Dehumidification Technologies for CEA
The two technologies that currently serve the CEA industry are Traditional and Wrap-Around. A flow diagram for each is shown below. The difference is in the power consumed by the cool coil, which largely dictates the overall power consumption. Also, only wrap-around is practical for use with chilled water.
TRADITIONAL (COOL/HEAT) TECHNOLOGY is the most popular solution offered today and available from most dehumidification equipment manufacturers.
- Step 1: Room air (T1), is cooled below its dewpoint and dehumidified in one pass through a cooling coil, T1-T3.
- Step 2: Over-cooled air (T3) gets heated through a hot-gas heating coil T3-T5. The supply-air T5 temperature and dewpoint are suitable for maintaining room temperature and humidity.
Note: Hot gas heat is a byproduct of the dehumidification and cooling process and therefore “free.”
WRAP-AROUND PLATE TECHNOLOGY represents the next generation of climate control for CEA facilities.
- Step 1: Room air (T1) is precooled below its dewpoint and dehumidified in the first pass through an air-to-air heat exchanger, T1-T2. (Note: The precooling between T1-T2, reduces the cooling requirement at T2-T3 by up to 60%.)
- Step 2: Air is further cooled and dehumidified through a cooling coil at T2-T3.
- Step 3: Air is heated in the second pass through the air-to-air heat exchanger, T3-T4
- Step 4: The supply-air T5 temperature and dewpoint are suitable for maintaining room temperature and humidity.
Besides the 60-90% efficient wrap-around plate technology are the 30%-50% efficient wrap-around heat pipes and water coil technologies illustrated below.
WRAP-AROUND HEAT PIPE COILS
WRAP-AROUND WATER COILS
A WORD ABOUT DESICCANT DEHUMIDIFICATION TECHNOLOGIES
Desiccant dehumidification technologies are suitable for applications requiring the control of dewpoint below freezing. Desiccant technologies work very well in these applications, while refrigerated dehumidification technologies are usually not appropriate. However, this author knows of no argument, financial or technical, that can justify the use of Desiccant dehumidification technologies, where wrap-around dehumidification technologies are an option.