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
  • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
  • F25B9/06—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using expanders
• • 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
  • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
  • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
  • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
• • 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
  • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
• • 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
  • F25B2309/00—Gas cycle refrigeration machines
  • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
  • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
• • 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
  • F25B2400/14—Power generation using energy from the expansion of 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
  • F25B2600/00—Control issues
  • F25B2600/25—Control of valves
  • F25B2600/2501—Bypass valves

Definitions

• This application relates to refrigerant systems, wherein the expansion process is provided by an expander.
• the capacity of the expander can be varied by controlling the amount of refrigerant that is diverted to an intermediate expansion point in the expander. By controlling the amount of diverted refrigerant, the overall refrigerant system can be more efficiently controlled and operated, as will be explained below.
• Refrigerant systems are known in the air conditioning and refrigeration art, and are utilized to condition a secondary fluid, such as air, water or glycol solution, that is delivered to a climate-controlled zone or space.
• a compressor compresses a refrigerant and delivers it downstream to a first heat exchanger, where heat is rejected, directly or indirectly, from the refrigerant to an ambient environment. From this first heat exchanger, the refrigerant passes through an expansion process, where it is expanded to a lower pressure and temperature, and then through a second heat exchanger, where heat is accepted by the refrigerant from a secondary fluid to cool this secondary fluid to be delivered to an indoor environment.
• the first heat exchanger is normally called a condenser, for system operation below the refrigerant critical point, or so-called subcritical operation, and is called a gas cooler, for system operation above the refrigerant critical point, or so- called supercritical operation.
• the second heat exchanger typically operates in a subcritical two-phase region and is called an evaporator.
• One performance enhancement option that is utilized in known refrigerant systems is the use of an expander.
• the expander offers advantages of a more efficient isentropic expansion process, resulting in a higher refrigerant cooling potential in the evaporator, as compared to an isenthalpic process for restriction type expansion devices.
• some expansion work can be recovered to assist in driving at least one of refrigerant system components. Both expansion work recovery and 60,246-542; 1656 additional refrigerant cooling potential realized in the evaporator are beneficial to the refrigerant system operation, since they augment refrigerant system capacity and efficiency.
• the use of the expanders for CO 2 refrigerant applications is especially important, as on a relative basis, the expanders provide much larger thermodynamic cycle improvements for CO 2 refrigerant than for the traditional refrigerants. It is also important to use expanders within the CO 2 systems, as these systems are not as thermodynamically efficient, on an absolute scale, as the systems with conventional refrigerants, such as R22, R410A, R404A, R407C, Rl 34a, etc.
• One problem in using the expanders is related to a difficulty of controlling the amount of refrigerant passing through the expander. Further, because of their transcritical nature of the CO 2 cycle, these systems are more sensitive to the refrigerant charge management than systems with conventional refrigerants.
• an expander capacity is adjusted by providing an intermediate pressure port in the expander. If it is desirable to pass more refrigerant through the expander, then a portion of the refrigerant flow from an expander inlet is diverted to the intermediate expansion port.
• the amount of refrigerant passing through the expander is controlled by appropriate sizing and/or adequate restriction placed in the bypass line.
• the flow of refrigerant in the bypass line is controlled by a flow control device such as a valve.
• this valve can be of an ON/OFF type, such as a solenoid valve.
• the valve can also be of 60,246-542; 1656 an adjustable restriction (modulation) type or of a pulsation type, for even more precise control of the refrigerant flow through the bypass line.
• a similar technique can be used if an expander consists of multiple expansion stages or expanders that are installed in series with each other. In this case, some of the refrigerant is diverted from the inlet of the upstream expansion stage into the inlet of the expansion stage located downstream. In other words, in this case, the refrigerant is injected between the expansion stages.
• the efficiency of the expansion process is improved by eliminating the direct "leak" path from a high pressure heat rejection heat exchanger to a low pressure evaporator, while maintaining the ability to provide precise control over the amount of refrigerant passing through the expander. Furthermore, due to additional work recovery obtained from the bypassed refrigerant and more efficient isentropic process, the refrigerant system's operational performance is improved.
• Figure 1 schematically shows a prior art refrigerant system.
• Figure 2 shows an inventive refrigerant system.
• FIG 3 shows another schematic of an inventive refrigerant system.
• FIG. 1 A prior art refrigerant system 20 is illustrated in Figure 1.
• a compressor 22 compresses a refrigerant and delivers it to a heat rejection heat exchanger 24, which is a condenser, for subcritical applications, and a gas cooler, for transcritical applications.
• a heat rejection heat exchanger 24 which is a condenser, for subcritical applications, and a gas cooler, for transcritical applications.
• the refrigerant expanding to a lower pressure and temperature, drives an expander 26.
• 26 is shown schematically and includes a moving member that is driven by the expanding fluid.
• the expansion work recovered by the expander may be utilized
• the expander can be connected to other system components, such as a compressor, a fan, or a pump, either directly through a coupling, a clutch, a gearbox, etc., or can be used to drive a generator to produce electric energy.
• the prior art refrigerant systems have utilized a bypass line 28 that routed at least a portion of the refrigerant from the outlet of the heat rejection heat exchanger 24 to the inlet of the evaporator 36, at operating conditions when the expander could not handle all of the expanding refrigerant flow.
• the present invention is shown in Figure 2 as a refrigerant system 50.
• the bypass inlet 32 leads to a bypass line 52.
• a restriction 54 can be positioned on the bypass line 52, and the point 56 terminates the bypass line 52 at an intermediate expansion point in the expander 26.
• the restriction 54 may be an ON/OFF, modulation or pulsation valve.
• the entire refrigerant still moves through and exits the expander 26.
• a portion of the refrigerant that bypasses through the valve 54 continues to undergo an expansion process from the intermediate expansion point 56 to the expander exit point 58.
• the present invention increases the efficiency and capacity of a refrigerant system by including a variable capacity expander, while at the same time, controlling the system operation to be in the optimum domain.
• the present invention can be extended to an expander consisting of several expansion stages, as for example, can be a case for a multi-stage turbine. It can also be extended to a system configuration of expanders installed in series with each other. In this case, as shown in Figure 3 for an embodiment 70, an intermediate expansion point 156 is located between the expansion stages (or independent expanders) 26 A and 26B.
• more than two expanders can be installed in series with the bypass line routed into the point between any stages. Further, more than one bypass line can be installed when more than two expansion stages are connected serially.
• bypass lines 52 there can be multiple bypass lines 52. As shown in Figure 3 embodiment, one bypass line 52 extends through the flow control valve 54 from a point 200 upstream of the first expansion stage 26A to an intermediate expansion point 202 within the same expansion stage 26A, while another bypass line 52, also incorporating the flow control valve 54, extends from a point 32 upstream of the first expansion stage 26 A to a point 156 intermediate of two expansion stages 26 A and 26B. Obviously, upstream points 32 and 200 can be combined into a single point.
• bypass valve 54 can be of a variable area type to provide condition dependant control of how much refrigerant is routed into the bypass line 52.
• the bypass valve 54 can also operate in a pulse width modulated manner, such that it is rapidly cycling between ON and OFF positions.
• the present invention is particularly well suited for use in refrigerant systems incorporating CO 2 as a refrigerant, where the benefits of using an expander are the most pronounced.
• expander and compressor types could be used in this invention.
• scroll, screw, rotary or reciprocating expanders and compressors can be employed. 60,246-542; 1656
• the refrigerant systems that utilize this invention can be used in many different applications, including, but not limited to, air conditioning systems, heat pump systems, marine container units, refrigeration truck-trailer units, and supermarket refrigeration systems.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
• Other Air-Conditioning Systems (AREA)

Applications Claiming Priority (1)

Publications (2)

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Citations (3)

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• 2007
  • 2007-03-16 CN CN2007800521986A patent/CN101636622B/zh not_active Expired - Fee Related
  • 2007-03-16 US US12/527,758 patent/US20100031677A1/en not_active Abandoned
  • 2007-03-16 EP EP07758650A patent/EP2142860A4/de not_active Withdrawn
  • 2007-03-16 WO PCT/US2007/064117 patent/WO2008115227A1/en active Application Filing
• 2010
  • 2010-07-21 HK HK10107054.6A patent/HK1140807A1/xx not_active IP Right Cessation

Patent Citations (3)

Non-Patent Citations (1)

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