Available Units and Unit sets

The default units for the thermophysical properties listed in Table 1 can be altered by using the base units listed in Table 2 using the SetUnits method. In addition to the default (FluidProp) unit set, two different unit sets can be specified: the SI and the Anglo-Saxon unit set. Units are per mass by default (cF. Table 1) but can be specified per mole as well. Non-dimensional properties can be obtained by defining a reference state by using the SetRefState method.

 

Table 1

Property name

Symbol

Default
unit set
 

SI
unit set

Anglo-Saxon
unit set

Pressure

P

bar

Pa

psia

Temperature

T

°C

K

°F

Specific volume

v

m^3/kg

m^3/kg

ft^3/lb

Density

d

kg/m^3

kg/m^3

lb/ft^3

Enthalpy

h

kJ/kg

J/kg

Btu/lb

Entropy

s

kJ/kg/K

J/kg/K

Btu/lb/°R

Internal energy

u

kJ/kg

J/kg

Btu/lb

Isobaric heat capacity

cp

kJ/kg/K

J/kg/K

Btu/lb/°R

Isochoric heat capacity

cv

kJ/kg/K

J/kg/K

Btu/lb/°R

Speed of sound

c

m/s

m/s

ft/s

(images/FluidProp00090011.gifP/images/FluidProp00090011.gifimages/FluidProp00090000.gif)u

alpha

m^2/s^2

m^2/s^2

ft^2/s^2

(images/FluidProp00090011.gifP/images/FluidProp00090011.gifu)images/FluidProp00090000.gif

beta

kg/m^3

kg/m^3

lb/ft^3

(images/FluidProp00090011.gifs/images/FluidProp00090011.gifimages/FluidProp00090000.gif)u

chi

N.m^4/kg^2/K

N.m^4/kg^2/K

lbf.ft^4/lb^2/°R

(images/FluidProp00090011.gifs/images/FluidProp00090011.gifu)images/FluidProp00090000.gif

fi

K^-1

K^-1

°R^-1

(images/FluidProp00090011.gifimages/FluidProp00090000.gif/images/FluidProp00090011.gifh)P

ksi

kg^2/N/m^4

kg^2/N/m^4

lb^2/lbf/ft^4

(images/FluidProp00090011.gifimages/FluidProp00090000.gif/images/FluidProp00090011.gifP)h

psi

s^2/m^2

s^2/m^2

s^2/ft^2

(images/FluidProp00090011.gifT/images/FluidProp00090011.gifv)u

zeta

kg.K/m^3

kg.K/m^3

lb.°R/ft^3

Volumetric thermal expansion coefficient

theta

K^-1

K^-1

°R^-1

Isothermal compressibility

kappa

bar^-1

Pa^-1

psia^-1

Dynamic viscosity

eta

Pa.s

Pa.s

lb/ft/s

Thermal conductivity

lambda

W/m/K

W/m/K

Btu/h/ft/°F

 

Table 2

Property name

Base units

Length

m

in

ft

yd

mi

 

Mass

g

lb

oz

 

 

 

Time

s

min

h

d

y

 

Temperature

K

°C

°F

°R

 

 

Temperature difference

K

°C

°F

°R

 

 

Area

m2

a

sq in

sq ft

sq yd

acre

Volume

m3

L

cu in

cu ft

cu yd

cc

Speed

m/s

mph

kn

 

 

 

Force

N

gf

lbf

 

 

 

Pressure, stress

Pa

bar

atm

mHg

psia

 

Energy, work, heat

J

Wh

cal

Btu

 

 

Power

W

hp

 

 

 

 

 

Base units can be preceded (if applicable) by the prefixes listed in Table 3.

 

Table 3

Prefix
symbol

Name

Factor

Prefix
symbol

Name

Factor

y

yocto

10^-24

da

deca

10^+1

z

zepto

10^-21

h

hecto

10^+2

a

atto

10^-18

k

kilo

10^+3

f

femto

10^-15

M

mega

10^+6

p

pico

10^-12

G

giga

10^+9

n

nano

10^-9

T

tera

10^+12

mu

micro

10^-6

P

peta

10^+15

m

milli

10^-3

E

exa

10^+18

c

centi

10^-2

Z

zeta

10^+21

d

deci

10^-1

Y

yotta

10^+24

 

Base units, possibly preceded by a prefix, can be used together in arbitrary combinations. For instance the unit of the specific heat capacity (J/kgK) can be formed by combining the units of energy, mass and temperature difference dT by means of the operators listed in Table 4.

 

Table 4

Operator
symbol

Name

Meaning

.

period

multiply

/

slash

divide

^

circumflex

power

 

A compound unit consists of a row of base units, possibly raised to a certain power, separated by a period or a slash. A base unit raised to a power consists of base unit followed by circumflex and after that a positive or negative number. If no power is specified, the power defaults to 1. For example if a pressure is to be specified as Newton per square meter then it can be written as N/m^2 (or N.m^-2). The number of base units in a compound unit is unlimited. Each base unit and its power form a unit itself. This means that a period or slash in front of the preceding unit does not affect the unit thereafter. Therefore the unit of the specific heat capacity must be written as J/kg/K, or J.kg^-1.K^-1, or J/kg.K^-1, or J.kg^-1/K and certainly not as J/kg.K.

 

For more examples, see SetUnits.