Hydrodynamic And Thermal Boundary Layers MCQs

Welcome to our comprehensive collection of Multiple Choice Questions (MCQs) on Hydrodynamic And Thermal Boundary Layers, a fundamental topic in the field of Heat Transfer. Whether you're preparing for competitive exams, honing your problem-solving skills, or simply looking to enhance your abilities in this field, our Hydrodynamic And Thermal Boundary Layers MCQs are designed to help you grasp the core concepts and excel in solving problems.

In this section, you'll find a wide range of Hydrodynamic And Thermal Boundary Layers mcq questions that explore various aspects of Hydrodynamic And Thermal Boundary Layers problems. Each MCQ is crafted to challenge your understanding of Hydrodynamic And Thermal Boundary Layers principles, enabling you to refine your problem-solving techniques. Whether you're a student aiming to ace Heat Transfer tests, a job seeker preparing for interviews, or someone simply interested in sharpening their skills, our Hydrodynamic And Thermal Boundary Layers MCQs are your pathway to success in mastering this essential Heat Transfer topic.

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Hydrodynamic And Thermal Boundary Layers MCQs | Page 2 of 5

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Q11.
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

Discuss
Answer: (a).5.83 W/m² K
Q12.
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 by

t – t S/t INFINITY – t S = 1.5 (y/δ t) – 0.5 (y/δ t)³

Determine the heat flux from plate to water

a.

266 W/m²

b.

1266 W/m²

c.

2266 W/m²

d.

3266 W/m²

Discuss
Answer: (b).1266 W/m²
Q13.
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

Discuss
Answer: (d).185.88 W
Q14.
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

Discuss
Answer: (c).2.67 m
Q15.
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

Discuss
Answer: (b).17.5 mm
Q16.
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

Discuss
Answer: (a).19.23 mm
Q17.
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

Discuss
Answer: (d).7.519 k J/m² hr degree
Q18.
Temperature and velocity profiles are identical when the dimensionless Prandtl number is

a.

1

b.

2

c.

3

d.

4

Discuss
Answer: (a).1
Q19.
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

Discuss
Answer: (c).Nu x/ (Re x) (Pr x) = St X = – ½ C F x
Q20.
The average drag coefficient for turbulent boundary layer flow past a thin plate is given by

Cf = 0.455/ (log10 Rel)^2.58

Where 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

Discuss
Answer: (b).63.38 N
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