MEASUREMENT OF THERMAL STRATIFICATION IN LARGE SINGLE-CELL BUILDINGS

This paper describes measured temperature profiles and thermal stratif ication in eight aircraft hangar buildings during the heating season. Presented also is the predicted impact of thermal stratification on he ating energy requirements. The hangar buildings included two main ceil ing heights (9.35 and 17.1 m (31 and 56 ft)), two ceiling types (flat and Quonset), two types of heating systems (vertical discharge forced warm air and downdraft convective unit heaters), and various types of large external doors. Measured stratification, expressed by floor-to-c eiling temperature differential, is in the range 4-11 degrees C (7.2-2 0 degrees F). Two air layers existed in the hangar bay area, a warm up per air layer and a cooler lower air layer. The lower air layer (up to 2 m (7 ft) high from the floor) is characterised by a steep vertical temperature gradient in the range 0.8-2.6 degrees C/m (0.4-1.4 degrees F/ft). In the upper air layer, above 2 m, the vertical temperature gr adient shallows considerably to 0.5 degrees C/m (0.3 degrees F/ft). Re sults indicate that thermal stratification can have a significant impa ct on the building's heating energy requirements. In the hangar buildi ngs studied, predicted excess heating energy requirements due to 8 deg rees C floor-to-ceiling temperature differential can be as much as 38% as compared to the case with no stratification.