Heat Transfer MCQ with Answer.

Q.no 31. A window glass of area (A) 1.5 m × 1 m and thickness (L) 6 mm is placed in a wall. If the outer (T1) and inner (T2) surface temperatures are 30°C and 20°C respectively, calculate the conduction heat transfer through the glass. Assume the thermal conductivity (K) of glass to be 0.78 W/mK.

A : 1740 W
B : 1590 W
C : 1660 W
D : 1950 W

Q.no 33. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is

A : free convection
B : entry length problem in laminar forced conduction (developing thermal boundary layer)
C : mixed convection (both free and forced)
D : forced convection

Q.no 34. The ratio of kinematic viscosity to thermal diffusivity is called the __________number.

A : Peclet
B : Prandtl
C : Stanton
D : Nusselt

Q.no 35. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by

A : Fourier’s law
B : Newton’s law of cooling
C : Fick’s law
D : none of these

Q.no 36. Value of Prandtl number for water ranges from

A : l to 2
B : 5 to 10
C : 100 to 500
D : 1000 to 2000

Q.no 37. Which of the following is not a fundamental law

A : The law of consrvation of mass
B : Newtons law of motion
C : The laws of thermodynamics
D : Fouriers law of heat conduction

Q.no 38. Thermodynamics deals with

A : Equillibrium
B : non-equillibrium
C : Steady state
D : Unsteady State

Q.no 39. The rate of heat transfer through a brick wall ( k=0.69W/m K) 35 cm thick is found to be 50 W/m2 . The temperature drop in the wall in steady state condition will be ——— 0C

A : 20.4
B : 25.4
C : 30.4
D : 22.4

Q.no 40. Thermal conductivity of glass-wool varies from sample to sample because of variation in

A : composition
B : Density
C : Porosity
D : all of the above.

Answer for Question No 31. is d
Answer for Question No 32. is b
Answer for Question No 33. is c
Answer for Question No 34. is b
Answer for Question No 35. is b
Answer for Question No 36. is b
Answer for Question No 37. is d
Answer for Question No 38. is a
Answer for Question No 39. is b
Answer for Question No 40. is d