1. The thermal resistance of A, B, C, and D are 1, 2, 2, 4 W/ °C, respectively. The total thermal resistance to the wall conductance will be TA - 200°C a. 9.0 W/ °C b. 5.5 W/ °C C. 6.0 W/ °C d. 16 W/°C 6 cm A B It 2 cm 2.5 cm + 3 cm D 4 cm Problem 1.34 Tp. = 50°C

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1. The thermal resistance of A, B, C, and D are 1, 2, 2, 4 W/ °C, respectively. The total
thermal resistance to the wall conductance will be
TAs = 200°C
a. 9.0 W/ °C
b. 5.5 W/ °C
C. 6.0 W/ °C
d. 16 W/ °C
a. 0.672
b. 0.232
C. 0.0672
d. 0.023289
a. 250 W/mK
b. 1.25 W/mK
6 cm
C. 0.25 W/mK
d. 0.125 W/mK
A
B
с
2 cm 2.5 cm
3 cm
g. 47.14%
h. 14.14%
3 cm
2. The heat transfer due to radiation from a surface of 2 cm² area at 800 °C to a very cold
enclosure is 5.0 W. Determine the emissivity of the surface at this temperature
D
4 cm
Problem 1.34
6 cm
3. An electric wire carrying current is covered with an insulating material. The critical
diameter of the insulation is 10 mm. The outside air has heat transfer coefficient of 25
W/m² K
TDs = 50°C
4. A hot potato is put in water bowl. Another hot potato of same temperature and size is
kept in open air at same temperature that of water. Which potato will cool quicker and
why?
a. Potato in water bowl, as there will high convection comparatively
b. Potato in water bowl, as there will high conduction comparatively
C. Potato in air, as there will high convection comparatively
d. Potato in air, as there will high conduction comparatively
5. The values of heat transfer coefficient, diameter of fin and thermal conductivity are
25 W/m² K, 0.01 m are 200 W/m K respectively. If the length of the long fin is 0.3 m,
then efficiency of the fin will be
e. 100%
f. 74.14%
Transcribed Image Text:1. The thermal resistance of A, B, C, and D are 1, 2, 2, 4 W/ °C, respectively. The total thermal resistance to the wall conductance will be TAs = 200°C a. 9.0 W/ °C b. 5.5 W/ °C C. 6.0 W/ °C d. 16 W/ °C a. 0.672 b. 0.232 C. 0.0672 d. 0.023289 a. 250 W/mK b. 1.25 W/mK 6 cm C. 0.25 W/mK d. 0.125 W/mK A B с 2 cm 2.5 cm 3 cm g. 47.14% h. 14.14% 3 cm 2. The heat transfer due to radiation from a surface of 2 cm² area at 800 °C to a very cold enclosure is 5.0 W. Determine the emissivity of the surface at this temperature D 4 cm Problem 1.34 6 cm 3. An electric wire carrying current is covered with an insulating material. The critical diameter of the insulation is 10 mm. The outside air has heat transfer coefficient of 25 W/m² K TDs = 50°C 4. A hot potato is put in water bowl. Another hot potato of same temperature and size is kept in open air at same temperature that of water. Which potato will cool quicker and why? a. Potato in water bowl, as there will high convection comparatively b. Potato in water bowl, as there will high conduction comparatively C. Potato in air, as there will high convection comparatively d. Potato in air, as there will high conduction comparatively 5. The values of heat transfer coefficient, diameter of fin and thermal conductivity are 25 W/m² K, 0.01 m are 200 W/m K respectively. If the length of the long fin is 0.3 m, then efficiency of the fin will be e. 100% f. 74.14%
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