DESICCANT DEHUMIDIFICATION VS MECHANICAL REFRIGERATION

Both desiccant dehumidifiers and mechanical refrigeration systems 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:
1.
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.
2.
Refrigeration-based dehumidification systems are more economical than desiccants at high temperatures and high moisture levels. In general, mechanical refrigeration systems 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 -1 deg C (30 deg F), 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 cumbersome and expensive.
3.
Desiccant-based systems are more economical than refrigeration systems at lower temperatures and lower moisture levels. Typically, a desiccant dehumidification systems is utilized for applications below 45% RH down to less than 1% RH. Thus, in many applications, a DX or chilled water pre-cooling coil is mounted directly at the dehumidifier inlet. This design allows for removal of much or the initial heat and moisture prior to entering the dehumidifier where the moisture is reduced even further.
4.
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 inexpensive and power costs are high, a desiccant-based system 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.