A 150 mm thick wall (k = 1.5 W/m•K, p = 2600 kg/m³, cp = 1000 J/kg⚫K) is well insulated at its left surface. The wall has a uniform original temperature of 25 °C, and its right surface is suddenly exposed to hot air (T = 900 °C, h = 30 W/m²K). (a) Calculate the Biot number of the wall. Does it has a uniform temperature? (b) After 2 hours, what is the temperature of the left surface? L = 150 mm knowns: ptions: dy flow p = 2600 kg/m³ k 1.5 W/m K Ts = 25°c wall h = 30 W/m² K Too 900 C1173K = 11 Hot air += 0.15m 1-1.5 W mk P = 2000 kg Cp 1000 m3 r kg ki T= 25°C 298K plane wall: Le L

Troom = 25°C Problem-4: An 8-m-internal-diameter spherical tank made of 1.5-cm-thick stainless steel (k = 15 W/m-K) is used to store iced water at 0°C. The tank is located in a room whose temperature is 25°C. The walls of the room are also at 25°C. The outer surface of the tank is black (emissivity = 1), and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m²-K and 10 W/m².K, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a 24-h period. The heat of the fusion of water at atmospheric pressure is hf5 333.7 kJ/kg. Iced water D D₁= 8 m Tin = 0°C 1.5 cm

The 0.5 m x 1.2 m wall of an industrial furnace is constructed from L = 0.15-m-thick fireclay brick having a thermal conductivity of 1.7 W/m-K. The temperature distribution, at an instant in time, is T(x) = a + bxwhere a = 1400 K and b = -950 K/m. Determine the heat fluxes, q, and heat rates, q,, atx = 0 and.x = L, in W/m2 and W respectively. Do steady-state conditions exist? i W/m? i W/m? Ix=0 = i W i W Ix=L = Steady-state conditions exist. ||

A 10 cm-thick beef steak is being frozen in a -40°C room. The product has 73% moisture content, density of 970 kg/m³, and thermal conductivity (frozen) of 1.1 W/(m K). Estimate the freezing time using Plank’s equation. The product has an initial freezing temperature of  -1.75°C, and the movement of air in the freezing room provides a convective heat-transfer coefficient of 10 W/(m² K). a. tf =... h