Deck 22: Heat Transfer and Boiling Point Elevation in Solutions

Question 1

Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.

A)Boiling point
B)Dynamic viscosity
C)Kinematic viscosity
D)Density

Answer 1

Boiling point

Question 2

In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is

A)Linear
B)Hyperbolic
C)Parabolic
D)None of these

Answer 2

Parabolic

Question 3

The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in laminar zone is related as

A)ha = 0.8hL
B)ha = 2hL
C)ha = hL
D)ha = 5hL

Answer 3

ha = 2hL

Question 4

Which has the lowest Prandtl number?

A)Liquid metal
B)Aqueous solution
C)Water
D)Lube oil

Question 5

Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K)

A)t4
B)T4
C)1/t4
D)1/T4

Question 6

The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is

A)2
B)1/2
C)4
D)1/4

Question 7

The equation, (NSt × N 2/3 Pr) = f/2, is the __________ analogy.

A)Colburn
B)Reynolds
C)Prandtl
D)None of these

Question 8

What is the geometric mean of two heat transfer areas A1 and A2?

A)?(A1 . A2)
B)?(A1 + A2)
C)½ ?(A1 . A2)
D)2 ?(A1 . A2)

Question 9

The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns.

A)0.38-0.78
B)0.5-50
C)100-1000
D)5-50

Question 10

Stefan's block body radiation law can also be derived from __________ law.

A)Kirchoff's
B)Planck's
C)Fourier's
D)None of these

Question 11

Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.

A)Boiling point (at the same pressure)
B)Viscosity
C)Density
D)Thermal conductivity

Question 12

Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around __________ BTU.

A)180
B)970
C)3.97
D)Data insufficient, can't be predicted

Question 13

Prandtl number for most of dry gases is about

A)0.001
B)0.72
C)70
D)150

Question 14

Pick out the wrong statement.

A)The emissivity of a surface decreases, if it gets corroded by atmospheric environment
B)The emissivity of a surface increases with increase in surface roughness
C)The emissivity of a polished surface is quite low
D)The emissivity of a non-metallic surface decreases with increase in the temperature

Question 15

Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the

A)Less corrosion problems
B)Flexibility possible in the baffle arrangement
C)Low pressure drop
D)High heat transfer co-efficient

Question 16

Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is

A)0.4
B)0.5
C)0.6
D)0.7

Question 17

The purpose of providing expansion bellows in the shell of tubular exchanger is to

A)Increase the heating load
B)Impart structural strength
C)Account for the uneven expansion of shell and tube bundles
D)Facilitate increase of shell length, if needed

Question 18

An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a

A)Boiler
B)Heat exchanger
C)Recuperator
D)Regenerator

Question 19

Multipass heat exchangers are used

A)Because of simplicity of fabrication
B)For low heat load
C)To obtain higher heat transfer co-efficient and shorter tube
D)To reduce the pressure drop

Question 20

A black body does not __________ radiation.

A)Absorb or emit
B)Refract
C)Reflect
D)Both (B) & (C)

Question 21

It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is

A)> 0.75
B)< 0.75
C)< 0.50
D)< 0.25

Question 22

Multiple effect evaporation accounts for

A)Steam economy
B)Lower operating costs
C)Investment economy
D)None of these

Question 23

Finned tube heat exchangers

A)Give larger area per tube
B)Use metal fins of low thermal conductivity
C)Facilitate very large temperature drop through tube wall
D)Are used for smaller heat load

Question 24

Tube expansion allowances exist in __________ heat exchanger.

A)Multipass fixed tube sheet
B)U-tube
C)Single pass fixed tube sheet
D)None of these

Question 25

Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.

A)Long tube
B)Falling film
C)High pressure
D)None of these