Heat Transfer Mock Test 9

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Question 1 of 10

1. 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

765.04 W

665.04 W

465.04 W

565.04 W

Question 1 of 10

Question 2 of 10

2. The energy transfer between the hot fluid and cold fluids is brought about by their complete physical mixing in

Direct contact heat exchanger

Boilers

Recuperators

Regenerators

Question 2 of 10

Question 3 of 10

3. What is the symbol used for thermal conductivity?

Question 3 of 10

Question 4 of 10

4. 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

1.557

1.247

1.347

1.447

Question 4 of 10

Question 5 of 10

5. Mark the wrong statement with respect to laminar flow condensation on a vertical plate

The average heat transfer coefficient is two third of the local heat transfer coefficient at the lower edge of the plate

The rate of condensation heat transfer is maximum at the upper edge of the plate and progressively decreases as the lower edge is approached

The film thickness increases as the fourth root of the distance down the upper edge

At a definite point on the heat transfer, the film coefficient is directly proportional to thermal conductivity and inversely proportional to thickness of film at the point

Question 5 of 10

Question 6 of 10

6. How many fluids remain at a constant temperature during the process of boiling and condensation?

Question 6 of 10

Question 7 of 10

7. Identify the correct expression for effectiveness

2 – exponential (- NTU)

1 – exponential (- NTU)

4 – exponential (- NTU)

3 – exponential (- NTU)

Question 7 of 10

Question 8 of 10

8. Which one is having the lowest value of fouling factor?

Distilled water

Transformers

Lubricating oil

Lake river

Question 8 of 10

Question 9 of 10

9. The convection of energy reduces the outward conduction in the fluid so temperature gradient

Constant

Increases

Becomes twice

Decreases

Question 9 of 10

Question 10 of 10

10. A steam condenser is transferring 250 k W of thermal energy at a condensing temperature of 65 degree Celsius. The cooling water enters the condenser at 20 degree Celsius with a flow rate of 7500 kg/hr. If overall heat transfer coefficient for the condenser surface is 1250 W/m² K, what surface area is required to handle this load?

6.08 m²

7.08 m²

5.08 m²

4.08 m²

Question 10 of 10