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

Correct Answer: Conduction

Conduction transfers heat via direct molecular collision. An area of greater kinetic energy will transfer thermal energy to an area with lower kinetic energy. Higher-speed particles will collide with slower speed particles. The slower-speed particles will increase in kinetic energy as a result. Conduction is the most common form of heat transfer and occurs via physical contact.
Bissoy MCQ
#Mechanical Engineering #Heat And Mass Transfer

Related Questions

Thermal conductivity based continuous flue gas analyser makes use of varying thermal conductivity of the constituents of flue gases. Which of the following constituents of flue gases has the maximum thermal conductivity?
A CO2
B N2
C O2
D CO
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
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 ratio of the energy required to produce the artificial draught (expressed in meters head or J/kg of flue gas) to the mechanical equivalent of extra heat carried away per kg of flue gases due to natural draught, is known as
A Efficiency of the boiler
B Efficiency of the chimney
C Efficiency of the fan
D Power of the boiler
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
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
A device used to heat feed water by utilizing the heat in me exhaust flue gases before leaving through the chimney, is known as
A Economizer
B Fusible plug
C Superheater
D Stop valve
Sensible heat of hot industrial flue gases can not be recovered by a/an
A Economiser
B Regenerator
C Ceramic recuperator
D None of these

Next steps