Collector is as shown in the figure 3. The collector has absorber plate of length L and average width W. The
air flow over the absorber plate is as shown in the figure 3. Consider a slice of trapezoidal collector having mean width
W having thickness ‘dx’ at a distance ‘x’ from the bottom edge of the collector, we write down energy balance for the
absorber plate, the transparent plastic cover, and air flowing in between[7,8]. We assume that,