In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by___________________?

A. Convection
B. Radiation
C. Conduction
D. Both convection and conduction

Unit of thermal diffusivity is_________________?

A. M2/hr
B. M2/hr°c
C. Kcal/m2 hr
D. Kcal/m.hr°c

Film coefficient is defined as Inside diameter of tube________________?

A. Equivalent thickness of film
B. Thermal conductivity equivalent thickness of film specific heat x viscocity
C. Thermal conductivity molecular diffusivity of momentum thermal diffusivity
D. Film coefficient x inside diameter thermalconductivity

Thermal conductivity of wood depends on_______________?

A. Mositure
B. Density
C. Temperature
D. All of the above

Thermal diffusivity is ____________________?

A. A dimensionless parameter
B. Function of temperature
C. Used as mathematical model
D. A physical property of the material

Moisture would find its way into insulation by vapour pressure unless it is prevented by __________________ ?

A. High thickness of insulation
B. High vapour pressure
C. Less thermal conductivity insulator
D. A vapour seal

Heat transfer by radiation mainly depends upon___________________?

A. Its temperature
B. Nature of the body
C. Kind and extent of its surface
D. All of the above

Which of the following has maximum value of thermal conductivity________________?

A. Aluminium
B. Steel
C. Brass
D. Copper

The amount of heat flow through a body by conduction is_______________?

A. directly proportional to the surface area of the body
B. directly proportional to the temperature difference on the two faces of the body
C. dependent upon the material of the body
D. inversely proportional to the thickness of the body

Heat flows from one body to other when they have_________________?

A. Different heat contents
B. Different specific heat
C. Different atomic structure
D. Different temperatures