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ASHRAE Fundamentals: moist air at 25 °C dry bulb, 50 % relative humidity, sea level (SI)

ToolPsychrometric Calculator
SourceAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (2021). ASHRAE Handbook: Fundamentals. ASHRAE, Peachtree Corners, GA. Chapter 1, Psychrometrics (Table 3 saturation properties and the moist-air property equations); Hyland, R. W., and Wexler, A. (1983). "Formulations for the Thermodynamic Properties of the Saturated Phases of H2O from 173.15 K to 473.15 K." ASHRAE Transactions, Vol. 89, No. 2A, pp. 500–519.
LevelProfessional

Problem

Find the saturation pressure, humidity ratio, enthalpy, wet-bulb and dew-point temperatures and specific volume of air at 25 °C dry bulb and 50 % relative humidity at 101.325 kPa.

Inputs to Enter

  • SI units; dry bulb 25 °C
  • Second property: relative humidity, 50 %
  • Altitude 0 m
Open the Psychrometric Calculator tool

Answers

  • p_ws(25 °C) = 3169.2 Pa (table 3169.7); p_ws(0 °C) = 611.2 Pa, p_ws(100 °C) = 101.42 kPa
  • W = 0.009881 kg/kg (0.009867); h = 50.32 kJ/kg (50.29)
  • Wet bulb 17.89 °C (17.86); dew point 13.89 °C (13.86); v = 0.8580 m³/kg (0.8581)
  • Standard pressure at 1,500 m altitude: 84.56 kPa (table 84.56)

Notes

Switch the form to SI and enter 25 for the dry bulb. Values from test-scripts/test_hvac.php (tolerances 0.1–0.5 %); the wet-bulb and dew-point round trips return the same W.

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