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
Z [m] |
p [Pa] |
T [K] |
ρ [kg/m^{3}] |
---|---|---|---|
-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·R_{0}/M·T
where
- Tis temperature in kelvin
- ρis density in kg/m^{3}
- pis pressure in pascals
- Zis altitude (above mean sea level) in metres
- R_{0}is the universal gas constant = 8134.4 J/kg/K
- Mis the molar mass of air = 28.9647 kg/kmol
Calculate pressure, temperature, and density at altitude online