160 Important Heat And Mass Transfer MCQ Question and Answer | PDF Free Download
1.Log mean temperature difference in case of counter flow compared to parallel flow will be
- ASame
- BMore
- CLess
- DDepends on other factors
2.Depending on the radiating properties, a body will be opaque when
- AP = 0, x = 0 and a = 1
- BP=1, x = 0 and a = 0
- CP = 0, x = 1 and a = 0
- DX = 0, a + p = 1
3.In case of liquids and gases, the heat transfer takes place according to
- AConduction
- BConvection
- CRadiation
- DNone of these
4.The heat transfer takes place according to
- AZeroth law of thermodynamics
- BFirst law of thermodynamics
- CSecond law of thermodynamics
- DKirchhoff's law
5.The insulation ability of an insulator with the presence of moisture would
- AIncrease
- BDecrease
- CRemain unaffected
- DMay increase/decrease depending on temperature and thickness of insulation
6.Thermal diffusivity of a substance is
- ADirectly proportional to the thermal conductivity
- BInversely proportional to density of substance
- CInversely proportional to specific heat
- DAll of the above
7.The heat of sun reaches to us according to
- AConduction
- BConvection
- CRadiation
- DNone of these
8.Emissivity of a white polished body in comparison to a black body is
- AHigher
- BLower
- CSame
- DDepends upon the shape of body
9.The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit)
- Atm = (Δt1 - Δt2)/ loge (Δt1/Δt2)
- Btm = loge (Δt1/Δt2)/ (Δt1 - Δt2)
- Ctm = tm = (Δt1 - Δt2) loge (Δt1/Δt2)
- Dtm = loge (Δt1 - Δt2)/ Δt1/Δt2
10.Thermal conductivity of non-metallic amorphous solids with decrease in temperature
- AIncreases
- BDecreases
- CRemain constant
- DMay increase or decrease depending on temperature
11.The critical temperature is the temperature
- ABelow which a gas does not obey gas laws
- BAbove which a gas may explode
- CBelow which a gas is always liquefied
- DAbove which a gas will never liquefied
12.According to Stefan's law, the total radiation from a black body per second per unit area is proportional to
- AAbsolute temperature
- BT2
- CT5
- DT
13.Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of
- A0.002
- B0.02
- C0.01
- D0.1
14.Thermal conductivity of water at 20°C is of the order of
- A0.1
- B0.23
- C0.42
- D0.51
15.Thermal conductivity of solid metals with rise in temperature normally
- AIncreases
- BDecreases
- CRemain constant
- DMay increase or decrease depending on temperature
16.Pick up the wrong case. Heat flowing from one side to other depends directly on
- AFace area
- BTime
- CThickness
- DTemperature difference
17.Cork is a good insulator because it has
- AFree electrons
- BAtoms colliding frequency
- CLow density
- DPorous body
18.According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the
- AAbsolute temperature
- BSquare of the absolute temperature
- CCube of the absolute temperature
- DFourth power of the absolute temperature
19.The transfer of heat by molecular collision is smallest in
- ASolids
- BLiquids
- CGases
- DNone of these
20.The thermal diffusivities for gases are generally
- AMore than those for liquids
- BLess than those for liquids
- CMore than those for solids
- DDependent on the viscosity