Dehumidification is crucial in a great many industries. Moisture control methods – desiccant-based and or mechanical refrigeration – are weighed, generally, according to application. Consideration of external temperatures and relative humidity levels is also a factor.
Both methods are effective at removing moisture from the air. But which one is the right choice for your customer’s needs?
Desiccant-based systems
Lower temperatures and moisture levels make a mechanical refrigeration system a less economic choice. Desiccant-based systems are well-suited to this environment, best used when the relative humidity is below 45%. Efficiency can be greatly improved with desiccant systems by mounting a direct-expansion refrigerant or chilled water pre-cooling coil at the intake. This will remove much of the heat and moisture from the air as it enters the system.
Cost of energy is another consideration here. Where the cost of thermal energies like gas or steam is low, but the cost of electrical power is high, a desiccant based system is definitely the better choice. Desiccant-based systems consume less electrical power by half than that of mechanical refrigeration systems.
Mechanical refrigeration systems
At higher temperatures, with relative humidity levels greater than 45%, a mechanical refrigeration system is the better choice. Lower humidity equals lower coil temperature. Frost will form on the coils at 30° F, resulting in less moisture control. Systems designed to prevent this are costly and often difficult to install.
By contrast to desiccant-based systems, however, where the cost of thermal energy is high but electricity is inexpensive – or at least reasonable – mechanical refrigeration is better, given the environmental conditions above.
Combined applications
Both a desiccant-based system and a mechanical refrigeration system used in tandem works best in most situations. Used together, both systems greatly improve efficiency and balance each other’s performance.
The addition of a desiccant-based system can reduce the operating costs of the existing cooling-based system.
An example would be spaces requiring continual refrigeration to below-zero temperatures. A desiccant dehumidifier can be added to the refrigeration system to overcome some of the cost of defrosting the coils.
Here’s another example, courtesy of Solid State Technology: Insights for Electronics Manufacturing Magazine: “When treating ventilation air in building HVAC systems the dehumidification of the fresh air with the desiccant-based system decreases the installed cost of the cooling system and eliminates deep coils with high air and liquid-side pressure drops. This saves considerable fan and pump energy as well.”
Q Applied Systems is a leading manufacturer’s representative for state-of-the-art HVAC, moisture control, fume and dust collection equipment. Contact us for a free consultation on your specific needs. Call (858) 435-2236 to speak with a representative or e-mail us at info@qappliedsystems.com today.
