CA2155011A1 - A method and apparatus for the cleansing of oil from refrigerating machines and heat pumps - Google Patents
A method and apparatus for the cleansing of oil from refrigerating machines and heat pumpsInfo
- Publication number
- CA2155011A1 CA2155011A1 CA 2155011 CA2155011A CA2155011A1 CA 2155011 A1 CA2155011 A1 CA 2155011A1 CA 2155011 CA2155011 CA 2155011 CA 2155011 A CA2155011 A CA 2155011A CA 2155011 A1 CA2155011 A1 CA 2155011A1
- Authority
- CA
- Canada
- Prior art keywords
- refrigerant
- oil
- external apparatus
- type
- cleansed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B45/00—Arrangements for charging or discharging refrigerant
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/18—Refrigerant conversion
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Lubricants (AREA)
Abstract
An arrangement for removing from a refrigerating system or heat pump system a lubricating oil used together with a first type of refrigerant in the system and replacing this oil with an oil which is compatible with a second type of refrigerant, in conjunction with converting the refrigerating system or heat pump system from a system which operates with the first type of refrigerant to a system which operates with the second type of refrigerant. The arrangement includes an external apparatus (2) which is intended for connection to the system (1) to be cleansed. The external apparatus includes means (7, 10) for flushing the system with circulating refrigerant of the first type, this refrigerant being capable of dissolving the oil and, because it has a higher density than oil, also able to lift and entrain the oil. These means are intended to circulate the refrigerant through the whole or a selected part of the system (1) and the external apparatus (2). The arrangement also includes means (8) for vapourizing the refrigerant and oil mixture leaving the system so as to separate the oil from the refrigerant prior to returning the refrigerant to the system (1). The invention also relates to a method of cleansing a refrigerating machine or heat pump from oil.
Description
WO94/173~ 5 5~ PCT/SE93/00067 .
A method and apparatus for the cleansing of oil from refrigerating machines and heat pumps The present invention is concerned with the conversion of a refrigerating machine or a heat pump from operation with a first type of refrigerant to operation with a second type of refrigerant and relates to a method of removing the lubricating oil that is contained by the system and used together with the first type of re~rigerant, and replacing this lubricating oil with another lubricating oil that is compatible with the second type of refrigerant. The invention also relates to an arrangement for use when carrying out the method.
Because the refrigerant typically used in refrigerating machines and heat pumps is comprised o~ CFC-compounds (fully halogenated chlorofluoro-substituted hydrocarbons) which have a deleterious effect on the atmospheric ozone layer, drastic measures have been ta~en to eliminate the Zo use of such compounds. Since the replacement HFC-compounds (hydrofluoro carbons) are chlorine-free, they require the use of other lubricants than the mineral oils or alkylben-zene oils used today. The lubricating oils are primarily used to lubricate and to seal the compressors of the refrigerating systems.
The oils mainly used together with chlorine-free refriger-ants are polyester oils. Since residues of mineral oil in the refigerating system can result in a number of problems, a limit of 1% has been placed on the amount of mineral oil that is allowed to remain in the system. ~owever, since oil is dispersed th~ou~hout the whole of the system, only some of this oil can be drained from the system through the compressor drainage hole; it will be observ~d that not all 35 CG~r e~sors are equipped with a drainage hole. When cirCumst~nc~C are favourable, about 80-90% of the oi~ can be le~oved from the system without difficulty. At least 3-4 - .
WO94/173~ PCTISE93/00067 21~011 oil changes are normally required to reach a residual mineral oil content of 1%. These oil changes must be made while running the system for a given length of time between each change, so that mineral oil is able to mix with the ester oil. The cost entailed by such a process is ~ery high, since it requires several visits by a service technician. Oil consumption also becomes relatively high.
The method also prssumes that the compressor is functional.
If a compressor malfunctions or brea~s down, it is not possible to terminate the system cleansing or purging process until a new compressor has been fitted, where~y this new compressor will also be "cont~m;n~ted" with the mineral oil. The compressors are to a very large part completely hermetic and are soldered in the circuit, which means that solder must be removed in order to allow oil to be drained-off.
Some manufacturers of refrigerating machines and heat pumps recommend replacement of the compressor when converting from CFC to HFC. This requires, however, dismantling the system and buying a new compressor.
The main object of the present invention is to pro~ide a method and an arrangement which will enable existing Z5 refrigerating machines and heat pumps to be cleansed or purged of oil in a simple and effective manner, without needing to dismantle the refrigerating machine or heat pump. Another object is to ena~le the refrigerating machine or the heat pump to be cleansed of oil quickly and at low cost.
The invention is based on the realization that because the refrigerant is able to dissolve oil and because the density of the refrigerant is higher than the density of the oil, whereby the refrigerant is ab}e to lift and transport the oil in the system, the refrigerant can also be used to cleanse the system of oil.
21~5~11 WO94/173~ PCT/SE93/00067 When tapping refrigerant from refrigerant carrying systems, for instance when servicing the systems, it has earlier been normal practice to separate the oil from the mixture of refrigerant and oil drained from the system. In this case, however, the oil removed is restricted to the amount of oil that a~om~;es the mixture drained from the system. Oil which is located b~neath the tapping level will therefore be left in the system.
When practicing the present invention, essentially all oil is removed, by flushing the system continu~usly with circulating refrigerant from which oil is separated prior to recirculating the refrigerant, and ~y delivering refrigerant in an amount such that all oil in the system will be lifted to a requisite level for transportation out of the system.
According to the present invention, a method of the ~ind defined in the first paragraph of the introduction is mainly characterized by f~ushing the system to be cl~n~e~
of oil with a circulating refrigerant of the first kind, which is able to dissolve the oil and to lift and entrain the oil because of its higher density: with the aid of external apparatus connected to the system, circulating refrigerant through the whole of said system or a selected part thereof and through said external apparatus; vapour-izing the refrigerant/ oil mixture leaving the system in the external apparatus so as to extract the oil from the refrigerant prior to returning said refrigerant to the system; and by maint~;ning circulation of refrigerant through the system and through said ext~rnal apparatus until the system has ~een cleansed of oil to the extent desired.
The inventive method thus enables the amount of mineral oil that re~;ns in the system to be brought to a desired leYel in one single stage, without needing to dismantle the WO94/173~ ~ ; PCTISE93/00067 2 1 5 ~
system. If necessary, in the case of larger systems, the procedure can be carried out in two stages which are separated by a given system running time.
It is preferred to use refrigerant in a quantity such that the level of the different components in the system will be sufficient to lift remaining oil to a level which will enable the oil to be carried away by the refrigerant. This will enable highly placed compressors and compressors which lack a draining plug to be effectively cleansed of oil.
The external apparatus is suitably connected to existing service points in the system, therewith enabling the cleansing process to be carried out without dismantling or interferring with the system. The refrigerant is preferably maintained at least partially in a liquid phase during its passage through the system.
The main characteristic features of an arrangement for use when carrying out the inventive method are made apparent in the following Claims.
The invention will now be described in more detail with reference to the accompanying drawings, in which Figures 1-3 illustrate selected exemplifying embodiments of externalapparatus according to the invention connected to a refrigerating machine, shown schematically in the drawings.
Figure 1 illustrates generally a conventional refrigerating machine 1 which comprises a compressor 2, a condensor 3, an expansion valve 4 and at least one evaporator 5. A refrig-erant, hitherto normally a CFC or HCFC type refrigerant, circulates in the refrigerating circuit when the circuit is at work. As illustrated, the valve 4 is controlled by the temperature prevailing downstream of the evaporator 5, so as to ensure that all refrigerant is evaporated in the evaporator prior to entering the compressor 2. This is the WO94/173~ 2 1 5 5 01 1 PCT/SE93/00067 normal, conventional mode of operation of a refrigerating system and will not therefore be described in more detail here. It will be understood that the system may also operate as a heat pump, in addition to operating as a refrigerating machine.
When converting the refrigerating machine for work with a different type of refrigerant, for instance a HFC-refriger-ant, which is to be preferred from an environmental aspect, the oil that was used as a lubricant and as a sealing agent in the CO~L e~sor 2 and which is dispersed throughout the whole of the system must be removed from the system. An HFC-type refrigerant contains no chlorine and therefore requires a different type of l~bricant to the mineral oils 1~ and alkylbenzene oils normally used. The oils mainly used together with the chlorine-free refrigerants are polyester oils and less than 1% of the mineral oil earlier used may remain when transferring to this type of refrigerant.
Accordingly, an external apparatus, generally referenced 6, is connected to two connection points of the refrigerating machine 1 in accordance with the invention. ~hese connec-tion points may, for instance, have the form of an oil drainage hole in the compressor 2, and a typical service 2s outlet on the high pressure side of the compressor. ~he external apparatus functions to circulate refrigerant of the earlier used kind through the now passive re~rigerating machine and therewith dissolve and/or lift the oil, which has a lower density than the refrigerant, and to carry the oil out of the system.
r To this end, the external apparatus 6 includes a c~ essor 7 which generates a pre~sure difference in the system, an evaporator 8 and an oil separator 9. A refrigerant contain-er lO is connected ~etween the refrigerating machine 1 and the external apparatus 6.
WO94/173~ PCTISE93/00067 2 ~ 6 When the co~Lessor 7 is working, refrigerant will be sucked from the compressor 2 of the refrigerating machine, through a pipe 11 and through a control}ed ~y~n~ion valve 12, from where it passes into the evaporator 8. The valve s 12 contro~s the flow of the refrigerant and oil mixture to the evaporator 8 in accordance with the temperature pre~ailing downstream of the evaporator, so as to maintain complete vaporization of the mixture delivered to the evaporator. The vaporized mixture is delivered to an oil separator 9, in which oil is separated from the mixture and discharged through a pipe 13, while the cleansed refriger-ant is deli~ered in a gaseous state to the compressor 7, through a pipe 14 and a filter 15.
The reference 16 identifies an oil separator which extracts oil slung from the compressor 7 and recycles this oil back to the inlet side of the colu~essor.
The hot gas compressed by the compressor 7 can be used as supplementary heat source in the oil separator 9 and for the vaporizing process in the evaporator 8. At least part of the hot gas will con~e~ce in the evaporator, before being delivered to the refrigerant container 10.
The aforedescribed external apparatus 6 functions to circulate refrigerant through the refrigerating machine 1, so as to entrain remaining mineral oil, this entrained oil being separated from the refrigerant in the external apparatus 6, whereafter the cleansed refrigerant is returned to the refrigerating machine via the refrigerant container 10, which functions as a buffer tank. This recycling of the refrigerant while continuously extracting oil therefrom is continued until the desired low content of residual mineral oil in th~ refrigerating machine 1 has been achieved. In the case of large refrigerating machines, it may be n~ceCc~y to di~ide the process into two stages while running the machine between said stages.
17348 ~ 15 5 ~1 1 rcTlsEs3looo67 ~he process is carried out under pressure conditions such that at least a part of the refrigerant will be in a li~uid phase during its passage through the machine. The onty energy emitted to the su, r oui~dings is that which is generated by the temperature of the refrigerant in the system rising to above ambient temperature. The system will thus reach a state of balance. It may be necessary to deliver heat to the sensors associated with the exp~ncion valve 4, in order to ensure that the valve is fully open.
The external apparatus can be connected to existing service connections on the refrigerating machine, thereby obviating the need to dismantle any component from the ~c~ine or to manipulate the system in any other way. Since the compres-sor outlet is seldom located at the lowest point of the~o~.~Lessor, it is normally necessary to raise the level of the oil/refrigerant mixture in the system, so that a level is reached in which all oil is lifted up to a le~el which enables it to be removed from the compressor.
When the desired residual mineral oil content has been reached, the refrigerating machine is emptied of refriger-ant. To this end, there is provided a ~alve 17 which by-passes the expansion valve 12 and the evaporator 8, so as to avoid an unn~c~cs~ry drop in pressure and excessive heating of the gas delivered to the compressor 7, as this would shorten the useful life of the compressor. The compressor can then be filled with an oil which is compati-ble to the new refri~L~,-L with which the refrigerating machine is filled.
Figure 2 illustrates a modified ~ho~iment of the external apparatus described with reference to Figure 1. ~hose parts which find direct correspond~c~ in Figure 1 have been identified with the same reference signs as those used in said Figure. The only difference ~e'~e_n the apparatus illustrated in Figure 1 and the apparatus illustrated in WO94/173~ PCT/SE93/00067 .
i 5 Q1 1 ~ 8 Figure 2 is that the Figure 2 ~mho~; ~ent does not include a combined refrigerant evaporator and condensor downstream of the compressor 7. Instead, the refrigerant is delivered to the passi~e refrigerating machine in an essentially gaseous state. Normally, the intermediate refrigerant container can also be omitted. In this regard, the gas condenses upon contact with the colder sur~aces in the refrigerating machine and initially essentially in the condensor 3. As the refrigerating ~c-hine heats up, the li~uid front moves forwards in the circuit and entrains the residual oil present therein.
The g~s/liquid mixture obtained from the re~rigerating machine is vaporized in a separate air-heated or water-lS heated evaporator 18 in the external apparatus 6. In otherrespects, the apparatus operates in the same manner as the earlier described apparatus. One a~vantage with the apparatus illustrated in Figure 2 is that it enab~es a reduction in the volume of refrigerant required, which is highly beneficial in large ~efrigerating systems in particular.
The embodiments illustrated in ~igures 1 and 2 can also be combined, and an optimal function can be obt~ine~ by swit~hi ng ~etween driving of the respective apparatus according to Figures 1 ~nd 2. The drive between these apparatus can be ~witched manual}y or automatically, wherein, for instance, the temperature of the refrigerating machine can first be rsised by delivering gaseous refriger-ant directly to the machine, and thereafter deliverliquid pulse.
Figure 3 illustrates a unit which can operate in accordance with either one of the two aforedescri~ed methods and which comprises two separate heat e~h~ngers 18 and ~9 respec-ti~ely, both of which operate with air or water. In this regard, the unit 18 functions as an e~aporator in 4~ 215 5 ~1 1 PCT/5~93/00067 accordance with the Figure 2 embodiment, while the unit l9 functions as a condensor. As will be understood by those skilled in this art, other intermediate forms are conceiv-able.
The aforedescribed exemplifying embodiments can also be varied in several respects within the scope of the follow-ing Claims. For instance, the points at which the external apparatus is connected to the refrigerating machine or the heat pump can be chosen from case to case in accordance with the possibilities that are available. The external apparatus can also be connected so that only part of the system will be flushed on each occasion. The system may also be flushed in different directions at different time periods.
In some cases, the illustrated container lO, which func-tions as a refrigerant buffer tank, can be omitted also in the external apparatus illustrated in Figure l. Additional heating of the oil separator 9 may also be omitted. The entire system is closed and refrigerant cannot therefore leak to atmosphere during the course of the process, and the external apparatus may also be used for final, closed drainage of refrigerant.
A method and apparatus for the cleansing of oil from refrigerating machines and heat pumps The present invention is concerned with the conversion of a refrigerating machine or a heat pump from operation with a first type of refrigerant to operation with a second type of refrigerant and relates to a method of removing the lubricating oil that is contained by the system and used together with the first type of re~rigerant, and replacing this lubricating oil with another lubricating oil that is compatible with the second type of refrigerant. The invention also relates to an arrangement for use when carrying out the method.
Because the refrigerant typically used in refrigerating machines and heat pumps is comprised o~ CFC-compounds (fully halogenated chlorofluoro-substituted hydrocarbons) which have a deleterious effect on the atmospheric ozone layer, drastic measures have been ta~en to eliminate the Zo use of such compounds. Since the replacement HFC-compounds (hydrofluoro carbons) are chlorine-free, they require the use of other lubricants than the mineral oils or alkylben-zene oils used today. The lubricating oils are primarily used to lubricate and to seal the compressors of the refrigerating systems.
The oils mainly used together with chlorine-free refriger-ants are polyester oils. Since residues of mineral oil in the refigerating system can result in a number of problems, a limit of 1% has been placed on the amount of mineral oil that is allowed to remain in the system. ~owever, since oil is dispersed th~ou~hout the whole of the system, only some of this oil can be drained from the system through the compressor drainage hole; it will be observ~d that not all 35 CG~r e~sors are equipped with a drainage hole. When cirCumst~nc~C are favourable, about 80-90% of the oi~ can be le~oved from the system without difficulty. At least 3-4 - .
WO94/173~ PCTISE93/00067 21~011 oil changes are normally required to reach a residual mineral oil content of 1%. These oil changes must be made while running the system for a given length of time between each change, so that mineral oil is able to mix with the ester oil. The cost entailed by such a process is ~ery high, since it requires several visits by a service technician. Oil consumption also becomes relatively high.
The method also prssumes that the compressor is functional.
If a compressor malfunctions or brea~s down, it is not possible to terminate the system cleansing or purging process until a new compressor has been fitted, where~y this new compressor will also be "cont~m;n~ted" with the mineral oil. The compressors are to a very large part completely hermetic and are soldered in the circuit, which means that solder must be removed in order to allow oil to be drained-off.
Some manufacturers of refrigerating machines and heat pumps recommend replacement of the compressor when converting from CFC to HFC. This requires, however, dismantling the system and buying a new compressor.
The main object of the present invention is to pro~ide a method and an arrangement which will enable existing Z5 refrigerating machines and heat pumps to be cleansed or purged of oil in a simple and effective manner, without needing to dismantle the refrigerating machine or heat pump. Another object is to ena~le the refrigerating machine or the heat pump to be cleansed of oil quickly and at low cost.
The invention is based on the realization that because the refrigerant is able to dissolve oil and because the density of the refrigerant is higher than the density of the oil, whereby the refrigerant is ab}e to lift and transport the oil in the system, the refrigerant can also be used to cleanse the system of oil.
21~5~11 WO94/173~ PCT/SE93/00067 When tapping refrigerant from refrigerant carrying systems, for instance when servicing the systems, it has earlier been normal practice to separate the oil from the mixture of refrigerant and oil drained from the system. In this case, however, the oil removed is restricted to the amount of oil that a~om~;es the mixture drained from the system. Oil which is located b~neath the tapping level will therefore be left in the system.
When practicing the present invention, essentially all oil is removed, by flushing the system continu~usly with circulating refrigerant from which oil is separated prior to recirculating the refrigerant, and ~y delivering refrigerant in an amount such that all oil in the system will be lifted to a requisite level for transportation out of the system.
According to the present invention, a method of the ~ind defined in the first paragraph of the introduction is mainly characterized by f~ushing the system to be cl~n~e~
of oil with a circulating refrigerant of the first kind, which is able to dissolve the oil and to lift and entrain the oil because of its higher density: with the aid of external apparatus connected to the system, circulating refrigerant through the whole of said system or a selected part thereof and through said external apparatus; vapour-izing the refrigerant/ oil mixture leaving the system in the external apparatus so as to extract the oil from the refrigerant prior to returning said refrigerant to the system; and by maint~;ning circulation of refrigerant through the system and through said ext~rnal apparatus until the system has ~een cleansed of oil to the extent desired.
The inventive method thus enables the amount of mineral oil that re~;ns in the system to be brought to a desired leYel in one single stage, without needing to dismantle the WO94/173~ ~ ; PCTISE93/00067 2 1 5 ~
system. If necessary, in the case of larger systems, the procedure can be carried out in two stages which are separated by a given system running time.
It is preferred to use refrigerant in a quantity such that the level of the different components in the system will be sufficient to lift remaining oil to a level which will enable the oil to be carried away by the refrigerant. This will enable highly placed compressors and compressors which lack a draining plug to be effectively cleansed of oil.
The external apparatus is suitably connected to existing service points in the system, therewith enabling the cleansing process to be carried out without dismantling or interferring with the system. The refrigerant is preferably maintained at least partially in a liquid phase during its passage through the system.
The main characteristic features of an arrangement for use when carrying out the inventive method are made apparent in the following Claims.
The invention will now be described in more detail with reference to the accompanying drawings, in which Figures 1-3 illustrate selected exemplifying embodiments of externalapparatus according to the invention connected to a refrigerating machine, shown schematically in the drawings.
Figure 1 illustrates generally a conventional refrigerating machine 1 which comprises a compressor 2, a condensor 3, an expansion valve 4 and at least one evaporator 5. A refrig-erant, hitherto normally a CFC or HCFC type refrigerant, circulates in the refrigerating circuit when the circuit is at work. As illustrated, the valve 4 is controlled by the temperature prevailing downstream of the evaporator 5, so as to ensure that all refrigerant is evaporated in the evaporator prior to entering the compressor 2. This is the WO94/173~ 2 1 5 5 01 1 PCT/SE93/00067 normal, conventional mode of operation of a refrigerating system and will not therefore be described in more detail here. It will be understood that the system may also operate as a heat pump, in addition to operating as a refrigerating machine.
When converting the refrigerating machine for work with a different type of refrigerant, for instance a HFC-refriger-ant, which is to be preferred from an environmental aspect, the oil that was used as a lubricant and as a sealing agent in the CO~L e~sor 2 and which is dispersed throughout the whole of the system must be removed from the system. An HFC-type refrigerant contains no chlorine and therefore requires a different type of l~bricant to the mineral oils 1~ and alkylbenzene oils normally used. The oils mainly used together with the chlorine-free refrigerants are polyester oils and less than 1% of the mineral oil earlier used may remain when transferring to this type of refrigerant.
Accordingly, an external apparatus, generally referenced 6, is connected to two connection points of the refrigerating machine 1 in accordance with the invention. ~hese connec-tion points may, for instance, have the form of an oil drainage hole in the compressor 2, and a typical service 2s outlet on the high pressure side of the compressor. ~he external apparatus functions to circulate refrigerant of the earlier used kind through the now passive re~rigerating machine and therewith dissolve and/or lift the oil, which has a lower density than the refrigerant, and to carry the oil out of the system.
r To this end, the external apparatus 6 includes a c~ essor 7 which generates a pre~sure difference in the system, an evaporator 8 and an oil separator 9. A refrigerant contain-er lO is connected ~etween the refrigerating machine 1 and the external apparatus 6.
WO94/173~ PCTISE93/00067 2 ~ 6 When the co~Lessor 7 is working, refrigerant will be sucked from the compressor 2 of the refrigerating machine, through a pipe 11 and through a control}ed ~y~n~ion valve 12, from where it passes into the evaporator 8. The valve s 12 contro~s the flow of the refrigerant and oil mixture to the evaporator 8 in accordance with the temperature pre~ailing downstream of the evaporator, so as to maintain complete vaporization of the mixture delivered to the evaporator. The vaporized mixture is delivered to an oil separator 9, in which oil is separated from the mixture and discharged through a pipe 13, while the cleansed refriger-ant is deli~ered in a gaseous state to the compressor 7, through a pipe 14 and a filter 15.
The reference 16 identifies an oil separator which extracts oil slung from the compressor 7 and recycles this oil back to the inlet side of the colu~essor.
The hot gas compressed by the compressor 7 can be used as supplementary heat source in the oil separator 9 and for the vaporizing process in the evaporator 8. At least part of the hot gas will con~e~ce in the evaporator, before being delivered to the refrigerant container 10.
The aforedescribed external apparatus 6 functions to circulate refrigerant through the refrigerating machine 1, so as to entrain remaining mineral oil, this entrained oil being separated from the refrigerant in the external apparatus 6, whereafter the cleansed refrigerant is returned to the refrigerating machine via the refrigerant container 10, which functions as a buffer tank. This recycling of the refrigerant while continuously extracting oil therefrom is continued until the desired low content of residual mineral oil in th~ refrigerating machine 1 has been achieved. In the case of large refrigerating machines, it may be n~ceCc~y to di~ide the process into two stages while running the machine between said stages.
17348 ~ 15 5 ~1 1 rcTlsEs3looo67 ~he process is carried out under pressure conditions such that at least a part of the refrigerant will be in a li~uid phase during its passage through the machine. The onty energy emitted to the su, r oui~dings is that which is generated by the temperature of the refrigerant in the system rising to above ambient temperature. The system will thus reach a state of balance. It may be necessary to deliver heat to the sensors associated with the exp~ncion valve 4, in order to ensure that the valve is fully open.
The external apparatus can be connected to existing service connections on the refrigerating machine, thereby obviating the need to dismantle any component from the ~c~ine or to manipulate the system in any other way. Since the compres-sor outlet is seldom located at the lowest point of the~o~.~Lessor, it is normally necessary to raise the level of the oil/refrigerant mixture in the system, so that a level is reached in which all oil is lifted up to a le~el which enables it to be removed from the compressor.
When the desired residual mineral oil content has been reached, the refrigerating machine is emptied of refriger-ant. To this end, there is provided a ~alve 17 which by-passes the expansion valve 12 and the evaporator 8, so as to avoid an unn~c~cs~ry drop in pressure and excessive heating of the gas delivered to the compressor 7, as this would shorten the useful life of the compressor. The compressor can then be filled with an oil which is compati-ble to the new refri~L~,-L with which the refrigerating machine is filled.
Figure 2 illustrates a modified ~ho~iment of the external apparatus described with reference to Figure 1. ~hose parts which find direct correspond~c~ in Figure 1 have been identified with the same reference signs as those used in said Figure. The only difference ~e'~e_n the apparatus illustrated in Figure 1 and the apparatus illustrated in WO94/173~ PCT/SE93/00067 .
i 5 Q1 1 ~ 8 Figure 2 is that the Figure 2 ~mho~; ~ent does not include a combined refrigerant evaporator and condensor downstream of the compressor 7. Instead, the refrigerant is delivered to the passi~e refrigerating machine in an essentially gaseous state. Normally, the intermediate refrigerant container can also be omitted. In this regard, the gas condenses upon contact with the colder sur~aces in the refrigerating machine and initially essentially in the condensor 3. As the refrigerating ~c-hine heats up, the li~uid front moves forwards in the circuit and entrains the residual oil present therein.
The g~s/liquid mixture obtained from the re~rigerating machine is vaporized in a separate air-heated or water-lS heated evaporator 18 in the external apparatus 6. In otherrespects, the apparatus operates in the same manner as the earlier described apparatus. One a~vantage with the apparatus illustrated in Figure 2 is that it enab~es a reduction in the volume of refrigerant required, which is highly beneficial in large ~efrigerating systems in particular.
The embodiments illustrated in ~igures 1 and 2 can also be combined, and an optimal function can be obt~ine~ by swit~hi ng ~etween driving of the respective apparatus according to Figures 1 ~nd 2. The drive between these apparatus can be ~witched manual}y or automatically, wherein, for instance, the temperature of the refrigerating machine can first be rsised by delivering gaseous refriger-ant directly to the machine, and thereafter deliverliquid pulse.
Figure 3 illustrates a unit which can operate in accordance with either one of the two aforedescri~ed methods and which comprises two separate heat e~h~ngers 18 and ~9 respec-ti~ely, both of which operate with air or water. In this regard, the unit 18 functions as an e~aporator in 4~ 215 5 ~1 1 PCT/5~93/00067 accordance with the Figure 2 embodiment, while the unit l9 functions as a condensor. As will be understood by those skilled in this art, other intermediate forms are conceiv-able.
The aforedescribed exemplifying embodiments can also be varied in several respects within the scope of the follow-ing Claims. For instance, the points at which the external apparatus is connected to the refrigerating machine or the heat pump can be chosen from case to case in accordance with the possibilities that are available. The external apparatus can also be connected so that only part of the system will be flushed on each occasion. The system may also be flushed in different directions at different time periods.
In some cases, the illustrated container lO, which func-tions as a refrigerant buffer tank, can be omitted also in the external apparatus illustrated in Figure l. Additional heating of the oil separator 9 may also be omitted. The entire system is closed and refrigerant cannot therefore leak to atmosphere during the course of the process, and the external apparatus may also be used for final, closed drainage of refrigerant.
Claims (9)
1. A method for removing from a refrigerating system or heat pump system a lubricating oil used together with a first type of refrigerant in said system and replacing this oil with an oil which is compatible with a second type of refrigerant, in conjunction with converting the refrigerat-ing system or heat pump system from a system which operates with said first type of refrigerant to a system which operates with said second type of refrigerant, character-ized by flushing the system to be cleansed of oil with a circulating refrigerant of said first type, wherein said refrigerant is capable of dissolving the oil and has a higher density than said oil so as to be able to lift and entrain the oil during the flushing process; circulating the refrigerant through the entire system or a selected part of said system and through an external apparatus used to circulate said refrigerant; using refrigerant in an amount which will ensure that the level of refrigerant in the various system components will be sufficient to lift residual oil to a level such as to enable said oil to be carried away by the refrigerant; evaporating in said external apparatus the mixture of refrigerant and oil leaving the system and separating the oil from the refrigerant prior to returning said refrigerant to the system; and maintaining circulation of the refrigerant through the system and the external apparatus until the system has been cleansed of oil to the desired extent.
2. A method according to Claim 1, characterized by causing at least part of the cleansed refrigerant to condense prior to being returned to the system or to condense in the first part of said system; and maintaining the refrigerant at least partially in a liquid phase during its passage through the system.
3. A method according to Claim 1 or 2, characterized by connecting the external apparatus to existing system service points; and by cleansing said system without dismantling any part thereof.
4. An arrangement for removing from a refrigerating system or heat pump system a lubricating oil that is used together with a first type of refrigerant in said system and replacing this oil with an oil which is compatible with a second type of refrigerant, in conjunction with convert-ing the refrigerating system or heat pump system from a system which operates with said first type of refrigerant to a system which operates with said second type of refrigerant, characterized in that the arrangement includes an external apparatus (2) which is provided with means for connecting said apparatus to the system (1) to be cleansed;
in that the external apparatus also includes means (7, 10) for flushing the system with circulating refrigerant of said first type, said refrigerant having the ability to dissolve the oil and also has a higher density than said oil so as to be able to lift and entrain the oil, said means being adapted to circulate the refrigerant through the entire system (1) and the external apparatus (2), or through a selected part of said system; and in that the arrangement further includes means (8) for evaporating the mixture of refrigerant and oil leaving the system and separating the oil from the refrigerant prior to returning said refrigerant to the system (1).
in that the external apparatus also includes means (7, 10) for flushing the system with circulating refrigerant of said first type, said refrigerant having the ability to dissolve the oil and also has a higher density than said oil so as to be able to lift and entrain the oil, said means being adapted to circulate the refrigerant through the entire system (1) and the external apparatus (2), or through a selected part of said system; and in that the arrangement further includes means (8) for evaporating the mixture of refrigerant and oil leaving the system and separating the oil from the refrigerant prior to returning said refrigerant to the system (1).
5. An arrangement according to Claim 4, characterized in that the external apparatus (2) includes means (8) for condensing the cleansed refrigerant at least partially prior to returning the refrigerant to the system (1), and a compressor (7) which functions to maintain in the system (1) a pressure such that the refrigerant will be maintained at least partially in a liquid phase during its passage through the system.
6. An arrangement according to Claim 5, characterized in that the external apparatus (2) includes an evaporator (8) to which heat from the gas compressed in the compressor (7) is delivered, this gas being condensed at least partially in conjunction therewith.
7. An arrangement according to Claim 6, characterized in that a regulating valve (12) is connected upstream of the evaporator (8) and regulates the flow of medium thereto, so as to obtain complete evaporation of the refrigerant and oil mixture delivered to the evaporator from the system (1).
8. An arrangement according to Claim 7, characterized by an oil separator (9) which is connected downstream of the evaporator (8) for separating oil from the gas mixture prior to its delivery to the compressor (7).
9. An arrangement according to any one of Claims 4-8, characterized by a closed refrigerant container (10) which is connected between the external apparatus (2) and the system connection point which is used as an inlet (1).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2155011 CA2155011A1 (en) | 1993-01-29 | 1993-01-29 | A method and apparatus for the cleansing of oil from refrigerating machines and heat pumps |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2155011 CA2155011A1 (en) | 1993-01-29 | 1993-01-29 | A method and apparatus for the cleansing of oil from refrigerating machines and heat pumps |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2155011A1 true CA2155011A1 (en) | 1994-08-04 |
Family
ID=4156322
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2155011 Abandoned CA2155011A1 (en) | 1993-01-29 | 1993-01-29 | A method and apparatus for the cleansing of oil from refrigerating machines and heat pumps |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2155011A1 (en) |
-
1993
- 1993-01-29 CA CA 2155011 patent/CA2155011A1/en not_active Abandoned
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