US2583812A - Dehydration unit - Google Patents

Description

Jan. 29, 1 s. w. BRIGGS ET AL DEI-IYDRATION UNIT Filed June 5, 1947 I/wmro SOUTHW/CK WBiE/GGS Wm TE C. BHUEAE Patented Jan. 29, 1952 UNITED STATES PAT ENT OFFICE DEHYDRATION UNIT Southwick W. Brig-gs, Washington, D. 0., and 'Wal'ter G. -B'auer, -Chevy Chase, and walteral. :Ewban'k, Beth'esda -Mdq said Ewbank andzsaid Bauer assignors to The BriggszFiltration Com- ;pany, Bethesda, .:-Md., a corporation ofv Mar-ykland Apfilication' June-5, 1947,S'eri'a1No. 7523754 1:1 This invention relates to "dehydrating apparatus and=more'particular1y to a dehydratorifor removingm'oisture'from refrigerants.

In the 'usual refrigerating apparatus the refrigerant, a fiuid having suitable volatility charatemperature 'of the-apparatus tobe cooled. The l zrefrigerantrisathen passedto the refrigerated unit .and::absdrbs.heat from that unit-before again :passing to the :compressor to repeat the cycle.

One 40f the :most :e'ommon difiiculties "en- :'countered with refrigerating: machinery is freez- W ring :of a moisture as it passes through the 1 1ex pan- -sion valve. Whenssubjected to theulow temperature on the discharge side of the expansion valve the moisture form's ice whichfiinter feres with the operation of lth'e valve. iIhe valve zmay then be r frozen :in the T013611 position 'whichrpermits Lexroe'ssiverrefrigerant :to ("pass into the :heat Iabsorbling? apparatus. Inzsuch a :case the refrigerant is mot :completely "vaporized in the aheat absorbing apparatus, and "either masses to the compressor z-as i'a iliquid or lowers the pressure :of the *vapor :sufficientiy to'impairwthe afiow .ofs gaseous :refriger- -ant tozthe compressor. I f:It is only :neeessary for the "usual refrigerant :torbemontaminated with traces ofsmoisture "to "cause the -.formation of sufficient ice to interifere with the operation rof the expansion valve. The moisture may enter the refrigeranta'at the compressor through wmoisture-contaminated oil used to lubricate the; compressor. "In most cases, however, the moisture is introduced through j leaks .-in the refrigerating system at ,points in the-apparatus where the refrigerant is 1 underlless than-atmospheric pressure. Many :of the.:most

'eommoni refrigerantsrnow used =Wi11: be atipre'ssures considerablyxbelow atmospheric during certain; periods of therrefrigerating cycle.

:Heretofore dehydrators 1 have :been employed in which the moisture r-absorbing :material is in *a lfinely divided storm. The finely divided :desic- .cants, however, possess the veryserious disadvvantage of tending tolzleave the body :of the 1 absorbent rmaterial &and enter the stream of the refrigerant. .iIhe desiccating materialuthenrmay .cause Eserious :damage r-to .the =fin'ely machined 2 parts of l the -refrigerating apparatus. This edifficulty is aggravatedby attritionofvthexparticles of desiccant whenit'is in a loose condition. The *movement of the particles as the refrigerant flows past them diminishes thesize of theparticles which, or -"course, facilitates their leaving the "body "of absorbent material. :Furthermore, there is -a -tendenoy for the refrigerant to channel through the loose absorbent materiaI, thereby reducing the efieotiveness of i the absorbent.

'Anobject of this invention is to provide a monolithic moisture absorbent 'body *for Lthe Ireunoval .of-moisture from refrigerants.

6A 'further objeot of this invention is: to :.pro-

-vide Jan reflective, :compact dehydrator :lhaving a large oapaoity for removing water from the reifrigerantsrand whichrmay bei manufacturedlat a zlo'wreost.

i'Another obj eot 'of this invention is :ito provide "a =dehydrator for refrigerants in which .a large 'blockiof bonde'd adsorbent issupported inawcasingand notchessare provided in the block 'to allow the refrigerant to bypass a portion of the block.

I-tiisalso an object of this invention to:provide alrugged compact dehydrator for refrigerant xin which the dehydrating amateri'aliis bonded'actiilvatedcalumina.

*Withzthese and:other rob iectsiinsmind thisxiniventio'nliresides in :a dehydrator for refrigerants iin which ailargemassxof-bonded adsorbentima'terrialiis supported-directly by -the Wa11s of a casing an-d in'otoh'es iin :the bonded zadsorbent==allow the refrigerant to bypass a portionmfitheiadsorbent. ;In .therdrawings:

aEigure I is :an "elevation*views-of-therdehydrator cconstruoted ia'coording to lthis invention; LEigure Z is a longitudinal sectional view :along the :line I'2.2 fofi Figure 1 of the dehydrator; and

.i'Figul-e 3 is an rexploded':perspeotive view "showaing the arrangement of the various parts within :thenc'asing (of the dehydrator int aninvertedaposiition. i IInzmost oasesitheidehydrator herein-described will be used to remove moisture .sfro'm ithe refrigerant "1 when the :refrigerant :is :in 'l the illiquid toiremovei the "moisturetfrom' afgaseous iirefriger- 1 an upper section 2 and a lower section 3. Sections 2 and 3 of the casing are generally cupshaped members preferably drawn from sheet metal. The bases 4 and 5 of cup- shaped sections 2 and 3 are apertured at 6 and 1, respectively, for the reception of nipples 8 and 9. Nipples 8 and 9 are threaded for connection with the conduit conveying the refrigerant through th refrigeration apparatus and provide an inlet and outlet to the dehydrator.

Immediately adjacent the bases 4 and 5 of the sections 2 and 3 of the casing are relatively restricted lateral portions I and II forming part of the lateral wall of the casing. These relatively restricted sections extend for a short length along the depth of the cup-shaped members and join with expanded wall portions 12 and I3 comprising the remainder of the lateral wall of the dehydrator. The cup- shaped sections 2 and 3 are joined along their rims l4 and I to form a hollow vessel closed at the ends by the bases 4 and 5 and having openings in the ends for the introduction and discharge of the refrigerant.

In the preferred form of the invention shown in the drawings, the rim M of one of the sections of the casing is flared outward to overlap the rim 15 of the other section. Rim 15 fits snugly against the inner wall of the flared rim and is secured thereto by a sweated joint. After the formation of the sweated joint, the extreme tip of rim I4 is rolled against the outer wall of the other section. This method of joining the. two sections of the casing provides an inexpensive means of forming a fiuid tight joint. Of course, other methods, such as the use of flanges to join the two sections, may be employed if desired.

Fitting within the casing and resting on the base 5 of section 3 of the casing at its juncture with the restricted tubular section II is a perforated plate I6. This plate is usually constructed of metal, preferably aluminum, and serves as a support for a disc of glass wool I'I resting on its upper surface, and the moisture absorbent material l8. A similar perforated plate l9 fits at the juncture of the restricted portion of the walls of section 2 and the base of that section and retains a second disc of glass wool resting on the upper surface of absorbent material l8. The absorbent material I 8 is of sufficient length to subject the perforated plates I6 and I9 to a slight stress when the sections of the casing are joined which aids in holding the absorbent material firmly in place.

The glass wool disc is ordinarily prepared from felted glass fibers of V extremely smallv diameter. The disc .has the appearance and feel of soft felt and is not brash as are the ordinary glass wools. Furthermore, the wool prepared from these extremely fine fibers does not break off in splinters as is common with most glass wools. By the use of this exceedingly fine glass fiber, the filtering properties of the disc l1 are enhanced and the danger of glass particles breaking free from the disc is minimized.

The disc I! is primarily to make sure that no solid particles will leave the dehydrator. It has also been found satisfactory to use a disc prepared from glass cloth. The weave'of the cloth should be sufliciently close to prevent any particles of the absorbent from passing therethrough. A disc prepared from glass cloth has some advantages in strength over the felted glass wool previously described.

The term absorbent material is herein used in its generic sense and includes material relying on adsorptive as well as absorptive properties for removing moisture from the refrigerant. It is essential, however, that the absorbent material be of a self-contained nature and not a loose porous bed of desiccant. The loose porous beds of desiccating material have the inherent disadvantage of tending to leave the enclosure retaining the material and entering the stream of refrigerant. Since many of the desiccating materials having the best moisture absorbing properties are of a hard granular nature, they might cause serious scoring of the refrigerating equipment if allowed to pass from the dehydrator.

It is preferred that the absorbent material be a single block or monolith of activated alumina. Such a block may be prepared by binding ground hydrated alumina with a binder, and heating the block to the temperature suii'icient to activate the alumina. The binder should be of a material capable of withstanding the temperature required for activation of the alumina. For example, hydrated alumina may be mixed with an aluminum phosphate binder of the type described in U. S. Patent No. 2,405,884 to form a plastic mass which may be molded into any desired shape. On air drying the aluminum phosphate binder sets to give the cast or molded block sufficient strength for ordinary handling. When the block is then heated to the temperature necessary to activate the aluminum'phosphate, the binder forms a hard, water-resistant binder which is excellent for use in a dehydrator. By control of the proportions of hydrated alumina, aluminum phosphate binder and water, a porous block is formed having absorbent properties equally as good as unbonded alumina. The bonded block, therefore, has all of the advantages inherent in a monolith of absorbent materials such'as resistance to attrition of the absorbent, channeling through the absorbent, and classification of the absorbent material without any loss of dehydrating properties.

For example, bauxite varying from 60 to 100 mesh in particle size may be mixed with an aluminum phosphate of the type described in Patent No. 2,405,884. The aluminum phosphate will comprise approximately 23-10% of the mixture. Sufiicient water is added to the mixture to give it the desired workability and a block of the proper shape is molded. After air drying, the block is heated to a temperature of 450 F. to 1200 F. to activate the bauxite. The time and temperature of activation will be determined by the degree of activation desired. This example is described only to illustrate a method of preparing the absorbent block, and limits the invention in no manner.

Binders other than those having an aluminum phosphate base have been used. Binding materials prepared from sodium silicates may be used, but they, in general, are not as water-resistant as the aluminum phosphate materials. Organic adhesive materials are not as satisfactory as the aluminum phosphate binders because they char on heating to activating temperatures.

It is, of course, within the scope of this invention to use other absorbent materials. Silica gel, for example, has been widely used a8 a desiccant because of its excellent water adsorptive proper ties. Silica gel, however, has a serious disadvantage of breaking up into fine particles when exposed to water in the liquid, rather than the gaseous, phase. In view of the hardness of the particles of silicagel, serious damage to thereanaemia era-gaming :apparatus' niight'ibe iincurred air the glass disc didmotsstopaall suchuragments of lthe gel. Furthermore, over an extended iperiod "of use the shap'e of the-absorbe'nt block would be varied because -of theifragments of the silica particles, and-the absorbentiblock might become within the teasing to prevent lserious by passing c n beiobtfained. It-is generally advisable =toiuse 'ja-fn imper-t?i ous binder 4| which 'not only insures aielose fit between-the wall of "the casing and F efabsorbent block but aids-inholding theblock firmly ln place-withinthe dehydrator. m sodium llcate birider-has been found-suitable for this tpurpojse. #iSimilarlyanorganic adhesive which is mesistant to -water-and the particular reh' igerant employed will be satisfactory. -since it will -not be subjected to high temperatures;-

i" "The amount of water which fin'ds its way into "the; refrigerant -inthe i ordinary refrigerating mechanism? is usually smalL- It'is desirableihow- ==ever, -to' provide a dehydrator having 'sumcient water absorbingwcapa'city-to:eliminate the necessity of ever removing the dehydrator from the refrigerating system for :replacement. It is, tnerefore, necessary that "the block of "absorbent "be sufficiently large to absorb "all water likely to enter the refrigerant during the life of the refrigerating machinery. There should, of course, be a safety factor allowing absorption capacity over and above that normally required for the absorption of water. In providing this large dehydrating capacity it must be borne in mind that the space available for the dehydrator is often somewhat limited. It is not, therefore, desirable to provide a dehydrator of relatively short length and very large cross-sectional area to permit the installation of the necessary absorption capacity. Furthermore, channeling is especially serious insuch a structure. n the other hand, if the dehydrator does not have a large diameter but is of considerable length, the pressure drop in the fluid flowing through the dehydrator will be excessive, and accurate control of the refrigerating operation is low.

In order to overcome the above difilcultles, block I8 is notched at 22 and 23 at its inlet end to allow some of the fluid to flow into the space 24 between the expanded portions I2 and I3 of the casing and the outer surface of the block. The fluid may then flow through this space towards the outlet of the dehydrator, but complete by-passing of the absorbent material is prevented by the close fit between the restricted portion of the casing and the block of absorbent. The refrigerant then flows from the upper end of the space 24 through the absorbent block to the outlet nipple 8. The discharge end of the absorbent block has been drilled to form a channel 25 providing direct communication between the interior of the absorbent materialand the outlet of the dehydrator. Channel 23 encourages radial flow from the space 24 substantially radially to the channel. The tendency of the refrigerant to flow to the upper end of space 24 before entering the absorbent is reduced thereby and more effective use is made of the total mass of the absorbent material.

F1 EA lilocktofz'lthe shape 'described:andilllustrated fin the drawings allowsithe tuse co'f can iabsorbent member. mailing :a llarge volume :and consequent large :moisture zzabsorbentacapacity. The notches 322:;and 23 :communicating with chamber 324 zallow itheausezof.a arelatively longl= blockwithout-increasling ithe I;pressure :droptnf vthe lirefrigjerant as ilt 'rflows :through :thecabsorbentiamaterial. .Itiszpos- "siblegthereforemto .pr'o'vid'e 5a compact :structure havingsa largeunoi'sturezabsorbing .capacityiwith .out increasing the aresistanee .tonflowaofithetreftrigerant :as :it :;-passes ithrough ithe tref'rigerating upparatus. a

. :Bycuseof:an'iabsorbentvblockiofzsufficientclength Ito :extend: into both Irestrl'ctedsections .l 0 .1. l ithe tblockris supported longitudinally by :the two .perforatdzplates its and l 9 a and laterally :atrboth :ends i'of .the blccklbycthe restrictedsectionsiof the "casing. .1;=Except :in (the region :of =ttheiinotches ll :andcfl, sthe outer 'edge 2 1 tofttheLinlet'end ofutlre absorbent material :s'n'ugly against :th

stricted section I I of the casing to provideil'ateral ssupport rfor the "block. The absorbent is, thereifl'e,llh'81d firmly in place within the =casing, 1 and .tlredanger of cracking theiblock:is obviated.

- hiidehydrating unitiforlrefrigerating" apparatus zh'aving :ax large xmoi'sture riabsorbing :capacity :has been described .sherin. The high :moisture .labiscrblngccapacityfihas been provided without rappr'eciably ii'ncreasing i'the Ispac'e "required *for huifrigerating w apparatus 'fand without cau'sl'ng tan :appreclablerpressurendrop in ith'effiuid i a'sit flows to-Etherexpansionlvalve. i.

The dehydrator comprising the present invention may be manufactured at a very low cost without any loss in effectiveness of the apparatus. A bonded moisture absorbent material is provided which effectively removes moisture and other impurities from the refrigerant. Furthermore, contamination of the refrigerant with particles of the moisture absorbing material is minimized.

The present invention has been illustrated and described in detail to clarify the disclosure of the invention. It is to be understood that the concept of the invention is not limited to the specific details herein set forth but falls within the scope of the appended claims.

We claim:

1. A dehydrator for the removal of moisture from fluids comprising a casing having an inlet at one end and an outlet at the other end, said casing having tubular sidewalls with a tubular section of large internal diameter at the center separating a tubular section of reduced internal diameter at each end of the sidewalls, a monolithic block of moisture absorbent material within the casing having its sides fitting snugly against the sidewalls of the casing at the area of reduced internal diameter and spaced from the sidewalls at the center whereby the block is supported in the casing by the sidewalls, a binder between the block and easing at the area of reduced internal diameter near the outlet end of the casing, joining the sidewalls of the casing and block and sealing openings between the block and casing to prevent by-passing of the block by the fluid, and notches in the block at its inlet end extending therefrom to the side of the block adjacent the section of large internal diameter thereby providing conduits allowing direct fiow,from the inlet to the space between the sidewalls of the casing and the block.

2. A dehydrator for the removal of moisture from fluids comprising a casing having an inlet lat one 'en'd and an outlet at the other end, said casing having' tubularsidewalls with a section of large internal diameter at the center separating asection: of reduced internal diameter at each end ofthe sidewalls, a monolithic block of bonded activatedzalumina. within the casing having its sides fitting snuglyagainst the sidewalls of the casing at the section of reduced internal diameter and spaced from the sidewalls at the center whereby -the block is supported in the casing by the-sidewalls, a binder between the block and "casing atthe section of reduced internal diameter near the'outlet end of the casing joining the sidewalls: Ofthe'casing and block and sealing 15' of large internal diameter thereby providing coni duitslallowingfidirect flow from the inlet to the the block.

3;;A dehydrator for removing moisture from fluids 'c0mprising a cylindrical casing having an inletatione end and an outlet at the other end,

a monolithic block of moisture absorbent material mounted within the casing, the side walls of said block engaging the side walls of the casing over an area adjacent the ends thereof and spaced from the side walls of the casing intermediate the ends, and notches in the block at the inlet end thereof extending to the sides in the region spaced from the side walls of the casing to pro- 8. vide conduits allowing direct flow from the inlet to the space between the side walls of the casing and the block. I

' SOUTHWICK W. BRIGGS.

WALTER C. BAUER. WALTER J. EWBANK.

H 7 REFERENCES CITED The following references are of record in the file of this patent: I I UNITED STATES PATENTS f Number Name Date.

425,431, Hyatt Apr. 1 5, 1890 526,027 Derham Sept. 18, 1894 571,474 Grandjean Nov. 17, 1896 752,873 Sweeney Feb. 23, 1904 1,809,834 Davenport June 16, 1931 1,954,236 Benjamin Apr. 10,1934 2,014,034 Williams Sept. 10,1935 2,243,949 'Fox June 3, 1941 2,249,681 Briggs July 15, 1941 2,292,632 Greger Aug. 11,1942 2,324,079 Greger July 13, 1943 2,341,429 Elsey Feb. 8, 1944 2,365,149 Anderson Dec. 19, 1944 2,401,797 Rasmussen June 11, 1945 2,456,292 Manwaring Dec. 14, 1948 2,468,862 Briggs May 3, 1949 1 FOREIGN PATENTS Number Country Date .501,176 .Great Britain Feb. 22, 1939 I 20,554

Demnark Sept. 13, 1915

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