EP0378933A2 - Anordnung von Verdampfer und Durchflussregelung bei einer Kältemaschine - Google Patents

Anordnung von Verdampfer und Durchflussregelung bei einer Kältemaschine Download PDF

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Publication number
EP0378933A2
EP0378933A2 EP89403410A EP89403410A EP0378933A2 EP 0378933 A2 EP0378933 A2 EP 0378933A2 EP 89403410 A EP89403410 A EP 89403410A EP 89403410 A EP89403410 A EP 89403410A EP 0378933 A2 EP0378933 A2 EP 0378933A2
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EP
European Patent Office
Prior art keywords
bulb
evaporator
discharge pipe
pressure
expansion valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89403410A
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English (en)
French (fr)
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EP0378933A3 (de
Inventor
Bernard Zimmern
Jean Louis Picouet
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Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0378933A2 publication Critical patent/EP0378933A2/de
Publication of EP0378933A3 publication Critical patent/EP0378933A3/de
Withdrawn legal-status Critical Current

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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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • F25B41/33—Expansion valves with the valve member being actuated by the fluid pressure, e.g. by the pressure of the refrigerant
    • F25B41/335—Expansion valves with the valve member being actuated by the fluid pressure, e.g. by the pressure of the refrigerant via diaphragms
    • 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
    • F25B2341/00—Details of ejectors not being used as compression device; Details of flow restrictors or expansion valves
    • F25B2341/06—Details of flow restrictors or expansion valves
    • F25B2341/068—Expansion valves combined with a sensor
    • F25B2341/0681—Expansion valves combined with a sensor the sensor is heated
    • 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
    • F25B2500/00—Problems to be solved
    • F25B2500/15—Hunting, i.e. oscillation of controlled refrigeration variables reaching undesirable values
    • 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
    • F25B2600/21—Refrigerant outlet evaporator temperature

Definitions

  • This invention relates to a method of using a thermal expansion valve device comprising a bulb at least partially filled with a liquid.
  • This invention also relates to an evaporator and flow control means assembly.
  • This invention further relates to a refrigerating machine.
  • refrigerating machines such as used for example for refrigeration or air-conditioning, comprise a compressor which compresses a refrigerant fluid in the gaseous state.
  • the fluid is then cooled and condensed by contact with a so-called “hot source” (less hot than the gas coming from the compressor) and the pressure of the condensed fluid is then dicreased through an expansion valve down to a pressure low enough for vaporization of the fluid by contact with a so-called “cold source”, whereafter the vaporized gas is returned to the compressor.
  • a so-called "hot source” less hot than the gas coming from the compressor
  • the pressure of the condensed fluid is then dicreased through an expansion valve down to a pressure low enough for vaporization of the fluid by contact with a so-called “cold source”, whereafter the vaporized gas is returned to the compressor.
  • the fluid absorbs heat from the cold source, thus creating the desired refrigerating effect.
  • This type of machine needs to be controlled so as to avoid two drawbacks : if the amount of heat available at the cold source is low, high quantities of unevaporated liquid may be returned to the compressor; this would damage the compressor and anyway corresponds to a waste of energy in the machine (the machine has produced more cold than necessary) on the contrary if the amount of heat available at the cold source is high, the liquid flow rate arriving at the evaporator may not be high enough for maintaining the cold source temperature at the desired low level.
  • a thermal expansion valve i.e. an expansion valve connected to a bulb partially filled with liquid, generally the same liquid as the fluid used in the refrigerating circuit.
  • a membrane has one side thereof exposed to the pressure in the bulb and an other side thereof exposed to the pressure in the evaporator. Said membrane acts on a valve flow control means of the expansion valve, against a tending spring.
  • the bulb is normally attached to the outside of the discharge pipe through which the refrigerant fluid leaves the evaporator towards the compressor, and the flow control means opens only when the superheat of the gas is heating the liquid in the bulb to a point where its pressure exceeds the pressure in the evaporator by the amount of the pressure provided by the spring.
  • Said superheat as is necessary for the regulation, means that the evaporator has to be substantially enlarged and this significantly increases the cost in the superheat area, the coefficient of thermal exchange is much lower than in the area where the evaporator contains some liquid.
  • water-­chillers where an intermediary medium, i.e. water, is cooled and in turn cools the air - the size of the evaporator could be roughly divided by half if the superheat, normally 5°C, could be eliminated.
  • the first object of this invention is a method of using a thermal expansion valve device comprising a bulb at least partially filled with a liquid, connected to one side of a differential pressure measuring device, an other side of said differential pressure measuring device being exposed to the pressure in the evaporator, said differential pressure measuring device acting against biasing means to control the position of flow controlling means, said bulb being connected to a discharge pipe of said evaporator and carrying heating means, and characterized by positioning said bulb at least partially in said discharge tube.
  • a second object of this invention is an evaporator and flow control means assembly comprising : - an evaporator having a refrigerant inlet connected to a thermal expansion valve and a refrigerant discharge pipe provided with a bulb at least partially filled with a liquid ; - a differential pressure measuring means having a first input connected to said bulb and a second input exposed to the pressure in said evaporator ; - means for positioning a flow control element of the thermal expansion valve as a function of a differential pressure as measured by the differential pressure measuring means ; - heating means connected to the bulb, characterized by the bulb being at least partially mounted in the discharge pipe of the evaporator so as to be at least partially exposed to refrigerant flow in the discharge pipe.
  • a third object of the invention is a refrigerating machine comprising an evaporator and flow control means assembly according to the second object.
  • the invention results in the gas discharged by the evaporator very often containing some liquid instead of being fully evaporated and superheated.
  • the zero degree superheat expansion valve according to the invention leads to some remarkable results.
  • this invention eliminates one of the major drawbacks of the prior art according to the US patent 4 467 613, i.e. operation uncertainties.
  • an outside bulb heated by a resistor could act as if the gas was containing a lot of liquid, due to a lot of heat being absorbed by the pipe ; this occurs when there is liquid on the inner wall of the pipe ; such liquid may be for instance oil returning to the compressor, or remaining drops of liquid refrigerant not yet fully vaporized.
  • the bulb is thermally insulated from the discharge pipe so as not to be thermally influenced by the liquid along the wall of the discharge pipe.
  • insulation may be for instance a plastic element which has, simultaneously, the advantage of easily being deformed and providing a good leak-tightness between the bulb and the discharge pipe, although the bulb is usually not perfectly cylindrical.
  • thermal expansion valves are not appropriate for accurately controlling an evaporator on a very large range of capacities.
  • a thermal expansion valve does not operate when the refrigerant flow rate is lower than one third of full load if this valve is appropriate for operating correctly at full load.
  • two or three valves of different capacities must be used in parallel so as to be able to still control the refrigerant liquid flow to the evaporator when the system and accordingly the compressor have to operate in the 10 - 30 % capacity range.
  • the invention has the unexpected effect of eliminating this drawback. More specifically, this invention allows the same valve to control the refrigerant system on the whole range of operation, usually from 10 - 20 % to full load.
  • the heating means are partially or totally disconnected when the requested cooling capacity drops below a certain value, for instance 50 % .
  • a certain value for instance 50 % .
  • Such disconnection can be actuated by the capacity control of the compressor (the compressor is provided with capacity control means which operate, usually automatically, for matching the amount of compressed fluid produced by the compressor to the flow rate of refrigerant fluid through the evaporator).
  • the bulb When the heating means are shut off (or, alternatively, partially disconnected) the bulb operates as a standard bulb, i.e. requests superheat from the evaporator. This is possible at part load even if the evaporator is relatively small-sized in view of its possible cooling capacity at full load. And now, with the invention, nothing prevents in the construction of the valve, to set the spring so as to double or treble the superheat requested for maximum opening of the valve, since, according to the invention, this superheat is given by the heater. This gives still a lot of superheat and spring bias available at part load, and this makes the valve responsive for much lower flow rates than in the prior art, as will be explained in the description hereinafter.
  • an example of a refrigerating machine schematically comprises a compressor 101 compressing refrigerating fluid in the gaseous state and discharging said fluid into a condenser 102, in which said fluid is condensed.
  • the condensed fluid is then sent through a duct 18 to a controlled expansion-valve 103, in which the refrigerating fluid pressure is decreased, and then, through a duct 19, to an evaporator 2 in which the fluid is vaporized and thus absorbs heat.
  • a refrigerant discharge pipe 1 of the evaporator 2 is connected to an inlet of the compressor 101.
  • the evaporator 2 comprises a refrigerant pipe 3 in a vessel 4 in which water to be cooled circulates between a water inlet pipe 5a and a water outlet pipe 5b along arrows 6 and 7.
  • the expansion valve comprises a membrane 10 having one side 11 exposed to the pressure of a bulb 104 which is secured to the refrigerant discharge pipe 1 of the evaporator and will be described later, and another side 12 exposed to the pressure in the discharge pipe 1 by an external equalizing line 13 ; the membrane 10 urges via rod 14 a flow control piston 15 away from its seat 16 against the biasing force of a spring 17.
  • the pressure inside the bulb 104 is transmitted to side 11 of the membrane 10 by a pressure transmitting means such as a capillary 9.
  • the bottom part of the bulb is surrounded by an electrical heating resistor 20 which is conventionnally made on a plastic foil partly covered by resistance material seen on 26, wrapped around the bulb ; it is maintained and pressed against the bulb by a cover 41 which is conceivably made of plastic. Electrical current is supplied to the resistor 20 by wires 21 and 22.
  • the bulb is held into the pipe 1 by a metal flange 23 having a conical bore 23a therethrough in which a plastic cone 24 - made for instance of PTFE (polytetrafluoroethylen) is pressed by flange 25.
  • the plastic cone 24 has a cylindrical through-bore axially therethrough, and the bulb 104 and wires 21 and 22 are leak-tightly mounted in said cylindrical through-bore.
  • the plastic cone deforms so as to let the passage for the electrical wires 21 and 22 while sealingly separating the inside of the pipe 1 containing refrigerant gas and liquid from the ambient air outside.
  • the plastic cone 24 maintains the bulb 104 in a position in which a major part, and especially the bottom part, of the bulb 104 extends inside the discharge pipe 1, transversely thereto, so as to be exposed to refrigerant flow inside discharge pipe 1.
  • the plastic cone 24 also provides to the bulb heat-insulation against heat or cold coming from the walls of the pipe 1. This allows the temperature inside the bulb to be basically dependant upon the amount of heat generated by the resistor and the amount of cold received by the area 27 of the bulb which is exposed to refrigerant flow.
  • the system operates as follows : When the compressor 101 operates at full load, the resistor 20 is energized and heats the liquid 8 in the bulb, thereby increasing the pressure in the bulb and in a volume adjacent side 11 of the membrane 10 which in turn pushes against the spring 17 and opens the piston 15 allowing liquid refrigerant coming from condenser 102 to flow into the evaporator 2.
  • the refrigerant fluid can no longer fully vaporize in evaporator 2 and droplets of liquid appear in discharge pipe 1. Only at this stage, i.e. when liquid droplets carried along in pipe 1 start hitting the area 27 of the bulb, the bulb cools down and the pressure in the bulb decreases, thereby reducing pressure on the membrane 10 and closing progressively the piston 15. It should be noted that an important feature of the invention is the close proximity between the area where heat is provided to the bulb, the area where cold is received by the bulb and the liquid contained in the bulb ; this insures that calories do not have to travel through lengthy pieces of copper.
  • Figure 3 shows the results achieved with this invention ; on positive asbcissa, it indicates the percentage in weight of the liquid carried along by the wet gas, the vertical line 28 corresponding to 0 % of liquid but the gas being without superheat ; the negative side of the abscissa shows the amount of superheat ; the ordinate shows the differential pressure across the membrane.
  • a bulb of approximately 15 mm in diameter and 110 mm in length is installed into a pipe having around 70 mm in diameter and actuates an expansion valve operating a 50 ton air-conditioning system ; the electrical resistor is providing around 25 watts to the bulb ; the system is operated with refrigerant R-22 and the evaporating temperature is set at 7°C ; the amount of liquid in the valve is limited so that it is fully vaporized when the differential pressure reaches around 3 bars as shown at 29 ; at that value, the valve is fully opened ; further superheat would not open it more ; the superheat at that point is around 1°C.
  • the power generated by resistor 20 can be reduced or set to zero, thus allowing the thermal expansion valve to operate in a conventional manner.
  • Figure 4 explains the advantage obtained thereby : It shows the amount of opening of the valve 103 in ordinate and the pressure differential in abscissa, the curve 32 being the curve of a conventional valve and the curve 33 being the curve of a preferred embodiment of this invention.
  • the slope of the curve 32 has to be steep, whereby the sensibility of the opening to a change in the superheat is quite high and the valve operation is therefore not very accurate ; furthermore, when the amount of superheat decreases to a point where the pressure differential comes close to value 34, the opening of the valve becomes erratic, one reason being that, in most valves, the piston 15 is not pressure balanced on its two sides with the result that it tends to close and remain closed or to open and remain open ; so the valve is not controlling well in the pressure differential area near point 34 corresponding to part load conditions generally below 35 or 40 %.
  • the maximum superheat seen by the bulb is no longer limited as it is dictated by the resistor, not by the superheat of the evaporator gas, and it is possible to have it operate with a much less steeper slope which allows a much greater sensibility and the possibility of still keeping large pressure difference across the membrane even at low part load.
  • Such valve is thus now able to operate down to 20 % load or even lower if needed, thereby eliminating the need to provide a plurality of valves operating in parallel.
  • the resistor could be mounted inside the bulb instead of around the bulb ; the bulb, instead of being mounted vertically, could be mounted obliquely or horizontally ; the external equalizer line could be replaced by a conventional internal equalizer or could be connected to another portion of the low-pressure part of the refrigerating machine, i.e.
  • the bulb instead of being a straight tube, could have a different shape, and for instance be curved ; the resistor shown at the bottom of the bulb could be mounted at the upper part, the cooling area in contact with the wet gas being in the lower part ; instead of using the same fluid in the bulb as in the refrigeration system, a different fluid could be used ; the amount of liquid in the bulb could be limited so as to limit the maximum pressure on the membrane to the value achieved when liquid is fully vaporized ; instead of using an electric heater, heat could be generated by other means, for instance a burner, and could be brought to the bulb by a thermal transfer means such a heat tube ; other means than a spring, such as pressure of a gaz, could be used to bias the membrane ; the membrane could be replaced by another differential pressure measuring device, such as a piston ; at part load, the heater could be disconnected progressively by steps in relation to the unloading of the system so as to go from 100 % heat to 0 % in relation to the
  • the bulb 104 is not necessarily secured to the discharge pipe 1 through a heat-insulating means (cone 24) .
  • Heat transfer from pipe 1 may be at least partially compensated for by increasing the surface of the bulb 104 exposed to the refrigerant flow in pipe 1 with respect to the surface in contact with the pipe, and/or by setting the ohmic value of the resistor and/or the bias force of the spring 17.
  • Such compensations for heat-transfer from pipe 1 to bulb 104 are especially easy in the evaporators in which the discharge pipe 1 remains at a substantially constant temperature, e.g.
  • the evaporators producing cold water wherein the discharge pipe 1 constantly has an external temperature nearly equal to that of water and an internal temperature nearly equal to that of refrigerant fluid, with said temperatures being permanently maintained within a narrow range slightly above 0°C.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
  • Temperature-Responsive Valves (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
EP89403410A 1988-12-09 1989-12-08 Anordnung von Verdampfer und Durchflussregelung bei einer Kältemaschine Withdrawn EP0378933A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8816207 1988-12-09
FR8816207 1988-12-09

Publications (2)

Publication Number Publication Date
EP0378933A2 true EP0378933A2 (de) 1990-07-25
EP0378933A3 EP0378933A3 (de) 1990-08-22

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EP89403410A Withdrawn EP0378933A3 (de) 1988-12-09 1989-12-08 Anordnung von Verdampfer und Durchflussregelung bei einer Kältemaschine

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EP (1) EP0378933A3 (de)
JP (1) JPH02263071A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992010710A1 (en) * 1990-12-07 1992-06-25 Stal Refrigeration Ab A method and arrangement for producing minimum refrigerant flows
DE4115693A1 (de) * 1991-05-14 1992-11-19 Erich Bauknecht Verfahren und vorrichtung zur automatisch gesteuerten leistungsanpassung von expansionsventilen, insbesondere in kaelteanlagen
DE4330522A1 (de) * 1993-08-16 1995-02-23 Escher Wyss Gmbh Kältemittelverdampfer
DE19537871A1 (de) * 1994-10-14 1996-04-18 Soprano Klimagerät, das durch eine einen Meßwert bezüglich des verwendeten Kühlfluids liefernde Vorrichtung gesteuert wird
WO1998022762A1 (en) * 1996-11-19 1998-05-28 Danfoss A/S Process for the control of a refrigeration system, as well as a refrigeration system and expansion valve
EP1439355A3 (de) * 2003-01-17 2005-05-25 Linde Kältetechnik GmbH & Co.KG Fühler für ein thermisches Einspritzventil

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1317537C (zh) * 2005-09-08 2007-05-23 上海交通大学 跨临界二氧化碳制冷系统节流短管
US11079150B2 (en) * 2018-02-20 2021-08-03 Blue Star Limited Method for controlling level of liquid within an evaporator and a system thereof

Family Cites Families (13)

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Publication number Priority date Publication date Assignee Title
US1969102A (en) * 1930-10-06 1934-08-07 Frick Co Refrigerant control for refrigerating systems
US2209101A (en) * 1938-05-05 1940-07-23 Honeywell Regulator Co Refrigeration system
US2240374A (en) * 1938-08-08 1941-04-29 Honeywell Regulator Co Expansion valve
US2367304A (en) * 1939-10-20 1945-01-16 Honeywell Regulator Co Refrigeration control system
US2534455A (en) * 1944-06-08 1950-12-19 Honeywell Regulator Co Refrigerating control apparatus
US2583178A (en) * 1948-10-21 1952-01-22 Honeywell Regulator Co Refrigeration control apparatus
US2624181A (en) * 1949-05-09 1953-01-06 Affiliated Gas Equipment Inc Means and method of controlling refrigeration systems
FR1178599A (fr) * 1956-06-29 1959-05-12 Sulzer Ag Procédé et dispositif de régulation d'une machine frigorifique
NL113978C (de) * 1959-08-17
GB1427926A (en) * 1972-04-05 1976-03-10 Axstane Properties Ltd Compression refrigeration systems
AU7321881A (en) * 1981-05-20 1982-12-07 Richard H. Alsenz Method and apparatus for controlling operation of a thermostatic expansion valve
DE3139044C1 (de) * 1981-10-01 1983-04-21 Danfoss A/S, 6430 Nordborg Kaelte- oder Waermepumpenkreislauf
US4467613A (en) * 1982-03-19 1984-08-28 Emerson Electric Co. Apparatus for and method of automatically adjusting the superheat setting of a thermostatic expansion valve

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992010710A1 (en) * 1990-12-07 1992-06-25 Stal Refrigeration Ab A method and arrangement for producing minimum refrigerant flows
DE4115693A1 (de) * 1991-05-14 1992-11-19 Erich Bauknecht Verfahren und vorrichtung zur automatisch gesteuerten leistungsanpassung von expansionsventilen, insbesondere in kaelteanlagen
DE4330522A1 (de) * 1993-08-16 1995-02-23 Escher Wyss Gmbh Kältemittelverdampfer
DE19537871A1 (de) * 1994-10-14 1996-04-18 Soprano Klimagerät, das durch eine einen Meßwert bezüglich des verwendeten Kühlfluids liefernde Vorrichtung gesteuert wird
DE19537871C2 (de) * 1994-10-14 1999-12-09 Soprano Vaulx Milieu Klimagerät
WO1998022762A1 (en) * 1996-11-19 1998-05-28 Danfoss A/S Process for the control of a refrigeration system, as well as a refrigeration system and expansion valve
EP1439355A3 (de) * 2003-01-17 2005-05-25 Linde Kältetechnik GmbH & Co.KG Fühler für ein thermisches Einspritzventil

Also Published As

Publication number Publication date
JPH02263071A (ja) 1990-10-25
EP0378933A3 (de) 1990-08-22

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