INVESTIGATION OF THERMAL BOUNDARY LAYER ALONG THE VERTICAL WALL OF A BUILDING

Abstract

Thermal boundary layers along the wall of a building were measured by using a thermocouple rake perpendicularly installed to the wall and a sonic anemometer with a high sampling frequency. In order to measure the temperature in the viscous layer, four thermocouples were set within 1mm from the wall surface. The Grashof number, Grx, which is a non-dimensional parameter of buoyant flows, was varied from 109 to 1012, to examine the scale effects. The boundary layer thickness normalized with similarity parameters for laminar natural convection was estimated, and the value is related to the fetch of heated wall. The measured temperature profiles were found to be composed of three layers. The layer closest to the wall is mainly controlled by the buoyancy flow due to heat from the wall, whereas in the farthest layer, the effects of the forced convection flows of the atmosphere become dominant. The middle layer is influenced by both the buoyancy flow and the forced convection flows.