Heat Transfer

6
Thermal diffusivity is given by


A. `(k)/(rho.C_p)`
B. `(rho.C_p)/(k)`
C. `(C_p mu)/(a)`
D. `(mu)/(h.C_p)`

7

Harmonic mean temperature difference is given by

A. `sqrt( Delta T_1 . Delta T_2)`
B. `(2 Delta_1.Delta_2)/((DeltaT_1 + DeltaT_2))`
C. `(2 Delta_1.Delta_2)/((DeltaT_1 - DeltaT_2))`
D. `(Delta T_1 - Delta T_2)/(Delta T_1 .DeltaT_2)`

8

Graetz number is given by

A. `(mC_p)/(KL)`
B. `(KL)/(mC_p)`
C. `(mC_p)/(Kmu)`
D. `(KL)/(mmu)`

9

Grashoff number, which is defined as g .`beta(T_s - T_oo ) rho^2. L^3// mu^2`  is proportional to the ratio of buoyancy force to __________ force.

A. viscous
B. elastic
C. inertial
D. none of these

10

In thermal radiation for a black body (where,` epsi` is emissivity and `alpha` is absorptivity)

A. `alpha = 1, epsi!= = 1`
B. `alpha != 1, epsi = 1`
C. `alpha != 1, epsi != 1 `
D. `alpha = 1, epsi = 1`