Q3( 12 marks): Consider a 0.6 m x 0.6 m thin square plate in a room at 30 C. one side of the plate is maintained at a temperature of 74 C while the other side is insulated. Determine the rate of heat transfer from the plate by natural convection if the plate. 1. Horizontal with hot surface facing up. 2. Horizontal with hot surface facing down. Air properties are : k=0.0279 W/m.C, Pr-0.708, v=1.815x 10-3 m2/s, B= 0.00308/ K

Q3( 12 marks): Consider a 0.6 m x 0.6 m thin square plate in a room at 30 C. one side of the plate is maintained at a temperature of 74 C while the other side is insulated. Determine the rate of heat transfer from the plate by natural convection if the plate. 1. Horizontal with hot surface facing up. 2. Horizontal with hot surface facing down. Air properties are : k=0.0279 W/m.C, Pr-0.708, v=1.815x 10-3 m2/s, B= 0.00308/ K

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) A 50 mm diameter carbon steel tube (ρ = 7833 kg/m3; Cp = 465 J/kg.K, k = 54 W/mK) at an initial uniform temperature of 18°C is heated in an oven with air circulation that is at a temperature of 250°C and has a convection heat transfer coefficient of 45 W/m2.K. How long must the tube be in the oven for the surface temperature to reach 100°C? b) The figure below illustrates the temperature distribution inside a flat solid at two instants for two different situations (A and B). In both situations is there heat transfer? What causes them to behave differently?
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Q2. Two concentric spheres of diameters 15 cm and 25 cm are separated by air at 1 atm pressure. The surface temperatures of the two spheres enclosing the air are 71=350 K and 72=275 K, respectively. Determine the rate of heat transfer from the inner sphere to the outer sphere by natural convection.
a) A 50 mm diameter carbon steel tube (ρ=7833 kg/m³; Cp = 465 J/kg.K, k = 54 W/mK) at an initial uniform temperature of 18°C is heated in an oven with air circulation that is at a temperature of 250°C and has a convection heat transfer coefficient of 45 W/m².K. How long must the tube be in the oven for the surface temperature to reach 100°C? b) The figure below illustrates the temperature distribution inside a flat solid at two instants for two different situations (A and B). In both situations is there heat transfer? What causes them to behave differently?
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Pls answer q3(as I am still not sure whether or not I did q2 correctly)
Q) An apple has been put into a freezer at (-18°C) to be cooled. Initially, the apple is at a uniform temperature of 17°C. The convection heat transfer coefficient on its surface is 6 W/m2°C. Assuming the apple as a sphere having a diameter of 10-cm and taking its properties as p = 750 kg/m³, p = 2850 J/kg°c, and k = 0.450 W/m°C, determine; (a) the center temperature of the apple in 45 minutes, (b) the actual amount of heat transfer from the apple, and (c) the final equilibrium temperature of the apple. Hint: consider the temperature is a function of location and time.
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نقطتان )2( A sphere ( k=204 W/m K) with inner diameter 4 cm and outer diameter of 8 cm. The inside temperature is 100C and the outer temperature 50 C. Calculate the rate of heat transfer
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