Heat Transfer MCQs

Question 1

In pipe flow, heat is transferred from hot wall to the liquid by

Accepted Answer

Forced convection and conduction

Answer

Conduction only

Answer

Forced convection only

Answer

Free and forced convection

Question 2

Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by

Accepted Answer

Conduction

Answer

Eddies current

Answer

Convection

Answer

None of these

Question 3

In a cooling tower, water becomes cool by

Accepted Answer

Loosing sensible heat

Answer

Heat transfer to surroundings

Answer

Vaporisation due to heat loss to air

Answer

Loosing latent heat

Question 4

Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C.

Accepted Answer

5000 - 15000

Answer

10 - 50

Answer

100 - 500

Answer

1000 - 1500

Question 5

LMTD for counterflow and prallel flow heat exchanger will be the same, when the

Accepted Answer

Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

Answer

Outlent temperature of both the hot and cold fluid are same

Answer

Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid

Answer

None of these

Question 6

In a shell and tube heat exchanger, floating head is used for

Accepted Answer

Large temperature differentials

Answer

High heat transfer co-efficient

Answer

Low pressure drop

Answer

Less corrosion of tubes

Question 7

What is the steam economy in case of a single effect evaporator system?

Accepted Answer

< 1

Answer

1

Answer

> 1

Answer

0.1

Question 8

Graetz number is given by

Accepted Answer

$$\frac{{{	ext{m}}{{	ext{C}}_{	ext{p}}}}}{{{	ext{kL}}}}$$

Answer

$$\frac{{{	ext{kL}}}}{{{	ext{m}}{{	ext{C}}_{	ext{p}}}}}$$

Answer

$$\frac{{{	ext{m}}{{	ext{C}}_{	ext{p}}}}}{{{	ext{k}}\mu }}$$

Answer

$$\frac{{{	ext{k}}\mu }}{{{	ext{m}}{{	ext{C}}_{	ext{p}}}}}$$

Question 9

Grashhoff number is given by

Accepted Answer

gD3.β.Δtρ2/μ2

Answer

gD2.β.Δtρ/μ2

Answer

gD2.β.ΔtP2μ

Answer

gD3.β.ΔtP2/μ