Humid Air Enthalpy
湿空气的比焓由干球温度与含湿量决定。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Moist air enthalpy | h = 1.006t + w(2501 + 1.86t) kJ/kg | ASHRAE Ch.1 |
| Humidity ratio | w = 0.622 p_v/(p − p_v) | Psychrometrics |
| Latent term | 2501 kJ/kg latent heat at 0 °C | Steam properties |
| Reference datum | 0 °C datum for dry air and liquid | ASHRAE convention |
| Applications | HVAC load, cooling towers, drying | HVAC engineering |
| Wet-bulb | Adiabatic saturation ≈ wet bulb | Psychrometric chart |
Constants used in the moist-air enthalpy formula and their authoritative sources, for verification and citation
| Constant | Value | Unit | Source |
|---|---|---|---|
| Specific heat of dry air c_p,a | 1.006 | kJ·kg⁻¹·K⁻¹ | ASHRAE Fundamentals (Chapter 1, moist air) |
| Specific heat of water vapour c_p,v | 1.86 | kJ·kg⁻¹·K⁻¹ | ASHRAE Fundamentals (page default) |
| Latent heat of vaporisation at 0 ℃, h_fg | 2501 | kJ·kg⁻¹ | IAPWS-IF97 (page default; same value in ASHRAE) |
| Gas constant of dry air R_a | 287.042 | J·kg⁻¹·K⁻¹ | Derived from R/M (CIPM 2007 dry-air M) |
| Standard atmosphere | 101 325 | Pa | ISO 2533 defining value (exact) |
Note: h = 1.006t + w(2501 + 1.86t) is the common engineering form referenced to liquid water at 0 ℃, valid for near-atmospheric HVAC conditions; use the ASHRAE real moist-air property library at high pressure or extreme humidity.