Patent Application
20130047635
The present invention relates to a method of operation of a refrigerant recovery, recycling and recharging system. Refrigerant recovery, recycling and recharging systems are known in the art for connecting to closed refrigeration circuits (e.g., air conditioning systems, including those of automobiles) to draw out used refrigerant. If the closed refrigeration circuit, or the automobile containing said circuit, is to be scrapped, the refrigerant may be stored and later recycled. If the closed refrigeration circuit is merely undergoing regular maintenance, the system can be used to recharge the refrigeration circuit by supplying at least one of new and purified refrigerant. For example, the system can take the original charge of refrigerant removed from the refrigeration circuit and purify it (e.g., by removing contaminants such as air, oil, and water) before returning it to the refrigeration circuit. A refrigerant recovery, recycling and recharging system includes a compressor operable to compress refrigerant for movement through the system and through the refrigeration circuit connected to the system. The compressor is most commonly a reciprocating type compressor, but some systems may utilize a rotary (e.g., scroll type) compressor. The pressure differential between the inlet and outlet sides of the compressor in the refrigerant recovery, recycling and recharging system can be significantly higher than that found in a typical recirculating refrigeration circuit. For example, the pressure differential between the inlet and outlet sides of the compressor in the refrigerant recovery, recycling and recharging system commonly exceeds 100 psig.
In one aspect, the invention provides a method for operating a refrigerant recovery, recycling and recharging system having a compressor to at least one of recover, recycle, and recharge the refrigerant in a closed refrigeration circuit coupled to the system. The method includes compressing refrigerant with the compressor, stopping the compressor, re-starting the compressor, and relieving a pressure differential across the compressor at the time of re-starting the compressor.
In another aspect, the invention provides a method for operating a refrigerant recovery, recycling and recharging system having a compressor to at least one of recover, recycle, and recharge the refrigerant in a closed refrigeration circuit coupled to the system. The method includes compressing refrigerant with the compressor, stopping the compressor, re-starting the compressor, and opening a valve coupling an inlet and an outlet of the compressor along a fluid path around the compressor, thereby reducing a pressure differential across the compressor at the time of re-starting the compressor.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
The FIGURE is a schematic diagram of a refrigerant recovery, recycling and recharging system.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
The FIGURE schematically illustrates one exemplary type of a refrigerant recovery, recycling and recharging system 10 for connection with a closed refrigeration circuit (not shown) to recover the refrigerant (e.g., R-134A and HFO-1234yf) therein and optionally recycle the refrigerant and recharge the closed refrigerant circuit. The system 10 includes a compressor C. In some constructions, the compressor C is a reciprocating type compressor (e.g., an electrically-powered hermitically-sealed reciprocating compressor) having a reciprocating piston for generating compression. In other constructions, the compressor C can take the form of other types of known compressors such as a scroll type rotary compressor. The compressor C has an inlet 14 and an outlet 18. As shown in the FIGURE, a fan F may be positioned adjacent the compressor C to provide a flow of cooling air over the compressor C. The compressor inlet 14 is in fluid communication with an inlet port 22 of the refrigerant recovery, recycling and recharging system 10 via an inlet line 23. Refrigerant from the inlet port 22 flows to the compressor inlet 14 through a low side pressure gauge 24, a solenoid valve SV, a check valve CV, a heated suction accumulator 26, a filter 28, and another check valve CV adjacent the compressor inlet 14. A pressure transducer PT is coupled to the heated suction accumulator 26 to monitor the internal pressure. Oil entrained in the compressed refrigerant can be extracted at the heated suction accumulator 26 and collected through a solenoid valve SV into an oil drain container 32 as shown in the FIGURE. A load cell LC may be placed under the oil drain container 32 and configured to measure the weight of oil collected. The filter 28 upstream of the compressor inlet 14 may be a combination debris/desiccant filter.
The compressor outlet 18 is coupled to an oil separator 36 through a high pressure control switch HPS on the discharge side of the compressor C. Oil separated from the compressed refrigerant at the oil separator 36 can be directed back to the suction side of the compressor C through an oil return line 40. A solenoid valve SV is positioned along the oil return line 40 to selectively open the oil return line 40. During normal operation of the system 10 while the compressor C is running, the solenoid valve SV along the oil return line 40 remains closed so that the compressor inlet 14 and outlet 18 are not coupled directly together, as coupling the inlet 14 and the outlet 18 directly together would create a bypass around the compressor C that would prevent the compressor C from generating the large pressure differential required by the system 10. When the oil return line 40 is closed by the solenoid valve SV and the compressor C is running, an operating pressure differential over 100 psig (e.g., about 150 psig) may be generated between the inlet 14 and the outlet 18 of the compressor C. The solenoid valve SV along the oil return line 40 can be controlled by a controller 42 as shown in the FIGURE. Although not illustrated to avoid complicating the drawing, the controller 42 can be a system controller coupled to all the devices of the system 10 capable of sending or receiving control signals for operating the system 10.
Compressed refrigerant exiting the oil separator 36 is directed through a solenoid valve SV and a check valve CV into and out of the heated suction accumulator 26. Upon exiting the heated suction accumulator 26, the refrigerant is directed through another solenoid valve SV into an internal cylinder 46. The internal cylinder 46 is positioned on a load cell LC configured to measure the weight of the refrigerant collected in the internal cylinder 46. Non-compressible gases present in the internal cylinder 46 can be intermittently released to atmosphere through an outlet pipe 48 having a pressure transducer PT, an orifice 50, and a solenoid valve SV, leaving the purified refrigerant in the internal cylinder 46. A temperature sensor TS is also coupled to the internal cylinder 46 to measure the temperature of the refrigerant therein. Refrigerant can be released from the internal cylinder 46 through a solenoid valve SV to an outlet port 54 of the refrigerant recovery, recycling and recharging system 10 via an outlet line 56. From the internal cylinder solenoid valve SV, the outlet line 56 includes a first connection point 58, a solenoid valve SV, a check valve CV, a second connection point 60, another solenoid valve SV, and a high side pressure gauge 64. Although the ports 22, 54 are referred to as “inlet” and “outlet” respectively, it should be appreciated that the system 20 can be configured to recycle (recover) refrigerant from a connected closed refrigeration circuit via both of the ports 22, 54, and furthermore, can be configured to charge refrigerant back into the closed refrigeration circuit through either one or both of the ports 22, 54. Thus, although the terms “inlet” and “outlet” are used for convenience in describing the system 20, they do not strictly limit the operation of the system 20 contemplated by the inventors.
The outlet line 56 is in selective communication with the inlet line 23 running between the system inlet port 22 and the compressor inlet 14 via a first connection line 68 with a solenoid valve SV and a check valve CV. The outlet line 56 is also in selective communication with the inlet line 23 at a further upstream location via a second connection line 72 with a solenoid valve SV. A pressure transducer PT is positioned along the second connection line 72 adjacent the inlet line 23. A vacuum line 76 is coupled to the second connection line 72 between the solenoid valve SV and the pressure transducer PT. From the second connection line 72, the vacuum line 76 includes a solenoid valve SV, a vacuum sensor VS, a second solenoid valve SV, and a vacuum pump VP.
The second connection point 60 along the outlet line 56 also serves to connect fresh charge containers 80A, 80B, 80C of UV dye, polyalkylene glycol (PAG) oil, and polyolester (POE) oil. Each of the containers 80A, 80B, 80C is coupled to the second connection point 60 along the outlet line 56 via a corresponding solenoid valve SV and a common check valve CV. The contents of the UV dye container 80A is monitored by measuring the weight with a first load cell LC, and the combined contents of the PAG oil and POE oil containers 80B, 80C is monitored by measuring the weight with a second load cell LC. Opening any of the solenoid valves SV in line with the fresh charge containers 80A, 80B, 80C enables quantity of the fresh charge contents to accompany the fresh refrigerant supplied to the external refrigeration circuit via the system outlet port 54.
The general operation of the refrigerant recovery, recycling and recharging system 10 is not discussed in detail herein. One of ordinary skill in the art will appreciate that the system 10 is operable to be coupled to a closed refrigeration circuit via the inlet port 22 and the outlet port 54 to remove used, contaminated refrigerant and, if the refrigeration circuit is intended for continued use, to recharge the refrigeration circuit with purified or fresh refrigerant. For further information on the general operation of the refrigerant recovery, recycling and recharging system 10, U.S. Pat. Nos. 5,094,087, 5,467,608, 5,533,358, 5,570,590, 5,598,714, and 7,895,844 are hereby incorporated by reference herein. The refrigerant recovery, recycling and recharging system 10 can be operated according to one or more methods disclosed in the above-identified patents. Furthermore, particular aspects of the operation of the system 10, such as those described in further detail below and defined in the claims of the present application, should be appreciated as being applicable to not only the illustrated refrigerant recovery, recycling and recharging system 10, but other known systems including but not limited to those disclosed in the above-identified patents that are incorporated by reference herein.
When the refrigerant recovery, recycling and recharging system 10 is operated and then stopped (i.e., when the compressor C, which has been operatively compressing refrigerant, is stopped), high pressure refrigerant that has just been compressed in a gaseous state is present at the compressor outlet 18, and a low pressure (in some cases vacuum pressure) is present at the compressor inlet 14. The resulting pressure differential across the compressor C can be over 100 psig, and in some cases can be 150 psig or more. When the system 10, including the compressor C, is commanded to subsequently re-start with this high pressure differential across the compressor C, significant strain and difficulty may be encountered. In fact, a fault condition may be encountered such as a manual reset circuit breaker tripping or thermal overload opening, due to excessive inrush current, as well as excessive duration of the inrush current. The fault condition may abort the process for the operator of the system 10, due to losing power to the compressor C, or in some cases to the entire system 10. In some cases, an operator of the system 10 may even determine the compressor C to be faulty and proceed to unnecessarily replace the compressor C, incurring excess maintenance cost. These problems may be especially true when the compressor C is a hermetically-sealed reciprocating compressor, and the piston is slightly below top dead center (TDC), although the method described below is not necessarily limited to such constructions or situations. To eliminate the hard starting condition and the corresponding potential fault condition upon compressor re-starting, the pressure differential across the inlet 14 and the outlet 18 of the compressor C can be relieved (i.e., reduced or completely eliminated) at compressor start up.
When the compressor C is ordered to start up (e.g., by a direct user command or a command from the controller 42), the solenoid valve SV along the oil return line 40 is first opened to fluidly couple the inlet 14 and the outlet 18 of the compressor C. The solenoid valve SV may be held open for a brief period of time to allow the pressure between the inlet 14 and the outlet 18 of the compressor C to become equal or nearly equal before the compressor C is started. The solenoid valve SV may also remain open for an additional period of time after the compressor C is started, ensuring that the high pressure differential condition across the compressor has been removed. After the compressor C has been operating for a sufficient period of time, the solenoid valve SV along the oil return line 40 is closed by command from the controller 42, and the compressor C will resume its normal compression cycle. In one construction, the solenoid valve SV along the oil return line 40 is held open for a period of 5 seconds prior to the compressor C being started, and an additional 5 seconds after the compressor C is started. The solenoid valve SV in the oil return line 40 may be positioned in the system with an over seat condition and may be controlled with a 12 VDC pulse width modulation (PWM) condition.
By opening the solenoid valve SV at the time of compressor starting (at least one of before, during, and immediately after the compressor begins operating) the electrical load of starting of the compressor C is significantly reduced. Inrush current is decreased, which reduces wear on electrical components such as the start capacitor, relay and thermal overload device. Excessive cycling of the thermal overload due to starting the compressor C when exposed to a high pressure differential can lead to the compressor C being replaced and discarded prematurely. Additionally, by balancing the inlet 14 and the outlet 18 of the compressor C as described above, some oil will be returned to the compressor C (e.g., to the crank case of a reciprocating type compressor) during the period that the compressor C is operated with the open solenoid valve SV in the oil return line 40. Thus, in addition to reducing wear on electrical components and conserving electrical power, oil is returned to the compressor C on a more frequent basis (e.g., maintaining proper oil level inside the compressor sump) to reduce wear on the internal mechanical components such as crankshaft seals and bearings.
The above-described method of equalizing the inlet 14 and the outlet 18 of the compressor C at the time of re-starting can also be used in refrigerant recovery, recycling and recharging systems having other types of compressors, including rotary type (e.g., scroll) compressors.
Various features and advantages of the invention are set forth in the following claims.
