By Randy Kruger and Norman Hall, R. L. Deppmann, and Chad Edmondson, JMP
The past couple of blogs used the psychrometric chart and formula to calculate the loads in humidification buildings and processes. This week we look at a valuable shortcut for determining these load: Dristeem DriCalc selection program.
Let’s use an example of a humidification load requirement for a school in Flint, Michigan on economizer cycle. Let’s assume we have a ducted system with 12,000 CFM of air flow and a requirement in the room of 40% RH at 70°F.
Next, let’s allow the program to use the location data from ASHRAE. We enter economizer calculation and the 55°F mixed temperature. The program tells us that Flint is at 768 feet above sea level and the design outdoor air temperature is 5.2°F. If the jobsite was near Flint but on a hill (Nor many Mountains in Michigan!) we could change the elevation.
Now we choose whether to use the 30 year typical numbers or the 30 year extreme numbers for our load calculation. If this was a museum or process application where the required RH was critical and constantly needed, we would choose the extreme. In the case of buildings, we the 30 year typical numbers.
The program calculates the load at a variety of outdoor temperatures and percent of outdoor air. That data is displayed in a table and the design load is the maximum shown in the table.
Our example indicates a need for 89.61 PPH when the outdoor temperature is 40°F and the makeup air is at 50%.
Well! We have a load, we have documentation for our files, and we never looked at a psych chart. If you would like to download the Dristeem DriCalc program visit our site under System Design/selection Tools or simply click here!