Heat Transfer Questions and Answers – Conduction Through a Sphere

This set of Heat Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Conduction Through A Sphere”.

1. The temperature distribution associated with radial conduction through a sphere is represented by
a) Parabola
b) Hyperbola
c) Linear
d) Ellipse
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2. The thermal resistance for heat conduction through a spherical wall is
a) (r₂-r₁)/2πkr₁r₂
b) (r₂-r₁)/3πkr₁r₂
c) (r₂-r₁)/πkr₁r₂
d) (r₂-r₁)/4πkr₁r₂
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3. The rate of conduction heat flow in case of a composite sphere is given by
a) Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r₃ – r₂ )/4πk₂r₂r₃
b) Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r₃ – r₂ )/4πk₂r₂r₃
c) Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r₃ – r₂ )/4πk₂r₂r₃
d) Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r₃ – r₂ )/4πk₂r₂r₃
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4. The thermal resistance for heat conduction through a hollow sphere of inner radius r₁ and outer radius r₂ is
a) r ₂ – r ₁/4πk r ₁r ₂
b) r ₂ /4πk r ₁r ₂
c) r ₁/4πk r ₁r ₂
d) 4πk r ₁r ₂
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5. A spherical vessel of 0.5 m outside diameter is insulated with 0.2 m thickness of insulation of thermal conductivity 0.04 W/m degree. The surface temperature of the vessel is – 195 degree Celsius and outside air is at 10 degree Celsius. Determine heat flow per m² based on inside area
a) – 63.79 W/m²
b) – 73.79 W/m²
c) – 83.79 W/m²
d) – 93.79 W/m²
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6. The quantity d t/Q for conduction of heat through a body i.e. spherical in shape is
a) ln (r₂/r₁)/2πLk
b) ln (r₂/r₁)/πLk
c) ln (r₂/r₁)/2Lk
d) ln (r₂/r₁)/2πk
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7. A spherical vessel of 0.5 m outside diameter is insulated with 0.2 m thickness of insulation of thermal conductivity 0.04 W/m degree. The surface temperature of the vessel is – 195 degree Celsius and outside air is at 10 degree Celsius. Determine heat flow
a) – 47.93 W
b) – 57.93 W
c) – 67.93 W
d) – 77.93 W
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8. If we increase the thickness of insulation of a circular rod, heat loss to surrounding due to
a) Convection and conduction increases
b) Convection and conduction decreases
c) Convection decreases while that due to conduction increases
d) Convection increases while that due to conduction decreases
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9. The following data pertains to a hollow cylinder and a hollow sphere made of same material and having the same temperature drop over the wall thickness
Inside radius = 0.1 m and outside surface area = 1 square meter
If the outside radius for both the geometrics is same, calculate the ratio of heat flow in the cylinder to that of sphere?
a) 0.056
b) 2.345
c) 1.756
d) 3.543
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10. The oven of an electric store, of total outside surface area 2.9 m² dissipates electric energy at the rate of 600 W. The surrounding room air is at 20 degree Celsius and the surface coefficient of heat transfer between the room air and the surface of the oven is estimated to be 11.35 W/m ² degree. Determine the average steady state temperature of the outside surface of the store

a) 38.22 degree Celsius
b) 48.22 degree Celsius
c) 58.22 degree Celsius
d) 68.22 degree Celsius
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Sanfoundry Global Education & Learning Series – Heat Transfer.

To practice all areas of Heat Transfer, here is complete set of 1000+ Multiple Choice Questions and Answers.

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