TSI Incorporated VELOCICALC Plus 8360, Руководство по эксплуатации и обслуживанию

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19
Appendix C
Standard Velocity vs. Actual Velocity
Since thermal air velocity sensors are sensitive to changes in air density and
air velocity, all thermal anemometers indicate velocities with reference to a
set of standard conditions. For TSI instruments, standard conditions are
defined as 70° F (21.1° C) and 14.7 psia (101.4 kPa). Other manufacturers
may use different values.
Standard velocity is the velocity the air would be moving if the temperature
and pressure were at standard conditions. It is usually the most useful
measure of airflow because it defines the heat-carrying capacity of the air.
Actual velocity is the velocity at which a microscopic particle of dust would
be traveling if it were in the air stream.
In some instances, actual air velocity rather than standard velocity may be of
interest. To obtain the value for actual velocity, multiply your standard
velocity by the following density correction factor:
Actual Velocity V
T
P
=
+
+

 
 
 

( )
.
Standard elocity
460
460 70
14 7
Where
T = Ambient temperature in degrees Fahrenheit
P = Ambient pressure in psia
If you use metric units, the equation becomes:
Actual Velocity (Standard elocity)
=
+
+

 

V
T
P
m
m
273
273 211
101
.
.4
Where
Tm = Ambient temperature in degrees Celsius
Pm = Ambient pressure in kPa