US3590597A - Cooling apparatus employing the joule-thomson effect - Google Patents

Cooling apparatus employing the joule-thomson effect Download PDF

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Publication number
US3590597A
US3590597A US847917A US3590597DA US3590597A US 3590597 A US3590597 A US 3590597A US 847917 A US847917 A US 847917A US 3590597D A US3590597D A US 3590597DA US 3590597 A US3590597 A US 3590597A
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stage
refrigerant
heat exchanger
nozzle
cooling
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US847917A
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English (en)
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David Neil Campbell
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Hymatic Engineering Co Ltd
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Hymatic Engineering 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
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/02—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using Joule-Thompson effect; using vortex effect
    • 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
    • F25B2309/02—Gas cycle refrigeration machines using the Joule-Thompson effect
    • F25B2309/022—Gas cycle refrigeration machines using the Joule-Thompson effect characterised by the expansion element
    • 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
    • F25B2309/02—Gas cycle refrigeration machines using the Joule-Thompson effect
    • F25B2309/023—Gas cycle refrigeration machines using the Joule-Thompson effect with two stage expansion

Definitions

  • a precooling refrigerant in liquid form is supplied to a metering nozzle which, havingno heat exchanger, is accommodated within the heat exchanger of the second stage, and this refrigerant evaporates to precool the second stage refrigerant.
  • the nozzle of each stage is automatically controlled to vary the flow of refrigerant in accordance with the demand for cooling.
  • the invention is particularly, though not exclusively, concerned with such coolers which are of miniature size, for example for cooling infrared detectors to the temperature of liquid nitrogen.
  • the complete cooler is largely situated within a cylindrical heat exchanger having a length of between 2 and 3 inches and a diameter of about a third of an inch and wound with a helical coil of finned tubing of which the diameter over the fins is less than one-twentieth of an inch.
  • the cooler itself should be of extremely small size, but in addition that the supply of compressed refrigerant required should also be as small and light as possible.
  • each refrigerant has a temperature, known as its inversion temperature, at which no cooling is produced by the Joule-Thomson efiect, that is to say by expanding the refrigerant gas through an expansion nozzle. Above the inversion temperature such expansion actually produces a rise of temperature, and it is only below it that it produces a cooling effect. Moreover at temperatures only slightly below the inversion temperature the cooling effect is correspondingly slight and if a substantial cooling effect is required the expansion must be carried out from a temperature substantially below the inversion temperature.
  • cooling apparatus includes two stages in the second of which a second stage refrigerant from a supply in gaseous form is passed through one path of a heat exchanger, expanded through an expansion nozzle and passed back through the other path of the heat exchanger to cool the incoming second stage refrigerant, and a precooling first stage in which a precooling refrigerant is supplied in liquid form under pressure through a metering nozzle to a space at reduced pressure where it evaporates to cool the second stage refrigerant before the latter passes through the heat exchanger, the effective area of the nozzle of each stage being automatically controlled in accordance with a parameter depending upon the relationship between cooling supplied and cooling demanded at that stage.
  • the apparatus is generally of tubular form, the heat exchanger comprising a finned tube wound to helical form with the second stage refrigerant flowing through it in one direction and past its outside in the opposite direction, the second stage expansion nozzle being at the cold end of the heat exchanger while the first stage metering nozzle is enclosed within its warm end.
  • the effective area of the nozzle of a Joule-Thomson cooler is automatically controlled, as by means of a needle valve, in accordance with a parameter depending on the relationship between cooling supplied and cooling demanded. This may be in accordance with a temperature at a point in the cold end of the cooling apparatus. In general, however, the apparatus will serve to produce a pool of liquid refrigerant,
  • the control is not directly in accordance with the temperature of the refrigerant but in accordance with the level of the liquid refrigerant which comes into contact with a sensor as the level rises, and controls the temperature of the sensor.
  • the control is in accordance with some other or intermediate function depending upon the supply and demand for cooling, for example the sensor may have an extended tail affording a path for the flow of heat to the liquid refrigerant, the length of which path varies with the level of refrigerant.
  • the sensor may be in heat exchange relationship with parts of the apparatus above the pool of liquid refrigerant so that its temperature will depend partly upon the level of liquid refrigerant and partly on the temperature of the vapor escaping from the nozzle.
  • the second stage expansion nozzle is arranged and controlled as described above and includes a needle valve controlled by a bellows the pressure upon which is determined by a sensor comprising a vapor bulb with an extended tail extending down to the pool of liquefied refrigerant.
  • the first stage is generally similar but in this case the sensor bulb is secured to a curved plate fitting within the body of the heat exchanger at about the level of the metering nozzle so as to respond primarily to the temperature of the heat exchanger at that part of the apparatus.
  • a cup is secured to the inside of the body of the heat exchanger to collect liquid refrigerant formed by the first stage refrigerant, and at the corresponding part of the length of the heat exchanger the helical finned tube is not finned but is soldered to the outer surface of the heat exchanger tube so as to transmit heat from the second stage refrigerant within it to the liquified first stage refrigerant in the cup within the body.
  • the invention is applied to a two-stage cooler of miniature size, perhaps 3 inches in length and onethird inch in diameter comprising two stages.
  • the first, precooling, stage is supplied with Freon which is stored in liquid form, under pressure but at atmospheric temperature, and is admitted past a metering orifice to a space where it can expand to atmospheric pressure, thereby effecting precooling.
  • It operates with nitrogen in gaseous form under pressure which is fed through the inner path of a helical tube heat exchanger to an expansion nozzle where it expands and cools due to the Joule-Thomson effect, producing a pool of liquid nitrogen, while the remaining gas escapes by the outer path of the heat exchanger, i.e. past the outside of the helical finned tube, cooling the incoming nitrogen.
  • the cooling apparatus is of elongated form, and for purposes of description it will be assumed that it is placed verti cally with its cold end at the bottom.
  • the apparatus includes an annular heat exchanger Mi comprising a tubular body 11 around which is helically wound a finned coiled tube 12.
  • An external coaxial tube 13 which may be the inner wall of a Dewar flask, is located around the finned coil and the space 14 between the body and the external tube provides a path for exhaust gas flowing past the fins to cool the incoming high-pressure working fluid within the helical tube.
  • the lower end of the external tube is closed to provide a reservoir (not shown) in which the liquid working fluid can accumulate.
  • This lower end may be combined with the device to be cooled so that the liquid nitrogen is in fact in contact with that device.
  • the upper end of the helical finned tube 12 communicates with a lateral coupling W for connection to the supply of nitrogen under pressure. Its lower end communicates with an expansion noz zle 22 which is arranged to be controlled by means of a needle valve 23 which is itself controlled by a bellows 2d.
  • the tubular body of the heat exchanger has secured in it a stout metal ring 28.
  • a stout metal ring 28 Secured to a point under this ring, and thus offset from the axis of the heat exchanger, is the expansion nozzle 22, while a sensor bulb 30 depends from a diametrically opposite point.
  • a threaded socket 32 is secured to the ring and receives the upper end of a screwed sleeve 33 on the lower end of which is threaded a screwed plug 34 in which the expansion nozzle 22 is formed.
  • the screwed sleeve also serves to retain a porous plug 35 or filter through which the working fluid is compelled to pass on its way to the expansion nozzle 22 so as to condense and filter out any impurities which might otherwise block the expansion nozzle.
  • the upper end of the needle valve projects into the expansion orifice while its lower end is of conical form engaging a seating formed in a screwed plug 26 threaded into a thimble 27 which is rigidly secured as by welding to the lower end of the tubular operating rod 25.
  • the thimble has secured to it a shroud 39 in the form of a partial cage formed of wire gauge which allows free escape of exhaust vapor while intercepting any liquid droplets to prevent them from impinging on the sensor.
  • the tubular operating rod 25 is provided with an S- shaped guide blade 29 serving to keep it centered and prevent it from being tilted by the offset pressure on the needle valve.
  • the sensor bulb 30 communicates through a hole in the ring 28 with the interior of the tubular body of the heat exchanger surrounding the bellows, so that the pressure in the vapor bulb of the sensor is communicatedto the outside of the bellows, and as the pressure rises it tends to push the bellows down, withdrawing the needle valve 23 from the expansion orifice 22 and increasing the flow of refrigerant to increase the amount of cooling.
  • the sensor bulb terminates a little below the level of the orifice and is provided with an extended tail 31 of metal projecting down some distance further. Thus as the level of liquid refrigerant rises it first comes into contact with the end of the extended tail so that heat flowing from the sensor bulb has to flow through its whole length. As the level of liquid refrigerant rises the extent of cooling of the sensor bulb increases progressively, giving a smooth control of the needle valve, and preventing hunting.
  • the upper part of the heat exchanger contains a first stage precooler supplied with Freon kept liquid under pressure.
  • the first stage is provided with a control valve 53 which constructionally is very similar to that of the second stage, although it should be noted that in this case it is merely a metering valve for liquid, and not an expansion valve employing the Joule-Thomson effect as in the second stage,
  • the first stage valve is situated coaxially with the heat exchanger and cooperates with a seating 54 carried by the lower end of an admission tube 55 the upper end of which is secured in a head 56 at the top of the exchanger and communicates with a lateral coupling 57 through which liquid Freon is supplied to it.
  • a thimble 61 seating the lower end of the needle valve 53 is carried at the lower end of a tubular operating member 62 the upper end of which is secured to the upper end ofa bellows 63.
  • the bellows is offset from the axis of the heat exchanger and is accommodated in a chamber surmounting the head 56 at the top of the heat exchanger.
  • the operating member extends up on one side of the tubular inlet pipe 55 carrying the seating 54 at its lower end, while at a diametrically opposite position a tube 67 forming a sensor bulb 69 extends down from an opening 70 in the head and has its lower end flattened and secured to a curved shoe 72 engaging die inner face of the tubular body of the heat exchanger.
  • the sensor bulb 69 contains a volatile liquid, for example Freon, so that the outside of the bellows 63 is subjected to its vapor pressure which varies in accordance with the temperature of the heat exchanger in the region of the first-stage orifice formed by the seating 54.
  • a volatile liquid for example Freon
  • a cup 7 5 the cylindrical wall of which is in heat exchange relationship with the body of the heat exchanger and which accommodates any Freon which may be liquefied by the first stage.
  • the cup contains a perforated heat collector 76 of tubular form so as to assist in transmitting heat from the body of the heat exchanger to any liquid Freon in the cup.
  • the part of the helical tube 12 surrounding the cup is deprived of its fins and wound in a close-pitched helix 77 round the body of the heat exchanger to which it is soldered so asto provide effective heat exchange between it and the cup.
  • the efficiency of a Joule-Thomson cooler is rather low if the refrigerant starts at a temperature only a little below the inversion temperature, and hence in these conditions waste of refrigerant can still occur even though there is automatic control.
  • the present arrangement by providing precooling, increases the efficiency of the Joule-Thomson second stage and thereby economizes in the supply of compressed nitrogen, while adding little or nothing to the bulk or weight of the cooler.
  • the automatic control is at least equally important in economizing the supply of liquid Freon.
  • the precooling may not be required, since the exhaust nitrogen from the second stage may sufficiently precool the incoming nitrogen for that stage to give efficient operation of the Joule- Thomson expansion cooling.
  • the precooling by liquid Freon is primarily required when the apparatus is used at ambient temperatures where the efficiency of Joule-Thomson cooling would otherwise diminish in a single stage cooler.
  • Cooling apparatus of the type in which cooling is produced by expansion, through a nozzle, of a refrigerant in gaseous form under pressure, which before expansion at the nozzle is at a temperature below its inversion temperature, including two stages in the second of which a second stage refrigerant from a supply in gaseous form is passed through one path ofa heat exchanger, expanded through an expansion nozzle and passed back through the other path of the heat exchanger to cool the incoming second stage refrigerant, a precooling first stage in which a precooling refrigerant is supplied in liquid form under pressure through a metering nozzle to a space at reduced pressure where it evaporates to cool the second stage refrigerant before the latter passes through the heat exchanger, and means for automatically controlling the effective area of the nozzle of each stage so that the amount of refrigerant flowing through each nozzle may be governed by the requirement of cooling at that stage.
  • Cooling apparatus as claimed in claim 1 in which the apparatus is generally of tubular form, the heat exchanger comprising a finned tube wound to helical form with the second stage refrigerant flowing through it in one direction and past its outside in the opposite direction, the second stage expansion nozzle being at the cold end of the heat exchanger while the first stage metering nozzle is enclosed within its warm end.
  • Cooling apparatus as claimed in claim 2 in which the second stage expansion nozzle includes a needle valve controlled by a bellows the pressure upon which is determined by said automatic control means which includes a sensor com prising a vapor bulb with an extended tail extending down to a pool of liquefied refrigerant.
  • Cooling apparatus as claimed in claim 3 in which the first stage metering nozzle includes a needle valve controlled by a bellows the pressure upon which is determined by said automatic control means which also includes a sensor bulb secured to a curved plate fitting within the body of the heat exchanger at about the level of the metering nozzle so as to respond primarily to the temperature of the heat exchanger at that part of the apparatus.
  • Cooling apparatus as claimed in claim 4 in which a cup is secured to the inside of the body of the heat exchanger, just below the metering nozzle, to collect liquid refrigerant formed by the first stage refrigerant, and at the corresponding part of the length of the heat exchanger the helical finned tube is not finned and is soldered to the outer surface of the heat exchanger tube so as to transmit heat from the second stage refrigerant in the cup within the body.
  • Cooling apparatus as claimed in claim 5 wherein the refrigerant is Freon in liquid form supplied under pressure and at atmospheric temperature.

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US847917A 1968-08-06 1969-08-06 Cooling apparatus employing the joule-thomson effect Expired - Lifetime US3590597A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3704597A (en) * 1969-12-08 1972-12-05 Hymatic Eng Co Ltd Cooling apparatus
US3728868A (en) * 1971-12-06 1973-04-24 Air Prod & Chem Cryogenic refrigeration system
US3782129A (en) * 1972-10-24 1974-01-01 Gen Dynamics Corp Proportionate flow cryostat
US3795116A (en) * 1970-03-31 1974-03-05 Alsthom Cgee Method and apparatus for supercooling of electrical devices
US3818720A (en) * 1973-09-06 1974-06-25 Hymatic Eng Co Ltd Cryogenic cooling apparatus
US3827252A (en) * 1972-03-23 1974-08-06 Air Liquide Method of regulation of the frigorific power of a joule-thomson refrigerator and a refrigerator utilizing said method
US4080802A (en) * 1976-07-14 1978-03-28 International Telephone And Telegraph Corporation Hybrid gas cryogenic cooler
US4343268A (en) * 1979-06-07 1982-08-10 Cummins Engine Company, Inc. Energy conserving exhaust passage for an internal combustion engine

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8627288D0 (en) * 1986-11-14 1986-12-17 Marconi Co Ltd Cold stage for microscope
DE3642683A1 (de) * 1986-12-13 1988-06-16 Bodenseewerk Geraetetech Kryostat zur kuehlung eines detektors
DE3941314A1 (de) * 1989-12-14 1991-06-20 Bodenseewerk Geraetetech Kuehlvorrichtung
US5077979A (en) 1990-03-22 1992-01-07 Hughes Aircraft Company Two-stage joule-thomson cryostat with gas supply management system, and uses thereof
GB2247517B (en) * 1990-08-07 1994-01-26 Hymatic Eng Co Ltd Cryogenic cooling apparatus
DE4135764C1 (es) * 1991-10-30 1993-02-25 Bodenseewerk Geraetetechnik Gmbh, 7770 Ueberlingen, De

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3431750A (en) * 1965-12-02 1969-03-11 Philips Corp Gas-expansion refrigerator

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3431750A (en) * 1965-12-02 1969-03-11 Philips Corp Gas-expansion refrigerator

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3704597A (en) * 1969-12-08 1972-12-05 Hymatic Eng Co Ltd Cooling apparatus
US3795116A (en) * 1970-03-31 1974-03-05 Alsthom Cgee Method and apparatus for supercooling of electrical devices
US3728868A (en) * 1971-12-06 1973-04-24 Air Prod & Chem Cryogenic refrigeration system
US3827252A (en) * 1972-03-23 1974-08-06 Air Liquide Method of regulation of the frigorific power of a joule-thomson refrigerator and a refrigerator utilizing said method
US3782129A (en) * 1972-10-24 1974-01-01 Gen Dynamics Corp Proportionate flow cryostat
US3818720A (en) * 1973-09-06 1974-06-25 Hymatic Eng Co Ltd Cryogenic cooling apparatus
US4080802A (en) * 1976-07-14 1978-03-28 International Telephone And Telegraph Corporation Hybrid gas cryogenic cooler
US4343268A (en) * 1979-06-07 1982-08-10 Cummins Engine Company, Inc. Energy conserving exhaust passage for an internal combustion engine

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