Moist Air Enthalpy (ASHRAE Psychrometrics)
Total heat content h = 0.240 t + W (1061 + 0.444 t) Btu per lb dry air.
Example
You enter
- Dry-bulb temperature (°F) 80
- Humidity ratio W (lb water / lb dry air) 0.0112
You get
- Enthalpy h 31.48 Btu/lb dry air
Checked against published worked examples from: ASHRAE.
Details, formula, and sources
ScopeThe state property every coil and air-mix calculation starts from. Return air at 80 F, W 0.0112 -> 31.48 Btu/lb; 55 F supply, W 0.009 -> 22.97. Pair with an outdoor-air mix calculation for W. A design aid; the chart and equipment ratings govern.
Formula or tableh = 0.240 t + W (1061 + 0.444 t) Btu per lb dry air.
Source and editionThe I-P moist-air enthalpy relation from the ASHRAE Handbook - Fundamentals, by name.
Free accessThe moist-air enthalpy relation and its sea-level coefficients are standard ASHRAE psychrometric results. A measured chart state and the equipment ratings govern.
What governsEstimate. AHJ and licensed professional govern.
API field namest_db_f, w_lb_lb, h
- Enthalpy relation h = 0.240 t + W (1061 + 0.444 t) Btu/lb dry airASHRAE Fundamentals
- Sea-level coefficients 0.240 dry-air cp, 1061 the enthalpy of saturated vapor at 0 F (from liquid water at 32 F), 0.444 vapor cpASHRAE
- Humidity-ratio input W is the moisture input (lb/lb); get it from RH via outdoor-air-mix or a chartscope of this tile