Deck 16: Heat Transfer Processes, Thermometers, and Evaporators

Question 1

All heat transfer processes

A)Obey Newton's law
B)Involve temperature difference between the bodies
C)Obey first law of thermodynamics
D)Obey second law of thermodynamics
E)Involve transfer of energy

Answer 1

Involve temperature difference between the bodies

Question 2

A Foreman of an automobile workshop wants to measure the temperature inside the piston of a car, whose temperature will be of the order of 700°C (accurate upto 1°C). The best thermometer to use is

A)Constant volume hydrogen thermometer
B)Thermo electric thermometer
C)Platinum resistance thermometer
D)Optical pyrometer
E)Constant volume nitrogen thermometer

Answer 2

Thermo electric thermometer

Question 3

When analogy is drawn between heat flow and electricity flow in circuits, the heat flow of thermal circuits is equated in the electrical circuit against

A)Charge (coulombs)
B)Resistance
C)1 ; 81
D)Current
E)Voltage

Answer 3

Current

Question 4

The ratio of the actual vapour pressure to the pressure of saturated vapour at the prevailing dry bulb temperature is known as

A)Humidity
B)Relative humidity
C)Specific humidity
D)Humidity ratio
E)Vapour humidity

Question 5

A liquid to liquid counterflow heat exchanger is used to heat cold fluid from 50°C to 150°C. Assuming that the hot fluid enters at 250°C and leaves at 200°C, the log mean temperature difference for the heat exchanger will be closer to

A)137°C
B)37,500 kg
C)128°C
D)133°C
E)100°C

Question 6

A liquid is boiling in a a air tight vessel. Using an exhaust tube, the vapour is pumped out at a faster rate. What happens to the liquid?

A)Temperature goes down, doiling continues
B)Temperature goes down, boiling stops
C)Temperature goes up, boiling continues
D)Nothing changes
E)Temperature goes up, boiling stops

Question 7

The surface which diffusely reflects and emits the same amount of energy which it receives by radiation is known as

A)A perfect black surface
B)A perfect grey surface
C)A perfect white surface
D)A perfect radiating surface
E)None of the above

Question 8

Which of the following have the same units?

A)Stefan's canstant and Boltzmann constant
B)Plank's constant and Stefan's constant
C)Planck's constant and angular momentum
D)Boltzmann constant and Planck's constant
E)37,500 kg

Question 9

In case of solids, the heat transfer takes place according to

A)radiation
B)conduction
C)convection
D)Both (A) and (C)
E)Nichrome

Question 10

Absolute zero is

A)0°C
B)0°R
C)0°F
D)0°K
E)273°C

Question 11

The heat of sum reaches to us according to

A)radiation
B)conduction
C)convection
D)None of the above
E)Nichrome

Question 12

A prototype is

A)a dynamically similar model on reduced scale
B)a kinematically similar model on reduced scale
C)37,500 kg
D)a geometrical similar model on reduced scale
E)a full size structure employed in actual engineering design

Question 13

The equation E = AT4 represents

A)Wein's Law
B)Kirchhoff's law
C)Stefan Boltzmann's law
D)None of the above
E)Nichrome

Question 14

Two pieces of wood are placed in sunlight. One is painted white and the other is painted black. It can be concluded that

A)White painted wood will not absorb any solar radiation
B)Black painted wood will not absorb any solar radiation
C)Black painted wood will absorb less heat as compared to white painted wood
D)37,500 kg
E)Black painted wood will absorb more hcat as compared to white painted wood

Question 15

A dimensionless group which represents the rate of the (product of intertial forces times buoyant forces) to viscous force squared is known as

A)Reynolds number
B)Mach number
C)Prandtl number
D)Grashof number
E)Nusselt number

Question 16

The ratio of heat transfer coefficient to the flow of heat per unit temperature rise due to the velocity of the fluid is known as

A)Stanton number
B)Weber number
C)Prandtl number
D)37,500 kg
E)Grashoff number

Question 17

Which evaporator is preferred for concentrating the fruit juice?

A)Agitated film evaporator
B)Falling film evaporator
C)Long vertical tube evaporator
D)Zig-zag film evaporator
E)Short vertical tube evaporator

Question 18

A perfect black body is the one which

A)Absorbs all incident radiation
B)Reflects all incident radiation
C)Absorbs most of the incident radiation
D)Is coated with lamp black
E)None of the above

Question 19

Three rods one made of glass, one of pure aluminium and one made of wrought iron are heated to 150°C. All the rods are 15 mm in diameter and 300 mm long. The lowest temperature at the free end of the rods will occur in case of

A)Glass rod
B)Wrought iron rod
C)Temperature will depend on the surrounding air temperature
D)Aluminium rod
E)Temperature will be same for all the three rods at free end

Question 20

Non-dimensional number generally involved in case of heat transfer from horizontal cylinder by natural convection is

A)Reynolds number
B)Nusselt number
C)Prandtl number
D)Grashof's numbr
E)(B), (C) and (D) above

Question 21

Body A is kept in contact with body B. Heat will flow from A to B, if

A)The heat content of A is greater than that of B
B)The temperature of A is greter than that of B
C)The specific heat of A is greater than that of B
D)The specific heat of A is lower than that of B
E)None of the above

Question 22

What energy transformation takes place when ice is converted into water

A)Heat energy to kinetic energy
B)Kinetic energy to heat energy
C)Heat energy to latent heat
D)Heat energy to potential energy
E)None of the above

Question 23

Which dimensionless number correlates the relative thickness of the hydrodynamic and thermal boundary layers?

A)Mach number
B)37,500 kg
C)Prandlt number
D)Nusselt number
E)Crash off number

Question 24

Prandtl number for gases is

A)more than 1000
B)37,500 kg
C)near unity
D)between 100 and 1000
E)between 10 to 100

Question 25

Molecular transmission of heat is smallest in case of

A)Alloys
B)Solids
C)Liquids with impurities
D)Gases
E)Liquids

Question 26

Which one of the following will have least value of thermal conductivity?

A)Silver
B)Water
C)Glass
D)Air
E)Copper

Question 27

Which of the following property of air does not increase with rise in temperature?

A)Specific volume
B)Specific gravity
C)Thermal conductivity
D)Thermal diffusivity
E)Kinematic viscosity

Question 28

Entrainment separator is used in evaporators to

A)Reduce the boiling point
B)Increase the boiling point
C)Separate liquid droplets from vapour
D)Prevent foaming
E)Discharge mud and other impurities

Question 29

Which of the following can be used to measure a temperature around -50°C?

A)Platinum resistance thermometer
B)Thermocouple
C)Alcohol thermometer
D)Mercury thermometer
E)37,500 kg

Question 30

The surface temperature of the sun is

A)20000°K
B)2000°K
C)6000°K
D)Infinitely large
E)Millions of degrees

Question 31

What whould be shape of an ideal thermometer?

A)Spherical
B)Cylindrical
C)Cubical
D)Rectangular
E)None of the above

Question 32

Fouling factor

A)Measures the heat transfer efficiency
B)Is used only in case of Newtonian fluids
C)Is used when a liquid exchanges heat with a gas
D)Is dimensionless
E)Is virtually a factor of safety in heat exchanger design

Question 33

A dimensionless number representing the ratio of inertia forces to viscous forces is known as

A)Mach number
B)Prandtl number
C)Reynolds number
D)Nusselt number
E)Stanton number

Question 34

Insulation in cavity walls is

A)Water
B)Air
C)Cork
D)Wood
E)None of the above

Question 35

Thermal conductivity of wood least depends on

A)Moisture
B)Density
C)Temperature
D)Grain orientation
E)All of the above

Question 36

Heat is transferred from an insulated pipe to the surrounding still air mainly by

A)Free convection
B)Forced convection
C)All above together
D)Radiation
E)Conduction

Question 37

Dynamic similarity refers to the similarity of

A)37,500 kg
B)temperature and heat flux
C)masses and forces
D)velocity and acceleration
E)physical dimensions

Question 38

A sphere 15 cm in diameter is covered with 5 cm of insulation (k = 0.057 kcal/m-hr-°C). The inside and outside surface temperature of the insulation are 315°C and 80°C respectively. The heat loss per sq. m of the outside surface will be closer to

A)80 kcal/hr
B)320 kcal/hr
C)160 kcal/hr
D)37,500 kg
E)40 kcal/hr

Question 39

The net radiant interchange per square metre for two large parallel planes at temperatures of 1000°K and 100°K respectively, would be roughly

A)240 kcal/hr
B)75 kcal/hr
C)25 kcal/hr
D)480 kcal/hr
E)120 kcal/hr

Question 40

Which variety of steel may be expected to have lowest value of thermal conductivity?

A)High carbon steel (0.83% C)
B)Low nickel steel (1.37% Ni)
C)Low chromium steel (0.46% Cr)
D)High chromium steel (0.26% Cr)
E)Chromium nickel steel (9% Ni, 18% Cr)

Question 41

In an air-conditioning plant a cooling tower is used to cool

A)air
B)refrigerant
C)condenser water
D)None of the above
E)37,500 kg

Question 42

Which method can be used for heating wood?

A)Flame heating
B)Resistance heating
C)Dielectric heating
D)Radiation heating
E)Any of the above

Question 43

A correction of LMTD is necessary in case of

A)Parallel flow heat exchanger
B)Counter current heat exchanger
C)Cross flow heat exchanger
D)All of the above
E)None of the above

Question 44

In which of the following heat exchange process, the value of overall heat transfer coefficient will be highest?

A)Air to carbondioxide
B)Air to heavy tars
C)37,500 kg
D)Steam condensers
E)Steam to oil

Question 45

A grey body has emissivity

A)37,500 kg
B)1
C)less than 1
D)more than 1
E)0.5

Question 46

The density of water is maximum at

A)Absolute zero
B)20°C
C)0°C
D)4°C
E)- 4°C

Question 47

A thin circulr disc has a concentric hole in it. On heating the diameter of hole will

A)decrease
B)remain constant
C)37,500 kg
D)increase

Question 48

Which is the unit of Stefan Boltzmann constant

A)W/m² K⁴
B)erg/cm²-sec-K⁴
C)cal/cm²-sec K⁴
D)kcal/m²-hr-K⁴
E)All of the above