CN113227678B - Cooling system - Google Patents

Cooling system Download PDF

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Publication number
CN113227678B
CN113227678B CN201980069677.1A CN201980069677A CN113227678B CN 113227678 B CN113227678 B CN 113227678B CN 201980069677 A CN201980069677 A CN 201980069677A CN 113227678 B CN113227678 B CN 113227678B
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Prior art keywords
conduit
outlet
inlet
evaporator
cooling system
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CN201980069677.1A
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CN113227678A (en
Inventor
莫滕·安德雷·恩根
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Asset Investment Co ltd
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Asset Investment Co ltd
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    • 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
    • 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
    • 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
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/39—Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same evaporator
    • 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
    • F25B41/40—Fluid line arrangements
    • 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
    • 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
    • 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
    • F25B2400/23—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
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2515—Flow valves
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/195—Pressures of the condenser
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/197—Pressures of the evaporator
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2116—Temperatures of a condenser
    • F25B2700/21163—Temperatures of a condenser of the refrigerant at the outlet of the condenser
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2117—Temperatures of an evaporator
    • F25B2700/21175—Temperatures of an evaporator of the refrigerant at the outlet of the evaporator
    • 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
    • F25B9/006—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant containing more than one component

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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)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)
  • Cooling Or The Like Of Electrical Apparatus (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
  • Air Conditioning Control Device (AREA)
  • Details Of Measuring And Other Instruments (AREA)

Abstract

The invention provides a cooling system (1), comprising a receiving tank (2), an evaporator (3), a compressor (4) and a gas cooler (5), wherein the receiving tank (2) comprises a fluid inlet (6), a liquid outlet (7) and a gas outlet (8); the evaporator (3) comprises an evaporator inlet (9) and an evaporator outlet (10), the compressor (4) comprising a compressor inlet (11) and a compressor outlet (12); the gas cooler (5) comprises a cooler inlet (13) and a cooler outlet (14); and the liquid outlet (7) of the receiving tank (2) is connected to the evaporator inlet (9) via a first conduit (15), the evaporator outlet (10) is connected to the compressor inlet (11) via a second conduit (16), the compressor outlet (12) is connected to the cooler inlet (13) via a third conduit (17), and the cooler outlet (14) is connected to the fluid inlet (6) of the receiving tank via a fourth conduit (18), wherein at least one of the first conduit (15) and the fourth conduit (18) comprises a pressure regulator (19, 25), and the gas outlet (8) of the receiving tank is connected to the evaporator inlet (9) via a fifth conduit (20) and a gas flow regulator (21, 22), such that during use the flow of liquid refrigerant in the first conduit (15) is controlled by operating the gas flow regulator (21, 22).

Description

Cooling system
Technical Field
The present invention relates to cooling systems, and more particularly to the use of CO 2 A direct expansion cooling system for a refrigerant medium.
Background
Direct expansion (DX) cooling systems are common refrigeration systems that use a vapor compression refrigeration cycle.
A common prior art DX cooling system is shown in fig. 1. In DX cooling systems, the pressure and temperature of the liquid refrigerant supplied to the evaporator 3 is typically controlled by using an expansion valve 25 (e.g., a regulating control valve or pressure regulator) disposed between the receiver tank 2 and the evaporator 3. When the refrigerant leaving the gas cooler 5 is transcritical, an additional expansion valve 19 is required between the gas cooler 5 and the receiving tank 2, ensuring a subcritical state in the receiving tank 2 to allow separation of the refrigerant into a gas phase and a liquid phase. In a transcritical DX cooling system, the refrigerant is in a subcritical state when leaving an expansion valve 19 arranged between the receiver tank and the gas cooler, and in a transcritical state when leaving the compressor 4. In the subcritical DX cooling system, the refrigerant is in a subcritical state throughout the system, and an expansion valve 19 arranged before the receiver tank 2 is not required.
In general, the capacity of the evaporator 3 is controlled by adjusting the action of the compressor 4 and the expansion valve 19 arranged between the gas cooler 5 and the receiving tank 2.
The DX cooling systems of the prior art have a number of drawbacks in controlling cooling capacity, especially when lower cooling capacity is required.
It is an object of the present invention to provide a DX cooling system that alleviates or eliminates at least some of the disadvantages of prior art cooling systems. More specifically, the present invention provides a DX cooling system having improved cooling capacity control, improved energy efficiency, and improved evaporator utilization.
Disclosure of Invention
The invention is defined by the appended claims and by the following:
in a first aspect, the present invention provides a cooling system comprising a receiving tank, an evaporator, a compressor and a gas cooler, wherein:
-the receiving tank comprises a fluid inlet, a liquid outlet and a gas outlet;
the evaporator comprises an evaporator inlet and an evaporator outlet,
-the compressor comprises a compressor inlet and a compressor outlet;
-the gas cooler comprises a cooler inlet and a cooler outlet; and is also provided with
The liquid outlet of the receiving tank is connected via a first conduit to the evaporator inlet, the evaporator outlet is connected via a second conduit to the compressor inlet, the compressor outlet is connected via a third conduit to the cooler inlet, and the cooler outlet is connected via a fourth conduit to the fluid inlet of the receiving tank, wherein:
at least one of the first conduit and the fourth conduit includes a pressure regulator, and
the gas outlet of the receiving tank is connected to the evaporator inlet via a fifth conduit and a gas flow regulator such that the flow of liquid refrigerant in the first conduit can be controlled during use by operating the gas flow regulator. That is, the flow of liquid refrigerant entering the evaporator inlet via the first conduit may be controlled during use by operating the gas flow regulator.
In other words, the gas outlet of the receiving tank is connected to the evaporator inlet via a fifth conduit and a gas flow regulator, such that during use a flow of gaseous refrigerant from the receiving tank may enter the evaporator.
The cooling system may operate as a transcritical cooling system or a subcritical cooling system. In a transcritical cooling system, the pressure and temperature conditions are set such that the refrigerant is transcritical in the gas cooler and subcritical in the receiver tank. In a subcritical cooling system, the refrigerant will be subcritical throughout the cooling system. In subcritical cooling systems, the gas cooler may also be referred to as a gas condenser.
The gas flow regulator may be defined as a regulating gas control valve. The pressure regulator may be a regulating fluid control valve. In transcritical cooling systems, the pressure regulator may also be referred to as a regulating high pressure control valve.
In one embodiment, the cooler outlet is connected to the fluid inlet of the receiving tank via a fourth conduit and a pressure regulator.
In an embodiment of the cooling system, the gas flow regulator is arranged such that decreasing the flow of gaseous refrigerant in the fifth conduit by operating the gas flow regulator will increase the flow of liquid refrigerant in the first conduit. In other words, decreasing the flow of gaseous refrigerant in the fifth conduit by operating the gas flow regulator will increase the pressure in the receiving tank, thereby increasing the flow of liquid refrigerant in the first conduit.
In an embodiment of the cooling system, the gas outlet of the receiving tank is connected to the evaporator inlet via a fifth conduit and a gas flow regulator such that during use a mixture of gaseous refrigerant from the fifth conduit and liquid refrigerant from the first conduit may enter the evaporator inlet.
In one embodiment of the cooling system, the fifth conduit comprises a first end connected to the gas outlet of the receiving tank and a second end connected to the first conduit such that during use, gaseous refrigerant from the gas outlet of the receiving tank and liquid refrigerant from the liquid outlet of the receiving tank may be mixed prior to entering the evaporator inlet.
In an embodiment of the cooling system, the liquid outlet of the receiving tank is arranged such that during use an increased pressure of the gaseous refrigerant in the receiving tank will force liquid out of the receiving tank via the liquid outlet.
In one embodiment of the cooling system, the first conduit and the fifth conduit are connected to the evaporator inlet via a sixth conduit.
In one embodiment of the cooling system, the fifth conduit is connected to the evaporator inlet via the first conduit.
In one embodiment of the cooling system, the sixth conduit has an internal cross-sectional area that is greater than the cross-sectional area of the first conduit.
In one embodiment of the cooling system, the gas flow regulator is a two-way valve. The two-way valve may be a regulating control valve.
In an embodiment of the cooling system, the two-way valve is arranged in or forms part of the fifth conduit.
In an embodiment of the cooling system, the first conduit, the fifth conduit and the sixth conduit are interconnected by a three-way coupling featuring a first inlet connected to the fifth conduit, a second inlet connected to the first conduit and an outlet connected to the evaporator inlet or the sixth conduit, wherein the second inlet is arranged at an angle with respect to the outlet such that during use the spraying of the gaseous refrigerant flow from the fifth conduit onto the liquid refrigerant in the first conduit is minimized. The angle may be about 90 °.
In one embodiment of the cooling system, the gas flow regulator is a three-way valve. The three-way valve may be a regulating control valve.
In one embodiment of the cooling system, the three-way valve comprises a first inlet connected to the first conduit, a second inlet connected to the fifth conduit and an outlet connected to the evaporator inlet or the sixth conduit.
In one embodiment, the cooling system includes a first pressure sensor and a first temperature sensor disposed in a second conduit, and a second pressure sensor and a second temperature sensor disposed in a fourth conduit. The second pressure sensor and the second temperature sensor may be arranged in the fourth conduit upstream of the pressure regulator in the fourth conduit.
In one embodiment of the cooling system, the second pressure sensor and the second temperature sensor may be replaced by pressure transmitters. In embodiments featuring pressure transmitters, the cooling system may be a subcritical cooling system. The pressure transmitter may be connected to any one of a gas cooler/condenser fan and a gas cooler/condenser pump.
In a second aspect, the present invention provides a method of controlling a cooling system, wherein the cooling system comprises a receiving tank, an evaporator, a compressor and a gas cooler, wherein:
the receiving tank comprises a fluid inlet, a liquid outlet and a gas outlet;
the evaporator comprises an evaporator inlet and an evaporator outlet,
the compressor includes a compressor inlet and a compressor outlet;
the gas cooler comprises a cooler inlet and a cooler outlet; and is also provided with
The liquid outlet of the receiving tank is connected via a first conduit to the evaporator inlet, the evaporator outlet is connected via a second conduit to the compressor inlet, the compressor outlet is connected via a third conduit to the cooler inlet, and the cooler outlet is connected via a fourth conduit to the fluid inlet of the receiving tank, wherein:
at least one of the first conduit and the fourth conduit includes a pressure regulator, and
the gas outlet of the receiving tank is connected to the evaporator inlet via a fifth conduit and a gas flow regulator, and the method comprises the steps of:
-increasing the flow of gaseous refrigerant in the fifth conduit by controlling the gas flow regulator such that the flow of liquid refrigerant in the first conduit is reduced and the cooling capacity in the evaporator (3) is reduced; or alternatively
-reducing the flow of gaseous refrigerant in the fifth conduit (20) by controlling the gas flow regulator (21, 22) such that the flow of liquid refrigerant in the first conduit (15) increases and the cooling capacity in the evaporator (3) increases.
The step of increasing the flow of gaseous refrigerant causes a decrease in the flow of liquid refrigerant in the first conduit by decreasing the pressure of the gaseous refrigerant in the receiver tank.
The step of reducing the flow of gaseous refrigerant increases the flow of liquid refrigerant in the first conduit by increasing the pressure of the gaseous refrigerant in the receiver tank.
The method of the second aspect may also be referred to as a method of adjusting the cooling capacity of a cooling system.
In an embodiment of the method according to the second aspect, the fourth conduit comprises a pressure regulator, and the step of increasing the flow of gaseous refrigerant comprises the step of controlling the pressure regulator to reduce the pressure drop between the cooler outlet and the fluid inlet of the receiving tank. In other words, the step of increasing the flow of gaseous refrigerant includes controlling the pressure regulator to increase the flow of refrigerant from the gas cooler to the receiving tank.
In an embodiment of the method according to the second aspect, the first conduit comprises a pressure regulator, and the step of increasing the flow of gaseous refrigerant comprises controlling the pressure regulator to increase the pressure drop over the first conduit.
In one embodiment, the method according to the second aspect comprises the initial steps of:
-measuring the temperature of the refrigerant in the second conduit to obtain a temperature difference profile with respect to the boiling temperature of the liquid refrigerant in the evaporator; and increasing or decreasing the flow of gaseous refrigerant in the fifth conduit depending on whether the temperature difference curve shows a decreasing temperature difference or an increasing temperature difference, respectively.
In a third aspect, the present invention provides a method of controlling a transcritical cooling system, wherein the cooling system comprises a receiving tank, an evaporator, a compressor, and a gas cooler, wherein:
the receiving tank comprises a fluid inlet, a liquid outlet and a gas outlet;
the evaporator comprises an evaporator inlet and an evaporator outlet;
the compressor includes a compressor inlet and a compressor outlet;
the gas cooler comprises a cooler inlet and a cooler outlet; and is also provided with
The liquid outlet of the receiving tank is connected via a first conduit to the evaporator inlet, the evaporator outlet is connected via a second conduit to the compressor inlet, the compressor outlet is connected via a third conduit to the cooler inlet, and the cooler outlet is connected via a fourth conduit and a pressure regulator to the fluid inlet of the receiving tank, wherein:
the gas outlet of the receiving tank is connected to the evaporator inlet via a fifth conduit and a gas flow regulator, and the method comprises the steps of:
-increasing the flow of gaseous refrigerant in the fifth conduit by controlling the pressure regulator to reduce the pressure drop between the cooler outlet and the fluid inlet of the receiving tank; or alternatively
-reducing the flow of gaseous refrigerant in the fifth conduit (20) by controlling the pressure regulator to increase the pressure drop between the cooler outlet and the fluid inlet of the receiving tank.
In other words, the flow of refrigerant to the receiver tank is increased or decreased by controlling the pressure regulator to reduce or increase the pressure drop between the cooler outlet and the fluid inlet of the receiver tank, and correspondingly also to increase or decrease the pressure in the gaseous refrigerant in the receiver tank.
The cooling system according to the method of the second and third aspects may comprise any feature of the cooling system according to the first aspect.
In an embodiment of any aspect of the invention, the cooling system is a direct expansion cooling system, preferably for CO as a refrigerant 2 Is expanded directly. When CO is to be treated 2 When used as a refrigerant, the cooling system operates in a transcritical condition, and the fourth conduit includes a pressure regulator.
The term "evaporator inlet" is intended to mean the inlet through which refrigerant must enter the heat transfer area of the evaporator. The evaporator inlet may be an internally arranged inlet of the evaporator unit to which the first and second conduits are connected or an external inlet to which the sixth conduit is connected.
Drawings
The invention is described in detail below, by way of example only, with reference to the following drawings:
fig. 1 is a schematic diagram of a DX cooling system of the prior art.
Fig. 2 is a schematic view of a first exemplary embodiment of a cooling system according to the present invention.
Fig. 3 is a schematic view of a second exemplary embodiment of a cooling system according to the present invention.
Fig. 4 is a schematic view of a third exemplary embodiment of a cooling system according to the present invention.
Fig. 5 is a schematic view of a fourth exemplary embodiment of a cooling system according to the present invention.
Detailed Description
The present invention provides a highly advantageous DX cooling system in which the cooling capacity of the evaporator can be adjusted/controlled in an improved manner. A particularly preferred refrigerant for the cooling system of the present invention is CO 2 . Corresponding or similar features of the cooling system shown in fig. 1-5 are denoted by the same reference numerals.
Fig. 2 shows a first exemplary cooling system according to the present invention. The cooling system is characterized by having a receiving tank 2, an evaporator 3, a compressor 4 and a gas cooler 5. The receiving tank 2 has a fluid inlet 6, a liquid outlet 7 and a gas outlet 8. The evaporator 3 has an evaporator inlet 9 and an evaporator outlet 10. The compressor 4 has a compressor inlet 11 and a compressor outlet 12, and the gas cooler 5 has a cooler inlet 13 and a cooler outlet 14.
The liquid outlet 7 of the receiving tank 2 is connected via a first conduit 15 to the evaporator inlet 9, the evaporator outlet 10 is connected via a second conduit 16 to the compressor inlet 11, the compressor outlet 12 is connected via a third conduit 17 to the cooler inlet 13, and the cooler outlet 14 is connected via a fourth conduit 18 and a pressure regulator 19 to the fluid inlet 6 of the receiving tank.
When the cooling system is a transcritical system, the refrigerant of the cooling system will be in a transcritical state between the compressor outlet 12 and the pressure regulator 19. The pressure regulator 19 is a regulating control valve arranged to reduce the pressure of the transcritical refrigerant flow leaving the gas cooler 5. In this way, the refrigerant will attain a subcritical state and separate into a gas phase and a liquid phase in the receiving tank 2. The cooling system can also be operated in subcritical conditions throughout the cooling system. The function of the pressure regulator 19 is to optimise the heat dissipation in the gas cooler relative to the rest of the cooling system by regulating the high pressure in the gas cooler. In addition, the pressure regulator 19 ensures that the refrigerant in the receiver tank 2 is subcritical. The receiver tank acts as a refrigerant buffer, which is necessary because the amount of refrigerant in the gas cooler 5 and the evaporator 3 will vary.
The gas outlet 8 of the receiving tank is connected to the evaporator inlet 9 via a fifth conduit 20 and a two-way gas valve 21 (i.e. a gas flow regulator). In this way, the pressure in the receiver tank 2, and thus the flow rate of the liquid refrigerant in the first conduit 15, can be controlled/adjusted by operating the vent valve 21.
A significant advantage of using the two-way gas valve 21 to control the flow of liquid refrigerant to the evaporator 2 (optionally in combination with the control of the pressure regulator 19) is that the cooling system can be operated at higher evaporation temperatures and pressures than in the prior art. In this way, the suction pressure (i.e. the pressure on the suction side of the compressor) is maintained, while the high pressure side (i.e. the part of the cooling system between the compressor outlet and the pressure regulator 19) may have a lower pressure.
In addition to providing improved refrigerant flow control, the cooling system of the present invention also ensures optimal energy efficiency because the refrigerant gas in the receiver tank 2 is used as the refrigerant in the evaporator 3. The gaseous refrigerant provides a small additional cooling effect of about 2-5%, which is not possible with prior art cooling systems.
Turbulence caused by mixing the liquid and gaseous refrigerant prior to entering the evaporator 3 provides for an optimal distribution of the refrigerant in the evaporator and an optimal use of the heat transfer area of the evaporator 3. Particularly at lower cooling capacities (i.e. low flow rates of liquid refrigerant to the evaporator 3), turbulence provides a significant advantage over prior art systems. In prior art systems, the lower cooling capacity generally results in uneven distribution of the liquid refrigerant, which in turn reduces the evaporation temperature and pressure. The reduced evaporation temperature may cause problems, as this may result in the temperature of the outside of the evaporator being too low for its intended use, for example, it may freeze the goods to be cooled.
In order to minimize any jet effect (ejector-effect) of the gas flow in the fifth conduit 20 on the liquid refrigerant in the first conduit 15, the fifth conduit and the first conduit are connected at an angle α of about 90 °. The combined refrigerant flow is connected to the evaporator 3 via a common conduit 23 (i.e. a sixth conduit). To further optimize the cooling system, the fifth conduit 20 and the first conduit 15 are connected to a mixing chamber 26 to obtain an optimal mixing of the gaseous refrigerant and the liquid refrigerant before entering the evaporator. In this embodiment, the mixing chamber 26 is a tee connection having a cross-sectional area that is greater than the cross-sectional area of the first conduit 15. The difference in cross-sectional area creates a slight pressure drop in the liquid refrigerant to ensure optimal evaporation conditions in the evaporator. In embodiments featuring no mixing chamber, a slight pressure drop may be obtained by ensuring that the cross-sectional area of the common conduit is greater than the cross-sectional area of the first conduit. It is noted that it is not essential to use a dedicated arrangement or device to obtain a slight pressure drop in the refrigerant before it enters the evaporator. Depending on the operating conditions, a slight pressure drop caused by the flow resistance in the first conduit and/or the common conduit may be sufficient.
In view of the prior art, the cooling system according to the invention is also more cost-effective, since there is no need to arrange an expansion valve between the liquid outlet 7 and the evaporator 3. Expansion valves are expensive and represent a significant percentage of the total cost of the system.
The condition of the refrigerant in the cooling system is monitored by a pressure sensor 27a and a temperature sensor 28a arranged near the evaporator outlet 10 and a pressure sensor 27b and a temperature sensor 28b arranged between the cooler outlet 14 and the pressure regulator 19.
The cooling system may feature a control system that can control the pressure regulator 19 and the two-way gas valve 21 based on inputs from the pressure sensors 27a, b, the temperature sensors 28a, b and any optional external temperature data.
The cooling system can be controlled by measuring the temperature of the refrigerant in the second conduit 16 to obtain a temperature difference profile with respect to the boiling temperature of the liquid refrigerant in the evaporator 3. Depending on whether the temperature difference curve shows a decreasing or increasing temperature difference, the flow of gaseous refrigerant in the fifth conduit 20 may be increased or decreased by adjusting the two-way gas valve and/or the pressure regulator 19, and the flow of liquid refrigerant may be decreased or increased accordingly. In the DX cooling system of the prior art, when the temperature difference curve increases (i.e. the temperature difference curve shows an increased superheat of the refrigerant), the flow of liquid refrigerant also increases, while when the temperature difference curve decreases, the flow of liquid refrigerant also decreases, but the flow of gaseous refrigerant into the evaporator may not be controlled.
The evaporator 3 may be used to cool any suitable external medium, such as air or liquid. Similarly, any suitable external medium may be used to obtain the desired cooling effect in the gas cooler 5.
Depending on the type of refrigerant, the operating conditions may vary over a wide range of temperatures and pressures. Suitable operating conditions will be apparent to those skilled in the art based on this disclosure.
Fig. 3 shows a second exemplary cooling system according to the present invention. The second exemplary cooling system is substantially similar to the cooling system of fig. 2 and provides the same advantages as described above. A second exemplary cooling system is characterized by a second regulating control valve 25 in the first conduit 15. The second control valve is not essential for controlling the cooling system, but may provide an additional control strategy, since the pressure and temperature of the liquid refrigerant may be controlled before mixing with the gaseous refrigerant from the fifth conduit. In addition, the second regulating control valve 25 may be used to prevent condensation of refrigerant in the evaporator when the cooling system is shut down.
Fig. 4 shows a third exemplary cooling system according to the present invention. The third exemplary cooling system functions substantially similar to the cooling system of fig. 3 and provides the same advantages as described above. However, in the third exemplary cooling system, the two-way gas valve 21 and the second regulation control valve 25 in fig. 3 are replaced by a single three-way control valve.
Fig. 5 shows a fourth exemplary cooling system according to the present invention. Most of the features of the cooling system are similar to those shown in fig. 3, except that the pressure regulator 19 has been removed and the second pressure sensor and the second temperature sensor have been replaced with a pressure transmitter 29. The cooling system is adapted to be used with a refrigerant having a subcritical state in the entire cooling system, and therefore, the pressure regulator 19 shown in fig. 2 to 4 is not required to reduce the pressure of the refrigerant before the refrigerant enters the receiver tank 2. Further, the pressure transmitter 29 may be arranged to control a gas cooler (or gas condenser) valve or pump to adjust the cooling capacity of the gas cooler. The required pressure drop in the liquid refrigerant may be provided by a second regulating control valve 25 (i.e., pressure regulator) or any suitable expansion valve/device. The cooling system may be controlled as described for the cooling system in fig. 2 and 3 by adjusting the air flow in the fifth conduit 20 using the two-way air valve 21 and optionally by using the second regulating control valve 25.

Claims (15)

1. A cooling system (1) comprising a receiving tank (2), an evaporator (3), a compressor (4) and a gas cooler (5), wherein:
-the receiving tank (2) comprises a fluid inlet (6), a liquid outlet (7) and a gas outlet (8);
-the evaporator (3) comprises an evaporator inlet (9) and an evaporator outlet (10);
-the compressor (4) comprises a compressor inlet (11) and a compressor outlet (12);
-the gas cooler (5) comprises a cooler inlet (13) and a cooler outlet (14); and is also provided with
The liquid outlet (7) of the receiving tank (2) is connected to the evaporator inlet (9) via a first conduit (15), the evaporator outlet (10) is connected to the compressor inlet (11) via a second conduit (16), the compressor outlet (12) is connected to the cooler inlet (13) via a third conduit (17), and the cooler outlet (14) is connected to the fluid inlet (6) of the receiving tank via a fourth conduit (18), wherein at least one of the first conduit (15) and the fourth conduit (18) comprises a pressure regulator (19, 25), and
the gas outlet (8) of the receiving tank is connected to the evaporator inlet (9) via a fifth conduit (20) and a gas flow regulator, so that the flow of liquid refrigerant in the first conduit (15) can be controlled during use by operating the gas flow regulator,
and wherein the second conduit (16) comprises a temperature sensor arranged to measure the temperature of the refrigerant in the second conduit (16), which temperature sensor is in communication with the gas flow regulator such that the cooling capacity of the evaporator can be adjusted during use by increasing or decreasing the flow of gaseous refrigerant in the fifth conduit (20).
2. The cooling system of claim 1, wherein the temperature sensor is in communication with the gas flow regulator via a control system.
3. A cooling system according to claim 1 or 2, wherein the gas flow regulator is arranged such that decreasing the flow of gaseous refrigerant in the fifth conduit (20) by operating the gas flow regulator will increase the flow of liquid refrigerant in the first conduit (15).
4. A cooling system according to claim 1 or 2, wherein the gas outlet (8) of the receiving tank is connected to the evaporator inlet (9) via the fifth conduit (20) and the gas flow regulator such that, during use, a mixture of gaseous refrigerant from the fifth conduit (20) and liquid refrigerant from the first conduit (15) can enter the evaporator inlet (9).
5. A cooling system according to claim 1 or 2, wherein the fifth conduit (20) comprises a first end connected to the gas outlet (8) of the receiving tank and a second end connected to the first conduit (15) such that during use gaseous refrigerant from the gas outlet (8) of the receiving tank and liquid refrigerant from the liquid outlet (7) of the receiving tank can mix before entering the evaporator inlet (9).
6. A cooling system according to claim 1 or 2, wherein the first and fifth conduits are connected to the evaporator inlet via a sixth conduit (23).
7. A cooling system according to claim 1 or 2, wherein the gas flow regulator is a two-way valve (21).
8. The cooling system according to claim 1 or 2, wherein the first conduit, the fifth conduit and the evaporator inlet (9) are interconnected by a three-way coupling (24) having a first inlet connected to the fifth conduit (20), a second inlet connected to the first conduit (15) and an outlet connected to the evaporator inlet (9), wherein the second inlet is arranged at an angle (α) with respect to the outlet such that during use the jetting effect of the gaseous refrigerant flow from the fifth conduit (20) on the liquid refrigerant in the first conduit (15) is minimized.
9. A cooling system according to claim 8, wherein the angle (a) is 90 °.
10. The cooling system according to claim 1 or 2, wherein the gas flow regulator is a three-way valve (22).
11. The cooling system according to claim 10, wherein the three-way valve (22) comprises a first inlet connected to the first conduit (15), a second inlet connected to the fifth conduit (20) and an outlet connected to the evaporator inlet (9).
12. The cooling system according to claim 1 or 2, comprising: -a first pressure sensor (27 a) and a first temperature sensor (28 a) arranged in the second conduit (16); and
a second pressure sensor (27 b) and a second temperature sensor (28 b) arranged in the fourth conduit upstream of the pressure regulator (19, 25), or a pressure transmitter (29) arranged in the fourth conduit upstream of the pressure regulator (19, 25).
13. A method of controlling a cooling system, wherein the cooling system comprises a receiving tank (2), an evaporator (3), a compressor (4) and a gas cooler (5), wherein:
the receiving tank (2) comprises a fluid inlet (6), a liquid outlet (7) and a gas outlet (8);
the evaporator (3) comprises an evaporator inlet (9) and an evaporator outlet (10);
the compressor (4) comprises a compressor inlet (11) and a compressor outlet (12);
the gas cooler (5) comprises a cooler inlet (13) and a cooler outlet (14); and is also provided with
The liquid outlet (7) of the receiving tank (2) is connected to the evaporator inlet (9) via a first conduit (15), the evaporator outlet (10) is connected to the compressor inlet (11) via a second conduit (16), the compressor outlet (12) is connected to the cooler inlet (13) via a third conduit (17), and the cooler outlet (14) is connected to the fluid inlet (6) of the receiving tank via a fourth conduit (18), wherein at least one of the first conduit (15) and the fourth conduit (18) comprises a pressure regulator (19, 25), and
the gas outlet (8) of the receiving tank is connected to the evaporator inlet (9) via a fifth conduit (20) and a gas flow regulator, and the method comprises the steps of:
-measuring the temperature of the refrigerant in the second conduit (16) to obtain a temperature difference profile with respect to the boiling temperature of the liquid refrigerant in the evaporator (3); and
-when the temperature difference curve shows a decreasing temperature difference, increasing the flow of gaseous refrigerant in the fifth conduit (20) by controlling the gas flow regulator such that the flow of liquid refrigerant in the first conduit (15) decreases and the cooling capacity in the evaporator (3) decreases; or alternatively
-when the temperature difference curve shows an elevated temperature difference, reducing the flow of gaseous refrigerant in the fifth conduit (20) by controlling the gas flow regulator such that the flow of liquid refrigerant in the first conduit (15) is increased and the cooling capacity in the evaporator (3) is increased.
14. The method according to claim 13, wherein the fourth conduit (18) comprises a pressure regulator (19), and the step of increasing the flow of gaseous refrigerant comprises controlling the pressure regulator (19) to reduce the pressure drop between the cooler outlet (14) and the fluid inlet (6) of the receiving tank (2).
15. The method of claim 13, wherein the first conduit (15) comprises a pressure regulator (25), and the step of increasing the flow of gaseous refrigerant comprises controlling the pressure regulator (25) to increase the pressure drop across the first conduit (15).
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