EP0954390B1 - Rauchabzug mit bistabiler wirbelströmung - Google Patents

Rauchabzug mit bistabiler wirbelströmung Download PDF

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Publication number
EP0954390B1
EP0954390B1 EP98902812A EP98902812A EP0954390B1 EP 0954390 B1 EP0954390 B1 EP 0954390B1 EP 98902812 A EP98902812 A EP 98902812A EP 98902812 A EP98902812 A EP 98902812A EP 0954390 B1 EP0954390 B1 EP 0954390B1
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EP
European Patent Office
Prior art keywords
hood
chamber
sash
accordance
vortex
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.)
Expired - Lifetime
Application number
EP98902812A
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English (en)
French (fr)
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EP0954390A1 (de
EP0954390A4 (de
Inventor
Robert A. Deluca
Robert H. Morris
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Flow Safe Inc and Labcrafters Inc jointly
Original Assignee
Flow Safe Inc and Labcrafters Inc jointly
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Publication date
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Publication of EP0954390A1 publication Critical patent/EP0954390A1/de
Publication of EP0954390A4 publication Critical patent/EP0954390A4/de
Application granted granted Critical
Publication of EP0954390B1 publication Critical patent/EP0954390B1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B15/00—Preventing escape of dirt or fumes from the area where they are produced; Collecting or removing dirt or fumes from that area
    • B08B15/02—Preventing escape of dirt or fumes from the area where they are produced; Collecting or removing dirt or fumes from that area using chambers or hoods covering the area
    • B08B15/023—Fume cabinets or cupboards, e.g. for laboratories

Definitions

  • the present invention relates to ventilated enclosures for containing and preventing the spread of vapors, such enclosures being commonly known as fume hoods, more particularly to fume hoods which are openable to permit to access to the interior, which opening may permit inadvertent escape of fumes to the exterior of the hood.
  • the first fume hoods were fireplaces used by alchemists. These early day fume hoods had very tall chimneys. The stack height, thermal gradients caused by a fire, and the aspirating effect of the outside wind conditions would create a considerable draft.
  • early day ventilation engineers (mid 1800's) added gas burning rings in the stack to achieve greater thermo-lift. During the industrial revolution, the gas rings gave way to a mechanical fan. It was about this time that laboratories were becoming better defined. Changes evolved such as adding a front sash instead of a hinged door and airfoil beneath the sash window. In the late 1940's, a back baffle system and streamlined shape entrance was introduced to all fume hoods.
  • a fume hood of the design just described is shown in FIG. 1 and labeled "Prior Art”.
  • Fume hood performance has always been based on a smoke visualization test, where a smoke bomb is placed within the inside the hood on its work surface and as long as the smoke is not seen exiting the sash face, the hood is considered working properly.
  • the recommended face velocity (the velocity of air flowing into the hood through the sash opening or "face") is between 30,48 and 45,72 m per minute (100 and 150 feet per minute (FPM)).
  • FPM feet per minute
  • fume hood users felt that the higher the face velocity, the better the containing hood.
  • High face velocities began to lose favor in the late 1960's with the introduction of the bypass-air hood (shown schematically in FIG. 2), which introduced air above the sash as the sash was closed.
  • FIG. 3 One of the applicants has developed and improved a vortex control system for fume hoods, illustrated in FIG. 3, and which is the subject of the U.S. Patent No. 5,697,838, issued to Robert H. Morris on December 16, 1997, which is hereby incorporated herein by reference.
  • Tracer gas studies conducted by Robert H. Morris have shown that the fume hoods are not inherently made safer by using variable volume fixed face velocity control techniques, although energy can be saved through the reduction in the exhaust airflow volume.
  • These tracer gas tests have indicated that the fume hood face velocity is influenced by the internal vortex of the fume hood, and operating variables such as room air distribution, supply air temperature, clutter inside the fume hood, and the location of the fume hood in the lab space.
  • the vortex control system of the 5,697,838 optimizes the flow of air through a fume hood by dynamically controlling the airflow to provide a stable vortex in the vortex chamber of the hood, which maximizes backflow of fume-laden air through the hood doorway.
  • a highly-sensitive pressure sensor disposed at in the vortex chamber side wall senses minute variations in the vortex pressure indicative of turbulence and sends signal via a transducer to an analog controller, which uses proportional interval and adaptive gain algorithms, to formulate output signals to an actuator which adjusts dampers in the hood system to change the airflow into the vortex chamber.
  • FIG. 4 is a schematic diagram of the chamber region of a hood. It is shown that a vortex bubble develops on the surface within the upper region of the vortex chamber.
  • the vortex is controlled by a laminar controlling jet along the back baffle surface in the vortex chamber area. This laminar jet stream causes a sustained pressure differential to develop and entrain some of the air surrounding it.
  • the entrained air on the wall side is trapped against the wall while ambient air from the face velocity replaces the entrained air from the opposite side.
  • FIG. 5 is a schematic diagram of a fume hood showing this mono-stable vortex.
  • the vortex in the conventional fume hoods therefore appears to be mono-stable.
  • the vortex will remain stationary on the wall as long as the controlling air jet stream remains laminar.
  • the laminar jet stream becomes disrupted, due to environmental conditions, such as room pressure fluctuations, cross-drafts, fume hood loading and thermal temperature changes of the supply makeup air, the vortex bubble becomes filled and the pressure gradient is lost.
  • the mono-stable vortex becomes chaotic and breaks down. The loss of the vortex bubble is the precursor to fume hood containment failure.
  • the mono-stable vortex cannot re-establish itself until the jet stream is once again laminar.
  • the present invention provides a fume hood having a bi-stable vortex hood.
  • the term "bi-stable vortex” as used herein refers to a vortex in a hood which is stable with the sash either open or closed.
  • the bi-stable vortex is provided by a baffle arrangement.
  • a bi-stable vortex bubble is produced on the same wall surface as the mono-stable vortex bubble, but is characterized by a much more symmetrical shape and it requires an opposing jet stream to disrupt it and to break down the vortex.
  • the invention has as a principal feature to use of the bi-stable vortex bubble in a fume hood.
  • a further feature of the invention is to provide an improved fume hood having a vortex chamber with a hydraulic radius ratio in relationship to the hydraulic radius ratio of the sash window of the hood.
  • a further feature of the invention is to provide a fume hood having an automatically repositionable baffle, a vortex chamber turning vane, and a multi-three entry airfoil which cooperates in forming a bi-stable vortex in a fume hood.
  • FIG. 1 is a schematic diagram showing a standard, conventional (Prior Art) fume hood in elevation.
  • FIG. 2 is a diagram similar to FIG. 1 of a Prior Art by-pass fume hood.
  • FIG. 3 is a diagram similar to FIG. 1 of a fume hood having a vortex control system in accordance with the invention of the US Patent No. 5,697,838 incorporated by reference above.
  • FIG. 4 is a schematic diagram of the upper portion of a fume hood showing the upper region of the vortex chamber and the vortex bubble formed by the flow therein.
  • FIG. 5 is a diagram similar to FIG. 1 showing the flow pattern which includes a mono-stable vortex in the vortex chamber thereof.
  • FIG. 6 is a schematic educational diagram of a fume hood and particularly the face velocity and vortex chambers thereof and having a bi-stable vortex, all in accordance with the present invention.
  • FIG. 7 is a schematic diagram showing a bi-stable vortex fume hood and the components thereof which provide the bi-stable vortex.
  • FIG. 8 is a perspective view of the fume hood shown in FIG. 7 and which has a front section containing the sash and its operating hardware;
  • FIGS. 9a and 9b are, respectively, fragmentary cross-sectional views taken along a horizontal plane, including 9-9 in FIG. 8, and showing alternative embodiments for aerodynamic shaping of the sash posts;
  • FIG. 10 is a fragmentary cross-sectional view taken along a vertical plane including line 10-10 in FIG. 8, showing an aerodynamic shaped sash handle used as a turning vane.
  • a prior art fume hood 10 has an enclosure 12 containing a working space 14 having a floor 15, a head space 16 generally above working space 14, a vertically-slidable sash window or door 18 having seals 20 along its top and bottom edges, an airfoil 22 defining a bottom stop for sash 18 and a floor sweep entry 24 for admission of make-up air 26 when sash 18 is closed.
  • air 27 is drawn into enclosure 12 through the sash opening 29.
  • a baffle 28 off-spaced from the back wall 30 of enclosure 12 to form plenum 31 and having upper 32, middle 34, and lower 36 transverse slots therein for admission of air to plenum 31.
  • Plenum 31 communicates with an exhaust duct 38 leading to an exhaust fan (not shown).
  • another embodiment 40 of a prior art fume hood provides for essentially constant flow of air to the hood exhaust by opening an air bypass port 42 equal in area to the gain or loss in area of sash opening 29 as sash 18 is opened or closed, respectively.
  • a bypass baffle 44 can be variably opened or closed to moderate the velocity of secondary make-up air 46 entering head space 16 through grille 48.
  • a fume hood 50 has a mono-stable vortex control system in accordance with the invention of the incorporated reference, US Patent No. 5,697,838.
  • a vortex sensor 52 mounted in an opening through the sidewall of the headspace 16, which now includes vortex chamber 54, continuously measures the pressure difference between the vortex chamber and the exterior of hood 50 and causes a controller 56 to vary the position of dampers 58 and 60, which control the open areas of slots 32 and 36, respectively, until a stable vortex 62 is achieved as indicated by a minimum variation in the pressure difference being measured by sensor 52.
  • this system can maintain a laminar flow of air into working space 14 while sash opening 29 is varied as the sash is opened or closed.
  • a fume hood 64 of typical sash height and linear length are shown. These dimensions of course will vary depending upon the user's need.
  • the hood vortex 62 is made bi-stable in accordance with the invention.
  • the bi-stable vortex is maintained by using the following relationship for the hydraulic radius of the open sash 29 window area versus the hydraulic radius ratio which will be required in the vortex chamber 54 above working chamber 14. (Eq. 1 below). These relationships are (a) the hydraulic ratio of the vortex chamber is between about 80% and about 90% of the hydraulic radius of the open sash window, and (b) that the vertical component (height) of the vortex chamber is between about 80% and about 85% of the maximum height of the sash window opening.
  • a turning vane 65 shown in FIG. 7, can be a useful adjunct, and its included angle ⁇ should be between about 30° and about 45°.
  • the turning vane may be about one half the height of the vortex chamber dimension.
  • a fume hood is most sensitive to environmental challenges when the sash 18 is fully opened and the vortex chamber 54 is at its smallest.
  • the automatic vortex control system shown in FIG. 3 senses the vortex and repositions the back baffle system as described above to compensate for variations in equipment loading and space pressure, cross-drafts, activity in front of the hood, and the like.
  • a bi-stable vortex baffle system in accordance with the invention further includes upper and lower interlocking or hinged, actuable baffles 66 and 68, respectively, which replace fixed baffle 28 in the prior art design, as shown in FIG. 7.
  • Baffles 66 and 68 are each pivotable about a horizontal axis, the upper end 70 of baffle 68 being keyed and slaved to the lower end of baffle 66, middle slot 34 being formed therebetween.
  • Upper slot 32 is formed at the top of baffle 66
  • lower slot 36 is formed at the bottom end 72 of baffle 68.
  • An actuator 74 is operationally disposed to turn baffle 66, and by slave extension baffle 68, in counter directions about their axes to vary simultaneously the size of the three slots and the geometry of the working chamber 14 and the vortex chamber 54.
  • the closed loop vortex control system energizes actuator 74 to rotate baffle 66 clockwise which tends to close the upper slot and while doing so cantilevers the center slot towards the sash, thereby inducing a clearing action in working chamber 14.
  • This feature is extremely important, as in a mono-stable hood the working chamber can become loaded with fumes which would otherwise tend to collect and spill out toward an operator as the sash is raised.
  • the action of the baffle system also moves the bi-stable vortex bubble further from the sash window as it turns along the work surface (compare the position of vortex 62 in FIG. 5, mono-stable location, vs. FIG. 6, bi-stable location).
  • airfoil 76 is mounted in the floor of the working chamber just inside the sash opening and has a multiple (three) slot configuration, the top and center slots 76a and b directing air toward the center baffle slot 34 and a third slot 76c directing air along the floor of the working chamber toward lower baffle slot 36, as shown in FIG. 7.
  • hoods for open loop control without involvement of a vortex sensor and vortex control system, wherein the action and position of the actuable baffles can be synchronized by trial and error to the position and movement of the sash through known electrical means such as a potentiometer or known mechanical means such as pulleys, gears, and the like.
  • This less sophisticated open loop control method can provide improved hood performance, for example, to an existing prior art hood at lower cost than a fully closed loop control system.
  • a hood assembly 78 in FIGS. 7 and 8, comprises a conventional working chamber 14 and head space 16 but also includes an additional forward hood portion 79 which may be attached to the front of a conventional hood enclosure 12 along line 80, either in a newly constructed hood or in a retrofit of an existing hood.
  • Assembly 78 is shown as a bench-mounted hood, although larger, floor-mounted, walk-in embodiments are within the scope of the invention.
  • hood assembly 78 extends substantially forward of the edge 81 of bench 82, permitting the placement of airfoil 76 behind the lower edge of sash opening 29 and within the bottom of the hood.
  • Forward portion 79 includes additional working space 14a and head space 16a, making those chambers deeper which can improve the geometrical relationships consistent with Equation 1.
  • the removable portion 79 enables a bi-stable vortex fume hood to be not limited to a size which would normally be able to fit through a standard doorway or easily placed on a lab bench.
  • a fume hood which can be assembled in the field to be larger than a conventional mono-stable vortex hood is still another feature of the invention.
  • FIGS. 9a, 9b, and 10 show desirable laminar-flow-promoting features relating to the sash opening.
  • left hood post 84 has a radiused corner 86 to the entrance to sash opening 29 and is provided immediately outside of sash channel 88 with an off-spaced airfoil vane 90 mounted on spacers 92 bolted to post 84 to form an open-ended plenum 93 between the vane and the post.
  • Vane 90 extends preferably over the entire height of sash opening 29. In practice, a mirror image vane installation is also provided for the right hood post.
  • FIG. 9b shows an alternative embodiment to the configuration of FIG. 9a. wherein comer 86 is perforated or slotted to permit passage of air and sash channel 88 is reconfigured with flange 89 to form air plenum 93.
  • FIG. 10 shows an aerodynamic handle 94 which extends preferably the full width of the bottom of sash 18 and provides laminar air flow across the lower edge of the sash when the sash is not fully closed, and an aerodynamic surface for top slot of the airfoil when the sash is fully closed.

Landscapes

  • Ventilation (AREA)
  • Air-Flow Control Members (AREA)
  • Prevention Of Fouling (AREA)

Claims (14)

  1. Ein Rauchabzug (64, 78) mit einer Kammer (14) mit einem beweglichen Abzugschieber (18) betätigbar in einer Abzugöffnung (29) entlang einer Vorderseite desselben, eine gelenkige Prallplattte (66, 68) innerhalb der Kammer, ein Luftleitelement (76) zum Leiten der Luftströmung in die Kammer zu dem erwähnten Prallsystem (66, 68) und Mittel (74) zur Bewegung des gelenkigen Prallelements (66, 68), um eine bistabile Vortex (62) innerhalb der Kammer (14) aufrechtzuerhalten.
  2. Abzug (64, 78) gemäß Anspruch 1, wobei die Mittel zur Bewegung ein Vortexabfühlsystem (52) aufweisen.
  3. Abzug (64, 78) nach Anspruch 1, wobei die Mittel zur Bewegung Mittel aufweisen zum Synchronisieren der Bewegung des gelenkigen Prallelements (66, 68) mit der Bewegung des Abzugschiebers (18) in der Abzugöffnung (29).
  4. Abzug (64, 78) nach Anspruch 1, wobei die gelenkige Prallplatte ein oberes (66) und ein unteres Prallelement (68) aufweist, wobei die Prallelemente gelenkig verbunden sind, um einen Schlitz (34) dazwischen zu bilden.
  5. Abzug (64, 78) nach Anspruch 4, wobei das Luftleitelement (76) an einem Bodenteil der Kammer angeordnet ist.
  6. Abzug (64, 78) nach Anspruch 5, wobei das Luftleitelement (76) mehrfach drei Schlitze aufweist einschließlich oberer Schlitze (76a) und mittlerer Schlitze (76b) zum Leiten der Luft zu der gelenkigen Verbindung und einen dritten Schlitz (76c) zum Leiten der Luft entlang des Bodens der Kammer.
  7. Abzug (64, 78) nach Anspruch 1, wobei der Abzug trennbare vordere und hintere Abschnitte aufweist, wobei der vordere Abschnitt das erwähnte Abzugselement und Mittel zu dessen Betätigung aufweist.
  8. Abzug (64, 78) nach Anspruch 1, wobei die Kammer eine Vortexkammer (54) besitzt, wobei das hydraulische Radiusverhältnis der Vortexkammer im Bereich von ungefähr 0,8 bis ungefähr 0,9 des hydraulischen Radius der Abzugöffnung ist, wenn das Abzugelement vollständig geöffnet ist und wobei die Vertikalhöhe der Vortexkammer im Bereich von ungefähr 0,8 bis ungefähr 0,85 der Höhe der Abzugöffnung dann ist, wenn der Abzug vollständig offen ist.
  9. Abzug (64, 78) nach Anspruch 8, wobei der erwähnte hydraulische Radius der Vortexkammer ein Verhältnis der Vortexkammer und des hydraulischen Radius der vollständig offenen Abzugöffnung ist, wobei jeder Radius erhalten wird aus √(4a/p), wobei a die Fläche der Kammer oder der Abzugöffnung ist, und p der Umfang der Kammer oder der Abzugöffnung, wobei dieses Verhältnis unabhängig von den tatsächlichen Einheiten ist.
  10. Abzug (64, 78) nach Anspruch 8, wobei ferner eine einstellbare Drehschaufel (65) innerhalb der Abzugkammer (14) vorgesehen ist.
  11. Abzug (64, 78) nach Anspruch 10, wobei die Drehschaufel (65) unter einem Winkel von zwischen ungefähr 30° und ungefähr 45° gegenüber der Wand der Kammer (14) angeordnet ist.
  12. Abzug (64, 78) nach Anspruch 10, wobei die Höhe der Dreh- oder Wendeschaufel (65) ungefähr der Hälfte der Höhe der Vortexkammer (54) ist.
  13. Abzug (64, 78) nach Anspruch 1, wobei die Abzugöffnung (29) mit Luftleitelementen (90) versehen ist, und zwar entlang der linken und rechten Seiten der Öffnung.
  14. Abzug (64, 78) nach Anspruch 1, wobei das Abzugelement mit einem Handgriff (94) versehen ist, und zwar mit einem Luftleitelement entlang einer unteren Kante desselben.
EP98902812A 1997-01-22 1998-01-16 Rauchabzug mit bistabiler wirbelströmung Expired - Lifetime EP0954390B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US3599797P 1997-01-22 1997-01-22
US35997P 1997-01-22
PCT/US1998/000956 WO1998031481A1 (en) 1997-01-22 1998-01-16 Fume hood having a bi-stable vortex

Publications (3)

Publication Number Publication Date
EP0954390A1 EP0954390A1 (de) 1999-11-10
EP0954390A4 EP0954390A4 (de) 2000-04-19
EP0954390B1 true EP0954390B1 (de) 2003-05-02

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EP98902812A Expired - Lifetime EP0954390B1 (de) 1997-01-22 1998-01-16 Rauchabzug mit bistabiler wirbelströmung

Country Status (7)

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EP (1) EP0954390B1 (de)
JP (1) JP2001518174A (de)
AU (1) AU5961698A (de)
DE (1) DE69814036T2 (de)
DK (1) DK0954390T3 (de)
ES (1) ES2197460T3 (de)
WO (1) WO1998031481A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108237132A (zh) * 2017-11-07 2018-07-03 苏州市凯利勋实验室设备有限公司 一种用于通风柜的自动补风装置
US20230278081A1 (en) * 2022-03-01 2023-09-07 Johnson Controls Tyco IP Holdings LLP Stable vortex fume hood control device
US12090526B2 (en) 2022-03-01 2024-09-17 Tyco Fire & Security Gmbh Stable vortex fume hood control device

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10146000A1 (de) 2001-09-18 2003-01-16 Waldner Laboreinrichtungen Abzug
EP2564948B1 (de) * 2011-09-02 2016-07-27 GFP Gesellschaft für Produktentwicklung und Produktivitätsplanung mbH Abzug und Verfahren zum Reduzieren der Schadstoffkonzentration
RU2487766C1 (ru) * 2012-01-12 2013-07-20 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Тюменский государственный нефтегазовый университет" (ТюмГНГУ) Щелевой конусообразный пылегазоприемник
JP6354312B2 (ja) 2014-05-15 2018-07-11 ダイキン工業株式会社 空気調和装置

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3218953A (en) * 1963-02-21 1965-11-23 Hamilton Mfg Co Fume hood construction
GB1595840A (en) * 1978-05-30 1981-08-19 Longworth A L Fume cupboards
US5697838A (en) * 1996-06-04 1997-12-16 Flow Safe Inc. Apparatus and method to optimize fume containment by a hood

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108237132A (zh) * 2017-11-07 2018-07-03 苏州市凯利勋实验室设备有限公司 一种用于通风柜的自动补风装置
US20230278081A1 (en) * 2022-03-01 2023-09-07 Johnson Controls Tyco IP Holdings LLP Stable vortex fume hood control device
US12064793B2 (en) * 2022-03-01 2024-08-20 Tyco Fire & Security Gmbh Stable vortex fume hood control device
US12090526B2 (en) 2022-03-01 2024-09-17 Tyco Fire & Security Gmbh Stable vortex fume hood control device

Also Published As

Publication number Publication date
WO1998031481A1 (en) 1998-07-23
EP0954390A1 (de) 1999-11-10
ES2197460T3 (es) 2004-01-01
WO1998031481A8 (en) 1999-04-22
DK0954390T3 (da) 2003-07-28
DE69814036D1 (de) 2003-06-05
AU5961698A (en) 1998-08-07
EP0954390A4 (de) 2000-04-19
JP2001518174A (ja) 2001-10-09
DE69814036T2 (de) 2004-04-08

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