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You need to login to ask any Questions from chapter Steady-State-Conduction of Heat-Transfer

Chapter:

Steady-State-Conduction

1. Consider above problem, what should be emissivity of a polished aluminum shield placed between m if heat flow is to be reduced to 40 percent of its original value?

0.337 0.347 0.357 0.367

0.347

(F _g)₁₂ = 1/E ₁ +1/E₂ +2/E ₃ ? 2 = 7.936.

Hint Answer

2. Find shape factor F ₁₂ for arrangement shown in figure. The areas A ₁and A₂are perpendicular but do not share common edge

$Find shape factor F 12 for arrangement shown in figure. The areas A 1 and A 2 are perpendicular but do not share common edge\r\n$

0.03 0.04 0.05 0.06

0.04

A₅= A ₁+ A ₃and A ₆= A ₂+ A ₄. The sequence of solution is, A ₅ F₅₆= A ₁F ₁₆+ A ₃ F ₃₆.

Hint Answer

3. Radiation shield is used between emitting surfaces such that

To reduce overall heat transfer To increase overall heat transfer To increase density To reduce density

To reduce overall heat transfer

Many situations are encountered where it is desired to reduce overall heat transfer between two radiating surfaces.

Hint Answer

4. What is shape factor of hemispherical surface closed by a plane surface of diameter d?

0 1.5 1 0.5

0.5

F ₁₁ + F₁₂ = 1 and F ₂₁ = 1. Therefore, F ₁₁ = 0.5.

Hint Answer

5. A 250 mm by 250 mm ingot casting, 1.5 m high and at 1225 K temperature, is stripped from its mold. The casting is made to stand on end on floor of a large foundry whose wall, floor and roof can be assumed to be at 300 K temperature. Make calculation for rate of radiant heat interchange between casting and room. The casting material has an emissivity of 0.85

161120 W 171120 W 181120 W 191120 W

171120 W

Q ₁₂= F ₁₂A ₁?_b(T ₁⁴ ? T ₂⁴). F ₁₂ = 0.85 and A ₁ = (0.25)² + 4(1.5) (0.25) = 1.5625 m².

Hint Answer

6. Two opposed, parallel, infinite planes are maintained at 420 K and 480 K. Calculate net heat flux between se planes if one has an emissivity of 0.8 and or an emissivity of 0.7

534.86 W/m² 634.86 W/m² 734.86 W/m² 834.86 W/m²

734.86 W/m²

Q ₁₂ = (F _g)₁₂A ₁ ? _b (T ₁⁴? T₂⁴) and (F _g)₁₂ = 1/ (I/E ₁ ? 1) + 1/F₁₂ + (I/E ₂ ? 1) A₂/A ₁.

Hint Answer

7. Two parallel square plates, each 4 m² area, are large compared to a gap of 5 mm separating m. One plate has a temperature of 800 K and surface emissivity of 0.6, while or has a temperature of 300 K and surface emissivity of 0.9. Find net energy exchange by radiations between plates

61.176 k W 51.176 k W 41.176 k W 31.176 k W

51.176 k W

Q ₁₂ = (F _g)₁₂ A₁?_b (T ₁⁴ ? T₂⁴).

Hint Answer

8. Establish a relation for shape factor for a conical cavity with respect to itself of depth h and diameter d. The cavity is closed on its outer surface with a flat plate

$Establish a relation for shape factor for a conical cavity with respect to itself of depth h and diameter d. The cavity is closed on its outer surface with a flat plate\r\n$

1 – d/ (4 h ² + d) ^1/2 1 – d/ (4 h ² + d ²) ^1/2 1 – d/ (4 h + d ²) ^1/2 1 – d/ (h ² + d ²) ^1/2

1 – d/ (4 h ² + d ²) ^1/2

F ₁₁ = 1 ? A ₂/ A ₁ = 1 ? 2 sin ? = 1 ? d/ (4 h ² + d ²) ^�.

Hint Answer

9. What is value of grey body factor for concentric cylinders?

3/ [1 – e ₁/e₁ + 1 + 1 – e ₂/e₂ (A ₁/A ₂)]. 4/ [1 – e ₁/e₁ + 1 + 1 – e ₂/e₂ (A ₁/A ₂)]. 1/ [1 – e ₁/e₁ + 1 + 1 – e ₂/e₂ (A ₁/A ₂)]. 2/ [1 – e ₁/e₁ + 1 + 1 – e ₂/e₂ (A ₁/A ₂)].

1/ [1 – e ₁/e₁ + 1 + 1 – e ₂/e₂ (A ₁/A ₂)].

Here, F ₁₂ = 1.

Hint Answer

10. The interchange factor is also known as

Equivalent emissivity Irradiation Radiosity Shape factor

Equivalent emissivity

The interchange factor is also known as equivalent emissivity.

Hint Answer

Nexttt

All Chapters

View all Chapter and number of question available From each chapter from Heat-Transfer

Definitions and Basic Concepts

Definitions and Basic Concepts

Fourier Equation and Thermal Conductivity

Fourier Equation and Thermal Conductivity

Steady State Conduction

Steady State Conduction

Conduction with Heat Generation

Conduction with Heat Generation

Heat Transfer from Extended Surfaces

Heat Transfer from Extended Surfaces

Transient (Unsteady State Heat Conduction)

Transient (Unsteady State Heat Conduction)

Radiation : Processes and Properties

Radiation : Processes and Properties

Radiation : Exchange between Surfaces

Radiation : Exchange between Surfaces

Convection : Processes and Properties

Convection : Processes and Properties

Dimensional Analysis

Dimensional Analysis

Empirical Correlations for Free and Forced convection

Empirical Correlations for Free and Forced convection

Condensation and Boiling

Condensation and Boiling

Hydrodynamic and Thermal Boundary Layers

Hydrodynamic and Thermal Boundary Layers

Heat Exchangers and Mass Transfer

Heat Exchangers and Mass Transfer

Topics

This Chapter Steady-State-Conduction consists of the following topics

Radiation : Exchange between Surfaces

Consider above problem, what should be emissivity of a polished aluminum shield placed between m if heat flow is to be reduced to 40 percent of its original value?

Find shape factor F ₁₂ for arrangement shown in figure. The areas A ₁and A₂are perpendicular but do not share common edge

$Find shape factor F 12 for arrangement shown in figure. The areas A 1 and A 2 are perpendicular but do not share common edge\r\n$

;

Radiation shield is used between emitting surfaces such that

What is shape factor of hemispherical surface closed by a plane surface of diameter d?

A 250 mm by 250 mm ingot casting, 1.5 m high and at 1225 K temperature, is stripped from its mold. The casting is made to stand on end on floor of a large foundry whose wall, floor and roof can be assumed to be at 300 K temperature. Make calculation for rate of radiant heat interchange between casting and room. The casting material has an emissivity of 0.85

Two opposed, parallel, infinite planes are maintained at 420 K and 480 K. Calculate net heat flux between se planes if one has an emissivity of 0.8 and or an emissivity of 0.7

Two parallel square plates, each 4 m² area, are large compared to a gap of 5 mm separating m. One plate has a temperature of 800 K and surface emissivity of 0.6, while or has a temperature of 300 K and surface emissivity of 0.9. Find net energy exchange by radiations between plates

Establish a relation for shape factor for a conical cavity with respect to itself of depth h and diameter d. The cavity is closed on its outer surface with a flat plate

$Establish a relation for shape factor for a conical cavity with respect to itself of depth h and diameter d. The cavity is closed on its outer surface with a flat plate\r\n$

;

What is value of grey body factor for concentric cylinders?

The interchange factor is also known as

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