Desiccant Dehumidification vs.Refrigerative Dehumidification
Both desiccant dehumidifiers and refrigerative dehumidifiers can remove moisture from the air, so the question is which type is best suited for a given application? There really are no simple answers to this question but there are several generally accepted guidelines which most dehumidifier manufacturers follow:
- Both desiccant-based and refrigeration-based dehumidification systems work most efficiently when used together. The advantages of each compensate for the limitations of the other.
- Refrigeration-based dehumidification systems are more economical than desiccants at high temperatures and high moisture levels. In general, refrigeration-based dehumdifier are seldom used for applications below 45% RH. For example, in order to maintain an outlet condition of 40% RH it would be necessary to bring the coil temperature down to 30º F(-1℃), which results in the formation of ice on the coil and a reduction in moisture removal capacity. Efforts to prevent this (defrost cycles, tandem coils, brine solutions etc.) can be very expensive.
- Desiccant dehumidifiers are more economical than refrigerative dehumidifiers at lower temperatures and lower moisture levels. Typically, a desiccant dehumidification system is utilized for applications below 45% RH down to 1% RH. Thus, in many applications, a DX or water cooled cooler is mounted directly at the dehumidifier inlet. This design allows for removal of much of the initial heat and moisture prior to entering the dehumidifier where the moisture is reduced even further.
- The difference in the costs of electrical power and thermal energy (i.e. natural gas or steam) will determine the ideal mix of desiccant to refrigeration-based dehumidification in a given application. If thermal energy is cheap and power costs are high, a desiccant dehumidifer will be most economical to remove the bulk of the moisture from the air. If power is inexpensive and thermal energy for reactivation is costly, a refrigeration based system is the most efficient choice.
The most common applications requiring this 45% RH level or below are: Pharmaceutical, Food and Candy, Chemical Laboratories. Automotive, Military, and Marine Storage.
Most applications requiring 50% RH or higher are probably not worth expending a whole lot of effort on because they can usually be achieved through refrigeration. In some cases, however, the use of a desiccant dehumidification system can reduce operating costs of the existing refrigeration system. For example, when treating ventilation air in building HVAC systems, the dehumidification of the fresh air with the desiccant 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.
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Post time: Sep-11-2019