Control system for refrigeration-based compressed-gas dryers

Abstract

Improved control system for refrigeration-based compressed-gas dryers comprising a refrigerating circuit with a compressor ( 10 ), a condenser ( 12 ), a throttling member ( 14 ) and an evaporator ( 16 ), and further comprising a heat exchanger ( 22 ), a condensate separator ( 18 ) and a condensate drain ( 20 ), in which the compressor ( 10 ) is by-passed by a hot-gas valve ( 30 ). Control means ( 38, 40 ) are provided for measuring the temperature of the thermal mass of the dryer, or a temperature correlating therewith, and actuating the compressor ( 10 ) into switching on and off, as well as operating an electromagnetic valve ( 36 ) associated upstream of the hot-gas valve ( 30 ), accordingly, so as to selectively cause the dryer to operate as a hot-gas dryer or a thermal-mass dryer for variable period of times depending on the thermal load.

1 . Improved control system for refrigeration-based compressed-gas dryers comprising a refrigerating circuit with a compressor ( 10 ), a condenser ( 12 ), a throttling member ( 14 ) and an evaporator ( 16 ), and further comprising a heat exchanger ( 22 ), a condensate separator ( 18 ) and a condensate drain ( 20 ), in which the compressor ( 10 ) is by-passed by a hot-gas valve ( 30 ), characterized in that there are provided control means ( 38 ,  40 ) for measuring the temperature of the thermal mass of the dryer, or a temperature correlating therewith, and actuating the compressor ( 10 ) into switching on and off, as well as operating an electromagnetic valve ( 36 ) associated upstream of the hot-gas valve ( 30 ), accordingly.  
     
     
         2 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 1 , characterized in that the control means ( 38 ,  40 ) are adapted to selectively cause the dryer to operate as a hot-gas dryer or a thermal-mass dryer for variable period of times depending on the thermal load.  
     
     
         3 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 1 , characterized in that the control means ( 38 ,  40 ) are adapted to cause the dryer to operate as a thermal-mass dryer when the thermal load is low, and are alternatively adapted to cause the dryer to operate as a hot-gas dryer and a thermal-mass dryer when the thermal load is a high one.  
     
     
         4 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 1 , characterized in that the control means comprise an electronic control unit ( 38 ) connected to a sensor ( 40 ) that is associated to the evaporator ( 16 ) of the refrigerating circuit.  
     
     
         5 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 4 , characterized in that the sensor ( 40 ) is a temperature sensor and is adapted to measure a temperature that is correlated to the dew point of the compressed air.  
     
     
         6 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 4 , characterized in that the sensor ( 40 ) is a temperature sensor and is adapted to measure the outlet temperature of the compressed air from the evaporator ( 16 ).  
     
     
         7 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 4 , characterized in that the sensor ( 40 ) is a temperature sensor and is adapted to measure the inlet temperature of the refrigerant medium entering the evaporator ( 16 ).  
     
     
         8 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 4 , characterized in that the sensor ( 40 ) is a pressure sensor and is adapted to measure the evaporating pressure of the refrigerant medium in the evaporator ( 16 ).  
     
     
         9 . Improved control system for refrigeration-based compressed-gas dryers according to  claim 1 , characterized in that upstream of the throttling member ( 14 ) there is provided a further electromagnetic valve ( 42 ) controlled by the electronic control unit ( 38 ) and adapted to be closed when the compressor ( 10 ) is switched off and to be re-opened when the compressor is started again.  
     
     
         10 . Improved control system for refrigeration-based compressed-gas dryers as described and illustrated with reference to the accompanying drawings, and intended for use in the afore-cited ways.