Fins MCQ

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• On heat transfer surface, fins are provided?
  ক

  To increase temperature gradient so as to enhance heat transfer

  খ

  To increase turbulence in flow for enhancing

  গ

  To increase surface area to promote the rate of heat transfer

  ঘ

  To decrease the pressure drop of the fluid
• A fin length l, protrudes from a surface held at temperature T0; it being higher than the ambient temperature Ta. The heat dissipation from the free end of the fin is stated to be negligibly small. What is the temperature gradient (dT/dx)x=l at the tip of the fin?
  ক

  Zero d) (Tl-T]/(T0-T] View Answer]

  খ

  (T0-Tl)/l

  গ

  h(T0-Ta)

  ঘ

  (Tl-Ta)/(T0-Ta)
• Heat pipe is widely used nowadays because _________
  ক

  It acts as an insulator

  খ

  It acts as conductor and insulator

  গ

  It acts as a superconductor

  ঘ

  It acts as a fin
• A finned surface consists of root or base area of 1m2 and fin surface area of 2m2. The average heat transfer coefficient for finned surface is 20W/m2K effectiveness of fins provided is 0.75. If finned surface with surface with root or base temperature of 50°C is transferring heat to fluid of 30°C, then the rate of heat transfer without using fin is _______
  ক

  400W

  খ

  800W

  গ

  1000W

  ঘ

  1200W
• On a heat transfer surface, fins are provided to
  ক

  Increase turbulence in flow for enhancing heat transfer

  খ

  Increase temperature gradient so as to enhance heat transfer

  গ

  Pressure drop of the fluid should be minimized

  ঘ

  Surface area is maximum to promote the rate of heat transfer
• A steel rod (k = 30 W/m degree) 1 cm in diameter and 5 cm long protrudes from a wall which is maintained at 10 degree Celsius. The rod is insulated at its tip and is exposed to an environment with h = 50 W/m2 degree and t a = 30 degree Celsius. Calculate the rate of heat dissipation
  ক

  2.658 W

  খ

  3.658 W

  গ

  4.658 W

  ঘ

  5.658 W
• In order to achieve maximum heat dissipation, the fin should be designed in such a way that has a
  ক

  Maximum lateral surface towards the tip side of fin

  খ

  Minimum lateral surface near the center line

  গ

  Maximum lateral surface at the root side of fin

  ঘ

  Maximum lateral surface near the center of fin
• If heat dissipation for one fin is given by 377.45 k J/hour, then what is the heat dissipation for 12 fins?
  ক

  7529.4 k J/hour

  খ

  6529.4 k J/hour

  গ

  5529.4 k J/hour

  ঘ

  4529.4 k J/hour
• If the fin is sufficiently thin, so heat flows pertain to
  ক

  One dimensional heat conduction

  খ

  Two dimensional heat conduction

  গ

  Three dimensional heat conduction

  ঘ

  No heat flow is there
• A steel rod (k = 30 W/m degree) 1 cm in diameter and 5 cm long protrudes from a wall which is maintained at 10 degree Celsius. The rod is insulated at its tip and is exposed to an environment with h = 50 W/m2 degree and t a = 30 degree Celsius. Calculate the fin efficiency
  ক

  56.57%

  খ

  66.57%

  গ

  76.57%

  ঘ

  86.57%
• It is said that fins can take a variety of forms (i) Longitudinal fins of rectangular cross section attached to a wall (ii) Cylindrical tubes with radial fins (iii) Conical rod protruding from a wall Identify the correct statement
  ক

  i only

  খ

  i and ii

  গ

  ii and iii

  ঘ

  i, ii and iii
• The extended surface used for the enhancement of heat dissipation is
  ক

  Convective coefficient

  খ

  Fourier number

  গ

  Fin

  ঘ

  No finned surface
• Common applications of finned surfaces are with (i) Electrical motors (ii) Economizers for steam power plant (iii) Convectors for steam and cold water heating systems (iv) Cooling coils Identify the correct option
  ক

  i, ii and iv

  খ

  i, ii and iii

  গ

  i, ii, iii and iv

  ঘ

  i and ii
• A very long copper rod 20 mm in diameter extends horizontally from a plane heated wall maintained at 100 degree Celsius. The surface of the rod is exposed to an air environment at 20 degree Celsius with convective heat transfer coefficient of 8.5 W/m2 degree. Workout the heat loss if the thermal conductivity of copper is 400 W/m degree
  ক

  10.71 W

  খ

  20.71 W

  গ

  30.71 W

  ঘ

  40.71 W