160 Important Heat And Mass Transfer MCQ Question and Answer | PDF Free Download
1.A non-dimensional number generally associated with natural convection heat transfer is
- AGrashoff number
- BNusselt number
- CWeber number
- DPrandtl number
2.Stefan Boltzmann law is applicable for heat transfer by
- AConduction
- BConvection
- CRadiation
- DConduction and radiation combined
3.When heat is transferred by molecular collision, it is referred to as heat transfer by
- AConduction
- BConvection
- CRadiation
- DScattering
4.The concept of overall coefficient of heat transfer is used in case of heat transfer by
- AConduction
- BConvection
- CRadiation
- DConduction and convection
5.When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by
- AConduction
- BConvection
- CRadiation
- DConduction and convection
6.The expression Q = ρ AT4 is called
- AFourier equation
- BStefan-Boltzmann equation
- CNewton Reichmann equation
- DJoseph-Stefan equation
7.Depending on the radiating properties, body will be transparent when (Where a = absorptivity, p = reflectivity, x = transmissivity)
- 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
8.Depending on the radiating properties, a body will be white when (Where a = absorptivity, p = reflectivity, x = transmissivity)
- AP = 0, x = 0 and a = 1
- BP=1, T = 0 and a = 0
- CP = 0, x = 1 and a = 0
- DX = 0, a + p = 1
9.The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as
- AThermal coefficient
- BThermal resistance
- CThermal conductivity
- DNone of these
10.Heat conducted through per unit area and unit thick face per unit time when temperature difference between opposite faces is unity, is called
- AThermal resistance
- BThermal coefficient
- CTemperature gradient
- DThermal conductivity
11.According to Prevost theory of heat exchange
- AIt is impossible to transfer heat from low temperature source to t high temperature source
- BHeat transfer by radiation requires no medium
- CAll bodies above absolute zero emit radiation
- DHeat transfer in most of the cases takes place by combination of conduction, convection and radiation
12.Which of the following has least value of conductivity?
- AGlass
- BWater
- CPlastic
- DAir
13.According to Wien's law, the wavelength corresponding to maximum energy is proportion to
- AAbsolute temperature (T)
- BI²
- CF
- DT
14.Unit of thermal conductivity in S.I. units is
- AJ/m² sec
- BJ/m °K sec
- CW/m °K
- DOption (B) and (C) above
15.The unit of overall coefficient of heat transfer is
- Akcal/m²
- Bkcal/hr °C
- Ckcal/m² hr °C
- Dkcal/m hr °C
16.Thermal diffusivity is
- AThermal diffusivity is
- BFunction of temperature
- CUsed as mathematical model
- DA physical property of the material
17.Heat transfer takes place as per
- AZeroth law of thermodynamics
- BFirst law of thermodynamic
- CSecond law of the thermodynamics
- DKirchoff's law
18.The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit
- ATemperature
- BThickness
- CArea
- DTime
19.The time constant of a thermocouple is`
- AThe time taken to attain the final temperature to be measured
- BThe time taken to attain 50% of the value of initial temperature difference
- CThe time taken to attain 63.2% of the value of initial temperature difference
- DDetermined by the time taken to reach 100°C from 0°C
20.In heat transfer, conductance equals conductivity (kcal/hr/sq.m/°C/cm) divided by
- AHr (time)
- BSq. m (area)
- C°C (temperature)
- DK.cal (heat)