Investigations on Multimode Heat Transfer From a Heated Vertical Plate

Abstract

The interaction of surface radiation and conduction with natural convection heat transfer from a vertical flat plate assembly, with an embedded heater, has been investigated, both experimentally (using differential interferometer) and numerically (using FLUENT), in the present work. In the absence of radiation, the asymptotic limits that can be attained by the heated plate are isothermal and isoflux conditions. High values of plate thermal conductivity tend to make the surface isothermal, where as, lower values of thermal conductivity tend to make it isoflux. Irrespective of the thermal conductivity of the plate, an increase in the emissivity reduces the average temperature of the plate and brings the plate toward isothermal condition. A new methodology has also been proposed to determine the thermophysical properties, emissivity and thermal conductivity, the consistency of which is tested by carrying out experiments for various heat inputs and comparing the estimated values with those available in literature.

Empirical Relationship Describing Total Convective and Radiative Heat Loss in Buildings

“…The results of experimental studies of heat exchange in the channel between two symmetrically heated isothermal vertical walls using a thermal imaging camera, in which the contribution of radiation was limited by the polished surfaces of aluminium plates, were given in the studies [31,32]. In paper [33] the relationship between radiation and convection from a vertical flat plate was interferometrically and numerically (with the FLUENT programme) investigated. The influence of its emissivity and internal heat conduction were also taken into consideration in it.…”

“…Apart from the values of B1 and B2, on the basis of which relationships (32) and (33) were derived, the values of their product B1• B2 were also calculated (see Table 1). To calculate them, the formulas obtained from the conversions of ( 29) and (30) as well as ( 32) and ( 33) to (34) and (35) were used: The values of B1• B2 calculated from these formulas are given in the relevant columns of Table 1 and in Figure 4.…”