Related Questions

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
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
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
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
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
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of
A 1
B 1.74
C 6.1
D 37
The velocity at which the flow changes from laminar flow to turbulent flow is called
A Critical velocity
B Velocity of approach
C Sub-sonic velocity
D Super-sonic velocity
The depth ‘d’ below the free surface at which the point velocity is equal to the average velocity of flow for a uniform laminar flow with a free surface, will be (where D is the depth of flow)
A 0.423 D
B 0.577 D
C 0.223 D
D 0.707 D
The scales form in heat exchanges after a period of operation and provide additional resistance to heat transfer with some heat transfer coefficient . The reciprocal of this scale heat transfer coefficient is called .
A scaling factor
B forming factor
C resisting factor
D fouling factor
Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the
A Surrounding temperature
B Average temperature of the fin
C Temperature of the fin end
D Constant temperature equal to that of the base

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