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
  • F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
  • F25B43/02—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat for separating lubricants from the 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
  • F25B1/00—Compression machines, plants or systems with non-reversible cycle
  • F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
  • F25B1/047—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of screw type
• • 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
  • F25B2400/23—Separators
• • 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
  • F25B31/00—Compressor arrangements
  • F25B31/002—Lubrication
  • F25B31/004—Lubrication oil recirculating arrangements

Definitions

• This invention deals with machines used for refrigeration and air conditioning or heat pumps with medium to high cooling capacity (typically about 100 kW and higher), using vapor compression cycles, including falling film or hybrid falling film evaporators, in conjunction with lubricated compressors connected to oil separators that are separate from the compressor.
• compressors In the context of research for energy savings and reduction of the emissions of greenhouse gasses, high equipment efficiency and low refrigerant charges are being sought. To achieve these goals, improvements are being made to all the components of the systems: compressors, variable speed drives, optimized choice of refrigerant, oil separators, heat exchangers, etc.
• Most of the compressors require an amount of lubrication, which lubrication similarly generates carry-over of an amount of oil from the compressor into the refrigerant circuit. This oil that is entrained into the refrigerant circuit must then be returned to the compressor by and adequate oil return system, in order to avoid different adverse effects like the deterioration of the performance of the heat exchangers.
• screw compressors these machines require a particularly large amount of lubrication in order to insure proper sealing of the gas between the rotors and to avoid the need for additional synchronization gears between the rotors. Therefore, screw compressors typically require a vessel, also commonly referred to as an oil separator, positioned between the compressor discharge and the inlet of the condenser.
• a vessel also commonly referred to as an oil separator
• One challenge associated with refrigeration machines and heat pumps is the management of the oil in the refrigerant circuits. This requires a careful combination between the oil carry-over, the oil return system and the technology of the heat exchangers.
• this vessel or oil separator or separator vessel usually also has the function of being the oil sump for the compressor.
• Separator vessels or oil separators can be based on several operating principles. The most common include:
• Impingement separation the two-phase mixture of oil and gas is projected onto a wall or to the end of the vessel, providing a first stage of separation.
• Filter pad separation the mix is forced through a pad of closely spaced and/or finely interwoven filaments or wires that acts as a filter.
• the filter pad may include a wire mesh.
• filter pads are normally installed horizontally, with gas circulation directed upwards. The filtration level of filter pads is relatively coarse; it would not stop very fine droplets entrained in the gas or mist, but still removes smaller droplets than gravity separation.
• centrifugal separation the two-phase oil and gas mixture is introduced tangentially in a cylindrical vessel.
• the whirling motion tends to project the oil droplets onto the cylindrical wall of the vessel where the droplets coalesce and fall to the bottom of the vessel.
• centrifugal separation allows removing the largest droplets of oil.
• coalescing filters the two-phase mixture of oil and gas is forced through a cartridge acting as a filter.
• the filter material is typically fiberglass.
• the filtration is much finer as compared with the filter pads (see above).
• coalescing filters substantially prevent droplets of 1 ⁇ (micrometers) or larger in diameter from passing through the coalescing filter during operation of a refrigerant circuit.
• the coalescing filters generally permit about 1 to 10 parts per million (PPM) by mass of oil droplets entrained in refrigerant flow to discharge from the separator.
• Figure 1 A horizontal design with coalescing filters.
• Figure 1 shows an example of this well-known design. The separation begins with impingement at one end of the vessel, continues with a gravity separation section that is also used as the oil sump, and is completed by coalescing filters.
• coalescing filters When properly implemented, these designs normally provide a highly efficient oil separation thanks to the coalescing elements. Yet, coalescing filters have some drawbacks. They tend to be relatively expensive. If the coalescing filters are not mounted properly, some separators in a series may not meet operating specifications. If the possibility of inspection and filter removal is desired, costly additional flanges or access-providing man holes are required that also increase the risk of refrigerant leaks. In addition, hydraulic pressure safety testing of vessels having internal coalescing filters raises risk of damaging these filters, as well as associated difficulties in emptying and drying the vessel properly after completing the testing.
• coalescing filters can also suffer loss of performance, and are susceptible to clogging and/or destruction under the effect of elevated fluid forces. Increased fluid mass flow is especially a problem for heat pump applications with high pressure halogenated refrigerants such as HFC's. Even when used in air conditioning applications, coalescers or coalescing filters need to be oversized when high pressure HFC's, such as R-410A or R-507 are used. Use of high temperature heat pumps increases problems associated with such applications. In such high temperature heat pumps, the evaporating temperature is substantially higher than when using the same machines and refrigerant in corresponding air conditioning applications, due to higher temperature of the water or other medium being cooled at the evaporator.
• the leaving water from the evaporator is typically above 20°C, and can reach up to 60°C or even higher.
• the resulting higher evaporation temperatures substantially increase density and hence the mass flow of refrigerant, even when using a relatively low pressure refrigerant such as R-134a or even lower pressure refrigerants like R-245fa for instance.
• R-134a relatively low pressure refrigerant
• R-245fa relatively low pressure refrigerant
• an oil separator having a radically simplified design that does not include coalescing filters, while providing a sufficient oil separation during operation.
• the present disclosure is directed to the use of falling film evaporators or hybrid falling film evaporators, such as described, for instance, in U.S. Patent No. 7,849,710, which is incorporated by reference in its entirety.
• falling film and hybrid falling film evaporator performance is less sensitive to oil carry-over than traditional flooded evaporators, permitting an oil separator, such as the filter pad, to be used without sacrificing evaporator performance.
• the term filter pad generally incorporates the following performance characteristics: substantially prevents droplets of about 5 ⁇ (micrometers) in diameter or larger from passing through the filter pad during operation of a refrigerant circuit.
• the filter pad operates between about 50 to about 100 parts per million (PPM) of oil entrained in refrigerant flow from the separator.
• the void percentage of the filter pad is between about 97 and about 99 percent.
• the diameter of filaments and/or wires generally ranges from between about 0.15 mm to about 0.35 mm (millimeters) in diameter.
• the present invention is directed to a refrigerant circuit using a vapor compression cycle, the circuit usable for air conditioning, refrigeration or heat pump purposes.
• the circuit includes a lubricated compressor connected to an oil separator vessel separate from the compressor, a falling film or hybrid falling film evaporator and a condenser.
• the oil separator vessel extends substantially horizontally.
• the oil separator vessel is separated into a primary space and a secondary space by a filter pad configured to substantially remove entrained oil droplets of about 5 ⁇ and larger from the refrigerant entering the oil separator vessel.
• the primary space is in fluid connection with a discharge of the compressor.
• the secondary space is in fluid connection with an inlet of the condenser.
• the circuit has an oil entrainment flow discharge of lubricant from the compressor of at least about two percent by mass relative to refrigerant flow.
• FIG. 1 shows a prior art oil separator.
• Figure 2 shows an exemplary embodiment of an oil separator of the present disclosure.
• Figure 3 shows an exemplary embodiment of an oil separator of the present disclosure.
• Figure 4 shows an exemplary embodiment of an oil separator of the present disclosure.
• Figure 5 schematically shows an exemplary embodiment of a vapor compression system of the present disclosure.
• Figure 6 schematically shows an exemplary embodiment of a vapor compression system of the present disclosure.
• Figure 7 shows an exemplary embodiment of an oil separator of the present disclosure.
• Figure 8 shows an exemplary embodiment of an oil separator of the present disclosure.
• Figure 2 shows a horizontal vessel 1 with a filter pad 2 providing a longitudinal separation of the vessel into two spaces: a primary space 3 having an inlet 4 to receive discharge from the compressor, and a secondary space 5 having an outlet 6 in communication with an inlet of a condenser (not shown).
• inlet 4 receives compressor discharge in which a gas and oil mixture 15 entering separator vessel 1 can be arranged to provide impingement separation at an end of vessel 1 in primary space 3.
• a second filter pad 7 can be disposed on or near end 17 of vessel 1 where this impingement occurs, to limit the re-entrainment of liquid with gas discharged from the compressor after the gas discharge collides with the end of the vessel.
• filter pad 2 is installed across the complete cross section of vessel 1 , transverse to the longitudinal direction of vessel 1.
• the lower part of vessel 1 is collecting liquid oil 19 and performing the function of an oil sump.
• the level of liquid oil 19 is essentially the same for both spaces. It is generally better to collect the liquid oil 19 from secondary space 5 through an oil pipe 8 to be returned to the compressor for lubrication, because the oil has an opportunity to become separated from foam and bubbles by filter pad 2 while migrating from primary space 3 to secondary space 5.
• evaporators 12 such as falling film evaporators or hybrid falling film evaporators
• the oil separator is separate from the compressor.
• a filter pad 2 separating respective primary and secondary spaces 3, 5 is substantially planar and is installed vertically, i.e., perpendicular to a longitudinal axis of vessel 1, and about at mid-length of the separator vessel.
• this filter pad 2 can be positioned non- perpendicular with respect to the vessel axis, such as shown in Figure 3.
• This arrangement has an advantage of reducing the velocity of the gas flowing through filter pad 2.
• a vessel of the present disclosure can have a smaller vessel diameter in comparison to the diameter of a vessel of conventional construction, with the smaller diameter vessel of the present disclosure operating with a gas flow velocity through the filter pad 2 that may be similar to the operating gas flow velocity through the filter pad 2 of the larger, conventional vessel of Figure 2.
• the smaller diameter vessel of the present disclosure may operate with a gas flow velocity through the filter pad 2 that may be less than the gas flow velocity of the larger, conventional vessel.
• filter pad 2 may be composed of two or more portions 2a, 2b arranged at an angle to each other, e.g., in the shape of a "V as shown in Figure 4, which is a plan view of the vessel.
• portions 2a, 2b may be of unequal length.
• two oil separation sections or spaces utilizing the same principle can be integrated in a single vessel 1, each section or space or secondary space 5 receiving approximately one half of the volume of discharge gas and oil from primary space 3.
• both outlets 6 can be connected to form a single pipe that extends to one condenser inlet.
• the condenser (not shown) can have two inlets, one inlet at each end; with each of the two separator outlets 6 being connected to one of the condenser inlets.
• the arrangement with two sections or spaces in a common vessel offers several advantages. As the flow to each section or space is reduced, such as being reduced by a factor of two, so too is a reduction of the required cross section of the vessel. Therefore, in spite of the additional length, the reduction in diameter will result in a less expensive vessel. A further advantage is that a vessel of smaller diameter will typically radiate less noise, because there is less potential for wall resonance in a shell of smaller diameter. Finally, the added length to the vessel does not raise packaging problems with other system components as long as the length of the separator or vessel does not substantially exceed that of the heat exchangers, such as the condenser and/or evaporator.
• the arrangement lends itself to easy packaging with horizontal shell and tube heat exchangers, and with a horizontal screw compressor driveline.
• the discharge of compressor 9 is directed downwards to separator vessel 1.
• the discharge of compressor 9 may be directed from one side of compressor 9 to oil separator vessel 1.
• the compressor discharge may be directed at an orientation that is between the downward direction and the side direction of the compressor to the oil separator vessel (not shown).
• the compressor driveline can be installed at least partially above the oil separator vessel.
• evaporator 12 is positioned above condenser 11 and arranged near the compressor driveline and separator vessel.
• evaporator 12 and condenser 11 may be positioned in different arrangements with respect to each other and/or to the compressor driveline and oil separator vessel.
• the compressor suction is directed vertically, such that compressor 9 is installed on top of evaporator 12, with compressor discharge from one side of the compressor to oil separator vessel 1.
• the compressor suction may extend outwardly from the side, or in yet another embodiment, the compressor suction may extend between a vertical and a side orientation with respect to the oil separator vessel 1.
• compressor 9 can be installed at least partially above evaporator 12.
• oil separator vessel 1 is shown positioned laterally beside compressor 9 and on top of condenser 11. In other embodiments, other arrangements between the compressor, oil separator vessel, condenser and evaporator may be utilized.
• This use of filter pads is especially advantageous for use with heat pumps using halogenated refrigerants like HFC's or HFO's, and when the evaporation temperature is significantly greater than evaporator temperatures normally associated with air conditioning applications (e.g., 5°C).
• the evaporation temperature can be up 30° to about 40°C with HFC refrigerant R-134a or possible equivalents, and even higher temperatures associated with lower pressure refrigerants such as R-245fa.
• the refrigerants may include hydrocarbons such as R-290 or R-1270.

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• 2012
  • 2012-03-29 US US13/434,169 patent/US20130255308A1/en not_active Abandoned
  • 2012-10-31 EP EP12795658.9A patent/EP2831519A1/en not_active Withdrawn
  • 2012-10-31 WO PCT/US2012/062741 patent/WO2013147931A1/en active Application Filing
  • 2012-10-31 JP JP2015503187A patent/JP2015512501A/ja active Pending
  • 2012-10-31 CN CN201280072076.4A patent/CN104204692A/zh active Pending
  • 2012-10-31 KR KR1020147027499A patent/KR101607509B1/ko not_active IP Right Cessation
  • 2012-11-22 TW TW101143672A patent/TWI509207B/zh not_active IP Right Cessation
• 2016
  • 2016-11-22 JP JP2016226618A patent/JP2017075776A/ja active Pending

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