CHAPTER 1 (BASICS OF HEAT TRANSFER)

Question 1

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

Answer 1

Heat Transfer

Question 2

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

Answer 2

design

Question 3

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

Answer 3

Heat

Question 3

• science that deals with the determination of the rates of
  energy

Answer 3

Heat Transfer

Question 4

The basic requirement for heat
transfer is the presence of

Answer 4

Temperature Difference

Question 5

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

Answer 5

middle of 19th century

Question 6

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

Answer 6

caloric theory

Question 7

Caloric theory proposed by

Answer 7

French chemist Antoine Lavoisier

Question 8

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

Answer 8

caloric theory

Question 9

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

Answer 9

Benjamin Thompson (Count Rumford) (1753–1814)

Question 10

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

Answer 10

James P. Joules (1843)

Question 11

are designed primarily on the basis of heat
transfer analysis.

Answer 11

Heat transfer equipment

Question 12

these are some of heat transfer equipments

Answer 12

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

Question 13

The heat transfer problems encountered in practice:

Answer 13

(1)rating and
(2)sizing problems.

Question 14

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

Answer 14

rating problems

Question 15

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

Answer 15

sizing problems

Question 16

can exist in numerous forms

Answer 16

energy

Question 17

other forms of energy aside from heat

Answer 17

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

Question 18

sum of all forms of energy of a system.

Answer 18

total energy

Question 19

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

Answer 19

microscopic energy

Question 20

sum of all microscopic
forms of energy of a system

Answer 20

internal energy (U)

Question 21

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

Answer 21

true

Question 22

SIunit of energy

Answer 22

Joule (J)

Question 23

English unit of energy

Answer 23

British thermal unit (Btu)

Question 24

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

Answer 24

BTU

Question 25

Another unit of energy is

Answer 25

calorie

Question 26

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

Answer 26

calorie

Question 27

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

Answer 27

sensible energy or sensible heat

Question 28

sum of the kinetic and potential energies of the molecules

Answer 28

internal energy

Question 29

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

Answer 29

internal energy

Question 30

internal energy associated with the phase of a system

Answer 30

latent energy or latent heat

Question 31

internal energy associated with the atomic bonds in a molecule

Answer 31

chemical energy

Question 32

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

Answer 32

nuclear energy

Question 33

energy needed to push a fluid and maintain flow

Answer 33

Flow energy (Pv)

Question 34

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

Answer 34

ideal gas

Question 35

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

Answer 35

specific heat

Question 36

The specific heat of a substance depends on

Answer 36

Temperature and Pressure

Question 37

The specific heat of an ideal gas depends on

Answer 37

Temperature only

Question 38

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

Answer 38

ideal gas behavior

Question 39

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

Answer 39

incompressible substance

Question 40

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

Answer 40

heat (Q) and work (W).

Question 41

work per unit time

Answer 41

power (W)

Question 42

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.

Answer 42

work

Question 43

Examples of engineering systems that produce work:

Answer 43

Steam Turbines Hydraulic Turbines Car engines

Question 44

Examples of engineering systems that consume work:

Answer 44

compressor mixer pumps

Question 45

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

Answer 45

heat flux

Question 46

The first law of thermodynamics, also known as

Answer 46

conservation of energy principle

Question 47

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

Answer 47

conservation of energy principle or the first law of thermodynamics

Question 48

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 _____

Answer 48

control volumes

Question 49

The opposite of steady is unsteady or

Answer 49

transient

Question 50

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

Answer 50

constant

Question 51

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

Answer 51

zero

Question 52

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

Answer 52

mass flow rate

Question 53

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

Answer 53

volume flow rate

Question 54

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

Answer 54

heat transfer

Question 55

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.

Answer 55

TRUE

Question 56

Heat can be transferred in three different modes namely

Answer 56

conduction, convection, and radiation

Question 57

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

Answer 57

zeroth law of thermodynamics

Question 58

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.

Answer 58

conduction

Question 59

Conduction can take place in

Answer 59

solids, liquids, or gases

Question 60

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

Answer 60

collisions and diffusion

Question 61

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.

Answer 61

TRUE

Question 62

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

Answer 62

- geometry of the medium, - thickness, -material of the medium, - temperature difference

Question 63

Heat transfer by conduction is also known as the

Answer 63

Fourier’s law of heat conduction

Question 64

measure of the ability of a material to conduct heat.

Answer 64

thermal conductivity (k)

Question 65

- the rate of heat transfer through a unit thickness of the material per unit area per unit temperature difference.

Answer 65

thermal conductivity (k)

Question 66

High value of thermal conductivity means the material is a

Answer 66

good heat conductor

Question 67

Low value of thermal conductivity means the materials is

Answer 67

low heat conductor or insulator

Question 68

Represents how fast heat diffuses through a material.

Answer 68

thermal diffusivity

Question 69

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

Answer 69

thermal diffusivity

Question 70

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

Answer 70

TRUE

Question 71

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.

Answer 71

T

Question 72

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

Answer 72

convection

Question 73

Itinvolves the combined effects of conduction and fluid motion.

Answer 73

convection

Question 74

Itinvolves the combined effects of conduction and fluid motion.

Answer 74

radiation

Question 75

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

Answer 75

radiation

Question 76

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

Answer 76

Stefan– Boltzmann

Question 77

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

Answer 77

emissivity

Question 78

the idealized surface that emits radiation at this maximum rate

Answer 78

blackbody

Question 79

radiation emitted by a blackbody

Answer 79

blackbody radiation

Question 80

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

Answer 80

absorptivity

Question 81

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

Answer 81

combined heat transfer coefficient

Question 82

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

Answer 82

T

Question 83

A _____may involve conduction and radiation but not convection

Answer 83

solid

Question 84

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

Answer 84

convection

Question 85

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

Answer 85

conduction and possibly by radiation

Question 86

heat transfer is by ____ and in a flowing fluid

Answer 86

convection and radiation

Question 87

can be viewed as combined conduction and fluid motion

Answer 87

convection

Question 88

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

Answer 88

surface energy balance

Question 89

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.

Answer 89

surface energy balance