Electrically heated draw batch furnaces are commonly used in the heat treatment industry. Consider a draw batch furnace front made of a 20-mm thick steel plate with a ther- mal conductivity of 25 W/m-K. The furnace is situated in a room with surrounding air temperature of 20°C and an aver- age convection heat transfer coefficient of 10 W/m²-K. If the inside surface of the furnace front is subjected to uniform heat flux of 5 kW/m² and the outer surface has an emissiv- ity of 0.30, determine the inside surface temperature of the furnace front. Turr = 20°C Furnace front 4, = 5 kW/m? Air, 20°C h = 10 W/m² K e = 0.30 k = 25 W/m-K To

The wall of a furnace consists of a 0.85 cm-thick layer of steel (ks = 15.1 W/m/K) and an outer layer of brick (kb = .72 W/m/K). The outer surface temperature of the brick, To = 50oC, and is exposed to convection with air at 20oC providing a heat transfer coefficient of 150 W/m^2/K. Determine the steady temperature at the steel brick interface, Tmid, and on the exposed steel surface, Ti, if the brick layer has thickness Lb = 5 cm.

Homework problem for unsteady-state heat transfer Consider a product to be sterilized if its coldest location during heating reaches 115°C. Consider sterilization of potatoes where potatoes (4 cm diameter) is heated in steam at 121°C. Assume symmetrical heating of potatoes and the heat transfer coefficient between the steam and the potatoes is 20 W/m² K. The thermal diffusivity for potatoes is 1.5 × 107m²/s and the thermal conductivity is 0.4 W/m K. The potatoes are initially at 30°C. 1) Calculate the heating time needed for sterilization. 2) Calculate the temperature at the center of the potato after heating 1000 s and 2000 s. Plot how the temperature at the center changes with time t. 3) Calculate the temperature at the surface of the potato at 2000 s. Qualitatively plot how the temperature changes across the apple at t = 2000 s.

The 10-mm-thick bottom of a 200-mm-diameter pan may be made from aluminum (k = 240 W/m-K) or copper (k = 390 W/m-K). When used to boil water, the surface of the bottom exposed to the water is nominally at 110°C and heat is transferred from the stove to the pan at a rate of 1200 W. What is the temperature of the surface in contact with the stove for each of the two materials? Aluminum: T = i °C Copper: T = °C Physical Properties Mathematical Functions