Through a metallic wall
By direct contact of hot flue gas with air
By heating an intermediate material (like chequor bricks) and then heating the air from this hot material
None of these
✅ The correct answer is option C.
Heat Transfer MCQs
292. Solid angle subtended by the finite surface at the radiating element is
Called the view factor
Called the angle of vision
Proportional to the square of the distance between surfaces
Expressed in terms of radians
✅ The correct answer is option B.
293. Dropwise condensation occurs on __________ surfaces.
Clean and dirt free
Smooth clean
Contaminated cooling
Polished
✅ The correct answer is option C.
294. A composite flat wall of a furnace is made of two materials ‘A’ and ‘B’. The thermal conductivity of ‘A’ is twice of that of material ‘B’, while the thickness of layer of ‘A’ is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material ‘A’ is
125
133
150
160
✅ The correct answer is option D.
295. The Stefan-Boltzman constant depends on the
Medium
Temperature
Surface
None of these
✅ The correct answer is option D.
296. The purpose of providing a ‘catchall’ in the vapor line of an evaporator is to
Create vacuum
Regulate the vapor flow
Vent the non-condensible gases
Arrest the entrained liquid
✅ The correct answer is option D.
297. Steady state one dimensional heat flow by conduction as given by Fourier’s low does not assume that
There is no internal heat generation
Boundary surfaces are isothermal
Material is anisotropic
Constant temperature gradient exists
✅ The correct answer is option C.
298. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)
0.2 D
0.5 D
0.66 D
0.80 D
✅ The correct answer is option A.
299. With increase in temperature, the thermal conductivity of a gas
Increases
Decreases
Remains same
May increase or decrease depending on the type of gas
✅ The correct answer is option A.
300. Which of the following is not used as a medium for high temperature heating?
Dowtherm
Mercury
Liquid metal (e.g. molten sodium)
Fused salts (e.g., an eutectic mixture of 53% KNO₃, 40% NaNO₂and 7% NaNO₃)
✅ The correct answer is option B.