The effects of multiple covers with condensation and optical degradation of a polyethylene windscreen on the performance of a sky cooling system

Abstract

This study evaluates the performance of a heat-pipe-augmented sky radiator system modelled using MATLAB. It was developed to simulate thermal networks with the following nodes: polyethylene cover(s), radiator plate with selective surface, heat pipe condenser end, heat pipe evaporator end, thermal storage fluid, fluid container wall, and room. Applying a windscreen of polyethylene that is mostly transparent to long-wave radiation, a drawback is its susceptibility to optical property degradation. Sky fractions of 100% were possible in cities with small cooling loads (Rock Springs, Seattle, San Diego and Denver). Sky fractions of over 50% were achieved in New Orleans and Houston and over 40% in Miami. A second study examined the degradation of polyethylene cover material. Louisville and two challenging climates (Miami and New Orleans) were simulated. In the Louisville, Miami and New Orleans climate, performance was reduced by 2.7, 14.1 and 9.0%, respectively, due to degradation of the cover’s material.

Keywords

• sky radiator
• passive system
• heat pipe