Attempts of Thermal Imaging Camera Usage in Estimations of the Convective Heat Loss From a Vertical Plate

Gdansk University of Technology, 80-233 Gdansk, Poland

^a Corresponding author: dendi8@wp.pl

Abstract

In this paper a new method for determining heat transfer coefficients using a gradient method has been developed. To verify accuracy of the proposed method vertical isothermal heating plate with natural convection mechanism has been examined. This configuration was deliberately chosen, because of the fact that such case is historically the earliest and most thoroughly studied and its rich scientific documentation – the most reliable. New method is based on temperature field visualization made in perpendicular plane to the heating surface of the plate using infrared camera. Because the camera does not record temperature of air itself but the surface only, therefore plastic mesh with low thermal conductivity has been used as a detector. Temperature of each mesh cell, placed perpendicular to the vertical heating surface and rinsed with convection stream of heated air could be already recorded by infrared camera. In the same time using IR camera surface of heating plate has been measured. By numerical processing of the results matrix temperature gradient on the surface ∂T/∂x │ x=0, local heat transfer coefficients α_y, and local values of Nusselt number Nu_y, can be calculated. After integration the average Nusselt number for entire plate can be calculated. Obtained relation characteristic numbers Nu = 0.647 Ra ^0.236 (R² = 0.943), has a good correlation with literature reports and proves usefulness of the method.