distance from the inlet diffusers. Also, the results showed that by using proper diffusers, while subjects’ thermal comfort maintains constant, the supply air temperature can be increased from 16 to 20 °C, which is a major step towards reducing energy consumption.