A Simple 1-D Boundary Condition Representing Combined Convective-Radiative Heat Transfer Across a Double Membrane Semi-Transparent Assembly

In computer simulations of buildings and other structures, in relation to HVAC and fire, it is fairly common to need to represent boundaries which are made up of double semi-transparent membranes. An obvious example is a double-glazed window. When setting up a Computational Fluid Dynamics (CFD) model of the building, it is sometimes the case that detailed representation of this type of boundary is superfluous, and the CFD user wishes simply to replace the assembly by thermal and radiative boundary conditions. The present paper reports a simple steady-state one-dimensional model of such assemblies, accounting for the influences of solar radiation and radiation originating inside the building, as well as convective transfer. The theory is well suited for CFD or zone (lumped-parameter) models.