40
95
70
50
✅ The correct answer is option C.
Heat Transfer MCQs
12. 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.
13. View factor is important in heat transfer by
Steady state conduction
Natural convection
Forced convection
Radiation
✅ The correct answer is option D.
14. 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.
15. 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.
16. 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.
17. In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid
Is inversely proportional to the resistance across which the drop occurs
And the wall are proportional to individual resistances
And the wall is not related
None of these
✅ The correct answer is option B.
18. In a 1-1 cocurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is
∞
0
Equal to the difference between hot and cold fluids inlet temperature
Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature
✅ The correct answer is option B.
19. h.D/K is called the __________ number.
Nusselt
Peclet
Rayleigh
Grashoff
✅ The correct answer is option A.
20. For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is
3
0.33
1
1.33
✅ The correct answer is option C.