A natural convection air heater consists of an array of parallel, equally spaced vertical plates, which may be maintained at a fixed temperature Ts by embedded electrical heaters.

The plates are of length and width L = W = 300 mm and are in quiescent, atmospheric air at T_∞ = 20°C. The total width of the array cannot exceed a value of W_ar = 150 mm. For T_s = 75°C, what is the plate spacing S that maximizes heat transfer from the array? For this spacing, how many plates comprise the array and what is the corresponding rate of heat transfer from the array?

Transcribed Image Text:

War N-1 N 1 2 3... -T, L. Ambient air, T