Heat Transfer Questions and Answers – Heat Generation Through Sphere

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

1. Consider heat conduction through a solid sphere of radius R. There are certain assumptions
(i) Unsteady state conditions
(ii) One-dimensional radial conduction
(iii) Constant thermal conductivity
Identify the correct statements
a) i and iii
b) ii and iii
c) i, ii and iii
d) i and ii
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2. An 8 cm diameter orange, approximately spherical in shape, undergoes ripening process and generates 18000 k J/m³ hr of energy. If external surface of the orange is at 6.5 degree Celsius, find out the temperature at the center of the orange. Take thermal conductivity = 0.8 k J/ m hr degree for the orange material
a) 13.5 degree Celsius
b) 12.5 degree Celsius
c) 11.5 degree Celsius
d) 10.5 degree Celsius
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3. An 8 cm diameter orange, approximately spherical in shape, generates 18000 kJ/m³·hr of energy during ripening. Calculate the heat flow from the outer surface of the orange, assuming the thermal conductivity of the orange material is 0.8 kJ/m·hr·°C.
a) 4.82 k J/hr
b) 5.82 k J/hr
c) 6.82 k J/hr
d) 7.82 k J/hr
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4. What is the heat flow for steady state conduction for sphere?
a) 4 Q _R + Q _G = Q _{R + d R}
b) 3 Q _R + Q _G = Q _{R + d R}
c) 2 Q _R + Q _G = Q _{R + d R}
d) Q _R + Q _G = Q _{R + d R}
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5. The general solution for temperature distribution in case of solid sphere is
a) t = t _W + q _g (R ₂ – r ₂)/4 k
b) t = t _W + q _g (R ₂ – r ₂)/8 k
c) t = t _W + q _g (R ₂ – r ₂)/6 k
d) t = t _W + q _g (R ₂ – r ₂)/2 k
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6. A solid sphere of 8 cm radius has a uniform heat generation 0f 4000000 W/m³. The outside surface is exposed to a fluid at 150 degree Celsius with convective heat transfer coefficient of 750 W/m² K. If thermal conductivity of the solid material is 30 W/m K, determine maximum temperature
a) 444.45 degree Celsius
b) 434.45 degree Celsius
c) 424.45 degree Celsius
d) 414.45 degree Celsius
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7. A solid sphere of 8 cm radius has a uniform heat generation rate of 4,000,000 W/m³. The thermal conductivity of the sphere’s material is 30 W/m·K, and the sphere is exposed to a fluid at 150°C with a convective heat transfer coefficient of 750 W/m²·K. Determine the temperature at a radius of 5 cm.
a) 348.9 degree Celsius
b) 358.9 degree Celsius
c) 368.9 degree Celsius
d) 378.9 degree Celsius
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8. Identify the correct boundary condition for a hollow sphere with inside surface insulated
a) At r = r ₁, the conduction region is perfectly insulated
b) At r = r ₁, the conduction region is partially insulated
c) Heat flow is infinity
d) Heat flow is negative
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9. A hollow sphere (k = 30 W/m K) of inner radius 6 cm and outside radius 8 cm has a heat generation rate of 4000000 W/m³. The inside surface is insulated and heat is removed by convection over the outside surface by a fluid at 100 degree Celsius with surface conductance 300 W/m² K. Make calculations for the temperature at the outside surfaces of the sphere
a) 105.6 degree Celsius
b) 205.6 degree Celsius
c) 305.6 degree Celsius
d) 405.6 degree Celsius
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10. A hollow sphere with a thermal conductivity of 30 W/m·K has an inner radius of 6 cm and an outer radius of 8 cm. The sphere generates heat at a rate of 4,000,000 W/m³, and the inside surface is insulated. The outside surface is exposed to a fluid at 100°C with a surface conductance of 300 W/m²·K. Determine the temperature at the inside surface of the sphere.
a) 138.3 degree Celsius
b) 327.8 degree Celsius
c) 254.7 degree Celsius
d) 984.9 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.