MCQOPTIONS
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MCQOPTIONS
This section includes 47 Mcqs, each offering curated multiple-choice questions to sharpen your Heat Transfer knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
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 |
| Answer» D. 1.67 m | |
| 2. |
The boundary layer thickness is taken to be at a distance from the plate surface to a point at which the velocity is given by |
| A. | u = 0.99 U INFINITY |
| B. | u = 0.75 U INFINITY |
| C. | u = 0.50 U INFINITY |
| D. | u = 0.33 U INFINITY |
| Answer» B. u = 0.75 U INFINITY | |
| 3. |
Air at 25 degree Celsius approaches a 0.9 m long and 0.6 m wide flat plate with a velocity 4.5 m/s. Let the plate is heated to a surface temperature of 135 degree Celsius. Find local heat transfer coefficient from the leading edge at a distance of 0.5 m |
| A. | 5.83 W/m² K |
| B. | 6. 83 W/m² K |
| C. | 7. 83 W/m² K |
| D. | 8. 83 W/m² K |
| Answer» B. 6. 83 W/m² K | |
| 4. |
Air at 25 degree Celsius flows over a flat surface with a sharp leading edge at 1.5 m/s. Find the boundary layer thickness at 0.5 from the leading edge. For air at 25 degree Celsius, kinematic viscosity = 15.53* 10n¯⁶ m²/s |
| A. | 4.1376 cm |
| B. | 3.1376 cm |
| C. | 2.1376 cm |
| D. | 1.1376 cm |
| Answer» E. | |
| 5. |
Boundary layer thickness is given by |
| A. | δ = 5.64 x/ (Re) ½ |
| B. | δ = 5.64 x/ (Re) ½ |
| C. | δ = 6.64 x/ (Re) ½ |
| D. | δ = 7.74 x/ (Re) ½ |
| Answer» D. δ = 7.74 x/ (Re) ½ | |
| 6. |
A small thermo-couple is positioned in a thermal boundary layer near a flat plate past which water flows at 30 degree Celsius and 0.15 m/s. The plate is heated to a surface temperature of 50 degree Celsius and at the location of the probe, the thickness is 15 mm. The probe is well-represented byt – t S/t INFINITY – t S = 1.5 (y/δ) – 0.5 (y/δ)³Determine the heat transfer coefficient |
| A. | 33.3 W/m² K |
| B. | 43.3 W/m² K |
| C. | 53.3 W/m² K |
| D. | 63.3 W/m² K |
| Answer» E. | |
| 7. |
During test-run, air flows at 215 m/s velocity and 25 degree Celsius temperature past a smooth thin model airfoil which can be idealized as a flat plate. If the chord length of the airfoil is 15 cm, find drag per unit width. The relevant physical properties of air arep = 1.82 kg/m³v = 15.53 * 10¯⁶ m²/s |
| A. | 25.42 N per unit width |
| B. | 35.42 N per unit width |
| C. | 45.42 N per unit width |
| D. | 55.42 N per unit width |
| Answer» B. 35.42 N per unit width | |
| 8. |
A single pass shell and tube heat exchanger, consisting of a bundle of 100 tubes (inner diameter 25 mm and thickness 2 mm) is used for heating 28 kg/s of water from 25 degree Celsius to 75 degree Celsius with the help of a steam condensing at atmospheric pressure on the shell side with condensing heat transfer coefficient 5000 W/m² degree. Make calculation for overall heat transfer coefficient based on the inner area. Take fouling factor on the water side to be 0.002 m² degree/W per tube and neglect effect of fouling factor on the shell side and thermal resistance of the tube wall |
| A. | 647.46 W/m² degree |
| B. | 747.46 W/m² degree |
| C. | 847.46 W/m² degree |
| D. | 947.46 W/m² degree |
| Answer» D. 947.46 W/m² degree | |
| 9. |
Temperature and velocity profiles are identical when the dimensionless Prandtl number is |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| 10. |
The assumptions for thermal boundary layer are(i) Steady compressible flow(ii) Negligible body forces, viscous heating and conduction in the flow direction(iii) Constant fluid properties evaluated at the film temperatureIdentify the correct option |
| A. | 1 and 3 |
| B. | 1, 2 and 3 |
| C. | 2 and 3 |
| D. | 1 and 2 |
| Answer» D. 1 and 2 | |
| 11. |
Reynolds analogy is given by |
| A. | Nu x/ (Re x) (Pr x) = 5 St X = – 2 C F x |
| B. | Nu x/ 2 (Re x) (Pr x) = 4 St X = – C F x /3 |
| C. | Nu x/ (Re x) (Pr x) = St X = – ½ C F x |
| D. | Nu x/ (Re x) (Pr x) = 2 St X = – C F x /4 |
| Answer» D. Nu x/ (Re x) (Pr x) = 2 St X = – C F x /4 | |
| 12. |
A flat plate 1 m by 1 m is placed in a wind tunnel. The velocity and temperature of free stream air are 80 m/s and 10 degree Celsius. The flow over the whole length of the plate is made turbulent by turbulizing grid placed upstream of the plate. Find the heat flow from the surface of the plate |
| A. | 9424.5 W |
| B. | 8424.5 W |
| C. | 7424.5 W |
| D. | 6424.5 W |
| Answer» D. 6424.5 W | |
| 13. |
A two pass surface condenser is required to handle the exhaust from a turbine developing 15 MW with specific steam consumption of 5 kg/k W h. The quality of exhaust steam is 0.9, the condenser vacuum is 66 cm of mercury while the bar meter reads 76 cm of mercury. The condenser tubes are 28 mm inside diameter, 4 mm thick and water flows through tubes with a speed of 3 m/s and inlet temperature 20 degree Celsius. All the steam is condensed, the condensate is saturated water and temperature of cooling water at exit is 5 degree Celsius less than the condensate temperature. Assuming that overall coefficient of heat transfer is 4 k W/m² degree, determine the mass of cooling water circulated. |
| A. | 746.13 kg/s |
| B. | 646.13 kg/s |
| C. | 546.13 kg/s |
| D. | 446.13 kg/s |
| Answer» E. | |
| 14. |
Consider the diagram given below and identify the correct option |
| A. | The velocity gradient is zero everywhere |
| B. | The velocity profile changes at every instant of time |
| C. | Boundary layers from the pipe walls meet the pipe anywhere |
| D. | Thickness of the boundary layer is limited to the pipe radius |
| Answer» E. | |
| 15. |
A plate 0.3 m long is placed at zero angle of incidence in a stream of 15 degree Celsius water moving at 1 m/s. Find out the maximum boundary layer thickness. For water at 15 degree Celsius. For water at 15 degree Celsiusp = 998.9 kg /m³µ = 415.85 * 10¯² kg/hr m |
| A. | 4.945 m |
| B. | 3.945 m |
| C. | 2.945 m |
| D. | 1.945 m |
| Answer» D. 1.945 m | |
| 16. |
Which is true for two dimensional boundary layer? |
| A. | d u/d x – d v/d y = 1 |
| B. | d u/d x – d v/d y = 0 |
| C. | d u/d x + d v/d y = 1 |
| D. | d u/d x + d v/d y = 0 |
| Answer» E. | |
| 17. |
Shear stress at the middle of the plate is given by |
| A. | T W = 0.964 p U INFINITY²/2 (Re)^1/2 |
| B. | T W = 0.864 p U INFINITY²/2 (Re)^1/2 |
| C. | T W = 0.764 p U INFINITY²/2 (Re)^1/2 |
| D. | T W = 0.664 p U INFINITY²/2 (Re)^1/2. |
| Answer» E. | |
| 18. |
The transition from laminar to turbulent pattern of flow occurs at values of Reynolds number between |
| A. | 1000-2000 |
| B. | 300000-500000 |
| C. | 500000-700000 |
| D. | 35750-45678 |
| Answer» C. 500000-700000 | |
| 19. |
The entrance length required for the flow to become fully-developed turbulent flow is dependent on(i) Surface finish(ii) Downstream conditions(iii) Fluid propertiesIdentify the correct answer |
| A. | 2 and 3 |
| B. | 1 and 3 |
| C. | 1, 2 and 3 |
| D. | 1 and 2 |
| Answer» D. 1 and 2 | |
| 20. |
What is the value of thickness of the boundary layer at leading edge of the plate? |
| A. | 0.33 |
| B. | 1 |
| C. | 0.5 |
| D. | 0 |
| Answer» E. | |
| 21. |
A flat plate 1 m by 1 m is placed in a wind tunnel. The velocity and temperature of free stream air are 80 m/s and 10 degree Celsius. The flow over the whole length of the plate is made turbulent by turbulizing grid placed upstream of the plate. Find the thickness of hydrodynamic boundary layer at trailing edge of the plate |
| A. | 19.55 mm |
| B. | 18.55 mm |
| C. | 17.55 mm |
| D. | 16.55 mm |
| Answer» E. | |
| 22. |
A plate 0.3 m long is placed at zero angle of incidence in a stream of 15 degree Celsius water moving at 1 m/s. Find out the stream wise velocity component at the mid-point of the boundary layer. For water at 15 degree Celsiusp = 998.9 kg /m³µ = 415.85 * 10¯² kg/hr m |
| A. | 0.736 m/s |
| B. | 0.636 m/s |
| C. | 0.536 m/s |
| D. | 0.436 m/s |
| Answer» B. 0.636 m/s | |
| 23. |
For a particular engine, the underside of the crankcase can be idealized as a flat plate measuring 80 cm by 20 cm. The engine runs at 80 km/hr and the crankcase is cooled by the air flowing past it at the same speed. Find loss of the heat from the crank case surface (t S = 25 degree Celsius). Assume the boundary layer to be turbulent |
| A. | 465.04 W |
| B. | 565.04 W |
| C. | 665.04 W |
| D. | 765.04 W |
| Answer» C. 665.04 W | |
| 24. |
Glycerin at 10 degree Celsius flows past a flat plate at 20 m/s. Workout the velocity components at a point P(x, y) in the fluid flow wherex = 2 m from the leading edge of the platey = 5 cm from the plate surfaceFor glycerin at 10 degree Celsius, kinematic viscosity = 2.79 * 10¯³ m²/s |
| A. | 15.92 m/s and 0.0952 m/s |
| B. | 16.92 m/s and 0.0952 m/s |
| C. | 17.92 m/s and 0.0752 m/s |
| D. | 18.92 m/s and 0.0752 m/s |
| Answer» C. 17.92 m/s and 0.0752 m/s | |
| 25. |
The free stream undisturbed flow has a uniform velocity U INFINITY in the |
| A. | X-direction |
| B. | Y-direction |
| C. | Z-direction |
| D. | Any direction |
| Answer» B. Y-direction | |
| 26. |
The thin layer where velocity changes continuously is called |
| A. | Differential layer |
| B. | Thermal boundary layer |
| C. | Hydrodynamic boundary layer |
| D. | Velocity distribution layer |
| Answer» D. Velocity distribution layer | |
| 27. |
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 thickness of the thermal boundary layer. Assume that transition occurs at a critical Reynolds number of 500000 |
| A. | 19.23 mm |
| B. | 18.23 mm |
| C. | 17.23 mm |
| D. | 16.23 mm |
| Answer» B. 18.23 mm | |
| 28. |
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 local convective heat transfer coefficient. Assume that transition occurs at a critical Reynolds number of 500000 |
| A. | 4.519 k J/m² hr degree |
| B. | 5.519 k J/m² hr degree |
| C. | 6.519 k J/m² hr degree |
| D. | 7.519 k J/m² hr degree |
| Answer» E. | |
| 29. |
The conditions for flow beyond the boundary layer and its outer edge are |
| A. | d u/d y = 0 and u = U 0 |
| B. | d u/d y = Infinity and u = U INFINITY |
| C. | d u/d y = 1 and u = U 0 |
| D. | d u/d y = 0 and u = U INFINITY |
| Answer» E. | |
| 30. |
The differential energy equation for flow past a flat plate is given by |
| A. | u d t/d x + v d t/d y = µ/p c (d u/d y)² + k d² t/p c d y² |
| B. | u d t/d x + v d t/d y = µ/p c (d u/d y) + k d² t/p c d y² |
| C. | u d t/d x + v d t/d y = k d² t/p c d y² + µ/p c (d u/d y)¯² |
| D. | u d t/d x + v d t/d y = µ/p c (d u/d y)¯¹ + k d² t/p c d y² |
| Answer» B. u d t/d x + v d t/d y = µ/p c (d u/d y) + k d² t/p c d y² | |
| 31. |
The pattern of flow in the boundary layer is judged by the |
| A. | Reynolds number |
| B. | Fourier number |
| C. | Peclet number |
| D. | Grashof number |
| Answer» B. Fourier number | |
| 32. |
The average drag coefficient for turbulent boundary layer flow past a thin plate is given byCf = 0.455/ (log10 Rel)^2.58Where R el is the Reynolds number based on plate length. A plate 50 cm wide and 5 m long is kept parallel to the flow of water with free stream velocity 3 m/s. Calculate the drag force on both sides of the plate. For water, kinematic viscosity = 0.01 stokes |
| A. | 53.38 N |
| B. | 63.38 N |
| C. | 73.38 N |
| D. | 83.38 N |
| Answer» C. 73.38 N | |
| 33. |
The relationship between the thermal and hydrodynamic boundary layer thickness is governed by the |
| A. | Peclet number |
| B. | Prandtl number |
| C. | Stanton number |
| D. | Fourier number |
| Answer» C. Stanton number | |
| 34. |
Air at 25 degree Celsius flows over a flat surface with a sharp leading edge at 1.5 m/s. Find the value of Reynolds number. For air at 25 degree Celsius, kinematic viscosity = 15.53* 10n¯⁶ m²/s |
| A. | 38694 |
| B. | 12846 |
| C. | 48294 |
| D. | 76386 |
| Answer» D. 76386 | |
| 35. |
A plate 0.3 m long is placed at zero angle of incidence in a stream of 15 degree Celsius water moving at 1 m/s. Find out the maximum value of the normal component of velocity at thr trailing edge of the plate. For water at 15 degree Celsiusp = 998.9 kg /m³µ = 415.85 * 10¯² kg/hr m |
| A. | 1.6885 * 10¯² m/s |
| B. | 1.6885 * 10¯³ m/s |
| C. | 1.6885 * 10¯⁴ m/s |
| D. | 1.6885 * 10¯⁵ m/s |
| Answer» C. 1.6885 * 10¯⁴ m/s | |
| 36. |
The lubricating oil for a large industrial gas turbine engine is cooled in a counter flow, concentric tube heat exchanger. The cooling water flows through the inner tube ( diameter = 25 mm) with inlet temperature 25 degree celsius and mass flow rate 0.2 kg/s. The oil flows through the annulus (diameter = 50 mm) with mass flow rate 0.125 kg/s and its temperature at entry and exit are 90 degree Celsius and 60 degree Celsius. Find outlet temperature of cooling water. |
| A. | 14.58 degree celsius |
| B. | 24.58 degree celsius |
| C. | 34.58 degree celsius |
| D. | 44.58 degree celsius |
| Answer» D. 44.58 degree celsius | |
| 37. |
A flat plate was positioned at zero incidence in a uniform flow stream of air. Assuming boundary layer to be turbulent over the entire plate, workout the ratio of skin-friction forces on the front and rear half part of the plate |
| A. | 1.557 |
| B. | 1.447 |
| C. | 1.347 |
| D. | 1.247 |
| Answer» D. 1.247 | |
| 38. |
A small thermo-couple is positioned in a thermal boundary layer near a flat plate past which water flows at 30 degree Celsius and 0.15 m/s. The plate is heated to a surface temperature of 50 degree Celsius and at the location of the probe, the thickness of thermal boundary layer is 15 mm. If the temperature profile as measured by the probe is well-represented byt – t S/t INFINITY – t S = 1.5 (y/δ t) – 0.5 (y/δ t)³Determine the heat flux from plate to water |
| A. | 266 W/m² |
| B. | 1266 W/m² |
| C. | 2266 W/m² |
| D. | 3266 W/m² |
| Answer» C. 2266 W/m² | |
| 39. |
Atmospheric air at 30 degree Celsius temperature and free stream velocity of 2.5 m/s flows along the length of a flat plate maintained at a uniform surface temperature of 90 degree Celsius. Let length = 100 cm, width = 50 cm and thickness = 2.5 cm. Thermal conductivity of the plate material is 25 W/m K, find heat lost by the plate |
| A. | 155.88 W |
| B. | 165.88 W |
| C. | 175.88 W |
| D. | 185.88 W |
| Answer» E. | |
| 40. |
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 thickness of the hydrodynamic boundary layer. Assume that transition occurs at a critical Reynolds number of 500000 |
| A. | 16.5 mm |
| B. | 17.5 mm |
| C. | 18.5 mm |
| D. | 19.5 mm |
| Answer» C. 18.5 mm | |
| 41. |
The concept of hydrodynamic boundary layer was first suggested by |
| A. | Isaac Newton |
| B. | Ludwig Prandtl |
| C. | Rodridge |
| D. | Fourier |
| Answer» C. Rodridge | |
| 42. |
Local skin friction coefficient is given by |
| A. | 0.646/ (Re)^1/2 |
| B. | 1.646/ (Re)^1/2 |
| C. | 2.646/ (Re)^1/2 |
| D. | 3.646/ (Re)^1/2 |
| Answer» B. 1.646/ (Re)^1/2 | |
| 43. |
The thickness of thermal boundary layer is arbitrarily defined as the distance from the plate surface at which |
| A. | t S – t/t S – t INFINITY = 0.34 |
| B. | t S – t/t S – t INFINITY = 0.10 |
| C. | t S – t/t S – t INFINITY = 0.99 |
| D. | t S – t/t S – t INFINITY = 0.87 |
| Answer» D. t S – t/t S – t INFINITY = 0.87 | |
| 44. |
The convection of energy reduces the outward conduction in the fluid so temperature gradient |
| A. | Decreases |
| B. | Increases |
| C. | Constant |
| D. | Becomes twice |
| Answer» B. Increases | |
| 45. |
Which field is set up when a fluid flows past a heated or cold surface? |
| A. | Energy |
| B. | Temperature |
| C. | Mass |
| D. | Time |
| Answer» C. Mass | |
| 46. |
The zone or thin layer wherein the temperature field exists is called the |
| A. | Single boundary layer |
| B. | Multi boundary layer |
| C. | Hydrodynamic boundary layer |
| D. | Thermal boundary layer |
| Answer» E. | |
| 47. |
The velocity profile of the hydrodynamic boundary layer is dependent upon |
| A. | Time |
| B. | Viscosity |
| C. | Temperature |
| D. | Mass |
| Answer» C. Temperature | |