Which of the following non-dimensional numbers is used for transition from laminar flow to turbulent flow in the free convection?

In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

A

Reynold's number

B

Grashoff's number

C

Reynold's number, Grashoff's number

D

Prandtl number, Grashoff's number

Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.

A

Grashoff

B

Reynolds

C

Both A & B

D

Prandtl & Grashoff

Transition from laminar to turbulent zone in free convection heat transfer is governed by the critical value of

A

Grashoff number

B

Grashoff number & Reynolds number

C

Reynolds number

D

Grashoff number & Prandtl number

Nusselt number is related to Grashoff number (Gr) in turbulent & laminar flow respectively, in respect of free convection over a vertical flat plate as

A

Gr^0.25, Gr

B

Gr^0.25, Gr^0.33

C

Gr, Gr^0.25

D

Gr^0.33, Gr^0.25

Transition from laminar flow to turbulent flow in fluid flow through a pipe does not depend upon the

A

Length of the pipe

B

Diameter of the pipe

C

Density of the fluid

D

Velocity of the fluid

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

In respect to free convection over a vertical flat plate, the Nusselt number for laminar and turbulent flows varies respectively with Grashoff number G r as

A

G r and G r1/4

B

G r1/2 and G r1/3

C

G r1/4 and G r1/3

D

G r1/3 and G r1/4

Transition from laminar flow to turbulent flow is aided by the

A

Surface roughness and curvature (i.e.sharp corners)

B

Vibration

C

Pressure gradient and the compressibility of the flowing medium

D

All of the above

There will be a transition from laminar flow to turbulent flow when______

A

Reynolds number increases

B

Reynolds number decreases

C

Reynolds number is the same

D

Froude’s number increases

Ambient air at 20 degree Celsius flows past a flat plate with a sharp leading edge at 3 m/s. The plate is heated uniformly throughout its entire length and is maintained at a surface temperature of 40 degree Celsius. Calculate the distance from the leading edge at which the flow in the boundary layer changes from laminar to turbulent conditions. Assume that transition occurs at a critical Reynolds number of 500000

A

4.67 m

B

3.67 m

C

2.67 m

D

1.67 m

Which of the following non-dimensional numbers is used for transition from laminar flow to turbulent flow in the free convection?

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