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PsyCalc uses industry standard calculations to determine psychrometric property values. Each time a change is made to the input values PsyCalc recalculates psychrometric properties. The program uses calculation methods and equations that have been generally accepted by the HVAC industry and ASHRAE.
Limits
The limits set within the program are imposed due to inaccuracies in the calculation methods and/or practical limits of the technology and industry for which PsyCalc was created. The current limits are:
Dry Bulb Temperature -60 to 400ºF (-51 to 204.4ºC)
Wet Bulb temperature -60 to 400ºF (-51 to 204.4ºC)
Dew Point Temperature -80 to 200ºF (-51 to 71.1ºC)
Altitude -500 to 65,000 Ft (-152 to 19,800 m) above sea level
Pressure .7 to 400 psia (5 to 2,757 kPa)
(Moisture content is directly limited by the dew point limit.)
Accuracy
There is no simple way to state the accuracy of the calculated values presented by PsyCalc over the entire range of its operation. Suffice it to say that standard industry recognized equations have been used and every effort made to avoid errors due to rounding.
PsyCalc 98 continues to utilize the improved psychrometric algorithms introduced in version 1.7.
Version 1.7 added more rigorous calculation techniques and therefore has improved accuracy. These algorithms produce results that agree with the satuaration vapor pressure and humidity ratio table for 14.696 psia presented in the 1997 ASHRAE Fundamentals Handbook to 4 or 5 decimal places. Many thanks to Roy Otterbein of Otterbein Engineering, Phoenix, AZ for help in improving our methods.
It is the users responsibility however to qualify the accuracy and its applicability to the work they do. PsyCalc was written for use by the HVAC industry and it is the authors opinion that it provides adequate accuracy for this industry. Please review the Disclaimer for further information.
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