Hi Ennes,
To model the humidifier for your PEM fuel cell at high altitude, you need to determine the moisture content in the air accurately. At high altitudes, the air pressure is lower, which affects the moisture content. The absolute humidity (moisture content) can be derived from the dew point temperature or the specific humidity. The dew point temperature is a more reliable measure than relative humidity at high altitudes. To calculate the absolute humidity from the dew point temperature, you can use an approximation of the Clausius-Clapeyron equation:
where E0 = 0.611 kPa, (L/Rv) = 5423 K (in Kelvin, over a flat surface of water), T0 = 273 K (Kelvin) and T is temperature (in Kelvin), and Td is dew point temperature (also in Kelvin).
At high altitudes, pressure changes can also affect moisture content. You may need to adjust calculations based on the local atmospheric pressure, which decreases with altitude. By focusing on these calculations, you can more accurately model the moisture content in the air, allowing you to fine-tune the control system of your ultrasonic humidifier for optimal performance in high-altitude conditions. For more information on the equations, you can refer the following resource:
- Calculating dew point when temperature and relative humadity is known: https://iridl.ldeo.columbia.edu/dochelp/QA/Basic/dewpoint.html
- Using humidity to derive dew point: https://www.ti.com/lit/ab/snaa368/snaa368.pdf
Hope this helps!
