Average Air Temperature Inside a Room With a Semitransparent Wall With a Solar Control Film: Effect of The Emissivity

Abstract

In this paper a theoretical study on conjugated heat transfer (natural convection, radiation and conduction) in a square

room (cavity) with turbulent flow is presented, taking into account variation on the opaque wall emissivity. The room is

formed by an isothermal vertical wall, two adiabatic horizontal walls and a semitransparent wall with and without a

control solar radiation film. The governing equations for turbulent flow in 2D were solved using a finite volume

formulation and k-? turbulent model. Results for an isothermal wall at 21°C and an external temperature of 35°C are

presented. The size of the room is 4.0 m length and height and the solar radiation falling directly on the

semitransparent wall was 750 W/m2 (AM2). The emissivity of the opaque walls was varied between 0.1 ? ?* ? 1.0.

Results show that, based on the air average temperature and the effective heat flux inside the room, the solar control

film under study was advantageous for energy saving purposes, for emissivity values of ?* ? 0.46. A correlation on

this system for the heat transfer as a function of the emissivities was determined.