How Moisture Moves

Six steps to compare the vapour pressure of the material with the air.

1. 01Assume the material is fully saturated, ERH approximately 100%.
2. 02Find the surface temperature of the material on the chart.
3. 03Go up vertically to the 100% RH curve, the saturation line.
4. 04From that point, draw a horizontal line to the vapour pressure scale on the right. That is the vapour pressure of the material.
5. 05Measure the vapour pressure of the air using psychrometric data, dry bulb plus RH.
6. 06Compare the two vapour pressures to find the differential. The larger the gap, the more effective the drying.