US2265415A

US2265415A - Thermo compressor

Info

Publication number: US2265415A
Application number: US275611A
Authority: US
Inventors: Bergquist Hugo
Original assignee: Elliott Co
Current assignee: Elliott Co
Priority date: 1939-05-25
Filing date: 1939-05-25
Publication date: 1941-12-09
Anticipated expiration: 1958-12-09

Description

Dec. 9, 1941. H. BERGQUIST THERMO COMPRESSOR Filed ma 25, 1959 2 Sheets-Sheet l a o e o o a I 0 o 0o o n 0 u 0 I 9 00 Dec. 9, 1941. H. BERGQUIST 2,255,415

THERMO COMPRESSOR Filed May 25, 1939 2 Sheets-Sheet 2 III/11111111111111 1112711111 111. 20d

INVENTOR gi /'41. 7% 1 A A Patented Dec. 9, 1941 THERMO COMPRESSOR Hugo Bergquist, Bwlssvale, Pa, aulgnor to Elliott Company, Jeannette lvania Pennsy Pa., a corporation of Application May 25, 1939, Serial No. 275,611

5Claims.

, This invention relates to thermo compressors, and more particularly, to thermo compressors of 1 an ejector type for producing a high vacuum.

As will be appreciated, an ejector operates entirely on a kinetic plan in that it expands a propelling gas, usually steam, through divergent nozzles in such a manner that the pressure energy of the steam is converted into velocity energy. Such.velocity is relatively high. The gas mingles with and entrains the vapors to be evacuated and imparts to them a portion of its velocity, at the same time being slightly decelerated, all prior to entering a diffuser. entrainment, the mixture of entrained gas and propelling gas passes into a convergent-divergent diifuser, where its velocity energy is to a great extent converted into static pressure, thus overcoming the vacuum created at the diffuser inlet.

Very low pressures or vacuums are today useful, for instance, in chemical processing in connection with vitamin distillation or in the evacuation of rectifier bulbs, radio tubes, incandescent lamps, etc. In'this connection, I have been able to provide a thermo compressor having a useful capacity of at least. .15 millimeter of mercury down to a minimum of at least .06 millimeter at shut-oil conditions. To obtain a high vacuum, a series of vacuum ejectors are connected in such a manner that one discharges progressively into the others. Whereapplied to high vacuum work, a final stage of ejector combination, such as a fourth stage, will normally be a relatively large structure capable of handling a relatively small quantity of material in terms of pounds per hour but an enormous number of cubic feet per hour.

It resembles a conventional lower vacuum booster ejector except that it is nozzled for a relativelyv and it'is necessary. to, get an absolute pressure After corresponding to a temperature that is available in the'water supply. Since the suitable cooling water temperature is not generally available at 'least between the third and fourth stages, the

condenser is generally omitted as above outlined. Where vapors'handled have a very low pressure and a relatively high condensing temperature at that pressure, an inter-condenser can be applied between the fourth and third stages.

The propelling steam nozzle of the fourth or last stage discharges into the region of pressure corresponding to a suction pressure of such stage which, as pointed out above, may be as low as .15 millimeter. The atmosphere or gas being evacuated may consist of high superheated water'vapor, sub-cooled water vapor, gases, or any number of volatile substances of complex chemical constitution, or a mixture of such gases or vapors.

It will be apparent that the ejector pressures which are being particularly considered are in the regions corresponding to ice rather than to water, since water freezes at .23" of mercury (5.8 mm.) I have found that a globule of water ejected into such a region will promptly freeze into ice as will many other substances having lower and higher freezing points. The ice thus formed, particularly under intermittent operation, tends to evaporate oil. As an example. I have found that a steam nozzle of 7 or 8" in length projecting into a high vacuum elector and emitting steam at 250 temperature will have ice formed upon it. Ice may'also occur upon other parts of the ejector ifthere is any impingement of vapor upon the cold part. As pointed out above, the ice will then evaporate if the liquid admission is intermittent, but it may persist for hours. when additional liquid impinges and freezes at the same rate that the ice is evaporated.

Propelling steam for the nozzles may be taken at any pressure that leaves suillclent energy in it after it is expanded through the nozzle to suction conditions in the ejector. This is true since the energy range of steam upon expanding to increasingly lower pressures has its greatest value in the region below zero pounds gauge instead of the region above zero pounds gauge. In practice, it is customary to take steam at a few pounds pressure, but nozzles can be proportioned to take it at any pressure available provided the bore does not become so small as to be stopped by dirt in the steam.

I have found that if wet steam containing defl- 7 nite amounts of moisture is used in propelling through a nozzle, the results are very poor and vacuum operation impractical. I have also found that it is very diflicult i: not impractical to supply steam, gas, 'etc.', that are in a true sense dry, and for this reason, I found it advisable to carry -perh'eate'd steam 7 I condition's'eoi' afieiector does not hevdtinie to condense,*passesi?through the ejector iif'a condi- 3 I -tionor superheatfandin' this condition ishighly 'eflectivefas apropelling neretorore, in ordinary been avoided upon the belief that the overall "'eiilciency is decreased. I have definitely determined that 35 overallemciency is' increaseuanda new low f scale or' 'xibtaina'ble- -vac'uumsais made' -possible by f I I a suitable utilizationoisuperheat. conclusion. I my determinations are'based upon'the discovery I tneturystesm through a nozzle under i eenditions oi an ejector doe'sf' not have time to- I through-the elector in acondition oi'superheat, and 'inthis condition is highly I eiiective as'a propelling'mediumif'On'tm other :hand; the vacuum'range is limited and the results are unsatisfactory where vacuum electors areactuated with wet steam; That is.

the-iwater 'in thes'te'ani ifpassing through the I :ejectorinozzle bygits'presence possiblytends to in- -terruptthe flow o'i the propelling steam, or it dis- ;integrates and furnishes nuclei-"oi condensation, sin additiontocausin'g icing conditions. 5 I -have ifurthen determined =that'-with' small I quantities oi steam: suchasan ejector utilizes, it isiiiflicult to obtain s'team'oia high enough initial I superheatedtemperature to' make it'us'able. Su-

perheataddedis destrOyed by conduction oi the 1 :conveying pipingprior to; its entrance to the nozmale, and ior this reason, Iiind-itadvantageous to i provide means for superheatingthe. steamimmeco :diately adJac'ent or 'prior vto the-"entrance point V .ornozzle; Such a meanscanbeemployed to inexpensively.-.provide,-.theadesired superheat in eia. I iective and-controllable mannerthat will best suit a theoperating conditionsor a thermo compressor 65' r l-havealso i'oundlit advantageous-to eliminate a small amount of superheat in the steam. In this manner, no moisture whatever will come to the nozzle discharge at the pressure at which it v the nozzle to be projected through it. Although I from a theoretical standpoint, steam'expanding from any practical gauge pressure through a nozzle into regions of vacuum would theoretically attain the temperature of the region into which it 1. rm ced t at in Mull! r qti esi wofildih vie to do n citrein y small fraction of a second due to its high velocity 1o 01' travel. The steam actually passes so rap; is through the nozzle, through the entrainingspace and into the compression diflusen' that' rceiv the propelling steam including. tbemixture lzgeip v evacuated, that it 'does r'fi thus, goes through the elec theoretical equilibrium. Suchrariation between the theoretical and the actuafis of" ing out my invention.

It is thus apparentthat suunnecessary conduction and radiation to'obtain a e" aided through-theme under d 'ih' 'aueuon o,

;;;; uch as an ejector and to determine a practical solution of the problem inv iscovered mtorsw discharges provided the steam had time to come into equilibrium with the atmosphere in such region. I

From the above discussion, it will appear that for obtaining high vacuums under practical conditions, I preferably provide a relatively high l-Q9?! 0,1 with? el'ti lwi i i me ;h a the maid acent to o ar entrance point, limit heat losses, prevent the formation of nuclei, eliminate wetness and prevent theoretical temperature equilibrium results. And in view of ucli considerations, it ha been an object of my invention to, provide new and improved procedure 7 vacuum pressures. ,ect 01' my invention has been to e i'actors heretofore limiting the'proviiu'um by thermo compression means utnother object has' bee to-provide improved formioi tliermobompressormechanism,

and' moreparticularly; to provide: for roducing-a low-rangewflvacuum pressures {in a llracticalcand enective' manner; i If fand many "other '-obleets oi my 'invention will appear to'th'ose skilled in thie art 'irom the d'rawi'ngsg. the specification "and the claims.

c Figure is'a-sideiview in elevation partially in ctio'n'randzi showing an 'eiector' apparatus emriiy inventlon; a": 1, --,i

'rFigiire 2 isa i'ront view in esteem alone the line II*1I:oirFigure* 1 showing a m ed or additionalaheatin'g arrangement; I

Flgure zA'ista similar mmmm m oi I Fl gures 3,4 view sin elevamm taken through 'devi'ces'constr'ucted =in -mom-, .-ance with the-principles of invention;

3;; Iigures 3a: and- 'iaareflsections taken along the Hu ins-ma ands Iva-Iva; respectively, 7 of 3 and4;respectively. v

Reierringparticularly to Figure 1", Ihave'shown -;anejector apparatus having 'a chamber I housing l lifprovid'edwith a rconvel'glnz-diverging discharge-nozzle or element Hand-having an in- -letli i'or-thegas or fluid tobe evacuated:

- An ejector:nozzle .-ll is-removably mmmted on I ,an inlet-tube I! hand 1provided with asisuitable strainer l6. .Steamrirom amain line ll isbled oi! through a steam chest or'.i"-1 ='3l; having-suitable v mounting flanges", through astrainer 32, past a controlvalveifl. to theinlettube 'i 'I. The inlet 7 tube l l; is shown provided with .a steam gauge connection; I 9,. andis shown as mounted to-extend througha gland orgasket il;;i.nto themixing chamber Ill. The steam thusintroduced into the tube i1 is superheated by asuitable agency such as electrical heating elements or grids '2. having electrical connections or: terminalsila :It will be seen thatthe steam entering tube ll'l passes-lon- ,gitudinally along andoverandbetween-the heat- 18mm. inzsucha mannertha't it is heated to dryness by conduction; convection. andradiation. I

In Figure 2; I. have or additional heating agency 2! that is aboutv th'egland or gasket 18 adjacent the entov the mixing Although this element may be gas orrelectrieally heatedgj! have for the mm ne oi. illustration shown 's steam coil type oiheattrsnsteragency: In'l'isure 2 {have shown an electric-element 22a.

Referringpartimlarlytol'igurestandiim! have shown a steaminlettube l'la having an encircling tube It positioned about a portion of chamber suchtubeandextendingintoamixing II. A nonle II is suitably moimted at or ad- Jacent the end of the tube combination provided Figures 4 and is, I have provided an inner tube "b, an intermediate tube 2|, and an outer tube It. Suitable insulation 21 r (such as asbestos. glass wool, an air space, etc.) may be interposed between the tubes 2! and i2 and substantially horizontally or longitudinally-extending baiile means 24 is substantially centrally positioned to extend along the spacing between the inner tube 1Tb and the intermediate tube II to direct a heating fluid such as steam entering from an inlet tube 23, along the bottom side of the tube i'lb towards the front thereof to a point adjacent the entrance to the nozzle it, then upwardly through a front oifset portion of such fin-like baiiiing 24 and backwardly and longitudinally along the upper half of the energizing steam tube i'lb to an outlet pipe 25. It will thus be seen that the energizing steam entering through tube "b is heated chiefly by radiation and conduction from a suitable fluid heating agency introduced through the pipe 23 and having a return flow with respect to such tube.

In the embodiment of my invention shown in' Figure 5, I provide insulation between the tube "a and the outer tube II. The energizing steam introduced through inlet it into a supplemental heat chest 28c is then conducted into the main tube inlet "c and to the ejector nozzle ii. A heating element 20b shown as an electrical element, is provided with a screwhead 200 for mounting in a longitudinally extending position within the chambers formed by the tube He and the chest 28c. In this manner, the steam is heated by conduction and radiation as well as convection, and is permitted to pass along and about the heating element 20b. The heating element is provided with electrical connections 24 leading to an energizing agency 25c through an automatic control device 25'. The unit 20b preferably includes a thermostatic metal having expansion and contraction qualities such that it will automatically ."break the electrical contact to the heating element through the control 25 when the temperature tends to go above a desired operating temperature range and will automatically "make" contact below such temperature; any suitable commercial form of thermostat can be employed. It will be apparent that'any suitable heating agencies may be employed in the various embodiments of my invention, for example, electrical, gas, steam, etc.

In Figure 1 of the drawings, I have indicated the normal fluid flow from the nozzle I! by the letter 1). In some cases, the propelling steam may be cooled down until, for example, at the suction of the third stage, it is so cool that fluid passing through the nozzle in the third stage, which may include a part of the operating steam in the first stage, will freeze at the location indicated by a in Figure 1. In installations where there is a possibility of ice formation at the point a, I preferably provide somesuitable fo'rmof heating element such as a calrod element 22a, seel'igure 2A,thatmaybemountedexternally about the housing It as shown. Of course, any suitable form of heating agency or, element may be employed in this connection. The element 22 of Figure 2 or the element 22a of will heat the interior 'of the elector adjacent the point a by conduction and thus prevent icing at this point.

When I speak of immediately in the speciflcation and claims, I have particular reference to the introduction of the reheated steam into the small throat area of the propelling noule il before it has lost its dryness or, in other words. before the eflectiveness of the reheating operation has been lost by condensation of a portion of the energizing fluid or steam.

Although for the purpose of illustration, I have shown representative embodiments of my invention, it will appear to those skilled in the art that many substitutions, additions, subtractions,

and modifications may be made without departing from the spirit and scope of the invention pressor adapted tooperate at a relatively highvelocity and below the pressure region of ice, a mixing chamber, a steam ejector nozzle for introducing propelling and energizing condensable fluids such as steam into. said mixing chamber, means connectedior supplying energizing steam at a suitable pressure to an inlet end of said ejector nozzle, said nozzle having a portion with a small throat opening at the inlet end thereof. such portion of said nozzle expanding towards a discharge end of said nozzle for converting pressure energy of the steam into velocity energy, and heating means operably disposed along said supply means upstream of the small throat opening of said nozzle, said heating means having an effective heat transfer area suflicient to insure at least dryness of the steam being supplied to the small throat opening of said nozzle.

2. In a low vacuum-producing thermo compressor adapted to operate at a-relatively high velocity and below the pressure region of ice, a mixing chamber, a steam ejector nozzle for supplying energizing and propelling condensable fluids such as steam to said mixing chamber, means connected for supplying energizing steam of at least a few pounds pressure to an inlet end of said nozzle, said nozzle having a throat portion provided with a relatively small bore at the inlet end thereof, said throat portion diverging outwardly from the small bore towards a discharge end of said nozzle to convert pressure energy at an inlet end of said nozzle into relatively high velocity energy at the discharge end sufllcient to prevent the steam from coming into temperature equilibrium with the atmosphere of said mixing chamber and suflicient to provide a pressure in said mixing chamber of as low as .15 millimeter a solute. and heating means operably positioned along said steam. su ply means, said heating means having a portion upstream of the small b re of the inlet end of said nozzle, said upstream portion of said heating means having an effective heat transfer relationship with the steam being supplied such that the steam will be heated to a heat sufllcient to insure at least dryness before entering the inlet of said nozzle and during its movement through the small bore of said nozzle throat portion.

prom te at airelativelyihizh 've lociii-ianll 'lt irrelatiyelyilow; lowithe-re'gicn hfice;=amixing3chamber-;fa steam' ejector nonleitorirsupplyingzenergizlngqandwpro fluids :such as: 'steam'xto connected itomsupplying I energizing atra suitablepressuretoln letxend o: nozzle; saidmozzl'efhaving aathroa mm relatively mu bore at the iniet endwi thereob'smh @throat. portion diverglngz outwardly towards a'disoharge end..=thereot, tovconvertpres disposed along connected supply means in .locity theLdlscharge'end, :heating a a otisteam-travehtherealong; Ta down-J s-r stream. end;

portion 701v saidiheating means being 2-: I

positioned upstream of the inlet "endzofzsald noz-,--.;; zle, said hating; means 1 being:- adapted. #to vh'eet the steam supplied to the inletend of. said noule toia superheat sumcient topinsure sat least; dryness; or? xdurlng: its ,zmovement if through the smallbore ofasaid nozzleithroatportion; isaid thmat portion being constructed and arran ed to provide-a velocity. flowinto said mixin: chamber sumcient to prevent the steam-from coming into temperature equilibrium with the ate mosphere'of: said mixing chamberm; 1 4. In a method of preventing. erratic prop eflect otan enersizlns fluid such assteam caused by' the tormatkm. oimoisture, in i an :expansion.

mien

throat otan ejector operating belowthe pressure ergizin' g tteam oilsuitablepr'asure toiinsure firy 'reheateddrylisteam throug'b-as. relativel -man byutheztormationg of moisture sin ansex ling-a: 'sumcient :"heat to; insure r dryiness; oi rthe' regionfot iee whichzeohsistciofiezadding :sumcfent heat toi a'jeondens'abler'energizingafluidiauchzssen nesrcthereomandscitherr immediately moving propelling: nozzle: hroatifareagi' and'r convertiug pressure energwot: thef'heatedsvsteain :into' rel'a diverging area towards the 'disch'a'r gew end :otsthei 5. n1 en ined oi m'vemng erri'nm pul sion eHectmt-anFenergizingv fluid'=i:si1ch as steam pansionzthroat oi-nan ejectonoperating-below the pressures' region o'fiice which-consists ofl provid ing' an gener'gizingnmd .cpropelllngisfluid such as steamaofi suitable =pres'sur'e:and temperature-fade!