A 1 m diameter cylinder, 1 m long, is maintained at 800 K and has an emissivity of 0.65. Another cylinder, 2 m in diameter and 1 m long, encloses the first cylinder and is perfectly insulated. Both cylinders are placed in a large room maintained at 300 K. Calculate the heat lost by the inner cylinder.

The work done when a gas is expanded in a cylinder is -220 J. A heat transfer of 190 J occurs from the surrounding to the gas. Calculate ∆E of the gas in J.

31 For approximate calculations, the sun may be considered a black body, emitting radiation with a maximum intensity at λ = 0.5 microns (5000 Å). With this information, estimate (a) the surface temperature of the sun, and (b) the emitted heat flux at the sun's surface.

A large slab of aluminum has a thickness of 10 cm and is initially uniform in temperatureat 400◦C. It is then suddenly exposed to a convection environment at 90◦Cwith h=1400 W/m2 · ◦C. How long does it take the center to cool to 180◦C?

The horizontal roof of a building has an emittance of 0.9. Air temperature is 1°C on a clear night. Sky acts as a black radiation sink at -60°C. If the underside of the roof is well insulated, estimate the roof temperature. Assume a convective heat transfer coefficient of 5 W/m2 K.

The wall of a spherical steel tank k, = 17 m. K thick contains hot oil at 100°C. On the outside of the tank 10mm of spray W urethane insulation k, = 0.026 m. K of 1m in diameter and 100 mm h = 16. is added to stop the oil from cooling. If the outside temperature is 25°C, W m².K needs to be added to keep the tank at 100°C for pumping reasons? What are the overall heat transfer coefficients (Uo and Ui)? and h = 5 (₁ m². K how much heat