US20110016895A1 - Methods and Systems for Injecting Liquid Into a Screw Compressor for Noise Suppression - Google Patents
Methods and Systems for Injecting Liquid Into a Screw Compressor for Noise Suppression Download PDFInfo
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- US20110016895A1 US20110016895A1 US12/933,729 US93372909A US2011016895A1 US 20110016895 A1 US20110016895 A1 US 20110016895A1 US 93372909 A US93372909 A US 93372909A US 2011016895 A1 US2011016895 A1 US 2011016895A1
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- Prior art keywords
- refrigerant
- compressor
- venturi tube
- condenser
- pressure
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/0007—Injection of a fluid in the working chamber for sealing, cooling and lubricating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B41/00—Pumping installations or systems specially adapted for elastic fluids
- F04B41/06—Combinations of two or more pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/0021—Systems for the equilibration of forces acting on the pump
- F04C29/0035—Equalization of pressure pulses
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/06—Silencing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04F—PUMPING OF FLUID BY DIRECT CONTACT OF ANOTHER FLUID OR BY USING INERTIA OF FLUID TO BE PUMPED; SIPHONS
- F04F5/00—Jet pumps, i.e. devices in which flow is induced by pressure drop caused by velocity of another fluid flow
- F04F5/54—Installations characterised by use of jet pumps, e.g. combinations of two or more jet pumps of different type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
- F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
- F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
- F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
- F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
- F04C18/165—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type having more than two rotary pistons with parallel axes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C2270/00—Control; Monitoring or safety arrangements
- F04C2270/13—Noise
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/04—Heating; Cooling; Heat insulation
- F04C29/042—Heating; Cooling; Heat insulation by injecting a fluid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/12—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet
Definitions
- the present invention relates to suppressing noise generated in mechanical systems.
- the present invention relates to noise suppression in screw compressors used in commercial and industrial air conditioning and refrigeration systems.
- compression type water-cooled chillers are the most common method of cooling air in medium or large commercial, industrial and institutional buildings.
- Compression type water-cooled chillers are usually electrically driven, but may also be driven by a combustion engine or other power source.
- compressors employed in water-cooled chillers.
- One common compressor is a screw compressor, which uses a rotary type positive displacement mechanism to compress a working fluid, such as a refrigerant.
- Water cooled chillers used in air conditioning and refrigeration systems are required to meet stringent noise level requirements, such as those prescribed by the Occupational Safety and Health Association (OSHA).
- OSHA Occupational Safety and Health Association
- screw chillers have a tendency to generate significant noise during operation.
- the primary source of noise generated in these types of chillers is pressure pulsations originating from the compressor, which generates noise, as well as vibration of adjoining components.
- the secondary sources of noise such as the evaporator, the condenser, and the economizer.
- Prior screw compressor designs have employed various devices and methods to suppress the noise generated by the compressor, such as mufflers and baffle plates arranged in the discharge chamber. Additionally, prior chillers have injected liquid refrigerant from the condenser into the gas refrigerant flow discharged from the compressor to suppress noise generated from pressure pulsations. However, under many operating conditions, these prior chiller designs have required a pressure application device, such as a pump, to compensate for a negative pressure differential between the condenser and the compressor. The addition of a pump, or other device, increases the cost and complexity of the system.
- a screw compressor for use in a chiller assembly includes cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor, a venturi tube arranged in a flow path of the refrigerant in the compressor downstream of the rotors, and an inlet port in fluid communication with a throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor.
- the venturi tube is configured to cause a pressure drop in the refrigerant in the compressor.
- the liquid refrigerant delivered from the condenser reduces pulsations in the pressure of the refrigerant discharged from the compressor.
- FIG. 1 is a perspective view of a screw chiller assembly according to the present invention.
- FIG. 2 is an axial section view of the screw compressor included in the chiller assembly of FIG. 1 .
- FIG. 3 is a schematic of the screw chiller assembly of FIG. 1 illustrating refrigerant flow through the system.
- FIGS. 4A and 4B are schematics of two embodiments of the compressor from the chiller assembly of FIG. 1 .
- FIG. 1 is a perspective view of screw chiller assembly 10 including screw compressor 12 , variable frequency drive 14 , condenser 16 , and evaporator 18 .
- the inlet of compressor 12 is fluidly connected to evaporator 18 and the outlet of compressor 12 is fluidly connected to condenser 16 .
- Condenser 16 is fluidly connected to evaporator 18 .
- Variable frequency drive 14 is mounted on condenser 16 .
- FIG. 2 is an axial section view of screw compressor 12 of FIG. 1 , which compressor 12 includes compressor housing 20 , drive screw 22 , two opposed screws 24 , 26 , bearing housing 28 , discharge housing 30 , discharge chamber 32 , discharge ports 34 , and motor 48 .
- Housing 20 receives central drive screw 22 and two opposed screws 24 and 26 .
- Housing 20 is connected to motor 48 , which is configured to drive screws 22 , 24 , 26 .
- Bearing housing 28 receives screw bearings 28 a that facilitate low friction rotation of drive screw 22 and opposed screws 24 , 26 .
- Bearing housing 28 also receives compressed refrigerant from compression chambers 36 and delivers this compressed refrigerant through discharge ports 34 in the bearing housing 28 to discharge chamber 32 in discharge housing 30 .
- the size of the discharge chamber 32 necks down with the inner peripheral surface 38 of the discharge housing 30 .
- FIG. 3 is a schematic of chiller assembly 10 illustrating flow of refrigerant through the system.
- Chiller assembly 10 is a closed loop system through which refrigerant is cycled in various states, such as liquid and vapor.
- fluid conduit 42 such as a steel pipe, or other conduit from evaporator 18 .
- Compressor 12 is driven by motor 48 under the control of variable frequency drive 14 .
- Variable frequency drive 14 controls the frequency of the alternating current (AC) supplied to motor 48 , thereby controlling the speed of motor 48 and the output of compressor 12 .
- AC alternating current
- Chiller assembly 10 may also include an oil separator (not shown) between compressor 12 and condenser 16 , which separates compressor lubricant from the refrigerant before delivering the refrigerant to condenser 16 .
- the gaseous refrigerant condenses into liquid as it gives up heat.
- the superheated gas refrigerant enters condenser 16 and is de-superheated, condensed, and sub-cooled through a heat exchange process with, for example, water flowing through condenser 16 to absorb heat.
- the liquid refrigerant is discharged from condenser 16 to metering device 44 , which may convert the higher temperature, high pressure sub-cooled liquid to a low temperature saturated liquid-vapor mixture.
- the low temperature saturated liquid-vapor refrigerant mixture enters evaporator 18 from metering device 44 through fluid conduit 42 .
- the low pressure environment in evaporator 18 causes the refrigerant to change states to a superheated gas and absorbs the required heat of vaporization from the chilled water, thus reducing the temperature of the water.
- the low pressure superheated gas is then drawn into the inlet of compressor 12 and the cycle is continually repeated.
- the chilled water is then circulated through a distribution system to cooling coils for providing air conditioning, or for other purposes.
- Chiller assembly 10 may commonly be located in relatively close proximity to people and as such may be designed to suppress noise production and radiation as much as possible.
- Screw compressor 12 is a significant contributor to noise generation, because of pressure pulsations created when the refrigerant is compressed. Pressure pulsations in compressor 12 result from unsteady mass flux caused by the refrigerant compression process performed within compressor 12 . The pressure pulsations in compressor 12 produce undesirable noise, which noise in turn is radiated from chiller assembly 10 . Additionally, the pressure pulsations may generate mechanical vibrations in components of chiller assembly 10 such as piping, heat exchangers, or compressor housing 20 itself. Mechanical vibrations propagating through chiller assembly 10 may themselves result in further noise generation and radiation.
- chiller assembly 10 includes liquid refrigerant conduit 46 shown in FIG. 3 .
- Conduit 46 is configured to deliver liquid refrigerant from condenser 16 to the superheated gas refrigerant flow in compressor 12 .
- conduit 46 is configured to deliver liquid refrigerant from condenser 16 to compressor 12 downstream of compression chambers 36 shown in FIG. 2 .
- conduit 46 may deliver liquid refrigerant to channels in bearing housing 28 , which channels deliver the superheated gas refrigerant from compression chambers 36 to discharge chamber 32 through discharge ports 34 .
- Noise in the gas refrigerant flow in compressor 12 is caused by pressure pulsations at frequencies in the audible range, which may range from approximately 20 to 20,000 Hz. Noise levels can be reduced by reducing the magnitude of such pressure pulsations.
- the objective of introducing liquid refrigerant from condenser 16 into gas refrigerant flow in compressor 12 is to reduce the strength of the pressure pulsations by transferring energy from the gas to liquid phase.
- Three mechanisms contribute to reduce pressure pulsations when liquid refrigerant droplets are injected into the gas refrigerant flow: a) viscous drag between liquid and gas refrigerant; b) heat transfer between liquid and gas refrigerant; and c) mass transfer from vaporization of liquid refrigerant to gas.
- the magnitude of noise attenuation depends on the mass flow rate and droplet size of liquid refrigerant delivered from condenser 16 .
- Noise suppression due to viscous drag and heat transfer are both functions of droplet size.
- Noise suppression due to mass transfer is a function of mass flow rate. Viscous drag and heat transfer are particularly effective to reduce noise at frequencies above 10,000 Hz, while vaporization, i.e. mass transfer, is effective at lower frequencies.
- Embodiments of the present invention therefore provide methods of and systems for inducing a pressure drop in the superheated gas refrigerant flow in compressor 12 sufficient to reduce the pressure in compressor 12 below the pressure in condenser 16 without the addition of work to the system.
- FIGS. 4A and 4B are schematics of two embodiments of compressor 12 configured to induce a pressure drop in the superheated gas refrigerant flow discharged from compressor 12 through bearing housing 28 and discharge chamber 32 .
- compressor 12 includes compressor housing 20 , bearing housing 28 , discharge housing 30 , motor 48 and venturi tubes 50 .
- compressor housing 20 Arranged in compressor housing 20 is compression chamber 36 , which chamber 36 includes drive screw 22 and two opposed screws 24 , 26 (shown in FIG. 2 ).
- Venturi tubes 50 also referred to as convergent-divergent or De Laval nozzles, include, in the direction of flow, a converging portion and diverging portion connected at a throat.
- venturi tubes 50 defines a location of minimum cross-sectional area and is in fluid communication with condenser 16 through conduit 46 , which may be, for example, a steel pipe.
- conduit 46 which may be, for example, a steel pipe.
- venturi tubes 50 are arranged in bearing housing 28 and are configured to direct refrigerant flow 52 from compressor 12 to discharge chamber 32 in discharge housing 30 .
- venturi tubes 50 As refrigerant flow 52 passes through venturi tubes 50 , the velocity of flow 52 increases while the pressure of flow 52 decreases.
- the throat of venturi tubes 50 defines not only the location of minimum cross-sectional area, but also the location of minimum pressure of refrigerant flow 52 .
- Venturi tubes 50 thereby induce a pressure drop in refrigerant flow 52 being discharged from compressor 12 through bearing housing 28 and discharge chamber 32 to condenser 16 .
- venturi tube 50 is configured to induce a pressure drop in refrigerant flow 52 sufficient to reduce the pressure of flow 52 at the throat of venturi tube 50 below the pressure of liquid refrigerant directed through conduit 46 from condenser 16 . Therefore the liquid refrigerant from condenser 16 used to suppress noise in compressor 12 may freely flow from condenser 16 to compressor 12 without adding work to the system, e.g., without the use of a pressure applicator like a pump.
- venturi tubes 50 are arranged within discharge chamber 32 of discharge housing 30 .
- refrigerant flow 52 passes through bearing housing 28 into venturi tubes 50 in discharge chamber 32 through discharge ports 34 .
- a pressure drop is induced in refrigerant flow 52 as the refrigerant passes through venturi tubes 50 , which pressure drop enables liquid refrigerant from condenser 16 to freely flow from condenser 16 through conduit 46 to compressor 12 without adding work to the system.
- Embodiments of the present invention provide methods of and systems for inducing a pressure drop in the superheated gas refrigerant flow in a screw compressor of a chiller assembly sufficient to reduce the pressure in the compressor below the pressure in a condenser without the addition of work to the system.
- Inducing a pressure drop in the compressor refrigerant flow enables liquid refrigerant from the condenser to freely flow to the compressor without the use of a pressure application device, such as a pump.
- Embodiments of the present invention thereby suppress noise generated from pressure pulsations in the screw compressor by injecting liquid from the condenser into the gas refrigerant flow in the compressor without significantly increasing the cost and complexity of the chiller assembly.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Applications Or Details Of Rotary Compressors (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Jet Pumps And Other Pumps (AREA)
Abstract
A screw compressor for use in a chiller assembly includes cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor, a venturi tube arranged in a flow path of the refrigerant in the compressor downstream of the rotors, and an inlet port in fluid communication with a throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor. The venturi tube is configured to cause a pressure drop in the refrigerant in the compressor. The liquid refrigerant delivered from the condenser reduces pulsations in the pressure of the refrigerant discharged from the compressor.
Description
- The present invention relates to suppressing noise generated in mechanical systems. In particular, the present invention relates to noise suppression in screw compressors used in commercial and industrial air conditioning and refrigeration systems.
- The use of compression type water-cooled chillers is the most common method of cooling air in medium or large commercial, industrial and institutional buildings. Compression type water-cooled chillers are usually electrically driven, but may also be driven by a combustion engine or other power source. There are several types of compressors employed in water-cooled chillers. One common compressor is a screw compressor, which uses a rotary type positive displacement mechanism to compress a working fluid, such as a refrigerant.
- Water cooled chillers used in air conditioning and refrigeration systems are required to meet stringent noise level requirements, such as those prescribed by the Occupational Safety and Health Association (OSHA). However, screw chillers have a tendency to generate significant noise during operation. The primary source of noise generated in these types of chillers is pressure pulsations originating from the compressor, which generates noise, as well as vibration of adjoining components. In addition to the screw compressor, there is a multitude of secondary sources of noise, such as the evaporator, the condenser, and the economizer.
- Prior screw compressor designs have employed various devices and methods to suppress the noise generated by the compressor, such as mufflers and baffle plates arranged in the discharge chamber. Additionally, prior chillers have injected liquid refrigerant from the condenser into the gas refrigerant flow discharged from the compressor to suppress noise generated from pressure pulsations. However, under many operating conditions, these prior chiller designs have required a pressure application device, such as a pump, to compensate for a negative pressure differential between the condenser and the compressor. The addition of a pump, or other device, increases the cost and complexity of the system.
- A screw compressor for use in a chiller assembly includes cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor, a venturi tube arranged in a flow path of the refrigerant in the compressor downstream of the rotors, and an inlet port in fluid communication with a throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor. The venturi tube is configured to cause a pressure drop in the refrigerant in the compressor. The liquid refrigerant delivered from the condenser reduces pulsations in the pressure of the refrigerant discharged from the compressor.
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FIG. 1 is a perspective view of a screw chiller assembly according to the present invention. -
FIG. 2 is an axial section view of the screw compressor included in the chiller assembly ofFIG. 1 . -
FIG. 3 is a schematic of the screw chiller assembly ofFIG. 1 illustrating refrigerant flow through the system. -
FIGS. 4A and 4B are schematics of two embodiments of the compressor from the chiller assembly ofFIG. 1 . -
FIG. 1 is a perspective view ofscrew chiller assembly 10 includingscrew compressor 12,variable frequency drive 14,condenser 16, andevaporator 18. InFIG. 1 , the inlet ofcompressor 12 is fluidly connected toevaporator 18 and the outlet ofcompressor 12 is fluidly connected tocondenser 16.Condenser 16 is fluidly connected toevaporator 18.Variable frequency drive 14 is mounted oncondenser 16. -
FIG. 2 is an axial section view ofscrew compressor 12 ofFIG. 1 , whichcompressor 12 includescompressor housing 20,drive screw 22, two opposedscrews housing 28,discharge housing 30,discharge chamber 32,discharge ports 34, andmotor 48.Housing 20 receivescentral drive screw 22 and two opposedscrews Housing 20 is connected tomotor 48, which is configured to drivescrews housing 28 receivesscrew bearings 28 a that facilitate low friction rotation ofdrive screw 22 and opposedscrews housing 28 also receives compressed refrigerant fromcompression chambers 36 and delivers this compressed refrigerant throughdischarge ports 34 in thebearing housing 28 todischarge chamber 32 indischarge housing 30. The size of thedischarge chamber 32 necks down with the innerperipheral surface 38 of thedischarge housing 30. -
FIG. 3 is a schematic ofchiller assembly 10 illustrating flow of refrigerant through the system.Chiller assembly 10 is a closed loop system through which refrigerant is cycled in various states, such as liquid and vapor. As a somewhat arbitrary starting point inchiller assembly 10 ofFIGS. 1-4 , a low temperature, low pressure superheated gas refrigerant is sucked intoscrew compressor 12 throughfluid conduit 42, such as a steel pipe, or other conduit fromevaporator 18.Compressor 12 is driven bymotor 48 under the control ofvariable frequency drive 14.Variable frequency drive 14 controls the frequency of the alternating current (AC) supplied tomotor 48, thereby controlling the speed ofmotor 48 and the output ofcompressor 12. Refrigerant is sucked intocompressor 12 throughinlet ports 40, and compressed betweenscrews discharge ports 34 in bearinghousing 28. The compressed refrigerant entersdischarge chamber 32 throughdischarge ports 34. After the refrigerant is compressed, the high temperature, high pressure superheated gas is discharged fromcompressor 12 throughfluid conduit 42 to condenser 16.Chiller assembly 10 may also include an oil separator (not shown) betweencompressor 12 andcondenser 16, which separates compressor lubricant from the refrigerant before delivering the refrigerant to condenser 16. Incondenser 16, the gaseous refrigerant condenses into liquid as it gives up heat. The superheated gas refrigerant enterscondenser 16 and is de-superheated, condensed, and sub-cooled through a heat exchange process with, for example, water flowing throughcondenser 16 to absorb heat. The liquid refrigerant is discharged fromcondenser 16 tometering device 44, which may convert the higher temperature, high pressure sub-cooled liquid to a low temperature saturated liquid-vapor mixture. The low temperature saturated liquid-vapor refrigerant mixture entersevaporator 18 frommetering device 44 throughfluid conduit 42. The low pressure environment inevaporator 18 causes the refrigerant to change states to a superheated gas and absorbs the required heat of vaporization from the chilled water, thus reducing the temperature of the water. The low pressure superheated gas is then drawn into the inlet ofcompressor 12 and the cycle is continually repeated. The chilled water is then circulated through a distribution system to cooling coils for providing air conditioning, or for other purposes. -
Chiller assembly 10 may commonly be located in relatively close proximity to people and as such may be designed to suppress noise production and radiation as much as possible.Screw compressor 12 is a significant contributor to noise generation, because of pressure pulsations created when the refrigerant is compressed. Pressure pulsations incompressor 12 result from unsteady mass flux caused by the refrigerant compression process performed withincompressor 12. The pressure pulsations incompressor 12 produce undesirable noise, which noise in turn is radiated fromchiller assembly 10. Additionally, the pressure pulsations may generate mechanical vibrations in components ofchiller assembly 10 such as piping, heat exchangers, orcompressor housing 20 itself. Mechanical vibrations propagating throughchiller assembly 10 may themselves result in further noise generation and radiation. - In order to suppress noise generated from the pressure pulsations in
compressor 12,chiller assembly 10 includesliquid refrigerant conduit 46 shown inFIG. 3 . Conduit 46 is configured to deliver liquid refrigerant fromcondenser 16 to the superheated gas refrigerant flow incompressor 12. In particular,conduit 46 is configured to deliver liquid refrigerant fromcondenser 16 tocompressor 12 downstream ofcompression chambers 36 shown inFIG. 2 . For example,conduit 46 may deliver liquid refrigerant to channels in bearinghousing 28, which channels deliver the superheated gas refrigerant fromcompression chambers 36 todischarge chamber 32 throughdischarge ports 34. Noise in the gas refrigerant flow incompressor 12 is caused by pressure pulsations at frequencies in the audible range, which may range from approximately 20 to 20,000 Hz. Noise levels can be reduced by reducing the magnitude of such pressure pulsations. The objective of introducing liquid refrigerant fromcondenser 16 into gas refrigerant flow incompressor 12 is to reduce the strength of the pressure pulsations by transferring energy from the gas to liquid phase. Three mechanisms contribute to reduce pressure pulsations when liquid refrigerant droplets are injected into the gas refrigerant flow: a) viscous drag between liquid and gas refrigerant; b) heat transfer between liquid and gas refrigerant; and c) mass transfer from vaporization of liquid refrigerant to gas. Generally speaking, the magnitude of noise attenuation depends on the mass flow rate and droplet size of liquid refrigerant delivered fromcondenser 16. Noise suppression due to viscous drag and heat transfer are both functions of droplet size. Noise suppression due to mass transfer is a function of mass flow rate. Viscous drag and heat transfer are particularly effective to reduce noise at frequencies above 10,000 Hz, while vaporization, i.e. mass transfer, is effective at lower frequencies. - In order to deliver the liquid refrigerant from
condenser 16 to the superheated gas refrigerant flow incompressor 12, the pressure in thecondenser 16 must be greater than in thecompressor 12. However, downstream ofcompression chambers 36 the superheated gas refrigerant often has a higher pressure than the pressure of the liquid refrigerant incondenser 16. Embodiments of the present invention therefore provide methods of and systems for inducing a pressure drop in the superheated gas refrigerant flow incompressor 12 sufficient to reduce the pressure incompressor 12 below the pressure incondenser 16 without the addition of work to the system. -
FIGS. 4A and 4B are schematics of two embodiments ofcompressor 12 configured to induce a pressure drop in the superheated gas refrigerant flow discharged fromcompressor 12 through bearinghousing 28 anddischarge chamber 32. InFIGS. 4A and 4B ,compressor 12 includescompressor housing 20, bearinghousing 28, dischargehousing 30,motor 48 andventuri tubes 50. Arranged incompressor housing 20 iscompression chamber 36, whichchamber 36 includesdrive screw 22 and twoopposed screws 24, 26 (shown inFIG. 2 ).Venturi tubes 50, also referred to as convergent-divergent or De Laval nozzles, include, in the direction of flow, a converging portion and diverging portion connected at a throat. The throat ofventuri tubes 50 defines a location of minimum cross-sectional area and is in fluid communication withcondenser 16 throughconduit 46, which may be, for example, a steel pipe. In the embodiment ofFIG. 4A ,venturi tubes 50 are arranged in bearinghousing 28 and are configured to directrefrigerant flow 52 fromcompressor 12 to dischargechamber 32 indischarge housing 30. - As
refrigerant flow 52 passes throughventuri tubes 50, the velocity offlow 52 increases while the pressure offlow 52 decreases. The throat ofventuri tubes 50 defines not only the location of minimum cross-sectional area, but also the location of minimum pressure ofrefrigerant flow 52.Venturi tubes 50 thereby induce a pressure drop inrefrigerant flow 52 being discharged fromcompressor 12 through bearinghousing 28 anddischarge chamber 32 tocondenser 16. In embodiments of the present invention,venturi tube 50 is configured to induce a pressure drop inrefrigerant flow 52 sufficient to reduce the pressure offlow 52 at the throat ofventuri tube 50 below the pressure of liquid refrigerant directed throughconduit 46 fromcondenser 16. Therefore the liquid refrigerant fromcondenser 16 used to suppress noise incompressor 12 may freely flow fromcondenser 16 tocompressor 12 without adding work to the system, e.g., without the use of a pressure applicator like a pump. - In some applications, space constraints in
compressor 12 may not permitventuri tubes 50 to be disposed in bearinghousing 28. In an alternative embodiment (FIG. 4B ),venturi tubes 50 are arranged withindischarge chamber 32 ofdischarge housing 30. In the embodiment ofFIG. 4B ,refrigerant flow 52 passes through bearinghousing 28 intoventuri tubes 50 indischarge chamber 32 throughdischarge ports 34. A pressure drop is induced inrefrigerant flow 52 as the refrigerant passes throughventuri tubes 50, which pressure drop enables liquid refrigerant fromcondenser 16 to freely flow fromcondenser 16 throughconduit 46 tocompressor 12 without adding work to the system. - Embodiments of the present invention provide methods of and systems for inducing a pressure drop in the superheated gas refrigerant flow in a screw compressor of a chiller assembly sufficient to reduce the pressure in the compressor below the pressure in a condenser without the addition of work to the system. Inducing a pressure drop in the compressor refrigerant flow enables liquid refrigerant from the condenser to freely flow to the compressor without the use of a pressure application device, such as a pump. Embodiments of the present invention thereby suppress noise generated from pressure pulsations in the screw compressor by injecting liquid from the condenser into the gas refrigerant flow in the compressor without significantly increasing the cost and complexity of the chiller assembly.
- Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
Claims (20)
1. A screw compressor for use in a chiller assembly, the compressor comprising:
a plurality of cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor;
a first venturi tube arranged in a first flow path of the refrigerant in the compressor downstream of the rotors for causing a pressure drop in the refrigerant; and
a first inlet port in fluid communication with a throat of the first venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor for reducing pulsations in the pressure of the refrigerant discharged from the compressor.
2. The compressor of claim 1 , wherein the first venturi tube is located in a bearing housing of the compressor.
3. The compressor of claim 1 , wherein the first venturi tube is located in a discharge housing of the compressor.
4. The compressor of claim 1 further comprising:
a second venturi tube arranged in a second flow path of the refrigerant in the compressor; and
a second inlet port in fluid communication with a throat of the second venturi tube and configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the compressor.
5. The compressor of claim 1 , wherein the first venturi tube reduces the pressure of the refrigerant in the compressor below a pressure of the refrigerant in the condenser.
6. A chiller assembly comprising:
a screw compressor;
a condenser coupled to the screw compressor;
a first venturi tube arranged in a first flow path of a refrigerant passing through the compressor, wherein the first venturi tube comprises a convergent portion connected to a divergent portion at a throat; and
a first conduit coupled between the throat of the first venturi tube and the condenser and configured to deliver liquid refrigerant from the condenser to the first flow path of the refrigerant in the compressor for reducing pulsations in the compressed refrigerant exiting the compressor.
7. The assembly of claim 6 , wherein the screw compressor comprises:
a plurality of cooperating screw rotors configured to increase a pressure of the refrigerant flowing through the compressor, wherein the first venturi tube is arranged downstream of the screw rotors.
8. The assembly of claim 7 , wherein the first venturi tube is located in a bearing housing of the compressor.
9. The assembly of claim 7 , wherein the first venturi tube of the discharge chamber is located in a discharge housing of the compressor.
10. The assembly of claim 6 further comprising:
a second venturi tube arranged in a second flow path of the refrigerant in the compressor, wherein the second venturi tube comprises a convergent portion connected to a divergent portion at a throat; and
a second conduit coupled between the throat of the second venturi tube and the condenser is configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the compressor.
11. The assembly of claim 6 , wherein the first venturi tube reduces a pressure of the refrigerant in the compressor below a pressure of the refrigerant in the condenser.
12. A screw compressor for use in a chiller assembly, the compressor comprising:
a screw rotor bearing housing;
a first venturi tube disposed in the bearing housing and arranged in a first flow path of a refrigerant carried through the bearing housing for decreasing the pressure of the refrigerant; and
a first inlet port in fluid communication with a throat of the first venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the first flow path of the refrigerant in the bearing housing.
13. The compressor of claim 12 further comprising:
a second venturi tube disposed in the bearing housing and arranged in a second flow path of the refrigerant carried through the bearing housing; and
a second inlet port in fluid communication with a throat of the second venturi tube and configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the bearing housing.
14. The compressor of claim 12 , wherein the venturi tube reduces a pressure of the refrigerant in the bearing housing below a pressure of the refrigerant in the condenser.
15. A screw compressor for use in a chiller assembly, the compressor comprising:
a discharge housing;
a first venturi tube disposed in the discharge housing and arranged in a first flow path of the refrigerant carried through the discharge housing for decreasing the pressure of the refrigerant; and
a first inlet port in fluid communication with the throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the first flow path of the refrigerant in the discharge housing.
16. The compressor of claim 15 further comprising:
a second venturi tube disposed in the discharge housing and arranged in a second flow path of the refrigerant carried through the discharge housing; and
a second inlet port in fluid communication with a throat of the second venturi tube and configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the discharge housing.
17. The compressor of claim 15 , wherein the first venturi tube reduces a pressure of the refrigerant in the discharge housing below a pressure of the refrigerant in the condenser.
18. A method of suppressing noise in a screw compressor of a chiller assembly, the method comprising:
introducing a liquid refrigerant from a condenser of the chiller assembly into a compressed gas refrigerant flowing through the screw compressor to reduce pulsations in the refrigerant; and
reducing, without adding work, a pressure of the gas refrigerant in the compressor below a pressure of the liquid refrigerant in the condenser to facilitate introduction of the liquid refrigerant into the gas refrigerant.
19. The method of claim 18 , wherein the pressure of the gas refrigerant is reduced by passing the gas refrigerant through one or more venturi tubes.
20. The method of claim 18 , wherein the pressure of the gas refrigerant is reduced in one of a bearing housing or a discharge housing of the compressor.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/933,729 US20110016895A1 (en) | 2008-05-21 | 2009-05-19 | Methods and Systems for Injecting Liquid Into a Screw Compressor for Noise Suppression |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12846708P | 2008-05-21 | 2008-05-21 | |
PCT/US2009/044567 WO2009151895A2 (en) | 2008-05-21 | 2009-05-19 | Methods and systems for injecting liquid into a screw compressor for noise suppression |
US12/933,729 US20110016895A1 (en) | 2008-05-21 | 2009-05-19 | Methods and Systems for Injecting Liquid Into a Screw Compressor for Noise Suppression |
Publications (1)
Publication Number | Publication Date |
---|---|
US20110016895A1 true US20110016895A1 (en) | 2011-01-27 |
Family
ID=41417344
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/933,729 Abandoned US20110016895A1 (en) | 2008-05-21 | 2009-05-19 | Methods and Systems for Injecting Liquid Into a Screw Compressor for Noise Suppression |
Country Status (4)
Country | Link |
---|---|
US (1) | US20110016895A1 (en) |
EP (1) | EP2307733A4 (en) |
CN (1) | CN102037245B (en) |
WO (1) | WO2009151895A2 (en) |
Cited By (5)
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WO2016157445A1 (en) * | 2015-03-31 | 2016-10-06 | 株式会社日立産機システム | Screw compressor |
US10114604B2 (en) | 2014-12-26 | 2018-10-30 | Seiko Epson Corporation | Head-mounted display device, control method for head-mounted display device, and computer program |
CN109139464A (en) * | 2018-09-20 | 2019-01-04 | 李桂君 | A kind of double helix supercharging device and the engine comprising the double helix supercharging device |
US20220074415A1 (en) * | 2019-05-20 | 2022-03-10 | Carrier Corporation | Direct drive refrigerant screw compressor with refrigerant lubricated bearings |
US11808264B2 (en) | 2018-10-02 | 2023-11-07 | Carrier Corporation | Multi-stage resonator for compressor |
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CN102022870B (en) * | 2010-12-09 | 2014-02-19 | 海尔集团公司 | Method for improving supercooling degree of screw machine set and screw machine set adopting same |
BE1025222B1 (en) * | 2017-05-04 | 2018-12-13 | Atlas Copco Airpower Naamloze Vennootschap | Transmission and compressor or vacuum pump provided with such transmission |
CN111852860A (en) * | 2019-09-03 | 2020-10-30 | 乐清市芮易经济信息咨询有限公司 | Gas-liquid mixing and conveying device with three-jaw rotor |
CN114061162A (en) | 2020-07-31 | 2022-02-18 | 开利公司 | Refrigeration system and control method thereof |
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- 2009-05-19 EP EP09763186.5A patent/EP2307733A4/en not_active Withdrawn
- 2009-05-19 CN CN200980118281.8A patent/CN102037245B/en not_active Expired - Fee Related
- 2009-05-19 WO PCT/US2009/044567 patent/WO2009151895A2/en active Application Filing
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JPWO2016157445A1 (en) * | 2015-03-31 | 2018-01-11 | 株式会社日立産機システム | Screw compressor |
US20180058452A1 (en) * | 2015-03-31 | 2018-03-01 | Hitachi Industrial Equipment Systems Co., Ltd. | Screw Compressor |
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CN109139464A (en) * | 2018-09-20 | 2019-01-04 | 李桂君 | A kind of double helix supercharging device and the engine comprising the double helix supercharging device |
US11808264B2 (en) | 2018-10-02 | 2023-11-07 | Carrier Corporation | Multi-stage resonator for compressor |
US20220074415A1 (en) * | 2019-05-20 | 2022-03-10 | Carrier Corporation | Direct drive refrigerant screw compressor with refrigerant lubricated bearings |
US11959484B2 (en) * | 2019-05-20 | 2024-04-16 | Carrier Corporation | Direct drive refrigerant screw compressor with refrigerant lubricated bearings |
Also Published As
Publication number | Publication date |
---|---|
WO2009151895A3 (en) | 2010-04-22 |
EP2307733A4 (en) | 2014-07-02 |
EP2307733A2 (en) | 2011-04-13 |
CN102037245A (en) | 2011-04-27 |
CN102037245B (en) | 2013-12-25 |
WO2009151895A2 (en) | 2009-12-17 |
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Legal Events
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AS | Assignment |
Owner name: CARRIER CORPORATION, CONNECTICUT Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SISHTLA, VISHNU M.;REEL/FRAME:025020/0266 Effective date: 20080624 |
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STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- AFTER EXAMINER'S ANSWER OR BOARD OF APPEALS DECISION |