Mechanical Engineering

Question: In counter-current flow heat exchangers
[A].

both the fluids at inlet are in their hottest state

[B].

both the fluids at inlet are in their coldest state

[C].

both the fluids at exit are in their hottest state

[D].

one fluid is coldest and the other is hottest at inlet

Answer: Option A

Explanation:

No answer description available for this question.

Question: In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.
[A].

same

[B].

less

[C].

greater

Answer: Option C

Explanation:

No answer description available for this question.

Question: In a parallel flow heat exchanger, the rate of flow of heat and the rate of decrease of temperature are maximum.
[A].

Yes

[B].

No

Answer: Option A

Explanation:

No answer description available for this question.

Question: Logarithmic mean temperature difference is the same as the arithmetic mean temperature difference.
[A].

Agree

[B].

Disagree

Answer: Option B

Explanation:

No answer description available for this question.

Question: A device used for transfering heat from one fluid to another is called heat exchanger.
[A].

True

[B].

False

Answer: Option A

Explanation:

No answer description available for this question.

Question: Free convection flow depends on
[A].

density

[B].

coefficient of viscosity

[C].

gravitational force

[D].

all of these

Answer: Option D

Explanation:

No answer description available for this question.

Question: An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m2). The critical thickness of insulation will be
[A].

25 mm

[B].

40 mm

[C].

160 mm

[D].

800 mm

Answer: Option A

Explanation:

No answer description available for this question.

Question: Fourier’s law of heat conduction gives the heat flow for
[A].

irregular surfaces

[B].

non-uniform temperature surfaces

[C].

one dimensional cases only

[D].

two dimensional cases only

Answer: Option C

Explanation:

No answer description available for this question.

Question: A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is
[A].

h1 + h2 + h3

[B].

(h1h2h3)1/3

[C].

[D].

none of these

Answer: Option D

Explanation:

No answer description available for this question.

Question: Film coefficient is defined as the ratio of
[A].

thermal conductivity to the equivalent thickness of the film of fluid

[B].

temperature drop through the films of fluids to the thickness of film of fluids

[C].

thickness of film of fluid to the thermal conductivity

[D].

thickness of film of fluid to the temperature drop through the films of fluids

Answer: Option A

Explanation:

No answer description available for this question.