In an annealing process, a 50-mm-thick stainless steel plate (p = 8238 kg/m, cp = 468 J/kg-K, k= 13.4Wim-K, and a= 3.48 106 m2/s) was reheated in a furnace from an initial uniform temperature of 230°C.The ambient temperature inside the furnace is uniform at 1000°C, and the convection heat transfercoefficient is 215 W/m2.K. If the entire stainless steel plate is to be heated to at least 61O'C, determine thetime that the plate should be heated in the furnace using the analytical one-term approximation method.The time that the plate should be heated in the furnace is

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Answered: In an annealing process, a 50-mm-thick…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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A 0.025-mm-diameter stainless steel wire having K =16 W/m • C is connected to two electrodes. The length of the wire is 80 cm and it is exposed to a convection environment at 20 •C with h = 500 W/m2 • •C. A voltage is impressed on the wire that produces temperatures at each electrode of 200 -C. Determine the total heat lost by the wire in cal/hr.
Pr
An ice chest whose outer dimensions are 30 cm*40 cm*40 cm is made of 3 cm thick Styrofoam (k = 0.033 W/m°C). Initially, the chest is filled with 30 kg of ice at 0 °C, and the inner surface temperature of the ice chest can be taken to be 0 °C at all times. The heat of fusion of water at 0 °C is 333.7 kJ/kg, and the surrounding ambient air is at 20 °C. Disregarding any heat transfer from the 40 cm*40 cm base of the ice chest, determine how long it will take for the ice in the chest to melt completely if the ice chest is subjected to (a) calm air and (b) winds at 30 km/h (assume the heat transfer coefficient on the front, back and top surfaces to be the same as that on the side surfaces). Use the thermophysical properties of air as follows: k = 25.5×10-3 W/mK, ν = 15×10-6 m2/s, α = 21.1×10-6 m2/s, and β = 3.43×10-3 K-1.
A long 3-mm diameter rod of steel (ρ = 7840 kg/m3, c = 460 J/kgK, k = 43 W/mK)has a uniform initial temperature of 650C. The rod is then suddenly immersed in alarge container of 25C water. The hot rod causes the water immediately surroundingthe rod to boil, giving rise to a heat transfer coefficient of 5600 W/m2K. The boilingstops when the rod reaches a temperature of 100C, at which time the heat transfercoefficient becomes 750 W/m2K. Find the time period during which boiling occursand the total time required for the rod to reach a temperature of 40C. Use acharacteristic length for this problem.
Not sure where I went wrong on this please show a drawing also
Consider a stainless steel spoon ( k = 8.7 Btu/hrft°F) partially immersed in boiling water at 200 deg * F in a kitchen at 75°F. The handle of the spoon has a cross section of 0.08in * 0.5in and extends 7 inches into the air from the free surface of the water. If the heat transfer coefficient at the exposed surfaces of the spoon handle is 3 Btu/hrft²°F, determine the temperature of the tip of the spoon handle. Assume that the heat loss from the tip of the spoon is negligible.
A poor heat-conducting copper alloy (k = 45 BTU – ft/hr – ft² – °F) is drawn into 0.012-ft diameter wire for a critical aerospace application in an electronics enclosure. The conditions within the enclosure are maintained at 90°F by a forced air-cooling system. To keep the copper alloy below 270°F and to maximize heat transfer, the wire is to be covered with insulation (k = 0.03 BTU – ft/hr – ft² – °F ). The effective film coefficient for the insulation has been conservatively estimated as 2.0 BTU/hr – ft2 – °F. - - What insulation thickness should be used over the wire to maximize heat transfer? 2.
based on a large 4 cm thick plate that is initially at a uniform temperature of 20°C that is heated by passing it through a space maintained at 500°C. The plate remains in the space for a period of 7 min. Take the heat transfer coefficient to be 120-W/m2°C. Example 4-4 [k = 110-W/m°C, r = 8530-kg/m³, C, = 0.380-kJ/kg°C, a = 33.9 x 10-6 m²/s] The dimensionless distance from center to a point 0.4-cm below the outer surface is 0.5 0.8 none of the above 0.2
Citrus fruits are very susceptible to cold weather, and extended exposure to subfreezing temperatures can destroy them. Consider an 8-cm-diameter orange that is initially at 15°C. A cold front moves in one night, and the ambient temperature suddenly drops to –6°C, with a heat transfer coefficient of 15 W/m2·K. Using the properties of water for the orange and assuming the ambient conditions to remain constant for 20400 seconds before the cold front moves out, determine the surface temperature of orange that night. Solve this problem using analytical one-term approximation method. The properties of the orange are approximated by those of water at the average temperature of about 5°C, k = 0.571 W/m·°C and α = 0.136 × 10–6 m2/s. The surface temperature of orange that night is
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
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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