Analysis of movable louvers for temperature control

Abstract

Movable shutters or louvers are being employed on several spacecraft for active thermal control. The present analysis of an infinite louver array led to seven equations; six of them form a simultaneous set (three linear integral equations and three linear algebraic equations) which describes the heat-transfer characteristics of the array, and the seventh gives its relative thermal performance in terms of an effective emissivity. The equations are solved numerically, and effective emissivity is plotted as a function of louver blade position for various values of the dimensionless parameters that appear in the governing heat-transfer equations. The results are compared with experimental results obtained for the Mariner II spacecraft louver system; agreement is good when the test data are corrected for power dissipation from auxiliary hardware and the end losses of the finite array. The remaining 4.5% discrepancy at the full-open position is attributed to specular (rather than the assumed diffuse) reflection from the blades.