Psychrometric Chart 2-Condition Calculator

Instructions:

1. Review the methodology to ensure it aligns with your project's requirements.

2. Select Metric or US units

3. Select the first input parameter:

   • Temperature,Dry Bulb, oF [oC]

   • Temperature,Dew Point, oF [oC]

4. Enter the Entering and Exiting values for the first selected input parameter

5. Select the second input parameter:

   • Temperature,Wet Bulb*, oF [oC]

   • Relative Humidity, %

6. Enter the Entering and Exiting values for the second selected input parameter.

7. Enter the air flow rate to calculate the Total, Sensible, and Latent Cooling, Condensate Generated, and Air Flow Rate per ton. 

8. Enter the project's altitude. 

9. Click the Calculate button.

10. The results are shown in the Results table

* Temperature, Wet Bulb, is only available as an input when the first input is Temperature,Dry Bulb

 

Methodology:

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The following formulas are used in this calculator.  They have been adapted from the 2021 ASHRAE Handbook -Fundamentals. 

 

p = 14.696 (1-6.8754 x 10^(-6)Z)^5.2559

t = 59 - 0.00356620Z 

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For 32oF < t < 707.103oF:

p,ws = 145.03774 (2C / (-B + (B^2 - 4AC)^0.5))^4

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See ASHRAE Handbook-Fundamentals for Coefficient Values, A, B, and C.

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W = Mw / Mda

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RH% = (p,w / p,s)

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v = 0.370486 (t,db + 459.67)(1 + 1.607858) / p

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h = 0.240 t + W(1061 + 0.444t)

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p,w = p x W / (0.621945 + W )

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where

h = specific enthalpy [Btu/lb,da]

p = barometric pressure [psia]

p,w = water vapor partial pressure [psia]

p,s = saturation water vapor pressure [psia]

p,ws = saturation pressure [psia]

t = temperature [oF]

T,d = dew point temperature [oF]

t,db = dry bulb temperature [oF]

t,wb = wet bulb temperature [oF]

v = specific volume [ft^3/lb,da]

W = humidity ratio [lb,w / lb,da]

Z = Altitude [ft]