Page 39 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

QC: IML/FFX
P2: IML/FFX
P1: IML/FFX
AT029-Manual
June 22, 2007
AT029-01
1. INTRODUCTION 19
appropriately. The conversion factors among these units are
as follows: AT029-Manual-v7.cls T1: IML 14:26 unit for the molecular weight is not mentioned; however, one
must realize that it is not a dimensionless parameter. Most
5
1 year = 365 d = 8760 h = 5.256 × 10 min = 3.1536 × 10 s recent compilations of molar masses are provided by Coplen
7
[87].
1d = 2.743973 × 10 −3 year = 24 h = 1440 min = 8.64 × 10 s
4
1h = 1.14155 × 10 −4 year = 4.16667 × 10 −2 d
= 60 min = 3600 s 1.7.9 Units of Pressure
1 min = 1.89934 × 10 −6 year = 6.94444 × 10 −4 d Pressure is the force exerted by a fluid per unit area; therefore,
= 1.66667 × 10 −2 h = 60 s in the SI system it has the unit of N/m , which is called Pascal
2
2
1s = 3.17098 × 10 −8 year = 1.157407 × 10 −5 d (Pa), and in the English system has the unit of lb f /ft (psf) or
2
= 2.77777 × 10 −4 h = 1.66667 × 10 −2 min lb f /in. (psi). Other units commonly used for the pressure are
the bar (bar) and standard atmosphere (atm). Pressure may
also be expressed in terms of mm Hg. In this book units of
1.7.6 Units of Force MPa, kPa, bar, atm, or psi are commonly used for pressure.
As mentioned above, the unit of force in the SI system is The conversion factors are given as follows:
Newton (N) and in the English unit system is pound-force 1 atm = 1.01325 bar = 101 325 Pa = 101.325 kPa
(lb f ). 1 lb f is equivalent to the weight of a mass of 1 lb m at = 0.101325 MPa = 14.696 psi
the sea level where the acceleration of gravity is 32.174 ft/s 2 2
2
(9.807 m/s ). In the cgs system, the unit of force is dyne (dyn). 1 atm = 1.0322 kg f /cm = 760 mm Hg (torr) = 29.921 in. Hg
◦
Another unit for the force in the metric system is kg f , which = 10.333 m H 2 O(4 C)
5
is equivalent to the weight of a mass of 1 kg at the sea level. 1 bar = 0.98692 atm = 1 × 10 Pa = 100 kPa
The conversion factors are as follows: = 0.1 MPa = 14.5038 psi
5
1N = 1kg · m/s = 10 dyn = 0.2248 lb f = 1.01968 × 10 −1 kg f 1Pa = 1 × 10 −3 kPa = 1 × 10 −6 MPa = 9.8692 × 10 −6 atm
2
= 1 × 10 −5 bar = 1.45037 × 10 −4 psi
1lb f = 4.4482 N = 0.45359 kg f
1 psi = 6.804573 × 10 −2 atm = 6.89474 × 10 −2 bar
1kg f = 9.807 N = 2.204634 lb f −3
= 6.89474 × 10 MPa
1 dyn = 10 −5 N = 2.248 × 10 −6 lb f
1 psf = 144 psi = 9.79858 atm = 9.92843 bar = 0.99285 MPa
2
1kg f /cm = 0.96784 atm = 0.98067 bar = 14.223 psi
1.7.7 Units of Moles
The actual pressure of a fluid is the absolute pressure, which
Another unit to present amount of matter especially in en- is measured relative to vacuum. However, some pressure
gineering calculations is mole (mol), which is defined as the measurement devices are calibrated to read zero in the at-
ratio of mass (m) to molecular weight (M). mosphere and they show the difference between the abso-
m
(1.6) n = lute and atmospheric pressure. This difference is called gage
M pressure. Normally “a” is used to indicate the absolute value
In SI system the unit of mole is kmol, where m in the above (i.e., psia, bara) and “g” is used to show the gage pressure
equation is in kg. In the English system, the unit of mol is (i.e., psig). However, for absolute pressure very often “a” is
lbmol. In the cgs system, the unit of mol is gmol, which is dropped from the unit (i.e., psi, atm, bar). Another unit for
usually written as mol. For example, for methane (molecular the pressure is vacuum pressure that is defined for pressure
weight 16.04) 1 mol of the gas has mass of 16.04 g. One mole below atmospheric pressure. Relations between these units
of any substance contains 6.02 × 10 23 number of molecules are as follows:
(Avogadro’s number). The conversion factors between vari-
ous units of moles are the same as given for the mass in (1.7) P gage = P abs − P atm
Section 1.7.3. (1.8) P abs = P atm − P vac
1 kmol = 1000 mol = 2.204634 lbmol
Generally gage pressure unit is used to express pressures
1 lbmol = 0.45359 kmol = 453.59 mol above the atmospheric pressures and vacuum pressure unit is
1 mol = 0.001 kmol = 0.002204634 lbmol used for pressures below atmospheric and may be expressed
in various units (i.e., mm Hg, psi).
1.7.8 Units of Molecular Weight
1.7.10 Units of Temperature
Molecular weight or molar mass shown by M is a number
that 1 mol of any substance has equivalent mass of M g. In Temperature (T) is the most important parameter affecting
the SI system the unit of M is kg/kmol and in the English properties of fluids and it is represented in Centigrade ( C)
◦
system the unit is lb/lbmol, while in the cgs system the unit and Kelvin (K) in the SI system and in Fahrenheit ( F) and
◦
of M is g/mol. Molecular weight is represented by the same degrees Rankine ( R) in the English unit system. Temperature
◦
number in all unit systems regardless of the system used. As in most equations is in absolute degrees of Kelvin or Rank-
an example, methane has the molecular weight of 16 g/mol, ine. However, according to the definition of Kelvin and de-
16 lb/lbmol, and 16 kg/kmol in the unit systems of cgs, SI, grees Rankine where there is a temperature difference ( T),
and English, respectively. For this reason, in many cases the unit of C is the same as K and F is the same as R. These
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