Modern Engineering Thermodynamics

26 CHAPTER 1: The Beginning
systems when necessary. Finally, we saw how to apply the basic units systems to the calculation of the potential
and kinetic energy of systems.
Some of the more important equations developed in this chapter follow.
1. The equations for the conversion of temperature units:
Tð°FÞ = 9 × Tð°CÞ + 32 = TðRÞ − 459:67
5
Tð°CÞ = 5 × ½Tð°FÞ − 32Š = TðKÞ − 273:15
9
TðRÞ = 9 × TðKÞ = 1:8 × TðKÞ = Tð°FÞ + 459:67
5
TðKÞ = 5 9
× TðRÞ =
TðRÞ
1:8
2. By Newton’s second law, F = ma/g c , and the dimensional constant g c
g c = 32:174 lbm .ft
lbf .s 2
= Tð°CÞ + 273:15
for the Engineering English units system
g c = 1:0 ðdimensionlessÞ for the SI units system
3. The relation between mass (m) and moles (n) of a chemical substance with a molecular mass M:
4. The definitions of potential and kinetic energies:
n = m M
Potential Energy = PE = mgZ
g c
Translational Kinetic Energy = ðKEÞ trans
= mV 2
2g C
Rotational Kinetic Energy = ðKEÞ rot = Iω2
2g C
Some of the important technical terms introduced in this chapter are given in the glossary shown in Table 1.8.
Many of these terms are used throughout the remainder of the text without further explanation.
Table 1.8 Glossary of Technical Terms Introduced in Chapter 1
Technical Term
Meaning
metrology
The study of measurement
dimension
A measurable characteristic
duodecimal
A base 12 number system
sexagesimal
A base 60 number system
Newton’s second law F = ma/g c
newton 1 newton = 1 kg·m/s 2
dyne 1 dyne = 1 g·cm/s 2
poundal 1 poundal = 1 lbm·ft/s 2
slug
1 slug = 1 lbf·s 2 /ft
g c
The dimensional proportionality constant in Newton’s second law. In the Engineering English units system,
g c = 32.174 lbm·ft/(lbf·s 2 ), and in the SI units system g c = 1 and is dimensionless.
gmole
The amount of any chemical substance that has a mass in grams numerically equal to the molecular mass
of the substance. This is called simply a mole in chemistry textbooks.
kgmole
The amount of any chemical substance that has a mass in kilograms numerically equal to the molecular
mass of the substance.
lbmole
The amount of any chemical substance that has a mass in lbm (pounds mass) numerically equal to the
molecular mass of the substance.
SI
Le Systéme International d’Unités (French)
Psia
lbf/in 2 absolute (pressure)
Psig
lbf/in 2 gauge (pressure)