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Psychrometric Property Calculator

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Input Parameters

Unit System

Alternative Inputs

Currently using dry bulb temperature + relative humidity. Future versions will support wet bulb or dew point inputs.

Air Properties

Temperature Properties

75
Dry Bulb °F
61
Wet Bulb °F
55
Dew Point °F

Humidity Properties

Relative Humidity50 %
Absolute Humidity0.0092 lb/lb
Vapor Pressure0.214 psia
Saturation Pressure0.429 psia

Thermodynamic Properties

Specific Volume13.68 ft³/lb
Enthalpy28.07 BTU/lb

Comfort Analysis

✓ Within ASHRAE comfort zone

Psychrometric Chart

Detailed Psychrometric Analysis

Process Analysis

Dew Point Depression:19.7°F
Wet Bulb Depression:14.0°F
Vapor Pressure Ratio:50.0%

AC Process Potential

• Sensible cooling: 20.0°F potential
• Dehumidification: 8 grains/lb potential
• Evaporative cooling: 14.0°F potential

Energy Content

Sensible Heat:18.0 BTU/lb
Latent Heat:9.8 BTU/lb
Total Enthalpy:28.1 BTU/lb

Comfort & Health Indicators

Good
Humidity Level
Good
Temperature
Good
Mold Risk
821
CFM per lb/min

Psychrometric Calculation Steps

1

Input Air Conditions

Formula:
Tdb=dry bulb temperature,ϕ=relative humidityT_{db} = \text{dry bulb temperature}, \phi = \text{relative humidity}
Calculation:
Tdb=75°F,ϕ=50%T_{db} = 75\text{°F}, \phi = 50\%
Result:
75°F,5075°F, 50% \text{ }
2

Calculate Saturation Pressure

Formula:
Psat=Antoine equation for water vaporP_{sat} = \text{Antoine equation for water vapor}
Calculation:
Psat=f(Tdb)P_{sat} = f(T_{db})
Result:
0.429 psia0.429 \text{ psia}
3

Calculate Vapor Pressure

Formula:
Pv=ϕ100×PsatP_v = \frac{\phi}{100} \times P_{sat}
Calculation:
Pv=50100×0.429P_v = \frac{50}{100} \times 0.429
Result:
0.214 psia0.214 \text{ psia}
4

Calculate Humidity Ratio

Formula:
W=0.621945×PvPatm−PvW = 0.621945 \times \frac{P_v}{P_{atm} - P_v}
Calculation:
W=0.621945×0.21414.696−0.214W = 0.621945 \times \frac{0.214}{14.696 - 0.214}
Result:
0.0092 lb water/lb dry air0.0092 \text{ lb water/lb dry air}
5

Calculate Dew Point Temperature

Formula:
Tdp=temperature where Psat(Tdp)=PvT_{dp} = \text{temperature where } P_{sat}(T_{dp}) = P_v
Calculation:
Iterative solution: Psat(Tdp)=0.214\text{Iterative solution: } P_{sat}(T_{dp}) = 0.214
Result:
55.3 °F55.3 \text{ °F}
6

Calculate Wet Bulb Temperature

Formula:
Twb=psychrometric approximationT_{wb} = \text{psychrometric approximation}
Calculation:
Twb=f(Tdb,ϕ)T_{wb} = f(T_{db}, \phi)
Result:
61.0 °F61.0 \text{ °F}
7

Calculate Specific Volume

Formula:
v=0.370486×TR×(1+1.607858×W)Patmv = 0.370486 \times \frac{T_R \times (1 + 1.607858 \times W)}{P_{atm}}
Calculation:
v=0.370486×534.7×(1+1.607858×0.0092)14.696v = 0.370486 \times \frac{534.7 \times (1 + 1.607858 \times 0.0092)}{14.696}
Result:
13.678 ft³/lb13.678 \text{ ft³/lb}
8

Calculate Enthalpy

Formula:
h=0.240×Tdb+W×(1061+0.444×Tdb)h = 0.240 \times T_{db} + W \times (1061 + 0.444 \times T_{db})
Calculation:
h=0.240×75+0.0092×(1061+0.444×75)h = 0.240 \times 75 + 0.0092 \times (1061 + 0.444 \times 75)
Result:
28.07 BTU/lb28.07 \text{ BTU/lb}