Continuing my discussion of the psychrometric chart and how to use it, in my last column, I showed a psychrometric chart, plotting four points. Allow me to proceed with the topic by picking up our ongoing example and taking it further, by putting that air inside a piece of process equipment such as a dryer or oven.

Before you can understand the complete psychrometric chart and how it is useful for sizing an industrial dryer, you first must understand the terms and the many parts that make up the whole psychrometric chart. (If you haven't read "Big Air, Part 1 (The Psychrometric Chart Unraveled)," start there.)

My "Tools of the Trade" series dealt with various instruments used in the acquisition of system parameters. For the data collected to have some value requires understanding and manipulation of the data, ultimately resulting in a model of your system. The next few "Drying Files" will deal with the interpretation and manipulation of this data so that a better understanding of the operation can be gleaned.

The levels of initial drying rates also may enhance and modify the quality of the final product. For example, rehydration rates for products such as instant coffee or milk tend to follow the drying rate pattern.

For each and every product, there is a representative curve that describes the drying characteristics for that product at specific temperature, velocity and pressure conditions. This curve is referred to as the drying curve for a specific product. Variations in the curve will occur principally in rate relative to carrier velocity and temperature.