Heat Transfer MCQ Questions & Answers

51

For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, N_Pr = Prandtl number)

A) N_Pr B) $${\text{N}}_{{\text{Pr}}}^{\frac{1}{3}}$$ C) $${\text{N}}_{{\text{Pr}}}^{ - 1}$$ D) $${\text{N}}_{{\text{Pr}}}^{ - \frac{1}{3}}$$

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Answer & Solution

Answer: Option B

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52

The critical radius 'r' of insulation on a pipe is given by

A) $${\text{r}} = \frac{{2{\text{k}}}}{{\text{h}}}$$ B) $${\text{r}} = \frac{{\text{k}}}{{\text{h}}}$$ C) $${\text{r}} = \frac{{\text{k}}}{{2{\text{h}}}}$$ D) $${\text{r}} = \frac{{\text{h}}}{{\text{k}}}$$

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Answer & Solution

Answer: Option B

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53

Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by

A) Keeping the heat transfer surface clean B) Enhancing the fluid pumping rate C) Increasing the tube length D) None of these

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Answer & Solution

Answer: Option A

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54

Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface?

A) Liquid density B) Liquid viscosity C) Hot surface temperature D) Interfacial tension

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Answer & Solution

Answer: Option D

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55

Leidenfrost point is a term concerned with the

A) Condensation of the saturated vapor on a cold surface B) Concentration of a corrosive solution by evaporation C) Heat transfer between two highly viscous liquids D) Boiling of a liquid on a hot surface

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Answer & Solution

Answer: Option D

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56

The unit of conductance in SI unit is

A) W/m B) W/m² C) W/°K D) W/m°K

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Answer & Solution

Answer: Option C

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57

With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer

A) Decreases B) Increases C) Increases exponentially D) Remains unaffected

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Answer & Solution

Answer: Option A

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58

Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

A) Existence of thermal boundary layer B) Temperature gradient produced due to density difference C) Buoyancy of the bubbles produced at active nucleation site D) None of these

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Answer & Solution

Answer: Option B

Solution:

In natural convection heat transfer, fluid motion is driven by the temperature gradient produced due to density difference. As a fluid near a heated surface becomes warmer, it tends to rise due to a decrease in density. Conversely, the cooler fluid descends. This creates a continuous circulation known as natural convection currents.

Therefore, the correct answer is Option B: Temperature gradient produced due to density difference.

59

For a multipass shell and tube heat exchanger, the LMTD correction factor is always

A) 1 B) > 1 C) < 1 D) Between 1 & 2

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Answer & Solution

Answer: Option C

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60

The energy radiated from a surface Q at absolute temperature T is related as

A) Q ∝ T² B) Q ∝ T⁴ C) Q ∝ T³ D) None of these

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Answer & Solution

Answer: Option B

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Heat Transfer MCQ Questions & Answers | Chemical Engineering