Convective heat transfer coefficients between horizontal plastic shading nets and air

In this study, an energy balance was applied to a horizontal net under outdoor conditions to predict Qn−a and hn−a. Therefore, the net was tacked onto a wooden frame; energy balance was applied below and above the net surfaces and above a black substrate underneath the frame. The wind speed (V), net-air temperature difference (ΔT), downward and upward solar and thermal radiation fluxes were measured, on sunny days, below and above the net to be used for solving the energy balance equations. Accordingly, the time dependence of Qn−a and hn−a were investigated. Nets with different porosities and colors were used. For each net tested, hn−a was expressed as a function of V and ΔT. The results showed that hn−a depends mainly on the texture structure of the net rather than its color or porosity. Therefore, a similar net texture would have nearly the same hn−a value. These expressions can be used to estimate hn−a for nets having similar texture structures, different colors, and different porosities.