A. Is thicker than hydrodynamic boundary layer
B. Is thinner than hydrodynamic boundary layer
C. And the hydrodynamic boundary layers are identical
D. Disappears
Related Mcqs:
- Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is_________________?
A. 1
B. < 1
C. > 1
D. > 5 - A composite flat wall of a furnace is made of two materials ‘A’ and ‘B’. The thermal conductivity of ‘A’ is twice of that of material ‘B’, while the thickness of layer of ‘A’ is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material ‘A’ is________________?
A. 125
B. 133
C. 150
D. 160 - The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to ______________ analogy?
A. Von-Karman
B. Reynolds
C. Colburn
D. Prandtl - At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?
A. 1
B. 1
D. None of these - A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is ______________ °C?
A. 6
B. 12
C. 18
D. 24 - The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are _______________?
A. (COP)R = (COP)HP = 0.6
B. (COP)R = 2.5; (COP)HP = 1.5
C. (COP)R = 1.5; (COP)HP = 2.5
D. (COP)R = (COP)HP = 2.5 - The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in °K). The units of ‘a’ in SI system will be________________?
A. W/m.k
B. W/m
C. W/m.k2
D. None, ‘a’ is just a number - For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally ?
A. Decreases
B. Increases
C. Remains unchanged
D. Increases exponentially - The thickness of condensate layer in filmwise condensation depends on the__________________?
A. Condensation rate
B. Surface configuration
C. Liquid flow rate from the surface
D. All A., B. and C. - Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by__________________?
A. Eddies current
B. Conduction
C. Convection
D. None of these
