Wavelength of radiation
Surface temperature of the body
Nature of the surface
Shape and porosity of the body
✅ The correct answer is option D.
Heat Transfer MCQs
Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because
Convection becomes important
Conduction becomes important
Radiation becomes important
Sub-cooled boiling occurs
✅ The correct answer is option C.
Crystal size in a continuous crystalliser depends upon the
Rate of heat transfer
Degree of turbulence
Degree of supersaturation
All of the above
✅ The correct answer is option D.
Loss of heat from untagged steam pipe to the ambient air is by
Conduction
Convection
Radiation
All of the above
✅ The correct answer is option D.
Three material A, B and C of equal thick-nes and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of __________ °C.
40
95
70
50
✅ The correct answer is option C.
A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an
Ellipse
Straight line
Parabola
Circular arc
✅ The correct answer is option B.
View factor is important in heat transfer by
Steady state conduction
Natural convection
Forced convection
Radiation
✅ The correct answer is option D.
A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of
2
20.8
20.2
20.5
✅ The correct answer is option B.
The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m². The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67xl0⁻⁸ W/m².K⁴)
1000
727
800
1200
✅ The correct answer is option A.
Heat transfer by radiation between two bodies at T₁ & T₂ and in an ambient temperature of Ta°C depends on
T₁ – T₂
T₁ – Ta
T₂ – Ta
None of these
✅ The correct answer is option D.