FieldengThermal & HVAC
Humidity Ratio
W = 0.621945 Pv / (P − Pv) with Pv = RH × Psat(T) from Magnus saturation pressure.
Thermal & HVAC
W = 0.621945 Pv / (P − Pv) with Pv = RH × Psat(T) from Magnus saturation pressure.
App id: THERM-12. Reference version 1.0.
How to fill it
Fill the inputs. The tool shows the outputs.
On the tool screen, Calc is the working sheet. Presets stores values you reuse. Reference is the formula, assumptions, and provenance below.
Formula
W = 0.621945 Pv / (P − Pv)Inputs
| Name | Unit |
|---|---|
| Dry-bulb temperature (camera) | C |
| Relative humidity | % |
| Barometric pressure (optional) | kPa |
Outputs
| Name | Unit |
|---|---|
| Humidity ratio (hero result) | kg/kg |
| Vapor pressure | Pa |
Diagnose
Observations are context. They do not pass or fail a structure. See Diagnose.
| When | Observation | Severity |
|---|---|---|
RH > 0.7 | High relative humidity | caution |
RH < 0.2 | Low relative humidity | info |
Assumptions
- Ideal-gas moist air. Pressure is absolute.
Provenance
- Psat = 610.94 exp(17.625 T / (T + 243.04)) Pa, T in °C. Leave pressure blank for 101.325 kPa.