Air at a pressure of 90 psia and a temperature of 250 F enters an ideally designed converging-diverging nozzle from a large plenum chamber. The air is supposed to expand to ambient pressure without any shock wave present. (Assume isentropic expansion of dry air). Find (a) the area of the nozzle throat in square inches that will permit a mass flow rate of 3.0 lbm/s and (b) the Mach number and area at the nozzle exit

Consider a large isothermal enclosure that is maintained at a uniform temperature of 2000 k. calculate the emissive power of the radiation that emerges from a small aperture on the enclosure surface. what is the wavelength ? , below which 10% of the emission is concentrated? what is the wavelength ? 2 above which 10% of the emission is concentrated? determine the wavelength at which maximum spectral emissive power occurs. what is the irradiation incident on a small object placed inside the enclosure?

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

Modern high speed trains do not have perpendicular expansion gaps where rails are joined end-to-end any more they are mostly welded together but what might happen if there was a spell of particularly hot weather that causes inspection of the tracks?