Abstract: A method and apparatus are provided for controlling the amount of purging that occurs within a membrane separation device. The membrane separation device includes a membrane separation component and sweep controlling component. Within the membrane separation component, a major portion of the non-permeate gas is sent out of the membrane separation device to work, while a minor portion is diverted for use as a sweep gas. The sweep gas is controlled by a valve that cycles with a device, such as a compressor. Thus, the membrane separation device is on when the compressor is on and is off when the compressor is off. As such, the membrane separation device is not required to sweep at all times.

Abstract: A method and apparatus are provided for controlling the amount of purging that occurs within a membrane separation device. The membrane separation device includes a membrane separation component and sweep controlling component. Within the membrane separation component, a major portion of the non-permeate gas is sent out of the membrane separation device to work, while a minor portion is diverted for use as a sweep gas. The sweep gas is controlled by a valve that cycles with a device, such as a compressor. Thus, the membrane separation device is on when the compressor is on and is off when the compressor is off. As such, the membrane separation device is not required to sweep at all times.

Abstract: A variable evaporator control system and method in a gas dryer for maximizing the cooling which can be accomplished for a given length heat exchanger by adjusting the evaporator refrigerant approach temperature responsive to changes in the gas load on the system. Pressure and/or temperature sensors positioned at particular locations in the system provide feedback for controlling adjustments in the approach temperature depending on the gas load.