The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl num

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Question
The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is
Options
A. equal to one
B. greater than one
C. less than one
D. equal to Nusselt number

Correct Answer

equal to one

Heat Transfer, Refrigeration and Air Conditioning problems

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2. The C.O.P. of an absorption type refrigerator is given by (where T₁ = Temperature at which the working substance receives heat, T₂ = Temperature of cooling water, and T₃ = Evaporator temperature)
Options
A.
B.
C.
D.

7. Reynolds number (R_N) is given by (where h = Film coefficient, l = Linear dimension, V = Velocity of fluid, k = Thermal conductivity, t = Temperature, ? = Density of fluid, c_p = Specific heat at constant pressure, and ? = Coefficient of absolute viscosity)
Options
A.
B.
C.
D.

8. Thermal conductivity of water __________ with rise in temperature.
Options
A. remains same
B. decreases
C. increases
D. may increase or decrease depending upon temperature

9. A refrigeration system
Options
A. removes heat from a low temperature body and delivers it to a high temperature body
B. removes heat from a high temperature body and delivers it to a low temperature body
C. rejects energy to a low temperature body
D. none of the above

10. A perfect black body is one which
Options
A. is black in colour
B. absorbs heat radiations of all wave lengths falling on it
C. reflects all the heat radiations
D. transmits the heat radiations

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