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GATE 2019: Heat Transfer Super Quiz-2

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Question 1

A small sphere of outer area 2.4 m² is totally enclosed by a large cubical hall. The shape factor of hall w.r.t sphere is 0.004. What is the measure of the internal side of the cubical hall (in meters)?

Question 2

An enclosure consist of four surfaces 1,2,3 and 4 the view factors for radiation heat transfer (where the subscripts 1,2,3 and 4 refers to the respective surfaces) are F₁₁ = 0.1 F₁₂ = 0.5 and F₁₃ = 0.30. the surface areas A₁ and A₄ are 1 m² and 4 m² respectively. The view factor F₄₁ is

Question 3

Water flows through a cylinder of internal diameter 3 cm and length of 5m. If the system is to provide water at a rate of 10 lit/min. Determine the type of flow of discharge
Given properties are Kinematic viscosity(υ) = 0.658 x 10^-6 m²/sec

Question 4

The average Nusselt number in turbulent natural convection from a vertical wall at 290 °C with still air at 20 °C is found to be 48. If the wall temperature become 30 °C, all other parameters remaining same, the average Nusselt number will be

Question 5

Air flows over a heated plate at a velocity of 40 m/s. The local skin friction co efficient at a point on the plate 0.004. Determine the local heat transfer coefficient ( in W/m²K) at this point using Reynold’s Colburn analogy
Following are property of air

0.88 kg/m³, Cp =1001 J/kg °K, k = 0.035 W/mK,

Kg/ms

Question 6

Two infinite parallel plates are placed at a certain distance apart. If the heat transfer between the plate is to be reduced by 80%, then the number of radiation shields required to be inserted between the plates is ___________.
[Assume that the emissivities of plates and radiation shield are equal]

Question 7

Air at a temperature of T_∞ flows over a flat plate with a free stream velocity of U_∞. The plate is maintained at a constant temperature of T_W. Temperature,T of air at any location is given by,
$Description: Description: E:\Gate\SSC JE Mechanical Part 1\Made Easy Questions\08_Heat-Transfer_BLok_files\image034.png$
Where y is the distance measured from the plate along its normal,
and δ and δ_t are the hydrodynamic and thermal boundary layer thickness, respectively.
If the free stream temperature is 50°C and plate temperature is 200°C & the other properties of the fluid at mean temperature is given

and hydrodynamic boundary layer thickness (δ )= 0.5 mm

Then, the value of heat transfer coefficient?

Question 8

Two surfaces A₁ and A₂ of a body are analyzed for the heat transfer. If the area of surfaces are 300 mm² and 150 mm² respectively. What is the nature of surface 1 when A₂ is completely enclosed by area A₁?

Question 9

The main trunk duct of an air conditioning system is rectangular in cross-section (400 mm $Description: Description: E:\Gate\SSC JE Mechanical Part 1\Made Easy Questions\08_Heat-Transfer_BLok_files\image001.png$ 800mm) and has air at atmospheric pressure and at 20⁰C temperature flowing with a velocity of 7 m/s. estimate the heat leaskage (W) per meter length per unit temperature difference. Relevant physical properties of air are:
$Description: Description: E:\Gate\SSC JE Mechanical Part 1\Made Easy Questions\08_Heat-Transfer_BLok_files\image054.png$

Question 10

Two large parallel plates with emissivity of 0.6 each are maintained at different temperatures. Two equally large radiation shields of emissivity 0.05 are introduced in parallel to the plates. Find the percentage reduction in net radiative heat transfer.

Question 11

A metal plate 0.609 m high forms the vertical wall of an oven and is at a temperature of 161⁰C. Within the oven air is at a temperature of 93⁰C. Assuming the natural convection conditions hold near the plate.
The properties of air at 400 K are
$Description: Description: E:\Gate\SSC JE Mechanical Part 1\Made Easy Questions\08_Heat-Transfer_BLok_files\image041.png$
The Rayleigh number will be

Question 12

A domestic hot water tank (0.5 m diameter and 1 m high) is installed in a large space by the support of four small diameter rod. The ambient temperature is 25°C. If the tank surface is oxidized copper with an emissivity of 0.8 and is at a peak temperature of 80°C, the heat loss from the tank by radiation is

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