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ME101 Midterms Terms > CHAPTER 1 (BASICS OF HEAT TRANSFER) > Flashcards

CHAPTER 1 (BASICS OF HEAT TRANSFER) Flashcards

1
Q

is the basic
science that deals with
the rate of transfer of
thermal energy.

A

Heat Transfer

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2
Q

Heat transfer plays a crucial role in
the _______of vehicles,
power plants,
refrigerators, electronic
devices, buildings,
bridges, etc.

A

design

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3
Q

a form of energy that can be transferred from one system to
another as a result of temperature difference.

A

Heat

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3
Q
  • science that deals with the determination of the rates of
    energy
A

Heat Transfer

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4
Q

The basic requirement for heat
transfer is the presence of

A

Temperature Difference

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5
Q

This is when the Heat was defined as the energy associated with the random motion
of atoms and molecules

A

middle of 19th century

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6
Q

theory proposed by the French chemist Antoine Lavoisier (1743–
1794) in 1789.

A

caloric theory

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7
Q

Caloric theory proposed by

A

French chemist Antoine Lavoisier

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8
Q

this theory states that heat is a fluid-like substance called the
caloric that is a massless, colorless, odorless, and tasteless substance that
can be poured from one body into another

A

caloric theory

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9
Q

In 1798, ___________ showed in his
papers that heat can be generated continuously through friction

A

Benjamin Thompson (Count Rumford) (1753–1814)

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10
Q

convinced the skeptics that heat was not a substance after all,
and put the caloric theory to rest.

A

James P. Joules (1843)

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11
Q

are designed primarily on the basis of heat
transfer analysis.

A

Heat transfer equipment

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12
Q

these are some of heat transfer equipments

A

1.heat exchangers,
2.boilers,
3.condensers,
4. radiators,
5.heaters,
6.furnaces,
7. refrigerators,
8. solar collectors

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13
Q

The heat transfer problems encountered in practice:

A

(1)rating and
(2)sizing problems.

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14
Q

deal with the determination of the heat transfer rate for an existing
system at a specified temperature difference.

A

rating problems

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15
Q

deal with the determination of the size of a system in order to
transfer heat at a specified rate for a specified temperature
difference.

A

sizing problems

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16
Q

can exist in numerous forms

A

energy

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17
Q

other forms of energy aside from heat

A

thermal, mechanical, kinetic, potential, electrical,
magnetic, chemical, nuclear, etc.

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18
Q

sum of all forms of energy of a system.

A

total energy

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19
Q

forms of energy related to the molecular
structure of a system and the degree of the
molecular activity.

A

microscopic energy

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20
Q

sum of all microscopic
forms of energy of a system

A

internal energy (U)

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21
Q

true or false.
We can get energy
from trash and
sewage.

A

true

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22
Q

SIunit of energy

A

Joule (J)

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23
Q

English unit of energy

A

British thermal unit (Btu)

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24
Q

is the energy needed to raise the temperature of 1 lbm of
water at 60°F by 1°F.

A

BTU

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25
Q

Another unit of energy is

A

calorie

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26
Q

is the energy needed to raise the temperature of 1
gram of water at 14.5°C by 1°C.

A

calorie

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27
Q

portion of the internal energy of a system associated with the
kinetic energy of the molecules

A

sensible energy or sensible heat

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28
Q

sum of the kinetic and potential energies of the molecules

A

internal energy

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29
Q

associated with the intermolecular forces between the molecules
of a system.

A

internal energy

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30
Q

internal energy associated with the phase of a system

A

latent energy or latent heat

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31
Q

internal energy associated with the atomic bonds in a molecule

A

chemical energy

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32
Q

internal energy associated with the bonds within the nucleus of the
atom itself

A

nuclear energy

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33
Q

energy needed to push a fluid and maintain flow

A

Flow energy (Pv)

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34
Q

At low P and high T,the ρ of a gas decreases and
the gas behaves like an

A

ideal gas

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35
Q

energy required to raise the temperature of a unit mass of a
substance by one degree

A

specific heat

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36
Q

The specific heat of a substance depends on

A

Temperature and Pressure

37
Q

The specific heat of an ideal gas depends on

A

Temperature only

38
Q

At low P, all real gases approach _____-_ , and therefore
their specific heats depend on temperature only.

A

ideal gas behavior

39
Q

substance whose specific volume (or density) does not
change with temperature or pressure

A

incompressible substance

40
Q

Energy can be transferred to or from a given mass by these two mechanisms,

A

heat (Q) and work (W).

41
Q

work per unit time

A

power (W)

42
Q

is defined as the measure of energy transfer that occurs
when an object is moved over a distance by an external force at least
part of which is applied in the direction of the displacement.

A

work

43
Q

Examples of engineering systems that produce
work:

A

Steam Turbines
Hydraulic Turbines
Car engines

44
Q

Examples of engineering systems that consume
work:

A

compressor
mixer
pumps

45
Q

is the rate of heat transfer per unit area
normal to the direction of heat transfer.

A

heat flux

46
Q

The first law of thermodynamics, also known as

A

conservation of energy principle

47
Q

this states that
“Energy can neither be created nor destroyed; it can only
change forms.”

A

conservation of energy principle or the first law of thermodynamics

48
Q

A large number of engineering devices such as water heaters and
car radiators involve mass flow in and out of a system, and are
modeled as _____

A

control volumes

49
Q

The opposite of steady is unsteady or

A

transient

50
Q

The total energy content of a control volume during a steady-flow
process remains

A

constant

51
Q

the change in the total energy of the control volume
during such a process is

A

zero

52
Q

The amount of mass flowing through a cross section of a flow device
per unit time is called the

A

mass flow rate

53
Q

The volume of a fluid flowing through a pipe or duct per unit time
is called the

A

volume flow rate

54
Q

The science that deals with the determination of the rates of energy
transfers is

A

heat transfer

55
Q

TRUE OR FALSE
The transfer of energy as heat is ALWAYS from the higher - temperature
medium to the lower-temperature one, and heat transfer stops when
the two mediums reach the same temperature.

A

TRUE

56
Q

Heat can be transferred in three different modes namely

A

conduction,
convection, and radiation

57
Q

states that if two thermodynamic systems are both in thermal equilibrium with a third system, then the two systems are in thermal equilibrium

A

zeroth law of thermodynamics

58
Q

is the transfer of energy from the more energetic
particles of a substance to the adjacent less energetic ones as a
result of interactions between the particles.

A

conduction

59
Q

Conduction can take place in

A

solids, liquids, or gases

60
Q

In gases and liquids, conduction is due to the _______ of the molecules during their random motion.

A

collisions and
diffusion

61
Q

TRUE OR FALSE
In solids, it is due to the combination of vibrations of the molecules
in a lattice and the energy transport by free electrons.

A

TRUE

62
Q

The rate of heat transfer by conduction through a medium depends on
the

A
  • geometry of the medium,
  • thickness,
    -material of the medium,
  • temperature difference
63
Q

Heat transfer by conduction is also known as the

A

Fourier’s law of heat conduction

64
Q

measure of
the ability of a material to conduct
heat.

A

thermal conductivity (k)

65
Q
  • the rate of heat transfer through a unit thickness of the
    material
    per unit area per unit temperature difference.
A

thermal conductivity (k)

66
Q

High value of thermal conductivity means the material is a

A

good heat conductor

67
Q

Low value of thermal conductivity means the materials is

A

low heat conductor or insulator

68
Q

Represents how fast heat diffuses through a material.

A

thermal diffusivity

69
Q

Itis the ratio of the heat conducted through the material to
the heat stored per unit volume.

A

thermal diffusivity

70
Q

TRUE OR FALSE
The larger the thermal diffusivity, the faster the propagation of
heat into the medium.

A

TRUE

71
Q

T OR F

A small value of thermal diffusivity means that heat is mostly
absorbed by the material and a small amount of heat will be
conducted further.

A

T

72
Q

It is the mode of energy transfer between a solid surface and
the adjacent liquid or gas that is in motion.

A

convection

73
Q

Itinvolves the combined effects
of conduction and fluid motion.

A

convection

74
Q

Itinvolves the combined effects
of conduction and fluid motion.

A

radiation

75
Q

energy transfer by radia_____
and it suffers no attenuation in a vacuum. This is how the energy of the
sun reaches the earth.

A

radiation

76
Q

The rate of heat transferby radiation (𝑸𝒆𝒎𝒊𝒕) is governed by ______ equation

A

Stefan–
Boltzmann

77
Q

measure of how closely a
surface approximates a
blackbody for which ε =1

A

emissivity

78
Q

the idealized surface that
emits radiation at this
maximum rate

A

blackbody

79
Q

radiation emitted by a
blackbody

A

blackbody radiation

80
Q

the fraction of the radiation energy incident on a surface that
is absorbed by the surface.

A

absorptivity

81
Q

is essentially a
convection heat transfer coefficient modified to include the
effects of radiation.

A

combined heat transfer coefficient

82
Q

T OR F
Not all three can exist simultaneously in a medium.

A

T

83
Q

A _____may involve conduction and radiation but not convection

A

solid

84
Q

a solid may involve heat transfer by ____ and/or
radiation on its surfaces exposed to a fluid or other surfaces.

A

convection

85
Q

❑Heat transfer is
by ____ and ____ in a still fluid (no
bulk fluid motion)

A

conduction and possibly by radiation

86
Q

heat transfer is by ____ and in a flowing fluid

A

convection and radiation

87
Q

can be viewed as combined conduction and
fluid motion

A

convection

88
Q

This is valid for both steady and transient conditions, and the _________ does not involve heat generation since a surface does not have a volume.

A

surface energy balance

89
Q

It is necessary to keep track of the energy interactions at the surface, and this is done by applying the conservation of energy principle to the surface.

A

surface energy balance

ME101 Midterms Terms (5 decks)

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