A small oven consists of a cubical box of dimension L = 0.1 m , as shown. The floor of the box consists of a heater that supplies P = 400 W . The remaining walls lose heat to the surroundings outside the oven. which maintains their temperatures at T 3 = 400 K . A spherical object of diameter D = 30 mm is placed at the center of the oven. Sometime after the sphere is placed in the oven, its temperature is T 1 = 420 K . All surfaces have emissivities of 0.4. (a) Find the following view factors: F 1 2 , F 1 3 , F 2 1 , F 3 1 , F 2 3 , F 3 2 , F 3 3 . (b) Determine the temperature of the floor and the net rate of heat transfer leaving the sphere due to radiation. Is the sphere under steady-state conditions?
A small oven consists of a cubical box of dimension L = 0.1 m , as shown. The floor of the box consists of a heater that supplies P = 400 W . The remaining walls lose heat to the surroundings outside the oven. which maintains their temperatures at T 3 = 400 K . A spherical object of diameter D = 30 mm is placed at the center of the oven. Sometime after the sphere is placed in the oven, its temperature is T 1 = 420 K . All surfaces have emissivities of 0.4. (a) Find the following view factors: F 1 2 , F 1 3 , F 2 1 , F 3 1 , F 2 3 , F 3 2 , F 3 3 . (b) Determine the temperature of the floor and the net rate of heat transfer leaving the sphere due to radiation. Is the sphere under steady-state conditions?
Solution Summary: The author calculates the view factor using the reciprocity. The length of the surface is L=0.1m.
A small oven consists of a cubical box of dimension
L
=
0.1
m
, as shown. The floor of the box consists of a heater that supplies
P
=
400
W
. The remaining walls lose heat to the surroundings outside the oven. which maintains their temperatures at
T
3
=
400
K
. A spherical object of diameter
D
=
30
mm
is placed at the center of the oven. Sometime after the sphere is placed in the oven, its temperature is
T
1
=
420
K
. All surfaces have emissivities of 0.4.
(a) Find the following view factors: F12, F13, F21, F31, F23, F32, F33. (b) Determine the temperature of the floor and the net rate of heat transfer leaving the sphere due to radiation. Is the sphere under steady-state conditions?
In addition , the space between the upper cap, the lower cap, and the cylindrical wall is filled with linear insulating material of permeability u.
A window panel that measures 20.0 cm by 15.0 cm is set into the front door of a house. The glass is 0.32 cm thick. The temperature outdoors is −15°C and inside is 22°C. The single-paned window is replaced by a double-paned window with an argon gas gap of 12mm between the two panes. The inner surface of the inner pane is at 22°C, and the outer surface of the outer pane is at −15°C. ( C glass=0.63 W/mK)Specific heat of Argon is 0.52 J/g K. Latent Heat of Fusion of Argon is 1.188 kJ/mol
.calculat and compare the heat transfers
Can u continue the question 5 to 7
5. Calculate the change in heat energy of the submarine’s outer haul, when it descends from the surface to a depth of 3,500m (with an average temperature of 20°C).
6. Calculate the power of the submarine’s electrical heater needed, to maintain the interior of outer hull at 30°C. The exterior of outer hull is 10°C. (Assume heat of the submarine is only lost across the outer hull)
7. Suggest aerospace applications of ballast.
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