Answer Happy

Q2 a) A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use of a composite window separating the oven cavity from the room air (Figure 2a). The composite is to consist of two high-temperature plastics (A and B) of thicknesses LA = 2Lg and thermal conductivities ka = 0.15 W/m K and kg 0.08 W/m K. During the self-cleaning process, the oven wall and air temperatures, Tw and T., are 400°C, while the room air temperature To is 25°C. The inside convection and radiation heat transfer coefficients hi and h, as well as the outside convection coefficient ho, are each approximately 25 W/m²K. What is the minimum window thickness, L = LA + LB, needed to ensure a temperature that is 50°C or less at the outer surface of the window? This temperature must not be exceeded for safety reasons. (15 marks)