GATE MT Radiation PYQs & Answers

Questions 1–9 of 9. Imported answers require independent review unless marked reviewed.

A cylindrical furnace has 0.1 m inner diameter and 0.2 m height. Walls A₁ (inner section of cylindrical surface area) and A₂ (inner section of bottom surface area) are maintained at 1873 K. The sides and bottom are assumed to be black bodies, well insulated and heated electrically. The top area (A₃) is open to atmosphere maintained at 300 K, resulting in loss of heat ‘q̇’.

Given: View factors F₁₃ = 0.1175 and F₂₃ = 0.06, where Fᵢⱼ is the fraction of radiation leaving surface ‘i’ that is intercepted by surface ‘j’.

Stefan-Boltzman constant = 5.67 × 10⁻⁸ W/m²-K⁴

The power needed to maintain the furnace at 1873 K is (approximate to the nearest integer) _________________ W.

Diagram for Metallurgical Engineering question 59

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Radiative heat flux

at a hot surface at a temperature

can be expressed as

where

is a constant and

is the temperature of the surroundings (temperatures are expressed in K). The function

is given by _____.

Your answerChoose one option.

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A long metallic cylindrical rod of radius

, length

(

) and electrical resistivity

is kept in vacuum and is carrying an electric current of

. The only way it loses heat to the ambient is via radiation. If the ambient temperature is

, then the steady-state temperature of the rod is ________

. (Round off to the nearest integer).

Given: Stefan-Boltzmann constant =

Neglect the heat loss by the two flat ends of the rod and assume emissivity = 1.

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Match the transport processes in Column I with the relationships in Column II.

Column I (P) Molecular momentum transport (Q) Molecular mass transport (R) Molecular energy transport (S) Radiation energy transport

Column II (1) Stefan-Boltzmann law (2) Newton’s law of viscosity (3) Fick’s law (4) Fourier law

Your answerChoose one option.

P – 2, Q – 3, R – 4, S – 1

P – 4, Q – 3, R – 2, S – 1

P – 3, Q – 1, R – 4, S – 2

P – 2, Q – 1, R – 4, S – 3

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Two circular surfaces A and B with the values of emissivity

, temperature T, and respective view factors are shown in the figure. Consider heat radiation only between surfaces A and B.

Diagram for Metallurgical Engineering question 58

Given: Stefan-Boltzmann constant,

Net heat flow rate by radiation from surface A in kW is __________ (round off to 1 decimal place).

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Which of the following statement(s) is(are) TRUE about black body radiation?

Your answerSelect all correct options. You can choose more than one.

Among all radiation emitted by an ideal black body at room temperature, the most intense radiation falls in the visible light spectrum

The total emissive power of an ideal black body is proportional to the square of its absolute temperature

The emissive power of an ideal black body peaks at a wavelength

which is inversely proportional to its absolute temperature

The radiant energy emitted by an ideal black body is greater than that emitted by the non-black body at all temperatures above 0 K

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A solid sphere (0.5 m radius) is enclosed within a larger hollow sphere (1 m radius), as shown in figure. The radiation exchange takes place between the outer surface (surface 1) of the small sphere and the inner surface (surface 2) of the bigger sphere. The value of the view factor, F₂₂ is: ________ (round off to 2 decimal places).

Given: View factor (Fᵢⱼ) is the fraction of the radiation leaving surface i that is intercepted by surface j.

Diagram for Metallurgical Engineering question 55

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Select the correct spectra (shown on a log-log scale in the figures) for emission from a gray surface and a black body, both maintained at 1000 K.

Your answerChoose one option.

Diagram for Metallurgical Engineering question 12

Diagram for Metallurgical Engineering question 12 (figure 2)

Diagram for Metallurgical Engineering question 12 (figure 3)

Diagram for Metallurgical Engineering question 12 (figure 4)

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A continuous cast steel slab, 1 m × 1 m × 0.1 m, at 1298 K cools in air. The initial rate of heat loss (in kW) from the top surface of slab by radiation and convection is __________ (answer up to two decimal places)

Given: (i) Ambient temperature = 298 K, (ii) emissivity of steel = 0.8, (iii) convective heat transfer coefficient = 4.6 W m

, (iv) Stefan-Boltzmann constant (

) =

W m

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GATE MT Radiation PYQs

How to practice Radiation

Question 59

Question 39

Question 59

Question 37

Question 58

Question 43

Question 55

Question 12

Question 32