4-38 Carbon steel balls (p = 7833 kg/m2, k = 54 W/m K, c = 0.465 kJ/kg°C, and a 1.474 - 10-6 m2/s) 8 mm in diameter are annealed by heating them first to 900°C in a furnace and then page 300allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m2-K, determine how long the annealing process will take. If 2500 balls are to be annealed perhour, determine the total rate of heat transfer from the balls to the ambient air.FIGURE P4-38Air, 35°CFurnaceSteel ball 100C900°C

Assumptions:The balls have constant thermal properties.The shape of the balls is spherical having…

Answered: 4-38 Carbon steel balls (p = 7833…

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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I only need help with the assumptions ,don't need any work of how to solve. also could use help with how to draw the free body diagrams
A long rod of AISI 4130 steel initially at a uniform temperature of 400°C is suddenly exposed to 20°C air, where the heat transfer coefficient is 15 W/m2-K. The rod has a diameter of 4.8 cm. How long after being exposed to the 20°C air will the steel rod reach a temperature of 60°C? The properties of the rod are p = 7840 kg/m³, Cp = 460 J/kg.K and k = 43 W/m.K.
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An ordinary egg can be approximated as a 5.5-cm-diameter sphere whose thermal conductivity of roughly W overall density of p= 1000. mk' kg m² and heat capacity of Cp = 3000; kgk k = 0.6- : The egg is initially at a uniform temperature of T₁ = 10°C and is dropped into boiling water at T = 90°C Taking the convective heat transfer coefficient to be h = 10. - determine how long it will take for the egg to W m²K reach T = 70°C. In solving this problem, please use the One-term approximation model to compute the time needed by the center of the egg and the surface of the egg to reach the desired temperature of 70 C Please discuss the difference between the three results. In solving the problem, please follow the steps below. For the One-term approximation: 1. Compute the Biot number, use the egg radius (not the diameter) as the characteristic length T-Too 2. Compute the non-dimensional excess temperature 0 = Ti-Too 3. Look up in the table the values for A₁ and ₁ for the Biot number found…
In determining the average rate of heating of a tank of 20% sugar syrup, thetemperature at the beginning was 20°C and it took 30 min to heat to 80°C. Thevolume of the sugar syrup was 50 ft3 and its density 66.9 lb/ft3. The specific heat ofthe sugar syrup is 0.9 Btu lb-1°F-1.(a) Convert the specific heat to kJ kg-1°C-1.(b) Determine the rate of heating, that is the heat energy transferred in unit time, in SI units (kJ s-1)
Heat Transfer Course Copper balls with an initial temperature of 200 degrees centigrade(ρ = 8933 kg / m3, k = 401 W / m oC, cp = 385 J / kg oC, α = 1.166 * 10-4 m2 / s) in air at 30 degrees centigrade 2 it is allowed to cool down for a period of minutes. Since the balls are 2 cm in diameter and the heat transfer coefficient is 80 W / m2 oC,a) What is the temperature of the balls at the end of the cooling process?b) If 1000 balls per hour are left to be cooled, what is the total heat transfer from the balls to the air?
A 6.0 mm thick plate of pure copper has an initial temperature of 90°C. The plate is then suddenly immersed in 20°C water where the heat transfer coefficient is 250 W/m²-K. Show that the plate is lumped, and then find the time required for the plate to achieve a temperature of 40°C.
A pure copper cube 3 cm on each side is placed in a 15°C stream of water.If the initial temperature of the cube is initially at 215°C, how long does it take the cube to drop to 25°C? The convective heat transfer coefficient is 80W/m2∙K. Justify any assumptions.
In an annealing process, a 50-mm-thick stainless steelplate (r = 8238 kg/m3, cp = 468 J/kg·K, k = 13.4 W/m·K,and a = 3.48 * 10–6 m2/s) was reheated in a furnace from aninitial uniform temperature of 230°C. The ambient temperatureinside the furnace is at a uniform temperature of 1000°Cand has a convection heat transfer coefficient of 215 W/m2·K.If the entire stainless steel plate is to be heated to at least600°C, determine the time that the plate should be heated inthe furnace using (b) the Heisler char.
3- A building wall consists of 25 cm concrete (K= 1.75 W/m.K) and 1.9 cm plaster (K= 87 W/m.K) on the inside surface. The outside temperature is -18°C, while the room is held at 23.5°C DBT and 16.8°C WBT. (a) What is the temperature on the inside wall surface. (b) Will the moisture condense on the wall. (c) How many layers of 1.25 cm thick fiber-board insulation (K= 0.048 W/m.K) should be applied on the inside wall surface to prevent moisture to condense on it.
For heat transfer purposes, an egg can be considered to be a 5.5-cm-diameter sphere having the properties of water. An egg that is initially at 8°C is dropped into the boiling water at 86°C. The heat transfer coefficient at the surface of the egg is estimated to be 800 W/m2-K. If the egg is considered cooked when its center temperature reaches 60°C, determine how long the egg should be kept in the boiling/water. Solve this problem using analytical one-term approximation method (not the Heisler charts). The length of/time for the egg to be kept in boiling water is determined to be min.
A long 20 cm diameter shaft made of stainless steel 304 comes out of an oven at a uniform temperature of 600°C. The shaft is then allowed to cool slowly in an environment at 200°C with an average heat transfer coefficient of h = 80 W/m².K. Determine [a] the temperature at the center of the shaft and [b] the temperature of the outer surface of the shaft 45 minutes after the start of the cooling Given: Find: Schematic: Assume: Property Data: k= 14.9 W/m°C p= 7900 kg/m³ Cp = 477 J/kg:K a= 3.95 x 10-6 m²/s

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