Experimental study on thermal environment in a simulated classroom with different air distribution methods

Abstract To evaluate the thermal environment in the classrooms, the physical measurements were conducted in laboratory conditions. The objective of the study is to compare the performance of four typical air distribution methods in both heating and cooling modes in a mock-up classroom. The four air distribution methods included a corridor-wall grille, a displacement ventilation concept using two low-velocity units, a ceiling diffuser, and a perforated duct diffuser. There were three designed test condition in the classroom: summer conditions with full occupancy (heat gain of 54 W/m2) and partial occupancy (heat gain of 40 W/m2) and winter conditions with partial occupancy (heating demand of 38 W/m2). Based on the measured results, the wall-grille supply concept gave high velocities (around 0.4 m/s) in the occupied zone in both summer and winter conditions. The displacement ventilation was the least sensitive for different load conditions. The air distribution was quite unstable with a perforated duct diffuser which caused increased draft risk. During cooling mode, simulated window had an influence on the air distribution of a ceiling diffuser. However, air distribution was uniform in the heating case. With the ceiling diffuser and displacement concept, air velocities (below 0.23 m/s) and draft rate (less than 20%) were acceptable level in all cases. Based on the results, some air distribution methods are sensitive with thermal plumes. Thus, the air distribution methods selected for classroom should be robust to internal conditions and seasons. Together with displacement ventilation, the ceiling diffuser is the other appropriate solution for classrooms.