The vertical air layer formed between two walls may be treated as a
side heated cavity with a height of 0.6 m and width of 0.05 m. The two
surfaces are at 20 ◦C and −5 ◦C, respectively. What is the heat transfer
per unit surface area of the cavity wall? A consultant suggests that the
spacing be increased to 0.07 m such that the heat transfer across the
cavity is reduced. Would you agree with the consultant? Explain.