Heat Transfer Analysis of a Between-Panes Venetian Blind Using Effective Longwave Radiative Properties

Abstract

Center-glass thermal analysis programs based on one-dimensional models have proved to be exceptionally useful. Recently efforts have been made to extend the analysis to include venetian blinds. It is convenient to model the venetian blind as a planar, homogeneous layer that is characterized by spatially averaged, or “effective,” optical properties. The blind is then included in a series of planar glazing layers. Thermal resistance values were calculated for a window with two layers of uncoated glass and a venetian blind in an air-filled glazing cavity. Three pane spacings and a wide range of slat angles were examined. The longwave effective properties for the blind were obtained using the analysis presented by Yahoda and Wright in a companion paper. The simulation model was completed with one of two simple models dealing with convective heat transfer in the glazing cavity. Calculated results were compared with earlier guarded heater plate measurements, and the agreement was encouraging in spite of the crude convection models used.