US2415243A - Refrigeration apparatus and method of making same - Google Patents

Description

Feb. 4, 1947,

REFRIGERATION APPARATUS AND METHD OF MAKING SAME /adlr c. E. HlcKMAN 2 shefcs-sheet 1 Feb. 4, 1947. 2,415,243 l REFRIGERATION APPARATUS AND METHQD 0F MAKING SAME C. E.. HICKMAN Filed Oct. 20, 1943 2 Sheets-Sheet 2 1.. v. f v Ml am, a

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Patented Feb. d, i945? entre t tiene stur-Es Partnr ort-m REFRIGERATION APPARATUS AND METHOD F MAKING SAME l Charles E. Hickman, Adrian, Mich., assignorto Bohn Aluminum- & Brass Corporation, Detroit, Mich.,'a corporation of Michigan Application october zo. 194s, serial No. 506,984

` 1o claims. '(01.62-8) e i This invention relates to refrigerators, and more particularly to improvements in the lines used to feed liquid refrigerant to the evaporato and to` draw the vaporized refrigerant from the evaporator.

A particular object of the invention isto provide an eilicient arrangementfor heat-exchange between the warm liquid line and the cold suction line, thus pre-cooling the liquid refrigerant before it reaches the device which controls its passage to the evaporator. 'I'his object is accomplished by forming the liquid and vapor lines as parallel bores in a single piece of material hav- Y ing good thermal conductivity, such as aluminum, so that these two'lines may be kept in elllcient heatexchange for a major portion of their length. Preferably the piece of material in which the bores for these lines are formed is extruded, as this method of manufacture provides apart having the characteristics of wrought 'metal andentirely free from joints of. any kind between the bores.

A further object is to provide an improved y small-bore restrictor for controlling the flow of liquid refrigerant tothe evaporator. An eilicient and trouble-free restrictor is formed by inserting within the smooth bore of the line for Fig. s is a view simiiar to Fig. '1 but showing a modification in the shape of the wire.

Referring in generalto Fig. 1, the parts include the cabinet III, motor-compressor imit II, con

denser I2 and evaporator I3, all of which may be of any preferred construction. The numeral I 4- -indicates the combined heat-exchanger and small-bore restrictor of the present invention.

The construction vof part II-can be explained most readily by following the steps by whichv it may be fabricated. The iirst step is to extrudea strip having the cross-sectional shape illustrated in Fig. 6, which consists essentially of a small bore I5 and a large bore I6, the walls of these bores being connected together by a. solid web I'l. A

strip of this shape -can readily be extruded by' the apparatus shown in the patent to Schwerak, No. 2,031,008, and is preferably formed from a material having a high rate .of thermal conductivity, such as aluminumV or an alloy thereof. -In the appended claims the term aluminum ma.'-

terial is used to cover generically commercially pure aluminum and-all alloys in which aluminum liquid refrigerant, at a part near its connection tothe evaporator, helically-coiled wire, the inner diameter and length of the coil being correlated so as to properly meter the ow of refrigerant in the same manner as done by small bore restrictors heretofore in use.

The two structures above mentioned unite to form acombined small-bore restrictor and heat- Vexchanger of simple and unique construction.

The invention also provides methods for man# e ufacturing these structures.

These and other objects and advantages of the invention? will become apparent as the description proceeds.

While preferred forms are illustrated herein for purposes Vof illustration, it should be understood that various changes may be made without departing from -the spirit of the invention as herein set forth and claimed.

, In the drawings:

Fig. 1 is a side elevation partly in section of a household refrigerator embodying ,the invention. Fig. 2 is a plan view of a strip as extruded.

Fig. 3 is a view similar to Fig. 2 but showing thev strip after it has been partly processed.

Fig. 4 is an enlarged isometric view ofthe evaporator and the upper end of the combined small-bore re'strictor and heat-exchanger, parts of the latter being shown in section.

Fig. 5 is a cross section on line 5-5 of Fig. 4.

Fig. 6 is a cross section on line 6-6 of Fig. 4.

Fig.7 isa longitudinal section on line 1-1 of Fig. 5. Y

is the predominant element. This 'strip can be 'extruded in any economical mill length and is then cut 'into .pieces of the size required for fabrication, one of which is'shown in plan view in Fig. 2. A

'Ihe next step in producing the combined heatexchanger and small-bore restrictor illustrated in Figs. 1 and 4 is to saw a slot inwardly from each end of the strip as indicated at I8 in Fig. 3. Y

EachA of these slots cuts entirely through web I-l, thus separating the small bore I5 from the large bore I6 and forming them into separate tubes. 'I'he small bore I5 is to form the line carrying liquid refrigerant from the condenser I2 to the evaporator I3, while the large bore IB is to form the suction line carrying gaseous refrigerant from vtubes have sometimes been called capillary tubes," although' it is behaved that they operate, not by capillary action, but by retarding the flow of gas while permitting ametered flow of liquid on the vapor-lock principle, as indicated in the patent to.Keyes, No. 1,293,469. Some variation was permissible in the inner diameter of the tube,

but this diameter had to be correlated with the length of the 4tube in orderto obtain proper metering of liquid refrigerant to the evaporator. Thus for a household refrigerator of 6 cu. it. ca-` 3 pacity, if the tube had an inner diameter of .032 in. the tube could be approximately 6 ft. in length whereas if the tube had an inner diameter of .040 in. the Ytube would have to be approximately 17 ft. in length. But it has been found very diniclt to manufacture tubing of these small sizes and to assure that the bore is free lfrom obstructions 'both when the system is assembled and during the life of the refrigerator.

A departure from the plain, smooth-bore restrictor tube was suggested in the patent to Karmazin, No. 2,166,109, which shows a restrictor tube made by brazing together the loops of a helically-wound metal wire. l

The present applicant has discovered that an economical and efficient restrictor canbe produced by the simple method of inserting a helically-coiled wire I9 in the small bore I5 of the It has been found that in an average house-` hold refrigerator of the type in which the compressor is in the base of the box, efllcient operation is obtained when the inner diameter of the bore I5 is greater than .050 in. and less than .110 in.

In one example the bore I5 was vformed with an inner diameter of .080 in., and the coiled wire had ari outer diameter that permitted itto slide freely into the bore, while it had an innerdiameter of .030 in. It was found that with these diameters the length of the coiled wire needed for a 6 cu. ft: refrigerator was about 18 inches. This represents a verf considerablev shortening from the -6 ft. of .032 in. smooth-boretube used previously, as stated above, andv hence provides for a neater and more economical installation.

The inner diameterof the coil can of course be variedwithin limits, but using a smaller diameter will increase the difficulties of manufacture and thelposs'ibility of clogging, while using a larger diameter `will require using a greater length of -coiled wire. In any case the inner diameter and length of thecoil must be correlated 'so' as to properly meter the flow of refrigerant. n

In the example referred to, the-large bore I6 had an inner diameter of .250 in., but this diameter is not critical as long as it is adapted to meet the needs of the particular system.

After the coiled wire has been inserted in bore I5 the end tubes carrying bores I5 and I6` may be separated and each one given a. rounded external shape. Thev combined 'small-bore restrictor and heat-exchanger thus formed isthen ready for assembly in the refrigeration system.

In the form illustrated in Fig. 1, which is a' particular refrigerator of household size, lthe malnbody of the double-bore -strip I4 is located outside of, and attached to the back of, the cabinet I0. The upper end of the tube carrying the vvsmall bore I5 is first secured in contact with the shelf 20 and then is connected to the inlet header 2l of the evaporatorltf The lower end of this tube is connected to the outlet of the condenser I2. I'he tube carrying the large bore It has its upper end connected torthe outlet header '22 of evaporator I3, and its lower end connected to the inlet of the motor-compressor unit.

In the operation of the refrigerator the gaseous refrigerant, which is relatively cold` is drawn from the'evaporator to the compressor via the large -bore I6. After being compressed and condensed the refrigerant, warm and mainly in the liquid state, passes from the condenser to the.

evaporator via the smallbore I5. The restrictor formed by the coiled wire I9A permits a metered iloW of liquid refrigerant While the refrigerant in bore I5 is under suiilcient pressure. During idle periods of the compressor the restrictor remains open to permit substanial equalization of pressures throughout the system.

It should be noticed that in vthe main body of the. part I4 the warm liquid refriger-.nt is moving upwardly through the bore I5 while the 'cold gaseous refrigerantv is moving downwardly- .By forming bores I5 and I6 in a single piece of aluminum this heat-exchange takes place in a highly eilicient manner, since there are no joints .of any kind to. impede heat flow through the solid, homogeneously integralmass. i

The helically-coiled wire I9 is preferably formed of steel spring wire with adjacent convolutions in close contact witheach other, but neither of' these features is essential. It has been found that the coil functionsproperly if its convolutions are spaced' apart as much as .015 in. The wireA need not be of conventional round cross-section, but may have other appropriate cross-sectional shapes, such as the v shape of the Wire 23 ofFig.- 8. For-'convenience in manufacture several individua1 coils may be vplaced end-to-end to produce the desired overall length of coil. v

By using a relatively large bore I5 serting therein coiled Wire as described herein, it is possible to produce a small-bore restrictor of great accuracy and precision' at low expense.

The double-bore strip I4 is of extruded `metal which is quite malleable, and sinceV the coiled,-

wire is not anchored tothe wall of its fbore, the part of the tube which serves Ias the' restrictor can be readily bent without reducing or obstructing the inner diameter of the coils of the wire.

It will be clear. to' those skilled inthe art that the improved small-bore restrictor of' this invenl tion can be" used Iseparately from the heatexchanger disclosed, but that maximum efilciency .and economy-can be gained by the use of the two devices -in combination. An example of separate use of the restrictor would -be its. insertion in an` ordinary liquid line `ofany type, in which case the restrictor would serve as an economical metering device. Conversely thev double-bore Aheat-exchange tube can be used with any vtype of metering device such as an expansion valve oralow-slde float valve.`

In manufacturing, the particular sequence of steps set forth above need not be adhered to, but considerable latitude may be used in changing and inlat each end ci the strip.

annees the sequence to arrive at the most economical process under particular circumstances.

l their length to forma single, homogeneously in- The invention is, .of course, not limited to refrigeration systems of household size, but can be used on systems of commercial size.

I claim:

1. For use in refrigeration systems, a tube having a bore with a smooth inner wall, the inner tegral mass, the web being severed for a. distance extending inwardly from each end of the strip, thus placing the bores in separated tubes at each end of the strip, the small bore having a smooth wall and being of a, size too large to serve as a small-bore restrictor; and coiled wire inserted in one end of thesmall bore, the inner diameter and length of said coil being correlated so as to meter the liquid refrigerant, i

8. A combined-small-borehrestrictor and heatexchanger -`as set forth in" claim 7 in which the .oso in. and .11o in., and heiicaiiy-ccilea wire inserted within said bore, the coil of wire having a passageway oi substantially capillary -size and having a sliding nt in the bore, the-length of said coil being so correlated to the inner diameter of the passageway as to provide for the delivery of the desired amount of refrigerant.

3. For use in refrigeration systems. a tube having a smooth inner -bore of adiameter oi approximately .080 in., and helically-coiled wire having its convolutions arranged closely to each other inserted within said bore. the outer circumferential surface of the coil having a sliding fit in said bore, the inner diameter of the coil being approximately .030 in'and the length of the coil being approximately iii inches.

'strip is formed of extruded `aluminum material and the coiled wire is formed of steel.

9. A combinedsmall-bore restrictor and heatexchanger for the lines ci refrigeration systems which comprises a stripof eittrucledv aluminum, the strip having a small bore for liquid refrigerant and a larger bore for gaseous refrigerant, the walls of thebores being connected by a web over the major-portion of their length to form a single, homogeneously integral mass, the small bore having a smooth inner wall and a diameter of approximately .080 in.; and helically-coiled steel wire having its convolutions arranged closely to each other inserted within the bore, the

a. A heat-exchanger tor the gas and liquid I lines of refrigeration systems having an evaporator, which comprises: a strip of aluminum material having a small bore for liquid refrigerent, the inner diameter of said bore being too large to serve as a small-bore restrictor, and a larger bore for gaous refrigerant, the Walls of the bores being connected over the major portion of their length by a web forming therewith a homogeneously integral body ci such. mass as to cool the refrigerant so that it is delivered by the small -bore to the evaporator at substantially the temperature of the gas entering the large bore from the evaporator, the web being severed for a distance inwardly from each end of the strip thus placing the bores in separate tubes ii. combined small-bore restrictor d heatexchanger for the lines ot refrigeration systems which comprises: a strip oi material of good heat conductivity, the strip having a small bore for liquid refrigerant and alargar bore for gaseous refrigerant, the walls of the bores being con nea by a web over the maior portion oi their length to form a single, homogeneously integral mass, the small bore having a smooth wall and beingoi a size too large to serve as a small-bore restrictor; and coiled wire inserted in one end of the small bore, the inner diameter and length oi said coil haring correlated so as to meter the liquid refrigerant.

6. A combined small-bore restrictor and heat- 'exchanger as set forth in .claim 5 in which the strip is formed oi extruded aluminum material.`

'1. A combined small-bore restrictorand heat# exchanger for the lines of refrigeration systems which comprises: a strip oi material of good thermal conductivity, the strip having a small l outer diameter of the coil having a close sliding fit in said bore, the inner diameter ofthe coil being approximately .030 in., and the length of the coil being approximately 18 inches.

10. The method of manufacturing a combined small-bore restrictor and heat-earchanger for the lines of refrigeration-systems which comprises:

extruding a strip of material, the strip having a a ing wire into a close helical coll; and inserting the coil into the small mrc of said strip, the

correlated so as to meter liquid refrigerant and bending the tube containing vthe lsmall bore at a place where the wire coil is present.

n. rnc.

nersanncns einen -l` l: STATES PATENTS Number Name at@ 2,063,745 Kucher d, 1936 2,146,823 Karmazin Feb. 14, 1939 644,841 Allen Mar. 6, 1940' 2,281,207 Schoen A121228. 1942 1,823,919 Smith i- Sept. m, 1931 2,155,003 Benson Apr. 18, 19,39 2,329,139 Scullen Sept. 7,. 1943 2,166,109 Karmazin July i8, i939 2,210,031 Greene Aug. d. 1940 2,136,230 Berman Nov.,'8, 1938 97,448 Silsby Nov. 30, .1869

166,294 Orum Aug. 3. 1875 `2,181,856 McCloy Nov. gti. 1989 2,305,992 Quillen Dec. 22, 1942 2,155,003 Benson Apr. 18 1939

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