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Revision 2
May 2016
Thermodynamic
Units and
Properties
Student Guide
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Table of Contents
INTRODUCTION ..................................................................................................................... 2
TLO 1 THERMODYNAMIC PROPERTIES ................................................................................. 2
Overview .......................................................................................................................... 2
ELO 1.1 Properties and Definitions ................................................................................. 3
ELO 1.2 Thermodynamic Properties of Temperature ................................................... 16
ELO 1.3 Thermodynamic Properties of Pressure .......................................................... 20
TLO 1 Summary ............................................................................................................ 26
TLO 2 CONCEPTS OF HEAT, WORK, AND ENERGY .............................................................. 28
Overview ........................................................................................................................ 28
ELO 2.1 Laws of Thermodynamics ............................................................................... 28
ELO 2.2 Thermodynamic Properties of Energy ............................................................ 29
ELO 2.3 Relationship Between Work, Energy, and Power ........................................... 37
ELO 2.4 Thermodynamic Properties of Heat ................................................................ 43
TLO 2 Summary ............................................................................................................ 47
THERMODYNAMIC UNITS AND PROPERTIES SUMMARY....................................................... 48
KNOWLEDGE CHECK ANSWER KEY ...................................................................................... 1
ELO 1.1 Properties and Definitions ................................................................................. 1
ELO 1.2 Thermodynamic Properties of Temperature ..................................................... 2
ELO 1.3 Thermodynamic Properties of Pressure ............................................................ 2
ELO 2.2 Thermodynamic Properties of Energy .............................................................. 3
ELO 2.3 Relationship Between Work, Energy, and Power ............................................. 4
ELO 2.4 Thermodynamic Properties of Heat .................................................................. 4
iii
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Rev 1
iv
Thermodynamic Units and Properties
Revision History
Revision
Date
Revision
Number
Purpose for Revision
Performed
By
11/6/2014
0
New Module
OGF Team
12/11/2014
1
Added signature of OGF
Working Group Chair
OGF Team
5/4/2016
2
Changes as a result of PPT
Upgrade Project
OGF Team
Rev 1
1
Introduction
Thermodynamics is a branch of natural science concerned with heat and its
relation to energy and work. It defines macroscopic variables (such as
temperature, internal energy, entropy, and pressure) that characterize
materials and explains the ways they are related and the laws that govern
how they change with time.
Nuclear power plants generate thermal heat energy in the reactor core and
convert it into useful mechanical work energy with a turbine. To
understand the various aspects and ramifications of this energy conversion,
we must study the interplay of three significant thermal sciences—heat
transfer, thermodynamics, and fluid flow—as they specifically relate to the
normal and abnormal operations of the plant. We must also become very
familiar with the nature and behavior of water particularly as it relates to the
pressurized water reactor (PWR) energy conversion process.
A working knowledge of thermodynamics is required for operators in the
understanding of nuclear power plants. Before studying thermodynamics, it
is important to establish a basic system of dimensions and units. After
doing that, this chapter defines properties of a substance and introduces the
concepts of work, power, and energy.
At the completion of this training session, the trainee will demonstrate
mastery of this topic by passing a written exam with a grade of 80 percent
or higher on the following Terminal Learning Objectives (TLOs):
1. Describe thermodynamic properties and methods of measuring
intensive and extensive properties.
2. Explain the concepts of heat, work, and energy.
TLO 1 Thermodynamic Properties
Overview
Thermodynamic properties describe measurable characteristics of a
substance. These thermodynamic properties often identify substances or
distinguish between different substances.
Thermodynamics is concerned with both thermal and mechanical properties
of substances and their measurement. Such measurements are expressed in
units that characterize the substance under consideration. The operator
must be able to demonstrate understanding of thermodynamic properties
and the methods of measuring intensive and extensive properties.
Rev 1
2
Objectives
Upon completion of this lesson, you will be able to do the following:
1. Define the following properties:
a. Specific volume
b. Density
c. Mass
d. Weight
e. Intensive
f. Extensive
2. Define the thermodynamic properties of temperature and convert
between the Fahrenheit, Celsius, Kelvin, and Rankine scales.
3. Define the thermodynamic properties of pressure and convert between
all pressure scales.
ELO 1.1 Properties and Definitions
Introduction
The operator is provided with information that is displayed using various
units of measurement. The operator must be able to convert between these
units of measurement to ensure that the plant is operating within established
limits (for example, certain surveillances, RCS leak rates, converting
between inches of Hg vacuum and psia). Additionally, documents provided
by equipment vendors may also contain units of measurement that need
conversion from English units to metric units or vice versa.
Measurement Systems
English units and the International System of Units (SI) are the most
commonly used measurement systems available.
English Engineering Units of Measurement
The English system, primarily used in the United States, consists of various
units for each of the fundamental dimensions such as length, mass, and
time, shown below in the table.
Length
Mass
Time
Inch
Ounce
Second*
Foot*
Pound*
Minute
Yard
Ton
Hour
Mile
Day
NOTE: *Denotes standard unit of measure
Rev 1
3
The English Engineering, or foot-pound-second (FPS), system is used
within the United States in the engineering field.
International System of Units (SI)
The SI system is made up of two related systems, the meter-kilogramsecond (MKS) system, and the centimeter-gram-second (CGS) system.
The MKS and CGS systems each use a decimal-based system in which
prefixes are used to denote powers of ten. For example, one kilometer is
1,000 meters and one centimeter is 0.01 meters. Units of conversion in the
English system are not as straightforward. For example, a mile is 5,280 feet
and a foot is 12 inches.
The MKS system is used primarily for calculations in the field of physics,
while both the MKS and CGS systems are used in the field of chemistry.
The units for each of these systems are shown below in the two tables.
MKS Units of Measurement
Length
Mass
Time
Millimeter
Milligram
Second*
Meter*
Gram
Minute
Kilometer
Kilogram*
Hour
Day
NOTE: *Denotes standard unit of measure
CGS Units of Measurement
Length
Mass
Time
Centimeter*
Milligram
Second*
Meter
Gram*
Minute
Kilometer
Kilogram
Hour
Day
NOTE: *Denotes standard unit of measure
Rev 1
4
Metric System Prefixes
Some of these conversions might have already been done based on which
GFE section you started with. For example, if Rx Theory you have already
converted between PCM and Delta-k/K. PCM stands for Percent Milli Rho.
Percent is 10-2, Milli is 10-3. So, to convert between PCM and Delta-K/K
you multiply by 10-5.
Prefix Names, Symbols, Definitions, and Examples
Prefix Symbol Power of 10 Example
pico
p
10-12
1 picosecond (ps) = 10-12 seconds
nano
n
10-9
1 nanosecond (ns) = 10-9 seconds
micro
µ
10-6
1 micosecond (µs) = 10-6 seconds
milli
m
10-3
1 millimeter (mm) = 10-3 meters
centi
c
10-2
1 centimeter (cm) = 10-2 meters
deci
d
10-1
1 decigram (dg) = 10-1 grams
hecto
h
102
1 hectometer (hm) = 102 meters
kilo
k
103
1 kilogram (kg) = 103 grams
mega
M
106
1 megawatt (MW) = 106 watts
giga
G
109
1 gigawatt (GW) = 109 watts
Unit Conversions
It is necessary to develop relationships of known equivalents such as
conversion factors to apply measurements between and within the SI and
English systems. These equivalents are used to convert from the given units
of measure to the desired unit of measure.
Conversion Factors
Conversion factors are relationships (or ratios) of equivalent values and are
applied to a given measurement to convert it into the desired units. The
equivalent relationships between different units of measurement are defined
in conversion tables. Some examples are given below in the table.
Rev 1
5
Typical Conversion Table
Unit
English Engineering
Units of Measurement
Meter-Kilogram-Second
(MKS) Units of
Measurement
Length
1 yard (yd)
= 0.9144 meter (m)
12 inches (in.)
= 1 ft
5,280 feet (ft)
= 1 mi
1 (meter) m
= 3.281 ft
1 in.
= 0.0254 m
Time
60 seconds (sec) = 1 minute (min)
3,600 sec = 1 hour (hr)
Mass
1 pound mass (lbm) 0.4535 kg
2.205 lbm = 1 kg
1 kilogram (kg) = 1,000 grams (g)
Area
1 square foot (ft2) = 144 in.2
10.764 ft2 = 1 square meter (m2)
1 square yard (yd2) = 9 ft2
1 square mile (mi2) 3.098 x 106 yd2
Volume
7.48 gallon (gal) = 1 cubic foot (ft3)
1 gal = 3.785 l (liter)
1 liter (l) = 1,000 cubic centimeters
(cm3)
Rev 1
6
Performing Unit Conversions
Unit conversion is essentially a multiplication by one, which does not
change the magnitude of the original quantity, but only its measurementunit identity. To convert from one measurement unit to another (for
example, to convert 5 feet to inches), first select the appropriate equivalence
relationship from the conversion table (in this case, 1 ft = 12 in.).
Next, multiply the original quantity by the appropriate conversion factor in
such a manner that the unwanted unit (feet) cancels algebraically and the
desired unit (inches) remains.
Thus, 5 feet equals 60 inches.
Steps for Unit Conversion
Step Action
1.
Identify the units given and the units required.
2.
Choose the equivalence relationship(s)* for the two units.
3.
Arrange the equivalence ratio in the appropriate manner:
4.
Multiply the quantity by the ratio.
*If you cannot find a conversion relationship between the given
units and the desired units in the conversion tables, you may need to
use multiple conversion factors.
Example 1: Convert 795 meters to feet
The following example steps through the process for converting from a
given unit to a desired unit.
Rev 1
7
Solution 1: Convert 795 m to ft.
Step Action
1.
Identify the units given and the units required: meters to feet.
2.
Select the equivalence relationship from the conversion table:
3.
Arrange the equivalence ratio in the appropriate manner:
4.
Multiply the quantity by the ratio:
Multiple conversion factors must be used if an equivalence relationship
between the given units and the desired units cannot be found in the
conversion tables. The conversion is performed in several steps, until the
measurement is in the desired units. The given measurement must be
multiplied by each conversion factor; the answer will be in the desired units,
after the common units have been canceled.
Rev 1
8
Example 2: Convert 2.91 Square Miles to Square Meters
Step Action
1.
Select the equivalence relationship from the conversion table. Multiple
conversions will be necessary because there is no direct conversion
shown for square miles to square meters. For this example, the
following conversions will be used: square miles to square yards to
square feet to square meters.
2.
Express the relationship as a ratio (desired units/present units):
3.
Multiply the original quantity by the ratio:
4.
Repeat the steps, until the value is in the desired units.
Rev 1
9
All of the conversions can be performed in a single equation, as long as all
of the appropriate conversion factors are included.
Conversion Factors for Common Units of Mass
Unit
Gram
(g)
Kilogram
(kg)
Metric Ton
(t)
Pound-mass
(lbm)
1 gram (g)
1
0.001
10-5
2.2046 x 10-3
1 kilogram
(kg)
1,000
1
0.001
2.2046
1 metric ton
(t)
106
1,000
1
2204.6
1 pound-mass
(lbm)
453.59
0.45359
4.5359 x 10-4
1
1 slug
14.594
14.594
0.014594
32.174
Rev 1
10
Conversion Factors for Common Units of Length
Unit
Centimeter
(cm)
Meter
(m)
Kilometer Inch
(km)
(in.)
Foot (ft)
Mile (mi)
1
centimeter
(cm)
1
0.01
10-5
0.3937
0.032808
6.2137 x
10-6
1 meter
(m)
100
1
0.001
39.370
3.2808
6.2137 x
10-4
1
kilometer
(km)
105
1,000
1
39,370
3280.8
0.62137
1 inch (in.)
2.5400
0.025400
2.5400 x
10-5
1
0.083333
1.5783 x
10-5
1 foot (ft)
30.480
0.30480
3.0480 x
10-4
12.000
1
1.8939 x
10-4
1 mile (mi)
1.6093 x 105 1,609.3
1.6093
63,360
5,280
1
Rev 1
11
Conversion Factors for Common Units of Time
Unit
Second (s)
Minute
(min)
Hour (hr)
Day (d)
Year (yr)
1 second
(s)
1
0.017
2.7 x 10-4
1.16 x 10-5
3.1 x 10-8
1 minute
(min)
60
1
0.017
6.9 x 10-4
1.9 x 10-6
1 hour
(hr)
3,600
60
1
4.16 x 10-2
1.14 x 10-4
1 day (d)
86,400
1,440
24
1
2.74 x 10-3
5.26 x 105
8,760
365
1
1 year (yr) 3.15 x 107
Properties
Thermodynamic properties describe measurable characteristics of a
substance. These properties are used to identify substances or distinguish
between different substances.
Mass and Weight
A body's mass (m) measures the amount of material that is present in the
body. A body's weight is the force exerted by that body, when its mass is
accelerated in a gravitational field. Mass and weight are related by a
variation of Newton's Second Law of Motion, as shown below (in the
English system of units).
Where:
wt = weight, in units of pound-force (lbf)
m = mass (lbm)
g = acceleration due to gravity = 32.17 ft/s
= gravitational conversion constant = 32.17 lbm-ft/lbf-s2
This relationship is only true at sea level, where the acceleration due to
gravity is 32.17 ft/sec2.
Rev 1
12
In the above equation, acceleration (a) is often written as
gravity (g) because the acceleration is the gravitational
acceleration due to the earth’s gravitational field (g =
32.17 ft/sec2).
Note
The weight of a body is the force produced, when the mass of the body is
accelerated by gravity. The mass of a given body remains constant, even if
the gravitational acceleration acting upon that body (and, consequently, its
weight) changes.
The English system uses the pound-force (lbf) as the unit of weight. The
basic unit of mass in the English system is the slug; however, the unit of
mass generally used is the pound-mass (lbm), where 1 slug = 32.17 lbm.
The gravitational conversion constant (gc) modifies Newton’s second law,
such that 1 lbf of weight is generated by 1 lbm at the surface of the earth.
This relationship is only true at the surface of the earth, however, where the
acceleration due to gravity is exactly 32.17 ft/s2.
Example:
Using Newton’s second law, prove that 1 lbf is equivalent to 1 lbm on the
earth's surface.
Solution:
(for example, an equality)
Intensive and Extensive Properties
Thermodynamic properties can be divided into two general classes:
intensive and extensive. Intensive properties are independent of the actual
mass of the substance in question (for example, temperature, pressure,
specific volume, and density), whereas the value of an extensive property
varies directly with the amount mass under consideration (such as mass and
volume).
Rev 1
13
For example, if a homogeneous quantity of matter in a given state is divided
into two equal parts, each part will have the same values of the intensive
properties as the original, but one-half the values of the extensive
properties.
Specific Volume
The specific volume (v) of a substance is the total volume (V) of that
substance divided by its total mass (m); for example, the volume per unit
mass. It has units of cubic feet per pound-mass (ft3/lbm).
Where:
v = specific volume (ft3/lbm)
V = volume (ft3)
m = mass (lbm)
Density
The density ρ of a substance is the total mass (m) of that substance divided
by its total volume (V); for example, the mass per unit volume. An object is
said to be very dense if there is a large mass situated within a relatively
small volume. It has units of pound-mass per cubic feet (lbm/ft3). The
density (ρ) of a substance is the reciprocal of its specific volume (v).
Where:
ρ = density (lbm/ft3)
m = mass (lbm)
V = volume (ft3)
v = specific volume (ft3/lbm)
The density of a substance may be varied by changing the pressure applied
and/or temperature. For example, increasing the pressure on a substance
can increase its density, whereas increasing its temperature will lower its
density.
Rev 1
14
The effect of pressure on the densities of liquids and solids is relatively
small; however, the effect of temperature on the densities of steam and
gases can be substantial (as is the effect of pressure on the densities of
steam and gases).
Specific Gravity
Specific gravity (S.G.) identifies the relative density of a substance
compared to the density of water at a standard temperature and pressure
(typically, atmospheric pressure). Physicists use 39.2°F (4°C) as the
standard, since this is the temperature at which water is at its densest state.
The density of water is 1.00 g/cm3 at the standard temperature. The specific
gravity for a liquid has the same numerical value, therefore, as its density
(in units of g/cm3). Specific gravities must be determined and specified at
particular temperatures because the density of a liquid varies with
temperature.
Knowledge Check (Answer Key)
Which thermodynamic property is a measure of relative
density compared to the density of water?
Rev 1
A.
Specific volume
B.
Density
C.
Specific density
D.
Specific gravity
15
Knowledge Check (Answer Key)
Which one of the following is an example of an
extensive thermodynamic property?
A.
Temperature
B.
Pressure
C.
Volume
D.
Density
Knowledge Check (Answer Key)
A reactor core's thermal power is 2,000 megawatts
thermal (MWth). Convert this to BTU/hr.
A.
6.824E9 BTU/hr
B.
6,824E12 BTU/hr
C.
2.93E9 BTU/hr
D.
2.93E12 BTU/hr
ELO 1.2 Thermodynamic Properties of Temperature
Introduction
Thermodynamics uses several types of temperature scales that operators
must recognize and understand to perform their daily monitoring functions.
Temperature Scales
Temperature is a measure of the molecular activity of a substance (that is,
temperature is a relative measure of how hot or cold a substance is) and can
be used to predict the direction of heat transfer. Higher temperatures result
in greater molecular movement within a substance.
The Fahrenheit (F) and Celsius (C) scales are normally used for temperature
measurement purposes and specify the number of increments between the
freezing and boiling points of water at standard atmospheric pressure. The
Celsius scale has 100 units between these points, and the Fahrenheit scale
has 180 units.
Rev 1
16
The freezing point of water was selected as the zero point of the Celsius
scale. The freezing point of water on the Fahrenheit scale is 32°F; 0°F
corresponds to the freezing point of a brine-water solution.
The temperature at which water boils was set at 100°C on the Celsius scale
and is 212°F on the Fahrenheit scale; 100°F was historically chosen as the
temperature of a typical human body (approximately 98.6°F). The
relationship between these scales is shown by the following equations and
illustrated below in the figure.
Figure: Boiling and Freezing Points of Water for Celsius and Fahrenheit
Temperature Scales
Difference in Scales
The low-temperature condition at which all molecular or atomic motion
ceases is referred to as absolute zero (0) and serves as the basis for two
additional temperature scales. The absolute temperature scale that
corresponds to the Celsius scale is the Kelvin (K) scale and that which
corresponds to the Fahrenheit scale is the Rankine (R) scale. The
relationships between the absolute and relative temperature scales are
shown below in the following figure and equations.


Rev 1
3
17
Figure: Comparison of Temperature Scales
Comparison of Temperature Scales
The conversion from one temperature scale to another is sometimes
required and the operator should be familiar with the process. The
following are examples of temperature scale conversions:
Example 1: Temperature Scale Conversion
What is the Rankine equivalent of 80°C?
Solution 1:
Rev 1
18
Example 2: Temperature Scale Conversion
What is the Kelvin equivalent of 80°F?
Solution 2:
Practice Question
The water in the reactor coolant system returning to the
reactor is 550.4°F. What is this temperature in degrees
Celsius, Kelvin, and Rankine?
Knowledge Check (Answer Key)
The low-temperature condition at which all molecular or
atomic motion ceases is referred to as
.
Rev 1
A.
reference point
B.
freeze point
C.
absolute zero
D.
reference zero
19
ELO 1.3 Thermodynamic Properties of Pressure
Introduction
The pressure of a substance is the force exerted by the material (per unit
area) on the boundaries that surround it. This force is caused by the atomic
or molecular collisions that occur between the substance itself and its
boundaries. As the individual particles strike the boundaries, they exert
forces that attempt to push the boundaries outward.
Pressure is typically expressed in units of pounds-force per square inch
(lbf/in.2 or psi) in the English System of Measurement, but may also be
measured or expressed using equivalent columns of liquid, such as water or
mercury (inches of H2O or Hg). The height of a given column of liquid
generates a pressure at its base that converts to units of force per unit area
Direct conversions of columns of H20 or Hg to psi or psia are as follows:

0.491 psi = 1 inch of Hg

0.433 psi = 1 ft. of water

14.7 psia = 408 inches of water

14.7 psia = 29.9 inches of Hg
Pressure Scales
Pressure is measured relative to a perfect vacuum (the complete absence of
atoms/molecules) and is called absolute pressure (psia). Gauge pressure
(psig) is measured relative to atmospheric pressure at sea level (~ 14.7
psig). Most system-pressure gauges register zero (0), when open to the
atmosphere; hence, pressure gauges actually measure the pressure
difference between the observed substance and the surrounding atmosphere.
Figure: Pressure Scale Relationships
Rev 1
20
Pressure below atmospheric pressure is designated as a vacuum. A perfect
vacuum corresponds to an absolute pressure of zero (0) (or 0 psia); all
values of absolute pressure, therefore, are positive. Gauge pressures are
positive when above atmospheric pressure, and negative when below. The
figure above shows the relationships between absolute, gauge, vacuum, and
atmospheric pressures. Even though the above figure shows correct
numbers relating to atmospheric pressure and its relationship to vacuum, the
NRC uses 15.0 psia for atmospheric pressure and 30 inches Hg for a perfect
vacuum.
Below are some inches Hg vs. psia relationships:

Sum of inches Hg vacuum and inches Absolute equal 30
− 30 in Hg vacuum = 0 in Hg absolute
− 28 in Hg vacuum = 2 in Hg absolute

Sum of PSIA and PSIV equals 15
− 15 psia = 0 psiv
− 1 psia = 14 psiv

2 inches for every pound
− 15 psia = 30 inches absolute
− 14 psiv = 28 in Hg vacuum

Based on above:
− 28 in Hg vacuum = 1 psia (this is used extensively)
Rev 1
21
Example 1 Practice:
A pressure gauge on a condenser reads 27 inches of mercury (Hg) vacuum.
What is the absolute pressure corresponding to this vacuum (assume an
atmospheric pressure of 15 psia)?
A.
14.0 psia
B.
13.5 psia
C.
1.5 psia
D.
1.0 psia
Figure: Gauge and Absolute Pressure Scale Relationships
Solution – Practice Example 1:
NOTE: PSIV is rarely used and not referenced in GFES banks.
Since the sum of inches Hg Abs and inches Hg Vac = 30,
30 – 27” Hg Vac = 3”Hg Abs
Rev 1
22
Example 2 Practice:
Which one of the following is arranged from the lowest pressure to the
highest pressure?
A.
2 psig, 12 inches Hg absolute, 8 psia
B.
2 psig, 18 inches Hg absolute, 8 psia
C.
12 psia, 20 inches Hg absolute, 2 psig
D.
12 psia, 30 inches Hg absolute, 2 psig
Absolute
vacuum
Figure: Comparison of Pressure Scales
As discussed previously, pressure also can be measured in terms of an
equivalent column of liquid, usually water, or mercury, which is referred to
as hydrostatic pressure. Hydrostatic pressure at a given reference point is
the product of a fluid’s density, its height above a reference point, and the
acceleration due to gravity.
The greater the density or height of the fluid column, the more pressure it
exerts on a given area. The most common units of this type of measurement
are feet of water (ft H2O), inches of water (in H2O), and inches of mercury
(in. Hg). The different hydrostatic pressure measurements can be compared
using the following relationships, such as conversion factors:


Rev 1
0.491 psi = 1 inch Hg
0.433 psi = 1 ft H2O
23
Knowledge Check (Answer Key)
A pressure gauge on a condenser reads 27 inches of mercury (Hg) vacuum.
What is the absolute pressure corresponding to this vacuum? (Assume an
atmospheric pressure of 15 psia.)
A. 14.0 psia
B. 13.5 psia
C. 1.5 psia
D. 1.0 psia
Pressure due to a Column of Fluid
As stated earlier, pressure is typically expressed in units of pounds-force per
square inch (lbf/in.2 or psi) in the English System of Measurement, but may
also be measured or expressed using equivalent columns of liquid, such as
water or mercury (inches of H2O or Hg). The height of a given column of
liquid generates a pressure at its base that converts to units of force per unit
area per the following equation:
P =
Where:
P = pressure (lbf/in.2 or psi)
ρ = density (lbm/ft3)
g = acceleration due to gravity (32.17 ft/s2)
z = height of column (ft)
= gravitational conversion constant = 32.17 lbm-ft/lbf-s2
NOTE: the g/gc merely converts lbm to lbf
This formula requires an additional conversion factor, for completeness (for
example, 1 ft2 = 144 in.2).
Rev 1
24
Example: PSI to Height of Water
A water storage tank is vented to atmosphere. The tank is located at sea
level and contains 100,000 gallons of water at 60°F. A pressure gauge at the
bottom of the tank reads 9.0 psig. What is the approximate water level in
the tank?
Solution:
z
Pg c
g
Density at standard temp/press of 62.4 lbm/ft3can be used.
Only unit conversion needed is 144 in2/ft2
 9.0lb f
z  
2
 in
 ft 3  s 2  32.2 ft  lbm  144in 2 




2
 ft 2 


62
.
4
lb
32
.
2
ft
lb

s



m 
f

z = 20.7 ft
Example 4: Pressure Relationships
What is the absolute pressure at the bottom of a swimming pool 6 feet deep
that is filled with fresh water?
Assume
Solution 4:
In addition to pounds per square inch, pressure can be measured with
reference to the force that exists in a column of fluid at a certain height.
The most common of these are inches of water, inches of mercury, and
millimeters of mercury. Conversion factors are listed below:

14.7 psia = 408 inches of water

14.7 psia = 29.9 inches of mercury

1 inch of mercury = 25.4 millimeters of mercury
Rev 1
25
Knowledge Check (Answer Key)
Refer to the drawing of a tank with a differential pressure
(D/P) level detector (see figure below).
If the tank contains 30 feet of water at 60°F, what is the
approximate D/P sensed by the detector?
A.
7 psid
B.
13 psid
C.
20 psid
D.
28 psid
TLO 1 Summary
1. Define the following properties







Mass (m) is the measure of the amount of material present in that
body.
Weight (wt) is the force exerted by that body when its mass is
accelerated in a gravitational field.
Specific volume (v) is the total volume (V) of a substance divided
by the total mass (m) of that substance.
Density (ρ) is the total mass (m) of a substance divided by the total
volume (V) occupied by that substance.
Specific gravity (S.G.) is a measure of the relative density of a
substance compared to the density of water at a standard
temperature.
Intensive properties are properties that are independent of the
amount of mass.
Extensive properties are those that vary directly with mass.
2. Define the thermodynamic properties of temperature and convert
between the Fahrenheit, Celsius, Kelvin, and Rankine scales.

Temperature is a measure of the molecular activity of a substance.
o Absolute zero = -460°F or -273°C
o Freezing point of water = 32°F or 0°C
o Boiling point of water = 212°F or 100°C
 Conversions between the different scales can be made using the
following formulas:
o °F = 32 + (9/5)°C
Rev 1
26
o °C = (°F - 32)(5/9)
o °R = °F + 460
o °K = °C + 273
3. Define the thermodynamic properties of pressure and convert between
all pressure scales.

Pressure is a measure of the force per unit area exerted on the
boundaries of a substance (or system).
o
o

Converting between the different pressure units can be done using
the following conversions:
o
o
o
Objectives
Now that you have completed this lesson, you should be able to do the
following:
1. Define the following properties:
a. Specific volume
b. Density
d. Mass
f. Weight
g. Intensive
h. Extensive
2. Define the thermodynamic properties of temperature and convert
between the Fahrenheit, Celsius, Kelvin, and Rankine scales.
3. Define the thermodynamic properties of pressure and convert between
all pressure scales.
Rev 1
27
TLO 2 Concepts of Heat, Work, and Energy
Overview
Thermodynamics is the branch of science that deals with energy and the
transformation of energy from one form to another. It is necessary to
understand some basic energy concepts and terminology to gain a complete
understanding of many thermodynamic topics.
This lesson will identify and explain the different forms of energy, examine
the conversion of energy from one form to another, and explain concepts
and terminology related to energy, work, and power. In addition, the lesson
will describe the relationship between energy, work, and power, including
the equation that allows us to evaluate those relationships.
Objectives
Upon completion of this lesson, you will be able to do the following:
1. State the First and Second laws of thermodynamics and how they
relate to the conservation of energy.
2. Define the following thermodynamic properties:
a. Potential energy
b. Kinetic energy
c. Specific internal energy
d. Specific p-v energy
e. Specific enthalpy
f. Specific Entropy
3. Explain the relationship between work, energy, and power.
4. Define the following terms:
a. Heat
b. Sensible heat
c. Latent heat
d. Specific heat
e. Super heat
ELO 2.1 Laws of Thermodynamics
Introduction
Heat and work are two ways in which energy can be transferred across the
boundaries of a system. They define the methods by which energy is
transferred to and within our secondary system to convert heat energy to
mechanical energy, and finally electrical energy.
Rev 1
28
Energy
Energy is defined as the capacity to produce an effect, for example, perform
work or produce heat. It is difficult to define energy in a general sense, but
easier to define it in terms of the work done on or by a system. Specifically,
a given system possesses a certain quantity of energy that is decreased when
the system does work (on its surroundings or on another system) and
increased when work is done on the system. There are two laws of
thermodynamics that apply generally to all systems and specifically to our
nuclear plant systems. They are:
•
The First Law of Thermodynamics:
“Energy can be neither created nor destroyed, only altered in form.”
This means that in nuclear plant systems (even in the reactor), we
can neither create nor destroy energy but, rather, just convert it to
one form to another. Energy conversions that occur in our plants
include:
– Velocity energy to pressure energy (water hammer)
– Flow energy to internal energy (headloss)
– Heat energy to mechanical energy (turbine)
•
The Second Law of Thermodynamics states:
“No engine, actual or ideal, when operating in a cycle can convert all
the heat supplied it into mechanical work–heat must be rejected.”
This means that in nuclear plant systems, there will be inefficiencies
and energy losses. Our plant systems experience energy losses:
– Losses characterized by changes in “entropy” (you will learn
about entropy later in this course).
– A design goal of a nuclear plant (and most any other working
system) is to minimize energy losses.
ELO 2.2 Thermodynamic Properties of Energy
In a nuclear power plant, the primary means of transferring and converting
energy is accomplished through the use of water (in the form of a liquid or
steam). It is the plant’s “working fluid”. A working fluid is a substance that
receives, transfers, and transmits energy in a thermodynamic system. In
most systems, the working substance is a fluid (such as a liquid or gas). For
example, water is the working fluid in a nuclear steam supply system. Fluid
energy is decreased when work is done on the fluid and increased when the
fluid does work.
Rev 1
29
There are many different forms of energy, such as mechanical energy,
thermal energy, electrical energy, chemical energy, and nuclear energy.
The total energy of a substance, which is always conserved, is the sum of
the various forms of energy that the substance possesses.
Thermo-mechanical energy is classified as either stored energy (such as
energy contained within the mass) or transient energy (energy associated
with the conversion from one stored form to another or the transition from
one system to another).
The four forms of stored energy that are possessed by the working fluid in a
typical energy-transfer system are potential energy, kinetic energy, internal
energy, and PV (flow) energy. The two forms of transient energy are work
and heat.
Potential Energy
Potential energy (PE) is the energy that a substance possesses as a function
of its position relative to a given reference point. The amount of PE an
object contains is dependent upon its mass (m) and elevation relative to the
reference location (z). Potential energy will exist whenever an object that
has mass is positioned within a force field. The most common example is
an object situated within the earth's gravitational field, as shown below:
Figure: An Object Acted On By The Earth’s Gravity
Rev 1
30
Examples of Potential Energy
Using English system units, PE is defined as follows:
Where:
PE = potential energy (ft-lbf)
m = mass (lbm)
z = height above some reference level (ft)
g = acceleration due to gravity (ft/s2)
gc = gravitational conversion constant = 32.17 ft-lbm/lbf-s2
The acceleration due to gravity (g) is numerically equal to the gravitational
conversion constant (gc), although the units differ. Thus, the potential
energy (in. ft-lbf) numerically equals the product of the mass (in. lbm) and
the height (in. ft) above some reference level.
Example:
Determine the potential energy of 50.0 lbm of water that is located in a
storage tank 100 ft above the ground.
Solution:
Occasionally, in thermodynamics, energy is expressed in units of BTU
(British Thermal Units). To convert to BTU, the following conversion
factor is applied.
, or
Rev 1
31
Example:
Determine the potential energy (in BTU) associated with 1.0 lbm of water at
an elevation of 50 feet above a reference height.
Solution:
5.00 X 103 ft-lbf
To convert to BTUs, divide by (BTU/778 ft-lbf)
or
Kinetic Energy
Kinetic energy (KE) is the energy that a body possesses as a result of its
relative motion and may be defined as the energy needed to accelerate a
body from rest to its current velocity. The body will maintain this kinetic
energy, unless it experiences a new net force.
Example of Kinetic Energy
Where:
KE = kinetic energy (ft-lbf)
m = mass (lbm)
v = velocity (ft/s)
gc = gravitational conversion constant = 32.17 ft-lbm/lbf-s2
Rev 1
32
Example:
Determine the kinetic energy of 7 lbm of steam flowing through a pipe at a
velocity of 100.0 ft/sec.
Solution: Using Equation
Or, in terms of BTU:
Internal Energy
Both potential and kinetic energies exist as macroscopic (for example,
large-scale) forms of energy that can be observed in terms of the positions
and velocities of objects. A substance possesses several microscopic forms
of energy in addition to these macroscopic forms, which include those due
to the rotational, vibrational, and translational energies of the individual
atoms or molecules in a substance.
These microscopic forms of energy are not easily measured or evaluated
directly; hence, the change in their combined total is generally evaluated
instead. These microscopic forms of energy are collectively referred to as
internal energy, which is customarily represented by the symbol U and
expressed in units of BTU.
Rev 1
33
The specific internal energy (u) of a substance is its internal energy per unit
mass, which is an intensive property (that is, independent of mass). This
property is equal to the total internal energy (U) divided by total mass (m).
Where:
u = specific internal energy (BTU/lbm)
U = internal energy (total BTU)
m = mass (lbm)
Example:
Determine the specific internal energy of 12 lbm of steam, if its total
internal energy is 2.300 x 104 BTU.
Solution: Using Equation for Specific Internal Energy
PV (Flow) Energy
PV energy (also referred to as flow energy) is important to the
understanding of energy-transfer systems and is numerically equal to the
product of a system's pressure and volume. When the volume of an
enclosed substance is permitted to expand, work is performed on its
surroundings; hence, a fluid under pressure has the capacity to perform
work. The units of PV energy are (lbf/ft2)(ft3), which is equivalent to ft-lbf
(as with other forms of energy, such as PE).
The specific PV energy of a substance is its PV energy per unit mass and
equals the product of the system's pressure and volume divided by the total
mass (or the product of the pressure and specific volume). Its units are ftlbf/lbm.
Rev 1
34
Where:
P = pressure (lbf/ft2)
V = volume (ft3)
v = specific volume (ft3/lbm) = V/m
m = mass (lbm)
Example:
Determine the specific PV energy of 15.0 lbm of steam at 1,000 psia in an
18-ft3 tank.
Solution: Using Equation for Flow Energy
Enthalpy
Enthalpy (symbolized by H) is a thermodynamic property of a system that
is equivalent to the sum of its internal and flow energies, for example, H =
U + PV.
Specific enthalpy (h) is defined as the total enthalpy per unit mass;
therefore,
, where u is the specific internal energy (in.
BTU/lbm), P is the pressure (in. lbf/ft2), and v is the specific volume (in.
ft3/lbm).
Unlike pressure, temperature, and volume, enthalpy is a property of a
substance that cannot be measured directly; rather, the enthalpy of a
substance is measured with respect to a reference value. For example, the
specific enthalpy of water is based on a reference value of zero (0) at
Rev 1
35
0.01°C (32.02 oF) and normal atmospheric pressure (~14.7 psia). It is the
change in specific enthalpy, rather than the absolute value, that is of
importance in practical problems.
Entropy
Entropy (symbolized by S) is a measure of a system's inefficiency for doing
work, for a given amount of heat transferred. Specific entropy (s = S/m) is
useful in determining the amount of heat transferred to or from a system
that can and cannot be used to perform work. The change in entropy is
represented by ΔS (or Δs), as in the following relationships.
Where:
= the change in entropy of a system during some process (BTU/°R)
= the amount of heat transferred to or from the system during the
process (BTU)
Tabs = the absolute temperature at which the heat was transferred (°R)
= the change in specific entropy of a system during some process
(BTU/lbm-°R)
= the amount of heat transferred to/from the system during the process
(BTU/lbm)
Like enthalpy, entropy cannot be measured directly, but rather is measured
with respect to a reference value. For example, specific entropy of water is
considered to be zero (0) at 32.02°F and 14.7 psia, which define the
reference condition. While the absolute value of specific entropy may be
unknown, it is the change in specific entropy (Δs) that is important when
solving practical problems.
Rev 1
36
Knowledge Check (Answer Key)
___________ is the measure of energy content of the
fluid due to its temperature, pressure, and volume.
A.
Entropy
B.
Kinetic energy
C.
Enthalpy
D.
Specific internal energy
ELO 2.3 Relationship Between Work, Energy, and Power
Introduction
The purpose of a nuclear-powered generating station is to transfer the
thermal energy produced in the nuclear fuel to the turbine-generator where
the thermal energy is converted into mechanical work and then electrical
energy. Heat is a form of energy in transition and is caused by a difference
in temperature. Work is defined as the force used to move a mass,
multiplied by the distance that the mass was moved. Power is defined as
the rate of doing work (that is, the work done per unit time).Each of these
terms is related and must be understood to solve thermodynamic problems.
This lesson will identify and explain the different forms of work, examine
the conversion of energy from one form to another, and explain concepts
and terminology related to work and power. In addition, the lesson will
describe the relationship between energy, work, and power, including the
equation that allows us to evaluate those relationships.
Work
Kinetic, potential, internal, and PV energies are stored forms of energy and
considered properties of a system. Work is also a form of energy, but is
considered a form of energy in transit (like heat) and, consequently, is not a
system property; hence, work is a process done by or on a system, although
a system contains no work. It is important to understand the distinction
between the stored forms of energy, which are properties of a system, and
those forms of energy that are transferred to and from a system.
In thermodynamics, we are primarily concerned with two types of work:
mechanical work and flow (or PV) work.
Rev 1
37
Mechanical Work
In mechanical systems, work is defined as the action of a force on an object
through a distance and equals the product of the force (F) and its
displacement (d).
Where:
W = work (ft-lbf)
F = force (lbf)
d = displacement (ft)
Example:
Determine the amount of work done, if 150 lbf is applied to an object until
it has moved a distance of 30.0 feet.
Solution Using Work Equation:
It is important to distinguish between the work done by a system and that
done on a system by its surroundings. For example, work is done by a
system when its steam is used generate electricity in a turbine-generator or a
pump is used to move the working fluid from one location to another. Note
that when work is done by a system, the process leads to a lowering of the
system's total stored energy; hence, work done by a system is considered to
be a positive work.
Conversely, when work is done on a system, it is considered to be a
negative quantity since the system's total energy was increased by an
external force. The pump process of our thermodynamic cycle is an
example of work done ON the system (discussed in a later chapter). In
either case, energy is being converted from one stored form to another as
work is done. The actual amount of work done on or by a system depends
upon the specific process and not simply on the initial and final conditions
of the system (as is the case for the stored forms of energy).
Rev 1
38
In the English system of units, the foot-pound force (ft-lbf) is used for work
processes; the SI units are the Newton-meter (Nm) or joule (J).
Flow Work
Flow work (or flow energy) is the work that is required to maintain a
continuous, steady flow of fluid. Flow work is important, when it becomes
necessary to move a fluid from one point to another.
Figure: Pipe Boundary Volume For Flow Energy
This flow work is equivalent to a force acting through a distance (or length).
W=FxD
Since
Since
,
,
Where:
Wflow = flow work (ft-lbf)
P = pressure (lbf/ft2)
V = volume (ft3)
F = force (lbf)
A = area (ft2)
L = length (ft)
Flow work is a form of mechanical work and can also be expressed in units
of BTU. Flow work is also called flow energy. The flow energy per unit
mass of material (for example, w = W/m) is equivalent to Pv.
Rev 1
39
Power
Power is defined as the time rate of doing work and is equivalent to the rate
of energy transfer. Power has units of energy per unit time and may be
expressed in various units, which have established equivalences. In the
English system, the mechanical units of power are ft-lbf/s or ft-lbf/hr and
hp, the thermal units are BTU/hr, and the electrical units are watts (W) or
kilowatts (kW = 103 W). For engineering applications, the equivalence of
these units is expressed by the following relationships:



Horsepower is related to ft-lbf/sec by the following relationship:

= 745.7 watts
In SI units, power is measured in watts or joules (W or J). These
relationships can be used to convert between the English and SI systems.
•
P
Where:




Where:
P = power (W or ft-lbf/s)
F = force (N or lbf)
d = distance (m or ft)
t = time (sec)
P = power (hp)
F = force (lbf)
v = velocity (ft/s)
1 hp = 550 ft-lbf/sec
Energy and Power Equivalences
Three types of units are normally used to measure energy (EEU):
1. Mechanical units, such as the foot-pound-force (ft-lbf);
2. Thermal units, such as the British Thermal Unit (BTU); and
3. Electrical units, such as the watt-second (W-sec).
In the MKS and CGS systems, the mechanical units of energy are the joule
(J) and the erg, the thermal units are the kilocalorie (kcal) and the calorie
(cal), and the electrical units are the watt-second (W-sec) and the erg.
Although the units of the various forms of energy are different, they are
equivalent.
Rev 1
40
J. P. Joule, an English physicist, showed that one kilocalorie equals 4,186
joules. These same experiments, when performed using English system
units, show that one British Thermal Unit (BTU) equals 778.3 ft-lbf. These
experiments established the equivalence of mechanical and thermal energy.
Other experiments established the equivalence of electrical energy with
both mechanical and thermal energy. These equivalences are expressed by
the following relationships for engineering applications.



The horsepower-hour (hp-hr) is another unit of energy encountered in
engineering applications. It is a mechanical unit of energy defined by the
following relationship:


These relationships can be used to convert various forms of energy between
the English system units.
Most computations involving the working fluid energy in an energy transfer
system are performed in BTUs. Forms of mechanical energy such as
potential energy, kinetic energy, and mechanical work and other forms of
energy such as P-V energy, are usually given in foot-pounds-force. These
are converted to BTUs by using
.
Because this conversion factor is used frequently, a constant called the
mechanical equivalent of heat, usually denoted by the symbol J and
sometimes referred to as Joules constant, is defined as:
Rev 1
41
Example 1:
A pump provides a flow rate of 10,000 liters per minute (lpm). The pump
performs 1.5 x 108 joules of work every 100 minutes. What is the power of
the pump?
Solution 1:
Example 2:
A boy rolls a ball with a steady force of 1 lbf, giving the ball a constant
velocity of 5 ft/s.
What is the power used by the boy in rolling the ball?
Solution 2:
Rev 1
42
Example 3:
A racecar traveling at constant velocity can go one-quarter mile (1,320 ft) in
5 seconds. If the motor is generating a force of 1,890 lbf pushing the car,
what is the power of the motor in hp? Assume the car is already at full
speed at t = 0.
Solution 3:
Knowledge Check (Answer Key)
A 600 lbm casting is lifted 4 feet to the bed of a milling
machine. How much work is done?
A.
240 ft-lbs
B.
150 ft-lbs
C.
2,400 ft-lbs
D.
1,500 ft-lbs
ELO 2.4 Thermodynamic Properties of Heat
Introduction
Many thermodynamic analyses involve the transfer of energy between
systems and/or substances, via thermodynamic processes and cycles, which
will be discussed in later lessons. Heat, as previously stated, is energy in
transition that is caused by a difference in temperature.
Rev 1
43
Heat
Heat (Q), like work, is energy in transit; however, this form of energy
transfer occurs at the molecular level as a result of a temperature difference.
The BTU is the preferred unit of heat, in most steam-plant applications, and
it is the amount of energy that is necessary to raise the temperature of 1 lbm
of water by 1°F (conventionally, from 59.5°F to 60.5°F).
Like work, the actual amount of heat transferred to or from a system
depends upon the specific process and not simply on the initial and final
conditions of the system (as is the case for stored forms of energy). When
analyzing heat-transfer processes, a positive value for heat indicates that
heat is being added to the system (and, consequently, the system's total
energy rises); a loss of heat is denoted by a negative heat value.
The symbol q is used to indicate the amount of heat added to or removed
from a system per unit mass. It is equal to the total heat (Q) added or
removed, divided by the mass (m). The term specific heat is not used for q,
because this term has historically been used for another parameter (see
below).
Where:
q = heat transferred per unit mass (BTU/lbm)
Q = heat transferred (BTU)
m = mass (lbm)
Example:
Determine the heat transferred per unit mass if 1,500 BTU are transferred to
40.0 lbm of water.
Solution Using Heat Equation
Rev 1
44
Sensible Heat
A common means of quantifying the amount of heat that is added to or
removed from a system is to observe the change in the system's temperature
because of the heat-transfer process.
The temperature of a substance always increases when it is heated and
decreases when heat is removed (assuming no phase change accompanies
the process). The heat added to or removed from a substance that produces
a change in its temperature is referred to as sensible heat.
Latent Heat
Latent heat is the heat added to or removed from a substance resulting in a
change of phase, but no change in temperature. There are three specific
forms of latent heat, one for each type of phase change.
The latent heat of fusion/freezing is associated with the heat added to or
removed from a substance to change it from a solid to a liquid (and vice
versa). The latent heat of vaporization/condensation is associated with the
liquid-vapor phase change; and the latent heat of sublimation and/or
desublimation is associated with the solid-vapor phase change.
Specific Heat
The magnitude of the temperature change for a given amount of heat
transferred differs from one substance to another. The ratio of the heat (Q)
added to or removed from a substance to the resulting change in
temperature ( T) is referred to as the substance's heat capacity (Cp); the
specific heat (or specific heat capacity) of a substance (cp) is the heat
capacity per unit mass (that is, cp = Cp /m). The subscript p indicates that
the heat-transfer processes in question occurred under constant-pressure
conditions.
Rev 1
45
Where:
Cp = heat capacity at constant pressure (BTU/°F)
cp = specific heat at constant pressure (BTU/lbm-°F)
Q = heat transferred (BTU)
q = heat transferred per unit mass (BTU/lbm)
m = mass (lbm)
= temperature change (°F)
Example:
How much heat is required to raise the temperature of 5.00 lbm of water
from 50°F to 150°F? Assume that the specific heat (cp) for water is 1.0
BTU/lbm-°F.
Solution:
Super heat
The number of degrees a vapor is above the saturation temperature (boiling
point) at a specific pressure.
Rev 1
46
Knowledge Check (Answer Key)
Which of the following must be added to or removed
from a substance to produce a temperature change?
A.
Latent heat
B.
Specific heat
C.
Sensible heat
D.
Thermal heat
TLO 2 Summary
1. Define the following thermodynamic properties:
 Energy is the capacity of a system to perform work or produce heat.
 Potential energy (PE) is the energy of position.
 Kinetic energy (KE) is the energy that a body possesses due to its
motion.
 Latent heat is the amount of heat added or removed to produce only
a phase change.
 Sensible heat is heat added or removed that causes a temperature
change.
 Specific enthalpy (h) —
, where u is the specific
internal energy (BTU/lbm) of the system being studied, P is the
pressure of the system (lbf/ft2), and ν is the specific volume
(ft3/lbm) of the system.
 Entropy is a measure of the inability to do work for a given heat
transferred.
 Power is the time rate of doing work. It is equivalent to the rate of
the energy transfer. Power has units of energy per unit time.
2. Explain the relationship between, work, energy, and power
 Power is defined as the time rate of doing work.
o It is equivalent to the rate of the energy transfer and has units
of energy per unit time.
 Power equivalences:
o
o
o
 Horsepower is related to foot-pounds-force per second (ft-lbf/sec)
by the following relationship:
o
Rev 1
47
3. Define the following terms:
 Heat is energy in transit.
 Latent heat is the amount of heat added or removed to produce a
phase change.
 Sensible heat is the heat added or removed that causes a temperature
change.
 Specific heat capacity is the ratio of the heat (Q) added to or
removed from a substance to the resulting change in temperature
( T).
 Super heat is the number of degrees a vapor is above the saturation
temperature (boiling point) at a specific pressure.
Objectives
Now that you have completed this lesson, you should be able to do the
following:
1. State the First and Second laws of thermodynamics and how they
relate to the conservation of energy.
2. Define the following thermodynamic properties:
a. Potential energy
b. Kinetic energy
c. Specific internal energy
d. Specific p-v energy
e. Specific enthalpy
f. Specific Entropy
3. Explain the relationship between work, energy, and power.
4. Define the following terms:
a. Heat
b. Sensible heat
c. Latent heat
d. Specific heat
e. Super heat
Thermodynamic Units and Properties Summary
In this lesson, new terms were introduced to facilitate the understanding of
thermodynamic properties. Intensive and extensive properties and the
concepts of heat, work, and energy were also introduced. These concepts
and relationships will be used in the remaining chapters on
thermodynamics.
Water, as both a liquid and a vapor, serves as the working fluid in the PWR
energy-conversion cycle. Water absorbs, stores, transports, and transfers
energy throughout the PWR and its supporting systems. Analysis and
evaluation of the entire energy-conversion cycle is conducted by studying
the physical condition of the water at each point of interest within the PWR
and its cycle.
Rev 1
48
The state of water is defined by two independent intensive thermodynamic
properties. A thermodynamic property is a parameter that describes the
physical condition of a substance. When the state is defined by two
independent intensive properties, all other properties of the state are
implied.
Properties are divided into two classifications, extensive and intensive.
Extensive properties are mass dependent and include mass and volume.
Intensive properties are independent of mass and include temperature,
pressure, and specific volume. Temperature is a measure of the average
kinetic energy of the atoms or molecules of a substance and is measured by
the Fahrenheit and Celsius scales.
The Rankine or Kelvin scales are used for absolute temperature. Pressure is
the force per unit area acting on (or created by) a fluid and is measured in
psig, psiv, psid, inches of Hg (absolute), and inches of Hg (vacuum).
Absolute pressure is given in units of psia. Specific volume is the amount
of space a unit mass occupies and is measured in cubic feet per pound mass.
The inverse of specific volume is density.
Now that you have completed this module, you should be able to
demonstrate mastery of this topic by passing a written exam with a grade of
80 percent or higher on the following TLOs:
1. Demonstrate understanding of thermodynamic properties, and
methods of measuring intensive and extensive properties.
2. Explain the concepts of heat, work, and energy.
Rev 1
49
Thermodynamic Units and Properties Knowledge Check
Answer Key
Knowledge Check Answer Key
ELO 1.1 Properties and Definitions
Knowledge Check
Which thermodynamic property is a measure of relative
density compared to the density of water?
A.
Specific volume
B.
Density
C.
Specific density
D.
Specific gravity
Knowledge Check
Which one of the following is an example of an
extensive thermodynamic property?
A.
Temperature
B.
Pressure
C.
Volume
D.
Density
Knowledge Check
A reactor core's thermal power is 2,000 megawatts
thermal (MWth). Convert this to BTU/hr.
Rev 1
A.
6.824E9 BTU/hr
B.
6,824E12 BTU/hr
C.
2.93E9 BTU/hr
D.
2.93E12 BTU/hr
1
Thermodynamic Units and Properties Knowledge Check
Answer Key
ELO 1.2 Thermodynamic Properties of Temperature
Knowledge Check
The low-temperature condition at which all molecular or
atomic motion ceases is referred to as
.
A.
reference point
B.
freeze point
C.
absolute zero
D.
reference zero
ELO 1.3 Thermodynamic Properties of Pressure
Knowledge Check
A pressure gauge on a condenser reads 27 inches of
mercury (Hg) vacuum. What is the absolute pressure
corresponding to this vacuum? (Assume an atmospheric
pressure of 15 psia.)
A.
14.0 psia
B.
13.5 psia
C.
1.5 psia
D.
1.0 psia
Solution:
Pabs = Patm – Pvacuum
Pabs = 15 psia – 27”Hg (1psia/2.03”Hg)
Pabs = 15 psia – 13.5 psia = 1.5 psia
Rev 1
2
Thermodynamic Units and Properties Knowledge Check
Answer Key
Knowledge Check
Refer to the drawing of a tank with a differential pressure
(D/P) level detector (see figure below).
If the tank contains 30 feet of water at 60°F, what is the
approximate D/P sensed by the detector?
A.
7 psid
B.
13 psid
C.
20 psid
D.
28 psid
The volume of the tank is itself does not determine pressure due to the static
column of water; the height of the tank affects pressure at the bottom of the
tank. Note that atmospheric pressure acts on both sides of the D/P detector
and thus can be neglected. Since the temperature is relatively low you can
use the thumbrule of 1 ft water = 0.433 psi. Therefore, 30 x 0.433 = 13 psid
ELO 2.2 Thermodynamic Properties of Energy
Knowledge Check
___________ is the measure of energy content of the
fluid due to its temperature, pressure, and volume.
Rev 1
A.
Entropy
B.
Kinetic energy
C.
Enthalpy
D.
Specific internal energy
3
Thermodynamic Units and Properties Knowledge Check
Answer Key
ELO 2.3 Relationship Between Work, Energy, and Power
Knowledge Check
A 600 lbm casting is lifted 4 feet to the bed of a milling
machine. How much work is done?
A.
240 ft-lbs
B.
150 ft-lbs
C.
2,400 ft-lbs
D.
1,500 ft-lbs
ELO 2.4 Thermodynamic Properties of Heat
Knowledge Check
Which of the following must be added to or removed
from a substance to produce a temperature change?
Rev 1
A.
Latent heat
B.
Specific heat
C.
Sensible heat
D.
Thermal heat
4