US3134534A - Vapor-entrainment pumps - Google Patents

Description

May 26, 1954 H. JANCKE ETAL 3,134,534

VAPOR-ENTRAINMENT PUMPS Filed Feb. 16, 1961 3 Sheets-Sheet l lNv NToRs ATTO RNEY 3 Sheets-Sheet 2 Filed Feb. 16, 1961 Cocu/awr INVENToRs AfA/vs JIq/vck-E BY A64/vs .Bee-rz ATTO R N EY May 26, 1964 H. JANCKE ETAL 3,134,534

VAPOR-ENTRAINMENT PUMPS Filed Feb. 16, 1961 Tlc.

3 Sheets-Sheet 3 IN ENTORS Aly/ss ,4A/cme ATTORNEY United States Patent Oiice 3,134,534 Patented May 26, 1964 Akademie der Wissenschaten zu Berlin, Berlin-Adlershot, Germany Filed Feb. 16, 1951, Ser. N 89,782 Claims priority, application Germany Feb. 23, 1969 13 Claims. (Cl. 230-101) The present invention relates to singleand multi-stage vapor-entrainment or condensation pumps and more particularly to a novel arrangement of a heating system providing very short heating and cooling periods in such purnps.

It is known that in condensation-type pumps the entraining uid is heated to evaporation and then conveyed in a gaseous state, from the boiler to the ejector nozzle with a view to achieving the pressure required for the operation of the pump. Upon leaving the nozzle, the vaporized uid condenses on the enclosure walls, which are usually cooled by extraneous means, after which the huid returns in a liquid state to the reservoir or boiler.

In this type of arrangement it cannot be avoided that almost the entire amount of fluid has to be maintained at a relatively high evaporating temperature in the boiler although only a small portion thereof is being evaporated for useV at any given moment. Consequently, it takes a long time to heat up and to cool down the pump, resulting in diiculties which are particularly evident in case of intermittent use. Various diusion pumps have been designed which incorporate special fast-cooling devices in an attempt to overcome these dili'iculties.

The heat losses in these vapor-entrainment pumps originate not only from the necessity of removing the heat stored in the uid but also from excess evaporation of the entire tiuid surface. This circumstance also results in undesirable heat losses of the vapor which becomes unnecessarily cooled on its way to the ejector nozzle.

It is an object of the present invention to provide a novel vapor-entrainment pump overcoming the dilculties and drawbacks experienced with previous arrangements. In particular, object is to provide in such systems a special delivery pump for conveying the entraining iluid to a region of the vapor-entrainment pump close to the npzzle where the localized heating and evaporation takes piace.

It is another object to provide a vapor-entrainment pump wherein the riser tube leading to said region of localized heating is cooled so as to return as much entraining fluid as possible to theboiler.

The present invention represents a simple yet elective solution of the drawbacks characteristic of hitherto known types of condensation or vapor-entrainment pumps. One of the main features of the invention resides in the provision and disposition of the heating means adjacent the nozzle or nozzles-of the pump, adjacent the zone of use, rather than around or within the uid reservoir or boiler, remote from the zone of use. A conventional type of delivery pump may be used for raising the iiuid from the reservoir to the region of the heating means.

It is a further object of the invention to provide a cooling jacket around the riser tube of the delivery pump and/ or an overow tube which returns the excess fluid from the ejector means to the reservoir.

In a preferred embodiment using a conductive liquid metal, e.g. mercury, an electromagnetic pump is provided for conveying the entraining uid to a small pool adjacent the combined heating and ejector unit. Advantageously, the fluid in such a small pool can be heated by passing an electric current through the conductive liquid.

The invention oiiers several advantages over previous systems. The most marked dilierence is that the entire volume of fluid contained in the reservoir cools down to the coolant temperature shortly after the vapor-entrainment pump is disconnected. There is no need for compensating temperature dierences between the heater at the bottom of the boiler and thecooling jacket.

lt is a further advantage of the arrangement of the present invention that the operating pressure at the ejector nozzle, or at each of several nozzles of multi-stage systems, is simple to regulate. The vapor-pressure regulation has a negligibly small time constant due to the low heat capacity of the heated parts. Moreover, the heating of each separate nozzle stage in the multi-stage embodiment, can be controlled individually. Y

In multi-stage vapor-entrainment pumps equipped with one or more stages, according to the present invention, the quantities of entraining duid supplied to the individual stages can be easily adapted to the actual consumption.

These and other features and advantages or" the invention will become more apparent in the following description and the enclosed drawings, in which:

FlG. l is a partly schematic sectional view of a preferred embodiment of a single-stage vapor-entrainment pump according to the invention;

FlG. 2 is a similar View of a vapor-entrainment pump using an electrically conductive liquid metal as the entraining fluid; and

FIG. 3 shows a schematic arrangement of a multi-stage vapor-entrainrnent pump having a high-pressure forevacuum stage connected in series with two diffusion-type stages.

In FIG. 1, the vapor-entrairnnent pump is shown to comprise a housing or shell 10 enclosing an inner shell lila having a lower portion which forms a reservoir 11 containing the entraining fluid 12, which may be an-oil having low vapor pressure, as generally used in diffusion pumps. The Space between the shell and the housing serves as a cooling jacket 13 provided with an inlet 13a and an outlet 13b through which a coolant is circulated. A conduit 14 serves to connect the entrainment pump to a suitable source to establish a fore vacuum (not shown), while a conduit 15 provides a high-vacuum connection through which the pump may be connected to the system to be evacuated.

Above the reservoir 11, a delivery pump 16 is arranged within the inner shell 16a, with its inlet tube 16a reaching into the uid 12 in the reservoir 11 and with its outlet tube 16b rising substantially centrally within the shell 10a to the region of the ejector 17. The unit 17 is preferably supported by flanges 17a and 17b attached to the cover portion of housing 1t). The ejector unit 17 has a recessed portion 17C holding a pool 18 of the entrainment lluid supplied by the outlet or riser tube 1611 of delivery pump 16. A heater 19, shown here as a double annular electric heating element, fed from a source of current 21 through a variable resistor 22 or other conventional means, is disposed to heat the liquid in the pool 1S. The ejector 17 also has one or more nozzles, two of which are shown at 2tlg and 2Gb. The delivery pump 16 is energized from an electric source 23; this may be separate from or identical with the source of current 21 for the heater.

The ejector unit 17 may be provided with an overow tube 24 the upper end of which is flush with the Huid level in pool 1S. Both the overliow tube 24 and the riser tube 1617 of delivery pump 16 can be provided with cooling jackets 25a, 25h, respectively. These cooling systems may, of course, be operated parallel with or independently from the cooling system of jacket. 13 of the housing 1i).

' mally held at relatively low temperature.

the gas Within the inner shell 16a is rareiiedrto a desired extent, `the'delivery pump 1J and vshortly 'thereafter the heater 19 are put into operation. The duid 12 in reserlvoir 11 will remain substantially at its. original temperature, While the fluid in pool 18 of the ejector unit 17 will be heated suilciently to be vaporized, and the vapor will emerge, in the form of streams through the nozzles 2da, Zilb. The vapor streams trap the molecules of gas or air originally in the inner shell 16a, and those which diffuse intoV the shell from the system to be exhausted. The downward moving vapor streams carry the air or' gas down to the region where the fore-vacuum pump is effective to remove the gas andpass it to the atmosphere. Relatively high vacua can be obtained with this singlestage'vapor-entrainment pump system.

The cooling 'jacket 13, aided by the optional jackets a, 25b,7condenses the vapor streams which thus return in liquidl state along the inner walls of the shell 19a into the`V reservoir 11. The entraining iluid is consequently used over and over.

Byheating only the'small volume Vof liquid in poolv 18r to generate the vapor streams, the, large reservoir of liquid and the housing structure, generally, will be norapparatus may then be quickly restored to ambient ternperature at-the conclusion'of an operation.' This representsan important feature of the invention.

In FIG. 2, another embodiment of a single-stage vaporentrainment pump isshown, where a conductive liquid metaLcg. mercury, is used `for entrainment. Here the housing or shell 50 has a narrow bottom portion 51 serving as'a reservoir for the mercuryA 52. v,The coolingV v jacket 533k has an inlet 53a and an outlet 53h arranged in a fashionsimilar to that shown in FIG.` 1, with the difference, however, that the jacket of this embodiment surrounds only the upper portion of the pump structure 59. The fore-vacuum and high-vacuum apertures are designated 54 and 55,.respectively.

In this system, an electromagnetic pump56 is applied to raise the mercury 52 from the reservoir 51 into a tube 56h.k The pump 56 comprises an armature 56C which carries a coil 56d which is ed from an A.C. electric source 63. vThe alternating magnetic held-between poles 56e of the armature 55C imparts a pulsatingrmo'tion to the mercury within a throat Sf ofY the tube 56b, whereby the mercury is forced up through the tube 56b into apool 58 in a recessed portion 57C of the ejector unit 57. ln this embodiment, the ,mercury inthe poolV 58 is heated by means ofVY an arc discharge produced between an electrode 59a reaching into the pool 58 and themercury itself; the current is led from a source of current 61 through a regulator means l62 to the electrode 59a on the one hand and to the ejector-unit body on the other,

' the latter being provided with a terminal 59h. VElectrode j 59a is insulated from'theV unit 57; terminal 59h with the corresponding pole of source 61 is kept at ground potential, Vso that there will be no interference with other electrically conducting parts.

The ejector unit 57 Vhas nozzles tla, 691: and an over ow tube 64 carrying the excess mercury back tothe reservoir'Sl. In this embodiment, no additional cooling jackets are shown for the tubes 56h ando-4, although, it is to be understood, the cooling eiect can be achieved in ythe same manner as in the Vprevious illustration.

'I'hevapor-entrainment pump, according to the presentrinvention, may also be arranged in a single stage or Y in several stages of amulti-stage'pump, as schematically illustratedrin'FIG. 3. Thisembodiment is provided with a preliminary liquid-jet stage 77, an optional vaporor liquid-jet stage 37 and two ditusion stages 97 and 97', both of the latterk being similar to the ejector yunit 17 shownin HG. 1. The stagev77 has Ya construction Si) The entire for the passage of the entraining uid; stages 77 and are connected in series with the following parallel-acting stages 97 and 97. all the remaining stages are supplied by a delivery pump, or pumps 76 which have an inlet tube 7621 reaching into the tiuid 72 contained in a reservoir 71,V these elements being similar to the respective elements 16, 15a, 12 and 11 of the mst-described embodiment. In Ya similar way, the pump` housing or shell 79, the cooling jacket 73, its

connections 73a, 7311, the fore-vacuum connection 7.4 and the high-Vacuum aperture 75 all correspond to their counterparts 1t?, 13, 13a, 13b, 14 and 15, respectively,

of the i'lrst embodiment.

Owing to constricted nozzles 96a md 9i b of the vaporjet stage S7, this stage may be operated at a high pressure. An ample amount of Ventraining uid is supplied by the delivery pump, or pumps 76 through a riser tube db. Similar and parallel riser tubes 96b and 95h' are provided from the same delivery pump, or pumps to the ditusion stages 97 and 97", respectively. All riser tubes `have respective valve means 31, 91 and 91 individually i Y the sake of clarity, the supporting'flanges 17a, 17b, the

electric connections 21-23 to the heaters, and otherV structural details of FIG. l have been omitted fromthe Y' somewhat'schematic showing of FIG. 3. y

When the heating element 89 of stagey 87 is disconnected, this stage will perform as a liquid-jet stage; with the heater on, the iluid 72 will be .vaporized as in the diffusionrstages, so thatV the nozzles 90a, 90b will perform as vapor jets.

In ajmulti-stage entrainment-pump according to this invention, a very high'pumping stability is attained Vowing to the provision of the adjustable valve means 81, 91, 91'V which will allow the required individual pressure valuesk to be maintained forall stages without overloading them.

The stability can be increased by incorporating suitably selected owresistances into the ,fluid riser tubes or by other control means, eg. by providing the riser tubes With predetermined cross` sections. j

It will be obvious to those skilled in the art that various changes and modilications may be, made in theV vaporentrainment pumps according to this invention withoutA departing from the invention in its broader aspects. It w11l be appreciated, for example, thatV the conveying,

heating and ejector means may be substituted by other' equivalent means, e.g. a high-frequency heater or a steam coil maybe used, fed by respective external sources.

Also, the Vlast-described embodiment may be yprovided prising an enclosing shell, a reservoir in thelower portion j of sa1d shell, a vaporizable iluid in said reservoir, ejector means for the vapor thus obtained in said upper portionY of said shell, said shell having, below said-ejector means, a fore-vacuum port connectable to an external pressurereducing means of a known type, and having, above said` ejector means, a low-pressure port connectable to theV system to be evacuated, Vintermediate storage means between said lower and upper portions of said shell, iluid conveying means between said reservoir and said intermediate storage means for raising said uid from said Except for the liquid-jet stage 77,-

reservoir to said intermediate storage means, said intermediate storage means being in fluid communication with said ejector means, heating means provided for said huid in said intermediate storage means to vaporize said raised luid, whereby the vapor leaving the ejector means will entrain molecules of the gas v ithin the pump and guide them down to the region of the fore-vacuum port through which they are passed to the atmosphere, and a cooling jacket surrounding at least said upper portion of said shell and adapted to condense said vapor into fluid for return into said reservoir, and only a small proportion of the total amount of said vaporizable iluid is heated at one time.

2. A vapor-entrainment pump, according to claim 1 wherein said conveying means for the duid comprises a centrifugal pump, an inlet tube of said pump reaching into said reservoir and an outlet tube of said pump being connected to said intermediate storage means.

3. A vapor-entrainment pump, according to claim 1, wherein said conveying means comprises a duid displacement pump, an inlet tube of said pump reaching into said reservoir and an outlet tube of said pump being connected to said intermediate storage means.

4. A vapor-entrainment pump, according to claim 1, further comprising cooling means disposed adjacent to at least part of said conveyinfr means, for accelerating die condensation of said vapor after it emerges from said ejector means.

5. A vapor-entrainment pump, according to claim 1, further comprising an overflow tube leading from said intermediate storage means to said lower portion of said shell, whereby the excess quantity of the lluid raised by said conveying means is returned to said reservoir.

6. A vapor-entrainment pump, according to claim 5, further comprising a second cooling jacket around said overflow tube for equalizing the temperature difference of said duid within said reservoir and said ejector means.

7. A vapor-entrainment pump, according to claim 1, wherein said iiuid is a conductive liquid metal, and said conveying means comprises an electromagnetic pump raising said liquid metal from said reservoir to said ejector means, an inlet tube of said pump reaching into said reservoir and an outlet tube of said pump being connected to said intermediate storage means.

8. A vapor-entrainment pump, according to claim 7, wherein said heating means comprises at least one electrode connected to a source of electric current and contacting a pool of said liquid metal within said intermediate storage means so as to vaporize said liquid metal.

9. A vapor-entrainment pump for rarefying gases, comprising a pump shell, a reservoir in the lower portion of said shell, a vaporizable lsluid in said reservoir, a plurality of ejector stages within said pump shell, each having iluid storage and heating means for storage and heating of part of said vaporizable huid, separately controllable conve* ing means for said iluid storage means of each of said plurality of ejector stages, delivery pump means adapted to deliver said vaporizable fluid to the fluid storage means of said ejector stages via said conveying means, a highpressure port in said shell below said ejector stages, said high-pressure port being adapted to be connected to an eX- ternal pressure reducing means of a known type, and a low-pressure port above said ejector stages, whereby said part of said tluid in said storage means of at least one of said ejector stages is vaporized by said heating means associated with said storage means and the uid becomes vaporized and said vaporized uid is emitted through the ejector stage to entrain gas molecules sucked through said low-pressure port and pass them through said high-pressure port.

10. A Vapor-entrainment pump, according to claim 9, wherein said controllable conveying means comprises inlet tube means of said delivery pump means reaching into said reservoir rmd a plurality of outlet tubes of said delivery pump means, each outlet tube being connected to one of said ejector stages, and control means for regulating the amount or" huid delivered by said delivery pump means to each of said eje tor stages.

11. A vapor entrainment pump according to claim 10, wherien said delivery pump means comprises a plurality of delivery pumps, and said inlet tube means comprises an inlet tube for each of said delivery pumps.

12. A vapor-entrainment pump, according to claim 9, further comprising cooling means connected to at least part oi said shell and of said conveying means adapted for temperature compensation between the vaporized and liquid portions of said huid.

13. A vapor-entrainment pump, according to claim 9, further comprising an overilow tube leading from at least one of said ejector stages to said reservoir, whereby the excess quantity of the fluid raised by said delivery pump means and said conveying means is returned to said reservoir.

References Cited in the ille of this patent UNITED STATES PATENTS

Claims (1)

1. A VAPOR-ENTRAINMENT PUMP FOR RAREFYING GASES, COMPRISING AN ENCLOSING SHELL, A RESERVOIR IN THE LOWER PORTION OF SAID SHELL, A VAPORIZABLE FLUID IN SAID RESERVOIR, EJECTOR MEANS FOR THE VAPOR THUS OBTAINED IN SAID UPPER PORTION OF SAID SHELL, SAID SHELL HAVING, BELOW SAID EJECTOR MEANS, A FORE-VACUUM PORT CONNECTABLE TO AN EXTERNAL PRESSUREREDUCING MEANS OF A KNOWN TYPE, AND HAVING, ABOVE SAID EJECTOR MEANS, A LOW-PRESSURE PORT CONNECTABLE TO THE SYSTEM TO BE EVACUATED, INTERMEDIATE STORAGE MEANS BETWEEN SAID LOWER AND UPPER PORTIONS OF SAID SHELL, FLUID CONVEYING MEANS BETWEEN SAID RESERVOIR AND SAID INTERMEDIATE STORAGE MEANS FOR RAISING SAID FLUID FROM SAID RESERVOIR TO SAID INTERMEDIATE STORAGE MEANS, SAID INTERMEDIATE STORAGE MEANS BEING FLUID COMMUNICATION WITH SAID EJECTOR MEANS, HEATING MEANS PROVIDED FOR SAID FLUID IN SAID INTERMEDIATE STORAGE MEANS TO VAPORIZE SAID RAISED FLUID, WHEREBY THE VAPOR LEAVING THE EJECTOR MEANS WILL ENTRAIN MOLECULES OF THE GAS WITHIN THE PUMP AND GUIDE THEM DOWN TO THE REGION OF THE FORE-VACUUM PORT THROUGH WHICH THEY ARE PASSED TO THE ATMOSPHERE, AND A COOLING

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