Thermal performance of the floor-supply displacement ventilation system was
evaluated in a large climatic chamber designed to simulate a single span of
an office building. Detailed measurements were conducted to determine the indoor
environment and skin temperature of a thermal manikin. This floor-supply system
could keep the temperature gradient in the room smaller because of the cooling
effect through the air permeable floor. Heat transmission between the occupied
space and underfloor plenum due to the floor cooling effect of the floor-supply
displacement ventilation system kept the temperature gradient substantially low
in the occupied zone. 50-60 percent of the total heat load was treated by the
heat transmission through the floor panels. The lower the height of the heat
sources, the greater the vertical air temperature difference in the occupied zone.
An increase of heat load or a decrease of supply air volume also caused a
greater vertical air temperature difference in the occupied zone. The vertical
temperature difference between 0.1 m and 1.1 m was 2.1 degrees centigrade at the severest condition
for the case with 36 W/m2 of scattered heat load and 1890 m3/h of supply air.
A slight air temperature rise of 0.3-0.5 degrees centigrade was observed near the clustered heat
sources, but the temperature gradient was kept nearly constant below 1 degrees centigrade throughout
the room. The thermal stratification near the window was destroyed in a summer condition.
An effect of cold draft was observed in a winter condition, but the thermal
stratification above 0.6 m was kept undisturbed. For the case of winter, the cold
draft caused an increase of air velocity below the window up to 0.15 m/s.
All the estimated PMV values for scattered heat source conditions based on
1.1 met and 0.6 clo fell between 0 and 0.5 except for the case of summer and winter.
A strong influence of radiation and ambient air temperature on the skin temperature
of a thermal manikin was observed to be significant.