Multitech Engineers


1, non-cycling refrigerant dryer -, the refrigerant circulates continuously through the system. Since the flow of compressed air will vary and ambient temperatures also vary, a hot gas bypass valve or unloader valve often is used to regulate the flow of the refrigerant and maintain stable operating conditions within the refrigerant system. In most designs, the refrigerant evaporates within the air to refrigerant heat exchanger (evaporator) and is condensed after compression by an air or water to refrigerant heat exchanger (condenser).

This design provides rapid response to changes in operating loads. While older refrigerant type air dryers have used CFC refrigerants such as are in compliance with the Montreal Protocol and use chlorine-free refrigerants such environmentally friendly refrigerant blends.

The properties of these newer refrigerants require careful attention to the refrigeration system design, due to differences in operating pressures and temperatures. Please note that all refrigerant type dryers should only be serviced by a licensed and trained technician to assure that the refrigerant material is properly handled.

Most compressed air systems do not operate at a continuous, full-load condition. Fluctuations in equipment usage, the use of variable-speed compressors, variations in inlet temperature and pressure to the dryer, result in highly variable demand. Non-cycling dryers do not have the means to respond to these system variations. Cycling dryers, however, incorporate a design that permits the refrigeration system to cycle on and off in relation to the varying demands of the compressed air system, resulting in potentially significant savings in operating costs.

Cycling type refrigerant dryers chill a thermal mass medium which in turn is used to cool the compressed air. This mass may be a liquid such as glycol or a metal such as aluminium block, beads or related substance, which act as a heat sink. The temperature of the thermal mass medium increases as heat is exchanged with the compressed air in an air-to-thermal mass heat exchanger. Conversely, the temperature of this medium decreases as it is cooled by the refrigeration system in a separate refrigerant-to-thermal mass exchanger. The operation of the dryer�s refrigeration system is thermostatically controlled and enables the refrigeration system to cycle off during periods of reduced load.

2, cycling - type refrigerant dryers have typically higher acquisition costs than similar sized non-cycling dryers, over time they often make up for that difference in much lower operating costs.


Wet air passes directly through the desiccant medium which adsorbs the moisture. The desiccant medium has a finite capacity for adsorbing moisture before it must be dried out, or regenerated. To do this, the tower containing saturated desiccant medium is depressurized and the accumulated water is driven off. How this happens depends on the type of desiccant dryer:

  • Heatless dryers use only compressed air as a purge
  • Blower purge dryers use a combination of air from an external blower, heat and minimal compressed air
  • Heat of compression dryers use the heat of the compression


MULTITECH membrane dryers with pre-filters remove moisture, oil and particles from compressed air in the most demanding conditions. The dryers deliver the lowest pressure drop and purge air loss at the highest possible efficiency � saving you time and money. From small spaces to environments with fluctuating ambient temperatures, membrane dryers can perform in a wide variety of harsh and critical conditions. Two models are available to offer you the exact air treatment you require.