BACKGROUND OF THE INVENTION
[0001] The invention relates to compressor systems and, more particularly, the invention
relates to a system and method for controlled recovery of lubricant for such systems.
[0002] Compressors, for example screw compressors, are commonly used in various applications
including, for example, water-cooled chillers.
[0003] A typical compressor requires oil to lubricate bearings, seals, gaps between rotors
and between the rotors and adjacent stationary components such as the housing and
end plates, and the like.
[0004] The bearing load carrying capacity depends heavily upon oil viscosity. Further, the
sealing characteristics of the oil are dependent upon viscosity.
[0005] The oil to provide such sealing and lubrication is typically circulated through the
system along with refrigerant. Oil entrained with the refrigerant is circulated from
the compressor discharge through the system.
[0006] Separation and recycle of this oil, while maintaining acceptable oil viscosity, is
a pressing need in the industry.
[0007] It is therefore a primary object of the present invention to provide a system and
method whereby recovery of the oil and desired viscosity levels are efficiently accomplished
and maintained.
[0008] Other objects and advantages of the present invention will appear herein below.
[0009] A compressor system having the features of the preamble of claim 1 is disclosed in
US-A-6082982.
SUMMARY OF THE INVENTION
[0010] In accordance with the present invention, the foregoing objects and advantages have
been readily attained.
[0011] According to the invention, a compressor system with controlled lubricant reclaim
is provided as set forth in claim 1.
[0012] By controlling the rate of exposure of refrigerant- lubricant mixture to heat, control
of the resulting lubricant viscosity is advantageously accomplished.
[0013] In further accordance with the invention, a method is provided for controlling reclaim
of lubricant in a compressor system as set forth in claim 8.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] A detailed description of preferred embodiments of the present invention follows,
with reference to the attached drawings wherein:
Figure 1 schematically illustrates a system and method in accordance with the present
invention.
DETAILED DESCRIPTION
[0015] The invention relates to a system and method for controlled recovery of lubricant
such as oil in a compressor system whereby resulting viscosity of the oil can be controlled
and maintained.
[0017] Referring to Figure 1 herein, system 10 includes a compressor circuit including a
compressor 12, a condenser 14 and an evaporator 16 which are connected by refrigerant
lines 18, 20 for flow of refrigerant through these components as desired. A typical
system includes a further flow line from condenser 14 through an expansion device
(not shown) and to evaporator 16. These components and lines complete a typical compressor
circuit.
[0018] In further accordance with the invention, a lubricant circuit is provided for conveying
oil from an oil sump 22 through an oil pump 24 and to an oil inlet 26 of compressor
12. A filter 28 can be positioned along oil line 30, if desired. An oil drain 32 carries
oil from compressor 12 back to oil sump 22.
[0019] As set forth above, during operation of the compressor circuit and lubricant circuit,
oil or other suitable lubricant is mixed with refrigerant discharged through line
18 to condenser 14, the expansion device and evaporator 16. Separation and reclaim
of the oil for further use within the system, while maintaining oil viscosity at desired
values, is the focus of the present invention.
[0020] According to the invention, the mixture within evaporator 16 is therefore metered
or fed to a reclaim vaporizer 34, wherein the mixture is exposed to heat so as to
separate the refrigerant from the lubricant. This heat boils the refrigerant off from
the lubricant, and the refrigerant passes through vent lines 36 back to line 20 and
to the suction inlet 38 of compressor 12. Due to the control of the present invention,
remaining oil has at this point been sufficiently purged of refrigerant as to have
a viscosity suitable to maintain sealing and lubrication of the compressor as desired.
[0021] Note that a vent line 38 is also communicated with oil sump 22 for carrying any further
boiled off refrigerant from this location back to suction inlet 38 as well.
[0022] Oil separated within reclaim vaporizer 34 passes through an oil discharge line 40
and back to sump 22 for further circulation within the lubricant circuit.
[0023] In accordance with the invention, heat is preferably applied to the refrigerant-lubricant
mixture within vaporizer 34 from hot gas from the discharge of compressor 12, which
can be fed to vaporizer 34, for example through line 42 which advantageously is separated
off of main line 18 upstream of condenser 14. This hot gas from compressor 12 will
be at a temperature greater than the temperature of the mixture of refrigerant and
lubricant within evaporator 16. Thus, the gas discharge from compressor 12 can advantageously
be used to provide heat to the mixture, and the resulting cooled refrigerant is then
passed through line 44 to evaporator 16 and back to suction inlet 38 of compressor
12.
[0024] Under certain operating conditions, sufficient heat may not be provided from the
gas discharge of compressor 12, To this end, the system in accordance with the present
invention may further preferably include a supplemental heat source 46, which is schematically
shown in the drawings, and which can be a heater device and/or a further flow of fluid
from the system, either of which can be controlled to provide additional heat to vaporizer
34 as needed.
[0025] In accordance with the present invention, it has been found that the viscosity of
lubricant circulating within the lubricant circuit can be controlled by controlling
the rate of separation of refrigerant from the lubricant within vaporizer 34. To this
end, a control valve 48 is advantageously positioned along line 50 for carrying the
mixture from evaporator 44 to reclaim vaporizer 34. This valve 48 is advantageously
adapted to be controlled by a control unit 50 which includes sensors of the mixture
temperature (T
ref), for example within evaporator 44, and the temperature of reclaimed oil (T
oil), for example within line 40 to sump 22.
[0026] It has been found that the temperature differential between T
oil and T
ref is directly proportional to the resulting viscosity of this separated oil. Thus,
control unit 50 can advantageously be adapted to sense or otherwise determine these
temperatures, and then operate control valve 48 so as to control flow rate of the
mixture from evaporator 16 to reclaim vaporizer 34 and thereby control the temperature
difference between T
oil and T
ref. In accordance with the present invention, a pre-selected range of temperature difference
can be entered into control unit 50 and control unit 50 can be adapted or otherwise
programmed to control valve 48 so as to maintain the temperature difference within
this pre-selected range.
[0027] As the flow rate of mixture from evaporator 16 is increased, the amount of refrigerant
boiled off within reclaim vaporizer 34 per flow volume will decrease, and the viscosity
of resulting separated lubricant will be reduced. As the flow rate of mixture from
evaporator 16 is decreased, further separation is accomplished per flow volume by
the heat applied thereto, and the resulting separated lubricant will contain less
refrigerant and have a higher viscosity.
[0028] Control unit 50 can be any suitable processor unit programmed with proper command
instructions as set forth above. Specifically, control unit 50 is adapted to receive
signals that are indicative of the temperatures T
oil and T
ref, and to utilize these signals to determine a proper operating position for valve
48.
[0029] It should readily be appreciated that the system and method in accordance with the
present invention could readily be accomplished through other approaches as well.
Specifically, it is considered to be well within the scope of the present invention
to control resulting viscosity of separated lubricant by instead controlling the amount
of heat applied within vaporizer 34, and/or controlling both the amount of heat and
the flow rate through valve 48 as described above.
[0030] Also as shown in Figure 1, supplemental heater 46, if needed, is further advantageously
controlled by control unit 50. Such control would involve control unit 50 receiving
the sensed signal related to temperatures T
oil and T
ref, and would be programmed under situations where the difference between these temperatures
is insufficient and valve 48 cannot be further closed to operate supplemental heater
46 to apply further heat as desired.
[0031] It should readily be appreciated that while portions of the above disclosure refer
to the lubricant as oil, the system of the present invention is readily applicable
to systems utilizing other fluids as lubricant as well, so long as this other lubricant
is to be separated from refrigerant with which it is mixed during operation of the
compressor and lubricant circuits.
[0032] It should also be appreciated that while this disclosure is made in terms of a screw
compressor, the system and method of the present invention are readily applicable
to any type of compressor system wherein the lubricant is mixed with refrigerant during
some portion of operation, and must later be separated from same.
[0033] Finally, although the preferred embodiment of the present invention shows heat applied
to the mixture within reclaim vaporizer 34 being supplied from hot gas discharged
from compressor 12, the system of the present invention whereby heat exchange within
vaporizer 34 is controlled to provide desired lubricant viscosity could be accomplished
utilizing other sources of heat as well, and this is well within the broad scope of
the present invention.
[0034] An illustrative example of operation of the invention is provided herein. Assume
a system as shown in Figure 1 is operating with valve 48 fully open. Mixture from
evaporator 16 to reclaim vaporizer 34 is at a maximum flow rate. At this operation,
control unit 50 has been programmed to maintain a difference (ΔT) between T
oil and T
ref at between about a low value of X AND a high value of Y. Assume the temperature difference
ΔT drops to a level which is less than X. At this point, control unit 50 would partially
close valve 48 to slow the flow of mixture to reclaim vaporizer 34. This results in
greater heating of the mixture and a higher T
oil, which also leads to an increase in ΔT.
[0035] Assume that ΔT now exceeds the value Y. At this point, control unit 50 will open
valve 48 further to increase flow of mixture to reclaim vaporizer 34. In this way,
flow rate to reclaim vaporizer 34 is optimized to maximize oil reclaim volume while
maintaining the desired ΔT and, accordingly, a desired oil viscosity.
[0036] Assume next that after the first partial closing of valve 48, the ΔT value remains
less than X. Valve 48 is therefore closed further by control unit 50 to attempt to
raise ΔT to the desired value. Control unit 50 continues to close valve 48 until valve
48 reaches a maximum closed setting wherein a minimum flow is fed to reclaim vaporizer
34. If at this point, ΔT is still too low, supplemental heater 46 can be activated
to provide more heat and raise ΔT to the desired range.
[0037] It should be appreciated that a control system has been provided according to the
invention which advantageously provides control of oil viscosity in reclaimed oil
whereby the viscosity can be maintained at desired levels, for example to ensure good
lubrication and sealing at expected operating conditions of the compressor.
[0038] It is to be understood that the invention is not limited to the illustrations described
and shown herein, which are deemed to be merely illustrative of the best modes of
carrying out the invention, and which are susceptible of modification of form, size,
arrangement of parts and details of operation.
1. A compressor system (10) with controlled lubricant reclaim, comprising:
a compressor circuit comprising a compressor (12), a condenser (14), and an evaporator
(16) connected by refrigerant flow line;
a lubricant circuit for circulating lubricant to the compressor (12);
a reclaim vaporizer (34) adapted to heat a refrigerant-lubricant mixture from the
evaporator (16) whereby the mixture is heated and lubricant and refrigerant are separated
to provide reclaimed lubricant to the lubricant circuit and reclaimed refrigerant
to the compressor circuit; and
a control unit (50); characterised in that:
said control unit is adapted to control flow of the mixture from the evaporator (16)
to the reclaim vaporizer (34) based upon temperature (Tref) of the mixture from the evaporator (16) and temperature (Toil) of reclaimed lubricant leaving the reclaim vaporiser (34).
2. The system of claim 1, wherein the control unit (50) comprises a valve (48) positioned
along a discharge line (50) for conveying the mixture from the evaporator (16) to
the reclaim vaporizer (34).
3. The system of claim 2, wherein the control unit is adapted to operate the valve (48)
to control flow rate of the mixture to the reclaim vaporiser (34) so as to maintain
a temperature difference between the reclaimed lubricant and the mixture within a
preselected range.
4. The system of claim 1, wherein the control unit is adapted to control flow rate of
the mixture to the reclaim vaporiser (34) so as to maintain a temperature difference
between the reclaimed lubricant and the mixture within a preselected range.
5. The system of any preceding claim, wherein the reclaim vaporizer (34) is communicated
with discharge gas from the compressor (12) to heat the mixture.
6. The system of claim 5, further comprising a supplemental heater (46) for providing
additional heat to the mixture in the reclaim vaporizer (34).
7. The system of any preceding claim, wherein the compressor (12) is a screw compressor.
8. A method for controlling reclaim of lubricant in a compressor system (10) according
to claim 1, comprising the steps of:
operating the compressor circuit so as to provide a refrigerant-lubricant mixture
leaving the evaporator (16);
exposing the mixture to heat in the reclaim vaporizer (34) so as to provide reclaimed
lubricant to the lubricant circuit and reclaimed refrigerant to the compressor circuit;
characterized by
controlling flow rate of the mixture to the reclaim vaporizer (34) based upon temperature
(Tref) of the mixture leaving the evaporator and temperature (Toil) of the reclaimed lubricant leaving the reclaim vaporizer.
9. The method of claim 8, wherein the controlling step comprises sensing the temperature
of the mixture and the reclaimed lubricant, and controlling flow of the mixture to
the reclaim vaporizer to maintain a temperature difference between reclaimed lubricant
temperature and mixture temperature within a preselected range.
1. Kompressorsystem (10) mit gesteuerter Schmiermittelrückgewinnung, umfassend:
einen Kompressorkreislauf, umfassend einen Kompressor (12), einen Kondensator (14)
und einen Evaporator (16), die durch eine Kühlmittelflussleitung verbunden sind;
einen Schmiermittelkreislauf zum Zirkulieren von Schmiermittel zum Kompressor (12);
einen Rückgewinnungsverdampfer (34), der dazu ausgebildet ist, ein Kühlmittel-Schmiermittel-Gemisch
vom Evaporator (16) zu erwärmen, wodurch das Gemisch erwärmt wird und das Schmiermittel
und das Kühlmittel getrennt werden, um rückgewonnenes Schmiermittel an den Schmiermittelkreislauf
und rückgewonnenes Kühlmittel an den Kompressorkreislauf bereitzustellen; und
eine Steuereinheit (50), dadurch gekennzeichnet, dass:
die Steuereinheit dazu ausgebildet ist, den Fluss des Gemischs vom Evaporator (16)
zum Rückgewinnungsverdampfer (34) auf Grundlage der Temperatur (Tref) des Gemischs vom Evaporator (16) und der Temperatur (Toil) von rückgewonnenem Schmiermittel zu steuern, das den Rückgewinnungsverdampfer (34)
verlässt.
2. System nach Anspruch 1, wobei die Steuereinheit (50) ein Ventil (48) umfasst, das
an einer Auslaufleitung (50) zum Fördern des Gemischs vom Evaporator (16) zum Rückgewinnungsverdampfer
(34) angeordnet ist.
3. System nach Anspruch 2, wobei die Steuereinheit dazu ausgebildet ist, das Ventil (48)
so zu betätigen, dass die Durchflussrate des Gemischs zum Rückgewinnungsverdampfer
(34) gesteuert wird, um eine Temperaturdifferenz zwischen dem rückgewonnenen Schmiermittel
und dem Gemisch innerhalb eines im Voraus ausgewählten Bereichs zu halten.
4. System nach Anspruch 1, wobei die Steuereinheit dazu ausgebildet ist, die Durchflussrate
des Gemischs zum Rückgewinnungsverdampfer (34) zu steuern, um eine Temperaturdifferenz
zwischen dem rückgewonnenen Schmiermittel und dem Gemisch innerhalb eines im Voraus
ausgewählten Bereichs zu halten.
5. System nach einem der vorangehenden Ansprüche, wobei der Rückgewinnungsverdampfer
(34) mit Fördergas vom Kompressor (12) in Verbindung steht, um das Gemisch zu erwärmen.
6. System nach Anspruch 5, ferner umfassend eine ergänzende Heizeinrichtung (46) zum
Bereitstellen von zusätzlicher Wärme an das Gemisch im Rückgewinnungsverdampfer (34).
7. System nach einem der vorangehenden Ansprüche, wobei der Kompressor (12) ein Schneckenkompressor
ist.
8. Verfahren zum Steuern der Rückgewinnung von Schmiermittel in einem Kompressorsystem
(10) nach Anspruch 1, folgende Schritte umfassend:
Betreiben des Kompressorkreislaufs, um ein Kühlmittel-Schmiermittel-Gemisch bereitzustellen,
das den Evaporator (16) verlässt;
Aussetzen des Gemischs an Wärme im Rückgewinnungsverdampfer (34), um rückgewonnenes
Schmiermittel an den Schmiermittelkreislauf und rückgewonnenes Kühlmittel an den Kompressorkreislauf
bereitzustellen; gekennzeichnet durch
Steuern der Flussrate des Gemischs an den Rückgewinnungsverdampfer (34) auf Grundlage
der Temperatur (Tref) des Gemischs, das den Evaporator (16) verlässt, und der Temperatur (Toil) von rückgewonnenem Schmiermittel zu steuern, das den Rückgewinnungsverdampfer verlässt.
9. Verfahren nach Anspruch 8, wobei der Steuerschritt Folgendes umfasst: Messen der Temperatur
des Gemischs und des rückgewonnenen Schmiermittels, und Steuern des Flusses des Gemischs
zum Rückgewinnungsverdampfer, um eine Temperaturdifferenz zwischen der Temperatur
des rückgewonnenen Schmiermittels und der Gemischtemperatur innerhalb eines im Voraus
ausgewählten Bereichs zu halten.
1. Système à compresseur (10) à récupération régulée de lubrifiant, comprenant :
un circuit à compresseur comprenant un compresseur (12), un condenseur (14) et un
évaporateur (16) reliés par une ligne d'écoulement de réfrigérant ;
un circuit de lubrifiant permettant de faire circuler le lubrifiant vers le compresseur
(12) ;
un vaporisateur (34) de récupération conçu pour chauffer un mélange réfrigérant lubrifiant
à partir de l'évaporateur (16), moyennant quoi le mélange est chauffé et le lubrifiant
et le réfrigérant sont séparés pour obtenir du lubrifiant récupéré dans le circuit
de lubrifiant et un réfrigérant récupéré dans le circuit à compresseur ; et
une unité (50) de commande ; caractérisé en ce que :
ladite unité de commande est conçue pour réguler le débit du mélange à partir de l'évaporateur
(16) vers le vaporisateur (34) de récupération en fonction de la température (Tréf) du mélange partant de l'évaporateur (16) et de la température (TOIL) du lubrifiant récupéré quittant le vaporisateur (34) de récupération.
2. Système selon la revendication 1, dans lequel l'unité de commande (50) comprend une
soupape (48) positionnée le long d'une conduite d'évacuation (50) pour acheminer le
mélange à partir de l'évaporateur (16) vers le vaporisateur (34) de récupération.
3. Système selon la revendication 2, dans lequel l'unité de commande est conçue pour
actionner la soupape (48) pour réguler le débit du mélange acheminé vers le vaporisateur
(34) de récupération de manière à maintenir une différence de température entre le
lubrifiant récupéré et le mélange dans un intervalle présélectionné.
4. Système selon la revendication 1, dans lequel l'unité de commande est conçue pour
réguler le débit du mélange vers le vaporisateur (34) de récupération de manière à
maintenir une différence de température entre le lubrifiant récupéré et le mélange
dans un intervalle présélectionné.
5. Système selon l'une quelconque des revendications précédentes, dans lequel le vaporisateur
(34) de récupération communique avec le gaz d'évacuation provenant du compresseur
(12) afin de chauffer le mélange.
6. Système selon la revendication 5, comprenant en outre un dispositif supplémentaire
de chauffage (46) permettant de fournir une chaleur supplémentaire au mélange dans
le vaporisateur (34) de récupération.
7. Système selon l'une quelconque des revendications précédentes, dans lequel le compresseur
(12) est un compresseur à vis.
8. Procédé de régulation la récupération de lubrifiant dans un système à compresseur
(10) selon la revendication 1, comprenant les étapes suivantes :
actionnement du circuit à compresseur de manière à obtenir un mélange réfrigérant
lubrifiant quittant l'évaporateur (16) ;
exposition du mélange à la chaleur dans le vaporisateur (34) de récupération, de manière
à acheminer le lubrifiant récupéré dans le circuit à lubrifiant et le réfrigérant
récupéré vers le circuit à compresseur ; caractérisé par
la régulation du débit du mélange vers le vaporisateur (34) de récupération en fonction
de la température (Tréf) du mélange partant de l'évaporateur et de la température (TOIL) du lubrifiant récupéré quittant le vaporisateur de récupération.
9. Procédé selon la revendication 8, dans lequel l'étape de régulation comprend la détection
de la température du mélange et du lubrifiant récupéré, et la régulation du débit
du mélange vers le vaporisateur de récupération, afin de maintenir une différence
de température entre la température de lubrifiant récupéré et la température de mélange
dans un intervalle présélectionné.