A simplified model of heat transfer at an indoor window glazing surface with a Venetian blind

Abstract

In this article, a simplified model is developed to predict the radiative and convective heat transfer in a complex fenestration system consisting of a Venetian blind located adjacent to an indoor window glazing. Empirical correlations for natural convection in an asymmetrically heated channel and an isolated flat plate are used in this one-dimensional simplified model. In this simplified model, an energy balance is performed at the blind surface using a mean blind temperature. The radiative heat exchange between the blind, window and room is calculated using a four surface grey-diffuse model, which is coupled to the convective heat transfer. The simplified model has been developed using experimental and numerical data from the literature. Sample results are presented that illustrate the effect of blind slat angle, blind-to-window spacing and absorbed solar heat flux on the heat transfer at the window surface.

Experimental and Numerical Study of Free Convection in a Vertical Channel with Opposing Buoyancy Forces

“…Kotey et al (2009) developed a solar optical model for determining the radiative heat transfer. Lomanowski and Wright (2005) and Roeleveld et al (2010) have used a simplified convective model with this radiative model to determine the total heat transfer of blinds mounted adjacent to the indoor glazing surface of a window.…”

“…This can be approximated by natural convection in an asymmetrically heated vertical channel. Roeleveld et al (2010) used empirical correlations from the literature as the convective heat transfer model in a simplified model for fenestration systems. It should be noted that the simplified model uses a Venetian type blind, but that the blind is approximated as a solid wall for the convective model.…”

“…The simplified model of Roeleveld et al (2010) was compared with the experimental data collected by Machin (1997) and Collins (2001) for Venetian blinds mounted on an indoor window surface. Machin (1997) investigated cases where the window surface was heated above the ambient room temperature, but the blinds were unheated.…”

“…These cases have a single upwards buoyancy force inbetween the window and blind. Even though the geometry of a Venetian blind is much more complex than a flat channel wall, Roeleveld et al (2010) have…”

“…In the center-glass region, the temperatures are isothermal and this region neglects any end effects such as the window frame. This center-glass region approximation is used in VISION3 (Wright 1992) and other simplified models, such as Roeleveld et al (2010) and Lomanowski and Wright (2005).…”