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
  • F25B40/00—Subcoolers, desuperheaters or superheaters
• • 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
  • 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
  • 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
  • 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
  • F25B2600/2509—Economiser 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
  • F25B2700/04—Refrigerant level

Definitions

• the present invention refers to a refrigeration system by mechanical compression of vapor in which the compressor draws refrigerant fluid through a circuit with at least two suction pressure stages.
• the present refrigeration system can be applied to any type of refrigerant fluid, such as, for example, those containing carbon in their constitution.
• the refrigeration systems by mechanical compression of vapor are based on the principle of refrigeration obtained by evaporation of a volatile fluid when submitted to a pressure reduction and are used in most modern applications, since their conception (Gosney; W. B., 1982, Principles of Refrigeration, Cambridge University Press) , even with the existence of several other principles of refrigeration, such as: thermoelectric, Stirling, electro-caloric, and the like.
• the initial development of the refrigeration systems aimed at obtaining safe (non-toxic and non- inflammable) refrigerant fluids, and at adapting their reliability and operational characteristics for general use, as is the case of the household hermetic refrigeration systems initially available around 1930 (Nagengast; B.
• the refrigerant fluid comprises, in the evaporator inlet, a vapor part which is small in mass but large in volume, and a liquid part which is small in volume and large in mass.
• This vapor which is present in the evaporator inlet during the expansion process, upon passing through said evaporator, does not effect heat exchange, reducing heat transfer efficiency and thus generating a certain inefficiency of the refrigeration system, since the compressor consumes energy to move this refrigerant fluid along the whole evaporator and, afterwards, to compress it, without said refrigerant fluid in vapor form carrying out heat exchange.
• the compressor therefore, consumes energy to compress this vapor, from the low pressure to the discharge pressure.
• the refrigerant fluid in vapor form in the evaporator inlet actuates as a vapor fraction to be continuously drawn and pumped, without producing refrigeration capacity, but with energy consumption in the compressor.
• this energetic loss is minimized through a refrigeration system using a vapor separator in the refrigeration circuit to effect extraction of this vapor, so as to provide, to the circuit, a more efficient expansion process of refrigerant fluid by stages.
• Windhausen refrigeration system (Windhausen; F., 1901, "Improvements in carbonic anhydride refrigerating machine” British Patent GB9084 of 1901)
• Windhausen F., 1901, "Improvements in carbonic anhydride refrigerating machine” British Patent GB9084 of 1901
• considerably improves the energetic efficiency of the refrigeration cycle mainly for applications with great temperature difference (higher than 60 0 C) between hot and cold environments, specially for some refrigerant fluids as carbon dioxide and ammonia
• a first compressor 10 presenting an inlet 11 and an outlet 12 of refrigerant fluid in vapor form, has its outlet 12 connected, by a first vapor duct 20, to a condenser 30 (gas cooler) .
• the condenser 30 presents a vapor inlet 31 connected to the outlet 12 of the compressor 10 and a liquid outlet 32 connected, through an expansion device 120, particularly a high-expansion device 121 in the form of a valve, by a condensate duct 60, to a first inlet 51 of a separating means 50 (expansion or flash vapor separator) .
• the separating means 50 further presents: a second vapor inlet 52 connected, by a duct 70 where is mounted the second compressor 10 ', to an evaporator 90 operatively associated with a medium M to be cooled; a vapor outlet 53 connected to the inlet 11 of the compressor 10, through a second vapor duct 40; and a liquid outlet 54 connected, by a liquid duct 80, to an inlet of an expansion device 120, particularly a low-expansion device 122 in the form of a valve connected to the evaporator 90.
• the evaporator 90 presents a vapor-liquid mixture inlet 91 connected, through the liquid duct 80, to the high- expansion device 121 and a vapor-liquid mixture outlet 92 connected, through the duct 70, to the second inlet 52 of the separating means 50, through the second compressor 10' .
• Such expansion devices 120 can have the form of a fixed restriction orifice, such as a capillary tube or a restricting valve, of variable flow or not, such as an electronic control valve commanded by a control unit, so as to vary the degree of restriction of the refrigerant fluid flow, in the refrigeration circuit .
• the compressor starts the suction from the evaporator and, in a determined stage of the suction stroke, the motion of the piston opens an orifice provided in the compressor and which allows the vapor, in an intermediary pressure between the suction and discharge pressures, to be injected into the cylinder, so that the start of the compression process occurs at a pressure higher than the evaporation pressure.
• Another known refrigeration solution using a double-stage pressure cycle (Plank; R., 1912, technically manipulate an Kompressionskaltemaschinen, besides fur Ka.ltetra.ger mit tiefer Bayer Temperatur, German Patent DE278095) uses a pumping stage close to the expansion valve. The last step of cooling the compressed fluid reduces substantially the enthalpy before the expansion, thus increasing the refrigeration capacity. Due to the high refrigerant density in the second stage of compression
• the refrigerant fluid in vapor state which is present in the refrigeration circuit is also conducted to the compressor suction, but at an intermediary pressure between the suction and discharge pressures, being drawn by the compressor jointly with the refrigerant fluid in the vapor form and at a low pressure .
• these known refrigeration systems of multiple pressure stages reduce the energetic losses in relation to the conventional refrigeration systems, they require a complex and frequently costly construction, due to the need of a differentiated compression for the low-pressure vapor and for vapor at a higher pressure, requiring either duplicating the compressor quantity, in a single body or not, or the provision of elements in the refrigeration circuit which can change the pressure of the vapor which is present in the circuit and to be pumped jointly with the low-pressure vapor.
• the amount of refrigerant fluid in the form of expansion vapor (or flash vapor) is reduced and its pressure is raised when the compressor pumps it from the evaporation pressure level in the evaporator outlet to the discharge pressure of the compressor, thus reaching a higher energetic efficiency of the compressor.
• Another object of the present invention is to provide a system such as cited above and which need not change the characteristics of neither the compressor nor the evaporator of the refrigeration system.
• An additional object of the present invention is to provide a system of the type cited above and which allows obtaining a considerable improvement in the thermal yield of the refrigeration system and cost reduction, particularly in the case of refrigerant fluids as the CO 2 .
• a refrigeration system comprising: a compressor having an inlet and an outlet of refrigerant fluid in vapor form; a condenser (or “gas cooler") having a vapor inlet connected to the outlet of the compressor and a liquid outlet; a high expansion device having an inlet connected to the liquid outlet of the condenser and an outlet; a separating means having a first inlet connected to the liquid outlet of the condenser and a vapor outlet connected to the inlet of the compressor, and a liquid outlet; a low expansion device having an inlet connected to the liquid outlet of the separating means and an outlet; an evaporator having a vapor-liquid mixture inlet receiving refrigerant fluid from the separating means through the low-expansion device outlet and a vapor- liquid mixture outlet; a selecting valve having: a first vapor inlet connected with the vapor-liquid mixture outlet of the evaporator; a second vapor inlet connected to the vapor outlet
• the construction proposed by the present invention allows not only separating the vapor inside the separating means, making only the liquid refrigerant fluid be directed to the evaporator, but also allowing the vapor contained in the interior of the separating means to be selectively drawn by the compressor, in a respective operational condition of the selecting valve and at an intermediary pressure which is higher than that reigning in the evaporator outlet and lower than that of the discharge pressure of the compressor, requiring less energy consumption to return this gaseous part of the refrigerant fluid to the high-pressure side of the refrigeration circuit.
• Figure 1 schematically represents a prior art refrigeration system presenting a double-stage suction with two compressors
• Figure 2 schematically represents a refrigeration system constructed according to the present invention
• FIG 3 schematically represents another construction for the refrigeration system of the present invention, but presenting controls of higher level.
• Description of the Illustrated Embodiments The present invention will be described for a refrigeration system of the type which operates by double-stage mechanical compression of vapor, said refrigeration system comprising, as illustrated in figures 2 and 3 : a single compressor 10 presenting an inlet 11 and an outlet 12 of refrigerant fluid in the vapor form, said outlet 12 being connected to the condenser 30, as already previously described for the refrigeration system illustrated in figure 1.
• the liquid outlet 32 of the condenser 30 is connected, through the condensate duct 60, to an inlet of the high- expansion device 121, which presents an outlet connected to the first inlet 51 of the separating means 50.
• the separating means 50 in the construction of the present invention illustrated in figures 2 and 3, does not present the second inlet 52 which, in the prior art, connects the evaporator 90 to said separating means 50, as described below.
• the refrigeration system further comprises a selecting valve 100 (or sequence deviation valve) having: a first vapor inlet 101 connected with the vapor-liquid mixture outlet 92 of the evaporator 90; a second vapor inlet 102 connected to the vapor outlet 53 of the separating means 50; and a vapor outlet 103 connected to the vapor inlet 11 of the compressor 10, through the second vapor duct 40, said selecting valve 100 maintaining the refrigerant fluid in the second vapor inlet 102 of the selecting valve 100 and in the interior of the separating means 50 at a first suction pressure, superior to a second suction pressure reigning in the first vapor inlet 101 of the selecting valve 100 and in the vapor-liquid mixture outlet 92 of the evaporator 90, and being operated to selectively and alternatingly communicate its first and second vapor inlets 101, 102 with its vapor outlet 103, so as to allow the compressor 10 to draw refrigerant vapor from the separating means 50, at said first suction pressure, and refrigerant vapor
• the assembly defined by the separating means 50 and the selecting valve 100 defines a double-stage emulator (said assembly being illustrated in dashed line in figures 2 and 3) .
• the operation of the selecting valve 100 alternating the connection of its first and second vapor inlets to the suction of the compressor 10, is carried out in communication or commutation periods of time, for each said connection, proportional to the refrigeration system capacity or size, so that the smaller refrigeration systems will have a faster switching, whilst in greater refrigeration systems this switching is slower.
• the selecting valve 100 further presents the functions of: reducing the supply of vapor in the evaporator 90, through the liquid outlet 54 of the separating means 50; and allowing the vapor drawn by the compressor 10 and which is coming from the separating means 50 to be compressed at a compression rate, that is, at a ratio between the pressure reigning in the inlet 11 of the compressor 10 and the pressure reigning in the outlet 12 of said compressor 10, i.e., at a compression rate much smaller than that when the vapor is drawn from the evaporator 90, spending less energy.
• the switching of communication between the suction from the evaporator 90 and the suction from the separating means 50 to the vapor inlet 11 of the compressor 10, through the selecting valve 100 can be carried out by command of the control unit 110, in a predetermined and constant form, for example, as a function of the pre-established communication (or switching) time intervals, making the control easy to be implemented at a low cost .
• An example of these systems is illustrated in figure 2.
• the control unit 110 commands the operation of the selecting valve 100 from fixed communication time intervals between each one of the first and second vapor inlets 101, 102 and the vapor outlet 103 of the selecting valve 100, the communication time of the first vapor inlet 101 with the vapor outlet 103 being inferior to the communication time of the second vapor inlet 102 with said vapor outlet 103 of the selecting valve 100.
• the control unit 110 comprises a timer which determines the communication times between each of the first and second vapor inlets 101, 102 of the selecting valve 100 with the vapor outlet 103 of the latter.
• the communication time between the first and the second vapor inlets 101, 102 of the selecting valve 100 with the outlet de vapor 103 of the latter is constant and previously defined from the constructive characteristics of the refrigeration system, such as refrigerating capacity and thermal load, simplifying the command circuit and reducing the component costs .
• control unit 110 considers at least one variable parameter existing in the refrigeration system and/or also the refrigeration conditions of the medium to be cooled and to which said refrigeration system is coupled.
• control unit 110 commands the operation of the selecting valve 100 from variable communication times alternated between each of the first and second vapor inlets 101, 102 and the vapor outlet 103 of said selecting valve 100, said communication times being defined from at least one operational condition associated with the components of the refrigeration system and/or with the environment external to the latter.
• the present refrigeration system comprises a level sensor 111 ⁇
• level sensor 111 being capable of detecting predetermined maximum and minimum values of the liquid refrigerant fluid level in the interior of the separating means 50. It should be observed that the provision of a level sensor 111 is not compulsory, such provision being a constructive option in case the operation of the selecting valve 100 occurs as a function of variable parameters controlled by the control unit 110, such as in the construction of figure 3.
• the control unit 110 can command the operation of the selecting valve 100 based on the information received from said level sensor 111, which operates as a safety means of the refrigeration system.
• the present invention can present different levels of sophistication for the control unit 110, which are: as illustrated by figure 2, the commutation times can be fixed; or by monitoring the liquid level in the separating means 50 and other parameters of the refrigeration system, or also of the environment associated therewith (pressure, vapor and/or liquid amount in the separating means 50, temperature in the medium M to be cooled, temperature of the environment in which the condenser 30 and the compressor 10 are physically placed, temperature thereof, compressor motor operating frequency, etc.), as illustrated in figure 3.
• the control unit 110 will command the selective switching of the first and second vapor inlets 101, 102 of the selecting valve 100, as a function of determined values previously established as reference for the control parameters to be considered.
• control unit 110 operates with more than one variable to determine the commutation times of the vapor inlets 101, 102 of the selecting valve
• the present description exemplifies a possible operation of the control unit 110, which alternates the connection between the vapor inlets 101, 102 to the vapor outlet 103 of the selecting valve 100. Therefore, said operation, which considers the presence or not of sensor means and other means to determine the operation of the selecting valve 100, should not be considered as limiting the concept of the present invention.
• control unit 110 actuates on the selecting valve 100, so as to allow only one compressor 10 to alternatively draw vapor from the separating means 50 and from the evaporator 90.
• the control unit 100 allows the selective switching of the communication of each of the vapor inlets 101, 102 to the vapor outlet 103 of the selecting valve 100, maintaining the suctions from the separating means 50 and from the evaporator 90 at different pressures. This switching can be made in fixed or variable communication times, in order to provide a better stability of the control variables, apart from those related to a better reliability of the refrigeration system in determined specific situations detected by sensor means .
• the low-expansion device 122 and the high-expansion device 121 in the refrigeration system of the present invention can have the form of a fixed restriction orifice, such as a capillary tube or a restricting valve with variable flow or not, such as an electronic control valve commanded by the control unit 110, said low-expansion device 122 and high-expansion device 121 being operatively associated with the control unit 110 so as to be commanded by the latter to vary the degree of restriction in the refrigerant fluid flow in the refrigeration circuit .
• Said degree of restriction is defined as a function of the need to control the pressures in the refrigeration system, which restriction is determined by the suction pressure required by the compressor 10, when the selecting valve 100 communicates the separating means 50 to said compressor 10.
• Some of the advantages of the present invention are: reducing considerably the flash vapor in the evaporator inlet 90, which vapor must be eliminated or at least minimized , as it is a "parasite" that must be removed from the evaporator before admitted therein, since said vapor, upon passing through the evaporator, causes harm by not effecting heat exchange.
• the separating means 50 By using the separating means 50, the generation of flash vapor is minimized in the second expansion device between the separating means 50 and the evaporator 90, which vapor is prevented from passing through the evaporator 90.
• the flash vapors in the separating means 50 are compressed by the compressor 10, when the second vapor inlet 102 of the selecting valve 100 is connected to the vapor outlet 103 thereof, at an intermediary pressure which is superior to that of the evaporator 90 and inferior to that of the compressor discharge, requiring less work and consuming less energy of said compressor for pumping it back to the condenser 30 of the refrigeration system, this pumping occurring until the selecting valve 100 is instructed to operate the fluid communication between its second vapor inlet 102 and its vapor outlet 103.
• the present invention also provides, as a benefit, the possibility of controlling the pressures existing in different levels established in the system: pressure in the condenser 30 (or "gas-cooler") ; pressure in the separating means 50; and pressure in the evaporator 90.
• the control of the pressure levels and the possibility of compressing the vapor from the separating means 50 with a smaller compression rate provide economy in the consumption of energy to carry out the present process, which is different from the prior art processes by reducing the number of compressors.
• a possible constructive option for the present invention provides the integration of the selecting valve 100 (or sequence deviation valve) to the compressor 10. This integration aims at obtaining considerable gains of thermal yield for the system, due to the reduction of the dead volume relative to the presence of the second vapor duct 40 in the circuit.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Air Conditioning Control Device (AREA)
• Control Of Positive-Displacement Pumps (AREA)
• Compressor (AREA)
• Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
• Devices That Are Associated With Refrigeration Equipment (AREA)
• Details Of Measuring And Other Instruments (AREA)

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• 2008
  • 2008-06-18 BR BRPI0802382-4A patent/BRPI0802382B1/pt not_active IP Right Cessation
• 2009
  • 2009-06-15 ES ES09765281T patent/ES2378216T3/es active Active
  • 2009-06-15 AT AT09765281T patent/ATE543060T1/de active
  • 2009-06-15 JP JP2011513827A patent/JP5341182B2/ja not_active Expired - Fee Related
  • 2009-06-15 KR KR1020107029787A patent/KR101599516B1/ko not_active Expired - Fee Related
  • 2009-06-15 CN CN2009801310996A patent/CN102119307B/zh not_active Expired - Fee Related
  • 2009-06-15 WO PCT/BR2009/000170 patent/WO2009152593A1/en not_active Ceased
  • 2009-06-15 US US12/737,435 patent/US8671704B2/en not_active Expired - Fee Related
  • 2009-06-15 DK DK09765281.2T patent/DK2307825T3/da active
  • 2009-06-15 EP EP09765281A patent/EP2307825B1/en not_active Not-in-force

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