Patent GB-950750-A (GB)
Title: Purge mechanism for refrigeration system
IPC: F25B1/053
Filed: 1960-12-30
Abstract: 950,750. Refrigerating. CARRIER CORPORATION. Dec. 30, 1960 [Jan. 4, 1960], No. 44861/60. Heading F4H. A purging device for a refrigerating system comprises a chamber for receiving non-condensible gases and entrained refrigerant and water vapours, means for condensing said vapours, means for expelling the non-condensibles from the chamber and control means operable in conjunction with conduit means leading to the expulsion means either automatically to expel non-condensibles from the chamber or to isolate the chamber from the system and elevate its pressure to drain condensed water therefrom. As shown the device is used with a compression system of the type described in Specification 800,088 and comprises a chamber 24 having a central space which is traversed by tubes 29 which extend between headers 26 and 28 and are supplied with liquid refrigerant withdrawn from the evaporator 18 through line 30. Non-condensibles with entrained refrigerant and water vapour flow from the top of condenser 10 through line 45 to the chamber 24 where the vapours condense on tubes 29 and collect at the bottom 34 of the chamber. The non-condensibles are evacuated to atmosphere through lines 35, 36 and 41 and valve 43 by a pump 38 having a driving motor 60. Liquid refrigerant from space 34 is returned to header 26 through a U-line 62 and float chamber 64, while water floating on the refrigerant is removed, when this is observed to be necessary through a sight-glass 35<SP>1</SP>, through a line 70 having a valve 72. The pump 38 is controlled by a differential pressure switch 84 between the condenser and purge chamber and by a similar switch 86 between the condenser and evaporator, the latter switch being normally closed during operation of the refrigerating system but opening when the pressures in the condenser and evaporator tend to equalise due to inoperation of the compressor. During purging a valve 49 between line 35 and a line 48 leading from line 45 to the header 28, a valve 40 in a line 39 leading from line 36 to atmosphere and a valve 53 in a line 51 leading from line 41 to line 45 are all closed and a valve 37 in line 35 and a valve 42 in line 41 are opened. The arrangement may be used to test the system for leaks, prior to charging with refrigerant, by closing valves 37, 42, 49 and 53 and opening valve 40, and by connecting a conduit between lines 51 and 50 (shown in dotted lines in Fig. 1) so that pump 38 draws in atmospheric air through line 36 and discharges it to the condenser 10. To evacuate the system after this operation valves 37, 42 and 49 are opened and valve 40 is closed so that air is drawn from the system through lines 35 and 36 and discharged through line 41. When the system is operated at sub-atmospheric conditions the pressure in the purge chamber is periodically elevated to above atmospheric to enable water to be withdrawn therefrom. This is effected by closing valves 37 and 42 and opening valves 40 and 53 so that the pump draws air through line 39 and expels it through lines 41, 51 and 45 to the purge chamber. Lubricant separation from header 28 is effected by a switch 79 which is controlled by a float 77 in the header 28 and when closed energizes and opens solenoid valves 78 and 54 arranged in a discharge line 76 from the header and line 48 respectively. The valve 54 is a three-way valve which is normally positioned to effect communication between the header 28 and evaporator 18 through a line 55 but which effects communication between the condenser 10 and the header during lubricant separation. In Fig. 3 (not shown) the pump 38 is controlled by a single differential pressure switch which is sensitive to the pressure difference between the upper and lower parts of the condenser.