Deck 10: Heat Transfer and Thermal Properties: Part B

Question 1

Which liquid metal is supposed to be the best conductor

A)Zinc
B)Lead
C)Potassium
D)Mercury
E)Sodium

Answer 1

Sodium

Question 2

In sugar mills cane juice is evaporated in

A)Long vertical tube evaporators
B)Flash evaporator
C)Horizontal tube evaporators
D)Zig-zag tube evaporator
E)Short vertical tube evaporators

Answer 2

Long vertical tube evaporators

Question 3

The unit of thermal diffusivity is

A)m²/hr°C
B)m²/hr
C)m/hr°C
D)kcal/m²-hr
E)m/hr

Answer 3

m²/hr

Question 4

The diathermous body is one that

A)diffuses all the thermal rays in the different directions
B)allows all the incident radiation to pass through it
C)37,500 kg
D)negligible absorptivity but high reflectivity
E)absorbs all the thermal rays

Question 5

Thermal conductivity of water at 20°C is nearly

A)0.051
B)1
C)0.11
D)0.09
E)0.5

Question 6

Dropwise condensation occurs on a

A)Glazed surface
B)Smooth surface
C)Oily surface
D)Coated surface
E)None of the above

Question 7

The value of reheat factor is of the order of

A)37,500 kg
B)Less than 1
C)1.02 to 1.06
D)1.2 to 1.6
E)More than 2

Question 8

Heat is transferred by conduction, convection and radiation in

A)Melting of ice
B)Refrigerator freezer coils
C)Boiler furnaces
D)Condensation of steam in a condenser
E)Insulated pipes carrying hot water

Question 9

Which one of the following materials will have highest value of thermal conductivity?

A)Copper
B)Lead
C)Brass
D)Aluminium
E)Steel

Question 10

In the temperature of air above a pond is 8°C thermal conductivity of ice is 0.005 C.G.S. units, latent heat of fusion of ice is 79.9 cal/gram the density of ice is 1 gm/cu.m, the time taken for the formation of ice layer of 1 cm thickness is

A)200 seconds
B)100 seconds
C)12.5 seconds
D)10 seconds
E)None of the above

Question 11

The value of Prandtl number for air is of the order of

A)67
B)1000
C)0.7
D)9.7
E)0.065

Question 12

The temperature reading taken using Centigrade and Fahrenheit thermometers are plotted on a graph -°C along X-axis, °F along Y-axis. The shape of graph would be

A)Straight line cutting an intercept on the negative Y-axis
B)Straight line cutting an intercept on the positive Y-axis
C)Straight line cutting an intercept on the negative X-axis
D)273°C
E)Straight line cutting an intercept on the positive X-axis

Question 13

Agitated film evaporator is suitable for concentrating

A)Insulating liquids
B)Low temperature liquids
C)Viscous liquids
D)Corrosive liquids
E)Liquid metal

Question 14

Hygrometer is used to measure

A)Convective heat transfer coefficient
B)Heat exchanged due to vapour
C)Density of liquids
D)Relative humidity
E)None of the above

Question 15

a micron is equal to

A)10-6 metres
B)10^-8 metres
C)10-5 metres
D)10-12 metres
E)10-4 metres

Question 16

The process of heat transfer during the re-entry of satellites and missiles, at very high speeds, into the earth's atmosphere is known as

A)Radiation
B)Viscous dissipation
C)Triple flow
D)Ablation
E)None of the above

Question 17

A slab of ice has one-half covered with black cloth and the other half with white cloth. The slab is now placed in sunlight. It will be observed that

A)37,500 kg
B)more ice will melt under black cloth
C)more ice will melt under white cloth
D)ice will not melt
E)equal amount of ice will melt under the two cloths

Question 18

In which of the following will the evaporation rate be large?

A)Leaking water from pipe.
B)Near the mountain
C)Covered swimming pool
D)Narrow river surrounded by trees
E)Salt pan near the sea

Question 19

A body which transmits all the radiations falling on it is known as

A)Black body
B)Grey body
C)Transparent body
D)White body
E)None of the above

Question 20

The value of the wavelength for maximum emissive power is given by

A)Stefan law
B)Wein's law
C)Planck's law
D)Kirchhoff's law
E)D'Alembert's rule

Question 21

The material preferred for the fabrication of fruit juice concentrator is

A)Mild steel sheet
B)Brass
C)Cast iron
D)Stainless steel sheet
E)Copper

Question 22

Gases have poor

A)Absorptivity
B)Transmissivity
C)Reflectivity
D)Reflectivity + absorptivity
E)Absorptivity + transmissivity

Question 23

Which is not the assumption in Fourier's equation of heat conduction?

A)Uniform area of cross-section
B)Steady heat flow
C)Homogeneous substance
D)Constant temperature difference
E)Thermal conductivity independent of temperature

Question 24

Unsteady state of heat flow occurs in

A)Flow of heat through furnace walls
B)Flow of heat through insulated pipe with constant surface temperature
C)Annealing of castings
D)Flow of heat through refrigerator walls
E)None of the above

Question 25

Which of the following has higher thermal conductivity as compared to the remaining?

A)Air
B)Water
C)37,500 kg
D)Hydrogen
E)Oxygen

Question 26

Which of the following material has highest value of thermal diffusivity?

A)Steel
B)Concrete
C)Lead
D)Mineral wool
E)Wood

Question 27

The quantity of heat required to change the temperature of 1 gm of ice from -6°C to -5°C is known as

A)Freezing heat
B)Cold heat
C)Latent heat of freezing
D)Specific heat
E)Heat of vaporization

Question 28

For temperature below -40°C which one of the following substance can be used as thermometric substance

A)Alcohol
B)Pentane
C)Ether
D)Any of the above
E)None of the above

Question 29

The conditions under which three phases of matter can coexist in equilibrium, is known as

A)Common point
B)Triple point
C)Absolute point
D)Basic point
E)Standard point

Question 30

The process of removal of oil from oil cakes is known as

A)Leaching
B)Decoction
C)Osmosis
D)Soret effect
E)None of the above

Question 31

A thermistor is a

A)Miniature resistance
B)Thermo-couple
C)Thermometer
D)Thermal insulation
E)Thermal resistance

Question 32

In the electrical network analysis method the total radiation which leaves a surface per unit time per unit area is termed as

A)Flux
B)Potential
C)Irradiation
D)Spatial resistance
E)Radiosity

Question 33

If in a system ratios of the velocity and acceleration of the homologous particles are equal, the similarity being considered is

A)geometric similarity
B)kinematic similarity
C)dynamic similarity
D)thermal similarity
E)37,500 kg

Question 34

A wet solid is to be dried from 80% to 50% moisture (on wet basis). Calculate the moisture to be evaporated for 10 tonns of dried product?

A)3750 kg
B)37,500 kg
C)375 kg
D)7500 kg
E)13,750 kg

Question 35

Grashoff number has significant role in heat transfer by

A)37,500 kg
B)radiation
C)natural connection
D)conduction
E)Forced convection

Question 36

Least value of Prandlt number can be expected in case of

A)Salt solution
B)Water
C)Sugar solution
D)Petroleum products
E)Liquid metals

Question 37

Heat conduction does not occur

A)If the parts of a body are not in motion relative to one another
B)If the bodies are immersed in water
C)If the temperature difference between the bodies does not exist
D)If a physical body is impermeable to any kind of rays
E)If the bodies are kept in vacuum

Question 38

The triple point temperature for water is

A)0°K
B)0.1°C
C)0.01°C
D)0°C
E)0.001°C

Question 39

The numerical value of which property of air generally drops with rising temperature

A)Thermal diffusivity
B)Density
C)Kinematic viscosity
D)Thermal conductivity
E)Dynamic viscosity

Question 40

A black body absorbs all radiations. As a result of absorption of these radiations

A)A black body shines
B)The temperature of black body rises
C)Black body radiates energy to other bodies
D)Black body becomes good conductor of heat
E)None of the above

Question 41

Thermal diffusivity is least for

A)Mercury
B)Rubber
C)Lead
D)Iron
E)Aluminium

Question 42

A block of wood and a block of metal feel equally cold or equally hot when touched. Then their common temperature is

A)0°K
B)0°F
C)0°C
D)37,500 kg
E)the same as that of the human body

Question 43

The expression (A2-A1)/loge (A2/A1) for a hollow cylinder is known as

A)Logarithmic mean radius
B)Mean area of heat transfer
C)The rate of heat transfer
D)None of the above
E)Nichrome

Question 44

"The boiling point of a solution is a linear function of water at the same pressure". The above statement is associated with

A)Dubring's rule
B)Petit and Dulong law
C)Fick's rule
D)Reynolds law
E)None of the above

Question 45

When a vapour condenses into a liquid

A)It absorbs heat
B)It evolves heat
C)Its temperature rises
D)Its temperature drops
E)None of the above

Question 46

If the absorptivity plus reflectivity of a body equals 1, then the body is known as

A)Black body
B)Grey body
C)Opaque body
D)White body
E)None of the above

Question 47

Prandtl number for liquid metals is generally in the range

A)1000 to 10,000
B)0.003 to 0.01
C)10 to 100
D)100 to 1000
E)37,500 kg

Question 48

A sphere of radius 40 cm is lagged to a radius of 50 cm. The temperatures of outer and inner surfaces are 66°C and 235°C respectively. Thermal conductivity of logging per cm thickness is 0.7 kcal/m-hr°C. The rate of heat leakage will be

A)500 kcal/hr
B)1.49 kcal/hr
C)666 kcal/hr
D)298 kcal/hr
E)398 kcal/hr

Question 49

A non-dimensional number generally associated with natural convection heat transfer is

A)Prandtl number
B)Weber number
C)Peclet number
D)Nusselt number
E)Grashof number