Air at 20◦C blows over a hot plate 50 by 75 cm maintained at 250◦C. The convection heat-transfer coefficient is 25 W/m2◦C. Calculate the heat transfer. Assuming that the plate is made of carbon steel (1%) 2 cm thick and that 300 W is lost from the plate surface by radiation, calculate the inside plate temperature.

A circular pipe with inner diameter of 0.02 m has its inner surface covered with water at 300K. Dry air is flowing inside the pipe at the velocity of 0.8 m/s. The temperature of air is 300K and its pressure is at 1 atm. Calculate: a) Mass transfer from the 0.01 m length pipe b) Rate of heat transfer from pipe to air by mass convection and heat convection

You have an object with a characteristic length of 1.8 cm. For the following conditions, determine the Rayleigh Number (evaluate the fluid properties at the film temperature): a) Water at a free-stream temperature of 50°C; object at a temperature of 14°C. b) Unused Engine Oil, at a temperature of 13°C; object at a temperature of 61°C. c) Air at atmospheric pressure, and a temperature of 11°C; object at a temperature of 43°C.

In cold climates, weather reports usually give both the actual air temperature and the "wind-chill" temperature, which can be interpreted as follows. At the prevailing wind speed there is a rate of heat loss per unit area q, from a clothed person for an air temperature Te. The wind-chill temperature Twe is the air temperature that will give the same rate of heat loss on a calm day. Estimate the wind-chill temperature on a day when the air temperature is -10°C and the wind speed is 10m/s, giving a convective heat transfer coefficient of 50 W/m² K. A radiation heat transfer coefficient of 5 W/m² K can be used, and under calm conditions the convective heat transfer coefficient can be taken to be 5.0 W/m² K. Assume a 3 mm layer of skin (k = 0.35 W/m K), clothing equivalent to 8 mm-thick wool (k = 0.05 W/m K), and a temperature of 35°C below the skin. Also calculate the skin outer temperature.