INSTRUCTIONS

This on-line program calculates typical psychrometric state point properties. It will also provide a number of other thermodynamic properties not found on a typical psychrometric chart.

To calculate properties, the user must enter either a site elevation (from which an average barometric pressure is calculated) or an actual barometric pressure. User then enters the desired Dry Bulb temperature and one of three humidity metrics: Relative Humidity Wet BulbTemperature or Dew Point Temperature. At the end of the calculation, the user has the option to convert from the inch-pound to the SI (or vice versa) unit system.

Common atmospheric pressure values are:

• Sea Level Pressure - 14.696 psia / 101.325 kPa / 29.921 in Hg / 760 mm Hg    (Default when 'Actual Pressure' is selected)
• Average Barometric Pressure in Dayton, OH - 14.175 psia / 97.732 kPa / 28.860 in Hg / 733 mm Hg
• Site elevation for Dayton, OH - 997 ft amsl (306 m) based on the ASHRAE HOF.    (Default when Elevation is selected)
• User may override default input by selecting and entering new value.

FAQ

• There appears to be error in the calculations when converting from one unit system to another. Why?
• Why does this program show two different values of specific volume?
• What is the difference between the six different humidity metrics shown?
• You show a 'Virtual' Temperature under Thermodynamic properties. What is that?
• Why is the wind chill calculation only available some of the time?

DISCLAIMER

This program is provided for your use without charge. However, no warranty, either expressed or implied, is given with respect to the accuracy or the sufficiency of the information provided hereby, and the user must assume all risks and responsibility in connection with the use thereof.

COPYRIGHT

Copyright © 2006 Russell K. Marcks, P.E. and ASHRAE Dayton Chapter. All rights reserved. No part of this web page and associated script may be produced, transmitted, transcribed, stored in a retrieval system, or translated into any language in any form without the express written consent of the author.

    

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Site Design by Dayton ASHRAE Website Committee. This home page is maintained by the Dayton Chapter of the American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. ASHRAE chapters may not act for the Society and the information presented here has not had Society review. To learn more about ASHRAE activities on an international level, contact the ASHRAE home page at http://www.ashrae.org

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