A 300 mm thick wall (k= 1.5 W/mK, p = 2600 kg/m³, cp = 1000 J/kg⚫K) has a uniform originaltemperature of 900 °C. At the time t = 0, its both surfaces are suddenly exposed to air (T∞ = 25 °C,h = 30 W/m²K).(a) Calculate the Biot number of the wall. Does it have a uniform temperature?(b) After 3 hours, what is the temperature at the middle plane (@x = 0)?Symmetry½L= 300 mmh = 30 W/m² KwallT∞ = 25°Ch = 30 W/m² KTo=25°C9. Ah (T-ToG=eptHot airxp = 2600 kg/m³k=1.5 W/m K900cHot airTr= 96warrume teNow.

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Answered: A 300 mm thick wall (k= 1.5 W/mK, p =…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

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A spherical shaped vessel of 1.4 m outer diameter is 90 mm thick. Find the rate of heat leakage, if the temperature difference between the inner and outer surfaces is 220°C. Thermal conductivity of the material of the sphere is 0.083 W/mK.
A long rod with a thermal conductivity of 1 W / m · K is subjected to the boundary conditions given in the figure. Find the temperature distribution in the steady state with the energy balance method for ∆x = ∆y = 0.2m. Also calculate the heat transfer between rod and fluid per unit length.
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Q3/ A stainless steel alloy has cylindrical shape (k = 25 W/m.°C), diameter is 10 cm and 25 cm long, taken to furnace. The initial temperature is 90 °C, the furnace temperature is 1260 °C and the heat transfer coefficient is h = 100 W/m2.'C. Determine the time required for a stainless steel alloy to reach 830 °C. Take thermal diffusivity (k/pc= 0.45 × 10-5 m²/s).
You are designing a 3m x 3m floor with radiant heating. The floor has 12 parallel pex pipes (k = 40 W/mK) of L = 3m, OD = 25mm and ID = 20mm. Hot water (TInfintiy 1 = 90oC, h = 200 W/m2K) runs through the pipes continuously. The surface below the pipes is perfectly insulated. Above the pipes, there is a 3mm layer of bonding material (? = 12 W/mK) and a 9mm layer of tile (k = 2 W/mK). Above the tile, there is air (TInfinity 2 = 25oC, h = 20 W/m2K). Properties of Air: k = 0.025 W/mK, Pr = 0.72, v = 1.847 x 10−5, u = 16.84 x 10−6, p = 1.2 kg/m3, B = 1/Tf (ideal gas), Hint: Assume that the “layer” of pipe starts at the center point (e.g. for conduction purposes, the pipe is OD divided by 2 thick). For convection, consider the entire pipe surface. a) What is the total heat rate entering the room above the floor? b) What is the temperature of the top of the tile?
Steaks (2 cm thick, k = 0.45 W/m - °C, « = 0.91 x 107 m2/s) usually have an original temperature of 25 °C. They will be cooled in a refrigeration room. The said room has a temperature of -11 °C. The heat transfer coefficient on both sides of the steak is 9 W/m2 - °C. How long will it take for both surfaces of the meat to be cooled to 2 °C? Assume the geometry of steaks to be a flat slab.
A thin bar of length L = 3 meters is situated along the x axis so that one end is at x = 0 and the other end is at x = 3. The thermal diffusivity of the bar is k = 0.4. The bar's initial temperature f(x) = 300 degrees Celsius. The ends of the bar (x = 0 and x = 3) are then put in an icy bath and kept at a constant O degrees C. Let u(x, t) be the temperature in the bar at x at timet, with t measured in seconds. Find u(x, t) and then u7 (2, 0.1). Put uz (2, 0.1) calculated accurately to the nearest thousandth (3 decimal places) in the answer box.
A 1800-W iron plate has a thickness of 4 mm, cross-sectional area of 340 cm^2. The room convection heat transfer coefficient is 20 W/(m^2K) with a temperature of 20 C. Determine the time required for the iron plate to drop from 850 C to 250 C? Density, specific heat value and conductivity of the plate are 2750 kg/m^3, 900 J/(kgK) and 180 W/(mK), respectively. 500 seconds 635 seconds O none 450 seconds 800 seconds
Steel cubes 10 mm in width are annealed by heating to 1,377 K and then slowly cooling to 469 K in an air environment for which T∞ = 301 K and h = 24 W/m2-K. Assuming the properties of the steel to be k = 24 W/m · K, ρ = 7,047 kg/m3, and c = 916 J/kg · K, estimate the time required for the cooling process.

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