Heat Transfer Practice Problems
A food container has a total area of 0.242 m2. A warm liquid at 42°C is placed in the container. The temperature of the outer wall after thermal equilibrium has been established is found to be 35°C. The container loses heat to the surroundings at a rate of 2.4 mm. The container loses heat to the surroundings at a rate of 191 W. Using this data, determine the thermal conductivity of the material making the container.
An oven has its surface fitted with insulating 0.12 m2 rock wool that is 2.0 cm thick. At one instance of the oven's operation, the inner surface of the rock wool is at a temperature of 150°C and the outer surface has a temperature equal to room temperature (25°C). The thermal conductivity of rock wool is 0.040 W/m•K. Determine the heat current flowing through the rock wool insulation.
A 1.20 cm chromium cube (emissivity = 0.28) is used for heating. It is enclosed in a container that is nearly a vacuum, whose walls have a temperature of 283.0 K. Determine the rate of power supply to the cube that will keep it at a temperature of 811 K. Assume conduction by supports is negligible.
During a room heating exercise, a spherical 2.0 L container is filled with boiling water at 100°C. The emissivity of the container is 0.55 and the room temperature is 14.0°C. Determine the rate at which the water will lose heat through radiation.
A craftsman fabricates a 50.0 cm long aluminum bar that has a cross-sectional area of 5.07cm2. If the bar is used to transfer heat between reservoirs at TH = 100.0°C and TC = 25.0°C. Determine the steady-state temperature gradient for the bar.
A 0.400m long aluminum rod is joined end to end with a 0.750m copper rod for a heat transfer experiment. All sections on the compound rod have a cross-sectional area of 0.00860 m2. The copper end is inserted in boiling water while the aluminum end is inserted in an ice-water mixture. The experiment is conducted at atmospheric pressure. The rod is wrapped to prevent heat loss to the surroundings. Determine the mass of ice that will melt in 10 min using the heat supplied by the rod.