scope:

Purpose and Scope

The purpose of this data is to assemble psychrometric data in chart and equation form in both SI and USCS (US Customary System) and to provide equilibrium moisture data from ASAE D245 directly on abridged psychrometric charts.

Psychrometric charts are presented that give psychrometric data for dry bulb temperature ranges of −40°F to 600°F in USCS and 0°C to 120°C in SI units.

Most full psychrometric charts presented are Mollier-type; i.e., Mollier diagrams with the axes constructed at oblique angles so they appear similar to traditional psychrometric charts that have humidity ratio plotted against dry-bulb temperature with orthogonal axes. One full psychrometric chart with a large temperature range is presented as a semi-logarithmic plot of humidity ratio vs. dry-bulb temperature. Additional traditional charts are presented with abridged psychrometric data and equilibrium moisture data for eight common grains and oilseeds to facilitate grain drying and rewetting calculations.

The equations given in Sections 2 and 3 enable the calculation of all psychrometric data if any two independent psychrometric properties of an air-water vapor mixture are known in addition to the atmospheric pressure. In some cases, iteration procedures are necessary. In some instances, the range of data covered by the equation has been extended beyond that given in the original source. The equations yield results that agree closely with values given by Keenan and Keyes (1936) and existing psychrometric charts.