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Heat Transfer > Heat Transfer > Flashcards

Heat Transfer Flashcards

1
Q

“Heat” is defined as?

A. Energy transferred between matter as a result of differences in temperature

B. The energy required to raise the temperature of a given amount of a substance one degree

C. The measure of the average kinetic energy of the particles in matter.

D. The energy required to cause a change of state in a substance

A

A

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2
Q

Temperature is defined as?

A. A measure of the average kinetic energy of the particles in matter

B. A measure of the potential energy contained with in a sunstance

C. A measure of the entropy contained with in a substance

D. A measure of a substances ability to do work

A

A

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3
Q

Thermodynamics means:

A. Heat motion

B. Movement of temperature

C. Heat energy

D. The dynamics of motion

A

A

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4
Q

The Concorde supersonic airplane is approximately 20 cm (about 8 inches) longer when in flight at normal cruising speed and altitude than it is when parked. What causes this phenomenon?

A. Being closer to the sun at high altitudes which heats up the aircraft and causes it to expand

B. The extreme drag resulting from the very dense air at the high altitudes at which the Concorde flies

C. The lower air pressure at the high altitudes at which the Concorde flies which allows the skin of the aircraft to expand

D. The extreme air friction that results when an aircraft flies at supersonic speed causing the skin of the Concorde to heat up and expand

A

D

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5
Q

When liquids are cooled, they almost always:

A. Contract

B. Remain unchanged

C. Expand for a while, then contract

D. Expand

A

A

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6
Q

When liquids are heated, they almost always:

A. Contract

B. Expand for a while, then contract

C. Remain unchanged

D. Expand

A

D

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7
Q

The outside temperature is -15oC. Calculate how much is this on the Fahrenheit scale.

A. -40 degrees F

B. -26 degrees F

C. 9 degrees F

D. 5 degrees F

A

D

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8
Q

The outside temperature is -25oF. Calculate this temperature on the Celsius scale.

A. -3.9oC

B. 77oC

C. -31.66oC

D. -102.6oC

A

C

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9
Q

Bimetalic strips function by the mechanism of:

A. Differential pressure

B. Differential potential

C. Differential temperature

D. Differential expansion

A

D

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10
Q

Regarding a bimetallic strip, a temperature change will result in which of the following?

A. Differential potential between two bonded metals generating a signal

B. Differential expansion of the two bonded metals resulting in mechanical deformation of the strip

C. Change of the chemical properties of two bonded metals, changing the electrical charge

D. Change of resistance across the two bonded metals allowing a reading to be taken

A

B

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11
Q

Which of the following describes the general effect on liquid due to a change in temperature?

A. They change in volume only as they change phase

B. They decrease in density as temperature decreases and increase in density as temperature increases

C. They expand as temperature decreases and contract as temperature increases

D. They expand as temperature increases and contract as temperature decreases

A

D

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12
Q

Nearly all substances expand when heated and contract when cooled. How is water different from nearly all other substances when it is heated or cooled.

A. When water is heated, it contracts

B. When water is heated between 0°C and 4°C, it contracts

C. When water is cooled from 70°F to 65°F, it expands

D. When water is heated to temperatures between 100°C and 112°C, it contracts

A

B

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13
Q

Lakes are prevented from freezing from the bottom up because:

A. Water can only freeze from the top down

B. Water expands as it goes below 0°C

C. Unlike other liquids, water expands when it is cooled

D. Water density decreases as it is cooled from 4°C to 0°C

A

D

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14
Q

When a gas, such as nitrogen, is cooled, it:

A. Expands

B. Contracts

C. Remains unchanged

D. Contracts for a while, then expands

A

B

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15
Q

When a gas, such as nitrogen, is heated, it:

A. Expands

B. Contracts

C. Expands for a while, then contracts

D. Remains unchanged

A

A

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16
Q

Using the table of heat conduction coefficients below, determine which of the following is the best insulator.

 Heat Conduction Coefficients 
	Material		   Coefficient 
	Silver			100 (the standard)
	Copper			92
	Aluminum		50
	Iron			11
	Glass			0.20
	Water			0.12
	Wood			0.03
	Air			0.006
	Perfect Vacuum		0.00

A. Water

B. Iron

C. Copper

D. Air

A

D

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17
Q

A brass lamp and an empty aluminum soda can are both sitting on your desk. Each is at room temperature. The lamp feels colder to the touch than the empty soda can. Why?

A. Brass conducts heat better than aluminum

B. Brass has a higher coefficient of linear expansion than aluminum

C. Aluminum conducts heat better than brass

D. Brass is a more dense material

A

A

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18
Q

Using the table of heat conduction coefficients below, determine which of the following is the best conductor of heat.

 Heat Conduction Coefficients
	Material		     Coefficient 
	Silver			100 (the standard)
	Copper			92
	Aluminum		50
	Iron			11
	Glass			0.20
	Water			0.12
	Wood			0.03
	Air			0.006
	Perfect Vacuum		0.00

A. Water

B. Glass

C. Perfect vacuum

D. Iron

A

D

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19
Q

We know that the energy we receive from the sun is not transported by conduction or convection because:

A. Air is less dense at high altitudes

B. Interplanetary space is a good vacuum

C. The sun is gradually cooling off

D. There are always some clouds in the atmosphere

A

B

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20
Q

Which of the following best completes this sentence? Heat transfer by convection is the transfer of energy ….

A. by electromagnetic waves

B. from molecule to molecule

C. by neutron and protons

D. by the flow of a liquid or a gas

A

D

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21
Q

The use of a forced air heating system to heat a house is an example of heat transfer by?

A. Sensible

B. Radiation

C. Convection

D. Conduction

A

C

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22
Q

In theory, ice should be placed in the upper part of an ice chest because:

A. It will come in direct contact with the food

B. The water formed in melting can run out more readily

C. Convection will distribute the cooled air

D. It is easier to reach there

A

C

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23
Q

The best absorber of radiant energy is a body whose surface is:

A. White and fuzzy

B. Dull black

C. Glossy and gray

D. Mirrored

A

B

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24
Q

The best reflector of radiation is a body whose surface is:

A. Dull black

B. Glossy and gray

C. White and fuzzy

D. Mirrored

A

D

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25
Q

We know that the earth is heated by radiation from the sun because:

A. Inadequate space dust exists between earth and the sun to allow the sun to heat the earth by conduction

B. The sun is gradually heating up

C. Air is less dense at high altitudes, therefore making convection difficult

D. Interplanetary space is a good vacuum

A

D

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26
Q

Heat transfers out of a tightly sealed vacuum bottle (“thermos”) primarily by:

A. Osmosis

B. Radiation

C. Conduction

D. Convection

A

B

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27
Q

Which of the following best completes this sentence? Heat transfer by radiation is the transfer of energy…

A. by electromagnetic waves

B. by neutrons and protons

C. by the flow of a liquid or a gas

D. from molecule to molecule

A

A

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28
Q

The use of a vacuum between the walls of a vacuum bottle (thermos) in order to help keep hot liquids hot and cold liquids cold inside the bottle is an example of the application of the principle of heat transfer by:

A. Conduction

B. Convection

C. Radiation

D. Vaporization

A

C

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29
Q

The amount of heat transferred by conduction can be increased by:

A. Increasing the material thickness

B. Increasing the surface area

C. Decreasing the temperature difference

D. Using a material with a lower thermal conductivity

A

B

30
Q

Circle all of the following that are factors which affect conductive heat transfer:
(More than one correct answer)

1. thickness of the material
2. thermal conductivity of the material
3. surface area of the material
4. linear expansion coefficient of the material
5. temperature difference

A. 1, 2 and 5

B. 1, 2, 4 and 5

C. 1,2,3 and 5

D. 1 & 2

A

C

31
Q

In the formula q=hA(delta T), for convective heat transfer, what does the (DELTA T) stand for?

A. The difference between Tin and Tout

B. The difference between Thot and Tcold

C. The difference between Twall and Tbulk

D. The difference between Tair and Tfluid

A

C

32
Q

In the formula for convective heat transfer, Q=hA(delta T), what does the “h” stands for?

A. The fluid height

B. The convective heat transfer coefficient

C. The fluid enthalpy

D. The fluid head value

A

B

33
Q

Which of the following decribe the properties of a gas?

A. Fixed shape, fixed volume

B. Variable shape, fixed volume

C. Fixed shape, variable volume

D. Variable shape, variable volume

A

D

34
Q

Which of the following describes the properties of a liquid?

A. Fixed shape, variable volume

B. Variable shape, fixed volume

C. Fixed shape, fixed volume

D. Variable shape, variable volume

A

B

35
Q

“Heat that is added to or removed from a substance in order to produce a phase change” is the definition of:

A. Sensible heat

B. Conductive heat transfer coefficient

C. Latent heat

D. Specific heat

A

C

36
Q

“Latent” heat is:

A. The amount of heat added to or removed from a substance to produce a phase change

B. The quantity of heat added to or removed from a substance to cause a change of length, width or diameter

C. The quantity of heat required to raise the temperature of a given amount (1 g or 1 lb) of a substance by one degree (C or F)

D. The heat added to or removed from a substance to produce a change of temperature

A

A

37
Q

Which of the following best describes the term “sensible heat”?

A. The quantity of heat added to or removed from a substance to cause a change of length, width or diameter

B. The amount of heat added or removed from a substance to produce a phase change

C. The quantity of heat required to raise the temperature of a given amount (1 g or 1 lb) of a substance by one degree (C or F)

D. The heat added to or removed from a substance to produce a change of temperature

A

D

38
Q

Change of phase is defined as:

A. To change from conductive heat transfer to convective heat transfer

B. To change from an isolated system to a closed system

C. To change from a isolated system to an open system

D. To change from a solid to a liquid, liquid to a gas, or from a solid to a gas, or the reverse of each

A

D

39
Q

The heat added to or removed from a substance to produce a change of temperature is called:

A. Latent heat

B. Conductive heat

C. Specific heat

D. Sensible heat

A

D

40
Q

Pressurizing a liquid will cause the boiling point of the liquid to:

A. Approach the freezing point

B. Remain the same

C. Be lowered

D. Be raised

A

D

41
Q

From the following list, select what happens to a gas, such as steam, when it transfers most of its heat to another substance.

A. The gas vaporizes

B. The gas condenses into its liquid form

C. The temperature of the gas increases

D. The pressure of the gas increases

A

B

42
Q

De-pressurizing a liquid will cause the boiling point of the liquid to:

A. Raise above saturation

B. Remain the same

C. Be lowered

D. Be raised

A

C

43
Q

On Pike’s Peak, which is over 14,000 feet above sea level, water will begin to boil:

A. At a temperature less than 1000 F

B. At a temperature greater than 1000C

C. At 1000C

D. At a temperature less than 1000C

A

D

44
Q

Water inside of a sealed pressure cooker has a boiling point of?

A. 1000C

B. Less than 1000 F

C. Greater than 1000C

D. Less than 1000C

A

C

45
Q

Reducing the pressure on a liquid will cause the boiling point of the liquid to:

A. Be lowered

B. Be raised

C. Remain the same

D. Raise, then lower after 10 minutes

A

A

46
Q

Which of the following best defines the term “heat engine”?

A. A device that creates heat

B. A device that converts thermal energy into other forms of energy

C. A device that magnifies heat

D. A device that converts heat to fuel

A

B

47
Q

Which of the following statements is true regarding heat engines?

A. It is possible to build a heat engine that is 100 percent efficient

B. It is impossible to construct a device whose sole effect is to convert heat input into work output

C. It is possible to construct a device whose sole effect is to convert heat input into work output

D. All heat engines must create heat

A

B

48
Q

Which of the following is NOT true of the heat transfer process through a typical heat exchanger.

A. Heat is taken away from the heat exchanger by convection.

B. Heat transfers through the heat exchanger tube walls by conduction.

C. Heat transfers to the heat exchanger by convection.

D. Heat passes through the laminar layer by convection.

A

D

49
Q

Which of the following describes how heat is transfered through the tube wall in a tube and shell heat exchanger?

A. Osmosis

B. Conduction

C. Convection

D. Radiation

A

B

50
Q

No transfer of mass or energy across boundaries

A

Isolated system

51
Q

No transfer of mass but transfers energy across boundaries

A

Closed system

52
Q

Transfer of both mass and energy across boundaries

A

Open system

53
Q

Which of the following best defines the term heat?

A. Energy possessed by a fluid due to motion of it’s molecules

B. Energy possessed by an object or fluid due to it’s motion

C. Energy in motion due to a temperature difference

D. The action of a force acting through a displacement

A

C

54
Q

Which of the following best defines the term Work?

A. intrinsic material energy

B. transfer of molecular energy

C. molecular energy of a substance

D. energy resulting from a force

A

D

55
Q

Which of the following best defines the term flow energy?

A. Energy possessed by a fluid due to it’s pressure and volume

B. Energy possessed by an object or fluid due to it’s motion

C. Energy possessed by an object or fluid due to motion of it’s molecules

D. Energy possessed by an object or fluid due to it’s position

A

A

56
Q

Which of the following best defines the term internal energy?

A. Energy possessed by an object or fluid due to it’s position

B. Energy possessed by an object or fluid due to motion of it’s molecules

C. Energy possessed by an object or fluid due to it’s motion

D. Energy in transit due to a temperature difference

A

B

57
Q

Which of the following best defines the term kinetic energy?

A. Energy possessed by an object or fluid due to motion of it’s molecules

B. Energy possessed by an object or fluid due to it’s motion

C. Energy possessed by a fluid due to it’s pressure and volume

D. Energy possessed by an object or fluid due to it’s position

A

B

58
Q

Which of the following best defines the term potential energy?

A. Energy possessed by an object or fluid due to it’s position

B. Energy possessed by an object or fluid due to it’s pressure and volume

C. Energy possessed by an object or fluid due to it’s motion

D. Energy possessed by an object or fluid due to motion of it’s molecules

A

A

59
Q

Given fluid flowing in a closed system in steady flow, a throttle valve used to control fluid flow changes which type of energy?

A. flow energy

B. heat

C. potential energy

D. work

A

A

60
Q

Given fluid flowing in a closed system in steady flow, which of the following statements illustrates work done by the working fluid?

A. Fluid flowing through an eductor causing movement in another fluid

B. Fluid flowing through a heat exchanger causing a fluid temperature drop

C. Fluid flowing through a throttle valve causing a pressure drop and temperature rise

D. Fluid flowing through a pump causing a fluid pressure increase

A

A

61
Q

Given fluid flowing in a closed system in steady flow, which of the following mechanical devices do work on the working fluid?

A. The orifice serving to measure fluid flow

B. The valve controlling fluid flow rate

C. The pump causing fluid motion

D. The heat exchanger acting to cool the fluid

A

C

62
Q

Condition of being filled to capacity or having absorbed all that can be taken up

A

Saturation

63
Q

A vapor at a temperature above its saturation temperature

A

Superheated vapor

64
Q

A liquid at a temperature below its boiling point

A

Subcooled liquid

65
Q

Select the choice which describes what will happen to a liquid if its pressure drops without a change in temperature.

A. The saturation temperature of the liquid is increased

B. The saturation pressure of the liquid is decreased

C. The saturation pressure of the liquid is increased

D. The saturation temperature of the liquid is decreased

A

D

66
Q

A liquid at its saturation temperature has absorbed all heat energy possible for the existing pressure. What must be done to the liquid for it to resist a phase change to a vapor when more heat is to be added to the liquid.

A. Pressure must increase

B. Its temperature must be increased

C. Its density must be decreased

D. Its pressure must be decreased

A

A

67
Q

Select the choice which will increase the temperature at which a liquid will boil.

A. The pressure over the liquid is decreased

B. The temperature of the liquid is decreased

C. The temperature of the liquid is increased

D. The pressure over the liquid is increased

A

D

68
Q

Select the choice which describes what will happen to a liquid if its temperature rises without a change in pressure.

A. The saturation pressure of the liquid is increased

B. The saturation temperature of the liquid is increased

C. The saturation pressure of the liquid is decreased

D. The saturation temperature of the liquid is decreased

A

A

69
Q

Select the choice which will decrease the pressure at which a liquid will boil.

A. The temperature of the liquid is decreased

B. The pressure over the liquid is decreased

C. The pressure over the liquid is increased

D. The temperature of the liquid is increased

A

A

70
Q

When contaminants block the tubes of a heat exchanger, why does the heat transfer rate decrease?

A. An increase in heat exchanger flow

B. A decrease in heat exchanger area

C. An increase in fluid velocity through the remaining tubes

D. A decrease in fluid heat capacity

A

B

71
Q

From the choices below select the one that best explains why, over time, the heat transfer rate of a heat exchanger decreases.

A. Over time the heat capacity of coolant fluids reduces significantly

B. As heat exchangers sit idle they become less efficient

C. Over time the heat engine tends to produce less heat, which requires the heat exchanger to transfer less heat

D. Corrosion, scale, algae and other contaminates buildup on the heat exchanger tubes

A

D

Heat Transfer (1 decks)

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