# The International Standard Atmosphere

For the design of pans, evaporators, barometric condensers and in NPSH calculations for pumps it is neccessary to know the atmospheric pressure. While many cane sugar factories are close to the sea, there are those that are at higher altitudes where atmospheric pressure is below the well known 101325 Pa for sea level

There are tables of atmosphic pressure variation with altitude; the table below is the International Standard Atmosphere adapted from Thermodynamic and Transport Properties of Fluids arranged by GFC Rogers and YR Mayhew, 3rd edition

International Standard Atmosphere
Z
[m]
p
[Pa]
T
[K]
ρ
[kg/m3]
-2500 135210 304.4 1.5473
-2000 127780 301.2 1.4782
-1500 120700 297.9 1.4114
-1000 113930 294.7 1.3470
-500 107480 291.4 1.2849
0 101325 288.15 1.2250
500 95460 284.9 1.1673
1000 89880 281.7 1.1117
1500 84560 278.4 1.0582
2000 79500 275.2 1.0066
2500 74690 271.9 0.9570
3000 70120 268.7 0.9093
3500 65780 265.4 0.8634
4000 61660 262.2 0.8194
4500 57750 258.9 0.7770
5000 54050 255.7 0.7365
5500 50540 252.4 0.6975
6000 47220 249.2 0.6602
6500 44080 245.9 0.6243
7000 41110 242.7 0.5901
7500 38300 239.5 0.5573
8000 35650 236.2 0.5258
8500 33150 233.0 0.4958
9000 30800 229.7 0.4671
9500 28580 226.5 0.4397
10000 26500 223.3 0.4136
10500 24540 220.0 0.3886
11000 22700 216.8 0.3648

Tables are not convenient for computer calculations: regression formulae have been prepared from the above data for temperature and density; pressure can then be calculated from the universal gas law.

T = 288.15 - 0.006492255 · Z

ρ = 1.225 · e(-0.09543718·(Z/1000) - 0.001321598·(Z/1000)2)

p = ρ·R0/M·T

where

• T
is temperature in kelvin
• ρ
is density in kg/m3
• p
is pressure in pascals
• Z
is altitude (above mean sea level) in metres
• R0
is the universal gas constant = 8134.4 J/kg/K
• M
is the molar mass of air = 28.9647 kg/kmol

Calculate pressure, temperature, and density at altitude online