A grey body is one whose absorptivity _________________?

A. Varies with temperature
B. Varies with the wave length of incident ray
C. Varies with both
D. Does not vary with temperature and wave length of the incident ray

The thermal diffusivities for gases are generally_____________________?

A. More than those for liquids
B. Less than those for liquids
C. More than those for solids
D. Dependent on the viscosity

Thermal diffusivity of a substance is __________________?

A. Directly proportional to thermal con¬ductivity
B. Inversely proportional to density of substance
C. Inversely proportional to specific heat
D. All of the above

Stefan Boltzmann law is applicable for heat transfer by __________________?

A. Conduction
B. Convection
C. Radiation
D. Conduction and radiation combined

The unit of Stefan Boltzmann constant is ____________________?

A. Watt/cm2 °k
B. Watt/cm4 °k
C. Watt2/cm °k4
D. Watt/cm2 °k4

Log mean temperature difference in case of counter flow compared to parallel flow will be________________?

A. Same
B. More
C. Less
D. Depends on other factors

According to Stefan-Boltzmann law, ideal radiators emit radiant energy at a rate proportional to___________________?

A. Absolute temperature
B. Square of temperature
C. Fourth power of absolute temperature
D. Fourth power of temperature

In free con-vection heat transfer, Nusselt number is function of________________?

A. Grashoff no. and reynold no
B. Grashoff no and prandtl no.
C. Prandtl no. and reynold no
D. Grashoff no., prandtl no and reynold no

Which of the following property of air does not increase with rise in temperature ________________?

A. Thermal conductivity
B. Thermal diffusivity
C. Density
D. Dynamic viscosity

The energy distribution of an ideal reflector at higher temperatures is largely in the range of ___________________?

A. Shorter wavelength
B. Longer wavelength
C. Remains same at all wavelengths
D. Wavelength has nothing to do with it