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
  • F25B49/00—Arrangement or mounting of control or safety devices
  • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
  • F25B49/025—Motor control arrangements
• • 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
  • F04C18/02—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
  • F04C18/0207—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form
  • F04C18/0215—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form where only one member is moving
• • 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
  • F04C23/00—Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids
  • F04C23/008—Hermetic pumps
• • 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
  • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
  • F04C28/08—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by varying the rotational speed
• • 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
• • 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
  • F25B2400/13—Economisers
• • 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
  • F25B2600/00—Control issues
  • F25B2600/02—Compressor control
  • F25B2600/025—Compressor control by controlling speed
  • F25B2600/0252—Compressor control by controlling speed with two speeds
• • 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
  • F25B2600/00—Control issues
  • F25B2600/02—Compressor control
  • F25B2600/026—Compressor control by controlling unloaders
  • F25B2600/0261—Compressor control by controlling unloaders external to the compressor
• • 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
  • F25B41/00—Fluid-circulation arrangements
  • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
  • F25B41/22—Disposition of valves, e.g. of on-off valves or flow control valves between evaporator and compressor

Definitions

• This application relates to a refrigerant system wherein a compressor motor may operate at least at two speeds, and wherein a pulse width modulation control is provided to allow cycling the motor between the distinctive speeds at a specified adjustable rate to vary the refrigerant system capacity.
• Refrigerant systems are utilized to condition a secondary fluid, such as air.
• Compressors and refrigerant systems are typically sized to meet a maximum capacity demand. However, for the most part, a cooling or heating capacity demand is relatively low, and therefore, the refrigerant system needs to be unloaded by some means.
• a motor for a compressor is typically cycled between on and off operational stages.
• a suction modulation valve, or a variable speed compressor may be utilized. All of these methods of unloading have various drawbacks. When the unit is cycled on and off, the temperature and humidity of the environment to be conditioned cannot be precisely controlled. In the air conditioning case, this insufficient temperature control creates discomfort to the occupant of the indoor environment.
• the inadequate temperature control can lead to spoilage of goods that need to be refrigerated and kept within a specified temperature range.
• cycling losses occurring during compressor start-stop operation are detrimental to the efficiency of the refrigerant system.
• the use of a suction modulation valve has undesirable consequences, since an increased pressure ratio across the compressor reduces the refrigerant system efficiency and increases compressor discharge temperature.
• a suction modulation valve adds cost to the unit and becomes an additional reliability risk.
• a variable speed compressor a variable speed drive is also a significant cost adder.
• a compressor speed, while controlled by a variable speed drive often cannot be reduced below a certain value to meet tight temperature control requirements.
• variable speed drive systems introduce extra losses due to inefficiencies of the variable speed drives themselves. These extra losses are normally on the order of 5-6%. Also, additional expensive means to cool the variable speed drive are often required. Lastly, the use of a variable speed compressor and associated components introduce extra complexity into the system design, potentially leading to reliability problems.
• One of the methods proposed in the past to vary the system capacity was to rapidly cycle the refrigerant system components. For example, it is known to rapidly cycle a suction valve between open and closed positions (a so-called pulse width modulation control), to control the amount of refrigerant delivered to a compressor. In this manner, the capacity provided by the overall refrigerant system is reduced.
• a compressor in a refrigerant system is provided with a multi-speed motor.
• a motor can be designed to operate at two or more distinct speeds by, for instance, being wound with pole changing windings.
• a particular motor speed can be selected by changing external connections. Switching between the motor speeds can be accomplished by so-called solid state contactors. (Though more expensive than normal switching controls, the solid state contactors offer higher reliability when fast switching between the speeds might be required.)
• a control for selecting the motor operating speed is provided with pulse width modulation capability. When it is determined that a reduced capacity should be provided, the pulse width modulation control cycles the compressor motor between a higher and lower speed at a required rate to satisfy thermal load demands in a conditioned space.
• pulse width modulation of the compressor motor can be used in conjunction with other unloading techniques such as switching on and off an economizer circuit, employment of a compressor bypass valve and utilization of a suction modulation valve.
• the compressor motor is cycled sufficiently fast between its operating speeds that the cycling rate would normally be faster than the system thermal inertia. In other words, the cycling rate is selected to be fast enough not to significantly affect the temperature of the air supplied to the environment to be conditioned when the compressor is switched from one operating speed to another.
• Figure IA is a schematic view of a refrigerant system incorporating the present invention.
• Figure IB shows another schematic incorporating the present invention.
• Figure 1C shows another schematic related to the present invention.
• Figure 2 is a speed versus time graph for one embodiment of the present invention.
• FIG. 1A shows a refrigerant system 20 incorporating a compressor 21 with a multi-speed motor 22 driving a shaft 24.
• the compressor 21 is illustrated as a scroll compressor having an orbiting scroll 26 interfitting with a non-orbiting scroll 28. It has to be noted, that although the description is primarily related to a scroll compressor type, any other compressor (screw, reciprocating, rotary, etc.) capable of running at multiple speeds is within the scope of the invention.
• the present invention would apply to different types of refrigerant systems. For example, these systems may include air conditioning units, heat pump units, chiller systems, and different types of refrigeration units including container units, truck and trailer units and supermarket cabinets and display cases.
• the present invention would also apply to different compressor-motor configurations, where the motor can be a part of a hermetic or semi-hermetic compressor shell that also includes compressor pumping elements (in this case, the compression elements can be referred to as the compressor).
• the motor 200 can be located outside the shell 202 containing the compression elements (a so-called open-drive compressor design), see Figure 1C.
• the motor 22 is a motor that can operate at least at two speeds, although the invention would extend to motors operable at multiple discrete speeds (or nearly discrete speeds, as it is the case with the induction motors, where the motor speed can vary slightly at each distinct speed due to a motor slip).
• a control 23 can control the motor to operate at a desired speed from a set of multiple discrete speeds mentioned above for a certain period of time.
• a switching device is included into the control 23 to switch from one operating speed to another operating speed. The switching rate can also be controlled, if desired.
• Refrigerant having been compressed by the compressor 21, passes through a discharge line 30, a condenser (or a gas cooler in transcritical operation) 32, and flows toward a main expansion device 33.
• the refrigerant system 20 can incorporate, as an option, an economizer cycle, including an economizer heat exchanger 34, where a tapped portion of refrigerant passes through an economizer expansion device 37, and then through the economizer heat exchanger 34.
• the expanded (to a lower pressure and temperature) refrigerant in the tap line 36 cools a refrigerant in a main refrigerant circuit, also flowing through the economizer heat exchanger 34 toward the main expansion device 33, to provide higher cooling thermal potential in an evaporator 40.
• the tapped refrigerant is shown passing in the same direction through the economizer heat exchanger 34, in practice, the two refrigerant flows are typically arranged in a counterflow configuration.
• an extra flow control device such as a valve 54 may be added to enable an economizer function when additional capacity is desired and to disengage it when extra capacity is not required.
• the economizer flow is tapped upstream of the economizer heat exchanger 34, as known in the art, downstream tap point locations are feasible and are within the scope of the invention.
• Downstream of the main expansion device 33 the refrigerant passes through the evaporator 40, and then to a line 41.
• a suction modulation valve 42 (also an optional component for the potposes of this invention) is shown for controlling the amount of refrigerant passing to a suction line 44 and back to the compressor 21.
• an unloader bypass line 4S incorporating an unloader valve 50 and selectively communicating at least a portion of partially compressed refrigerant from the compressor 21 to a line 46 and then to the suction line 44 to reduce the capacity of the refrigerant system 20 when desired.
• a return line 52 returns the tapped refrigerant, typically in a vapor state, downstream of the economizer heat exchanger 34 through the valve 54 and line 46 to an intermediate point in the compression process.
• the same ports are selectively utilized to inject the economized refrigerant when the valve 54 is open and to unload the compressor when the valve 50 is open.
• the economizer and unloader functions do not have to be mutually exclusive and may be engaged simultaneously.
• the economizer function, the unloader function, and the suction modulation valve are all known techniques of varying the capacity provided by the refrigerant system 20 to match thermal load demands in an environment to be conditioned.
• the present invention provides additional control over this capacity by utilizing a pulse width modulation technique from control 23 to rapidly switch the motor 22 between its higher and lower speeds.
• the motor may be cycled between the high speed and the lower speed at a specific rate to provide an average desired capacity Q DESIRED -
• the desired capacity is matched to the QTIME-AVE R AGED capacity.
• the Q TIME -A VER A G ED capacity is calculated as an integrated average of capacities delivered at high and low speeds of operation.
• the high speed is approximately twice as high as the lower speed (for example, the motor speed can be switched between 3500 RPM operation and 1750 RPM operation), and the time of operation at each speed may be controlled to achieve an exact time-averaged speed, in order to provide the desired capacity to precisely match thermal load demands in a conditioned space.
• this invention overcomes one of the limitations of the variable speed compressor, where the variable speed drive has to operate the compressor at a reduced speed for prolonged periods of time. The prolonged operation at a reduced speed can lead to compressor damage, since the amount of lubricating oil delivered to compressor components that needed to be lubricated can be reduced to an unacceptably low level.
• the required heating or cooling system capacity defines the ratio of how much time the compressor should operate at a high speed vs. operational time at a low speed.
• the cycling rate (how fast the compressor is cycled between the high and low speed) is normally determined by reliability and efficiency considerations. A too low cycling rate may present lubrication problems at lower speeds as well as cause unacceptable variations in the temperature of the air delivered to the conditioned environment within the time interval between the high and low speed of operation, as discussed above. On the other hand, an excessively high cycling rate may introduce reliability problems associated with the switching device or potential thermodynamic efficiency degradation.
• Figure IB is included to show an embodiment, wherein one of the various capacity control techniques mentioned in the Figure IA embodiment also includes an unloader function that controls the amount of refrigerant passing to a back pressure chamber 306 behind one of the scroll members 302 and 304 (the scroll member 304 in this case), and thus the refrigerant pressure in the back chamber 306, to allow the scroll members to engage and disengage with each other to compress and circulate a required amount of refrigerant throughout the refrigerant system.
• This technique will reduce overall system capacity by reducing the time-averaged amount of compressed refrigerant vapor.
• a valve 310 controls the amount of a higher pressure fluid from a source 308 reaching the back pressure chamber 306 such that an orbiting scroll 302 and non-orbiting scroll 304 can move in and out of contact with each other to control system capacity. If the valve 310 is controlled by a control 312 in a pulse width modulation manner at a specific rate, the scroll elements 302 and 304 will engage and disengage accordingly, providing required refrigerant flow for the system capacity to match thermal load requirements in a conditioned space.
• the valve 310 may be positioned internally or externally to the compressor 21, as well as the controls 23 and 312 may be separate stand-alone controls or combined with the control for the refrigerant system 20.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Applications Or Details Of Rotary Compressors (AREA)
• Control Of Positive-Displacement Pumps (AREA)

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• 2006
  • 2006-10-06 US US12/375,255 patent/US20090308086A1/en not_active Abandoned
  • 2006-10-06 EP EP06825706.2A patent/EP2074357A4/de not_active Withdrawn
  • 2006-10-06 WO PCT/US2006/039583 patent/WO2008041996A1/en active Application Filing
  • 2006-10-06 CN CN200680056044XA patent/CN101523129B/zh not_active Expired - Fee Related
• 2010
  • 2010-02-24 HK HK10101929.2A patent/HK1136617A1/xx not_active IP Right Cessation

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