Abstract: The present invention provides a system for effectively purging heat regenerating desiccant compressed air dryers from a moisture load, by a ‘tuned’ regenerating means with the use of a variable restriction on the blower purge air flows, a blower back-pressure set point, a heater discharge temperature set point, and a bottom area bed temperature of a vessel containing desiccant, a means to balance purge temperature to a stable, noncycling state preventing an under and overheating heating of desiccant, vessel and associated piping. A valve control means to terminate heating, cooling and dry purge operations selectively operated to allow purge flows to quickly cause water vapor captivated by the desiccant (in a drying cycle) to be released and purged out of the vessel (in a regeneration cycle), resulting in a regenerated tower vessel prepared for a compressed air drying cycle.

Abstract: A system for modulating refrigerant flow from an evaporator of an air or gas drying apparatus wherein the air or gas drying apparatus has an evaporator shell with at least one exit orifice for return of refrigerant to an accumulator or compressor. The system comprising a flow metering structure connected to the at least one exit orifice, the structure having an internal tube with a vertical rise from an evaporator shell end to an accumulator or compressor end, the internal tube having at least one return orifice (a) which allows passage of liquid refrigerant outside the internal tube into the internal tube, and at least one return orifice (b) which allows passage of gas outside the internal tube into the internal tube.