Wind-speed coefficient

[BenWinchester]

The wind-speed coefficient equation being used is incorrect.

The equation, based on Guarracino et al. utilises an equation for the performance of the collector,
$h_{\text{air}} = 3.8 v_\text{wind}$ + 3 \text{,}
whereas, based on Kumar et al., the equation should read
$h_{\text{air}} = 3 v_\text{wind}$ + 2.8 \text{.}

Kumar et al. then go on to discuss how this equation is not the most accurate, and they come up with their own equation:
$h_{\text{air}} = 6.90 v_\text{wind}$ + 3.97 \text{.}

I believe that it makes sense to update the HEATPanel model to include this new equation.