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UDC 621.56/.59 : 53.081 : 033.62
IS0
I NT ERN AT1 O N A L O R G A N IZ AT I O N FO R STA N DA RD IZATl O N
IS0 RECOMMENDATION
R 786
UNITS AND SYMBOLS FûR REFRIGERATION
1st EDITION
July 1968 -
(second printing, corrected in accordance with
lSO/R 786-1968 (E)/Erratum)
COPY RIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
Units and symbols for refrigeration, was drawn up by
The IS0 Recommendation R 786,
Technical Committee ISO/TC 86, Refngerution, the Secretariat of which is held by the British
Standards Institution (BSI).
Work on this question by the Technical Committee began in 1962 and led, in 1965, to the
adoption of a Draft IS0 Recommendation.
Y
In November 1966, this Draft IS0 Recommendation (No. 1053) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,by
the following Member Bodies :
Australia
Hungary Switzerland
Belgium
Ireland Turkey
Brazil Israel U.A.R.
Canada Italy United Kingdom
Chile Japan U.S.S.R.
Denmark Korea, Rep. of Yugoslavia
France Norway
Four Member Bodies opposed the approval of the Draft
Czechoslovakia Poland
Ne the rlands Sweden
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in July 1968, to accept it as an IS0 RECOMMENDATION.
L
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ISO/R 786-1968(E
IS0 Recommendation R 786 July 1968
UNITS AND SYMBOLS FOR REFRIGERATION
INTRODUCTION
This IS0 Recommendation is a collection of the principal quantities chiefly used in the field of
refrigeration, and of their symbols and units of measurement. For convenience, certain fundamental
quantities and their derivatives have been included, which have already been considered in IS0
Recommendation R 3 1.
The various quantities have been grouped in a logical order so as to facilitate their location by
users.
In certain cases, when the same symbol may have more than one meaning, a second symbol has been
proposed. The units are separated into two columns, the first giving units of the Système Inter-
national (SI) and the second units of other systems which are at present very widely used. In order to
obtain the values in SI units which are equivalent to those in other units, conversion factors have
been introduced near the latter.
A column reserved for “Definitions and Remarks” in the tables provides in certain cases definitions or
explanations supplementary to those found in IS0 Recommendation R 31.
The use of metric and SI units and their multiples and sub-multiples is particularly recommended.
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ISO/R 786-1%8(€
1. INDEXES FOR SPECIAL CASES
When it is necessary to define certain quantities by means of indexes, it is advisable to make use of
the following indications, the meaning of which should in every case be given.
Inferior indexes
1, 2, 3 . . . relating to different points of a system or of a cycle, or to different time intervals
a relating to air or to an adiabatic process
e to effective
f to an intermediate agent
an isenthalpic process
i to “indicated” or to
to upper pressure or temperature
k
1
to length
m to mass or mechanical
O to a lower pressure or temperature
to pressure, or to a polytropic process
P
to a state of saturation, or to an isentropic process
S
to temperature or to an isothermal process
t
V to volu.me
W to water
Superior indexes
“ relating to the gaseous phase
>> 7, >>
liquid ”
9, >> 13
O solid ”
Upper bar
Relating to the boundary layer, along the surface of separation between two phases, or to the mean
value of a quantity (e.g. mean speed).
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SI units
Symbol Dimensions
Quantity
Name Symbol
length 1 L metre m
area. surface A L2 square metre ni '
V cubic metre m3
volume
kilogramme
mass m
S
time 1 T second
frequency T -l hertz Hz
v, f
~~~
T -l I hertz HI
rotational speed n
kilogramme per
density (mass density)
P
cubic metre
specific volume V cubic metre per
kilogramme
mass flow rate MT-' I kilogramme per second
4rn
volume flow rate L3 T -' cubic metre per second m3 is
4"
T, O K
thermodynamic or
absolute temperature
customary temperature
t, e
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ISOlR 786-1968(1
I Other units
Conversion factor Definitions and remarks
Name Symbol
ft 1 ft = 0.3048 m (exactly)
1 in = 0.0254 m (exactly)
inch in
1 ft2 = 0.092 903 O m2
square foot
1 in2 = 6.4516 x 10-4 m2 (exactly)
cubic foot ft3 1 ft3 =28.3168 x 10-3 m3
cubic inch in 1 in3 = 16.3871 X 10-6 m3
lb 1 lb=0.453 592 37 kg (exactly)
pound
min 1 min = 60 s
minute
L-
h 1 h = 3600s
Also called “cycle per se-
cond”.
revolution per minute min-’ 1 min-’ =AHz
60
pound per cubic foot Ib/ft3 1 Ib/ft3 = 16.0185 kg/m3
cubic foot per pound ft3 :Ib 1 ft3/lb = 0.0624 m3/kg
1 lb/h = 126 X 10-6 kg/s Fluid mass flowing in unit
pound per hour
time.
Fluid volume flowing in
cubic foot per hour ft3 lh 1 ft3/h = 7.865 79 x 1OS6 m3/s
unit time.
if tC OC. t, OF, T, K and
OR
T, “R are referring to one
and the same physical sta-
te, the figures tc, t,, T,
and T, are evaluated as
tC = $ (tF - 32)
= T,-273.15
= $ TR- 273.15
Celsius degree OC tc = $ (t,-32) tC = T,-273.15
Fahrenheit degree OF
I, = TR-459.67
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~ ~~
SI units
Dimensions
Quantity Symbol
Name Symbol
K
temperature difference O kelvin
e-'
K-'
per kelvin
coefficient of linear
ffL
thermal expansion
K -I
per kelvin
coefficient of volume
ffV
thermal expansion
K -I
per kelvin
coefficient of thermal
B
pressure increase
square metre m2 IN
M-l LT~
coefficient
X
per newton
of compressibility
~~
newton N
F MLT -'
force
N/m2
ML-~ T -' newton per square metre
pressure
P
N/ m
U MT-' I newton per metre
surface tension
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ISO/R 786-1%8(E)
Other units
Conversion factor Definitions and remarks
Name Symbol
Celsius degree OC
Fahrenheit degree OF ~“F=$K
Oc-’
per Celsius degree 1 dl
1 dt
OF-]
per Fahrenheit degree
~
per Celsius degree
per Fahrenheit degree
per Celsius degree
p,l?) p di v
per Fahrenheit degree
1 du
square inch per in2 /lbf 1 in2 /lbf = 1.450 37 x 1 O-4 mZ/N
Xt,. = -; (.p) t, .
pound-force
1 dyn = lO-’ N (exactly)
dyne
dYn
kilogramme-force 1 kgf = 9.806 65 N (exactly) Also called “kiiopond”
kgf
@Pl.
pound-force lbf 1 lbf = 4.448 22 N
~~
This unit is also called
“pascal”.
bar bar bar = los N/m2 (exactly) 1 bar = 1 hectopieze (hpz)
kilogramme-force per kgf/cm2 kgf/cm2 = 98 066.5 N/m2 1 kgf/cmz
square centimetre (exactly) = 1 technical atmosphere(at
normal atmosphere atm atm = 101 325 N/mZ(exactly)
pound-force per lbf/ft2 lbf/ft2 = 47.8803 N/m2
square foot
pound-force per lbf/in2 lbf/in2 = 6894.76 N/mZ
square inch
millimetre of water* mmH, O mmH, O = 9.806 65 N/m2
(exactly)
mmHg mmHg = 133.322 N/m2 1 mmHg = 1 torr
millimetre of mercury#
O
inch of water* inHz inH20 = 249.089 N/m2
inch of mercury* inHg inHg = 3386.39 N/m2
dyne per centimetre dyn/cm 1 dyn/cm= 10‘3 N/m(exactly)
* Conventional units.
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2. TABLE OF SYMBOLS AND UNITS (continuai)
SI units
Symbol Dimensions
Quantity
Name Symbol
ML-' T -' newton second per
dynamic viscosity
P
square metre
kinematic viscosity 2, square metre per second m2 is
ML* T -2 joule J
work W
W
P ML2 T -3 watt
power
~~
L~T-~ joule per kilogramme Jlkg
specific work W
~~
J
ML~T -z joule
heat quantity
Q
W
heat flow rate MLZ T -3 watt
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lSO/R 786-1%8(1
Other units
Converaon factor Definitions and remarks
Symbol
poise P 1 P = 0.1 N$m2 (exactly)
1 N.s/m2 = 1 kg/(m.s)
1 P = 1 dyn.s/cm2
= 1 g/(cm.s)
kilogramme-force kgfs/m2
1 kgf.s/m2 = 9.806 65 N.s/m2
second per square metre
(exactly)
pound-force second
lbfs/ft 1 lbfs/ft2 = 47.8803 N.s/m2
per square foot
stokes
St i St = O.OOOi m2/s
i St = i cm2/s
square foot per second ft2 ,is 1 ft2 1s = 0.092 903 O m2/s
L-2
kilowatt hour kWh
1 kWh = 3.6 x 106 J (exactly)
1 erg = lO-’ J (exactly)
erg erg
kilogramme-force
kgf.m 1 kgf.m = 9.806 6
...