A. Temperature gradient of the wall to that across the entire pipe
B. Temperature difference to the temperature gradient at the wall
C. Heat flux at the wall to that across the entire pipe
D. None of these
A. Thermal diffusivity/Momentum diffusivity
B. Thermal diffusivity × Momentum
C. Thermal diffusivity × Mass diffusivity
D. Mass diffusivity × Momentum diffusivity
A. 1
B. > 1
C. < 1
D. Between 1 & 2
A. Decreases
B. Increases
C. Remains unchanged
D. May increase or decrease; depends on the gas
A. εx + εy
B. εx . εy
C. 1/εx + 1/εy
D. (εx + εy)/( εx + εy – εx . εy)
A. Increases
B. Decreases
C. Remain same
D. May increase or decrease depending on the type of gas
A. Logarithmic mean area
B. Arithmetic mean area
C. Geometric mean area
D. None of these
A. Wavelength of radiation
B. Surface temperature of the body
C. Nature of the surface
D. Shape and porosity of the body
A. Loosing sensible heat
B. Heat transfer to surroundings
C. Vaporisation due to heat loss to air
D. Loosing latent heat
A. (r1 – r2)/ln(r1/r2)
B. (r1 – r2)/ln(r2/r1)
C. (r2 – r1)/ln(r1/r2)
D. (r1 – r2)/-ln(r1/r2)