US2898748A - Refrigerator employing secondary refrigeration system - Google Patents

Description

1959 H. M. ULLSTRAND 2,898,748

2 Sheets-Sheet 1 0a INVENTOR.

fir /MMLZJ /7 3 A90 Aug. 11, 1959 H. M. ULLSTRAND 2,898,748

I REFRIGERATOR EMPLOYING SECONDARY REFRIGERATION SYSTEM 2 Sheets-Sheet 2 Filed March 8, 1956 I INVENTOR,

p #Mam QM f A fli'idi/VE/ Patented Aug. 11, 1959 ice REFRIGERATOR EMPLOYING SECONDARY REFRIGERATION SYSTEM Hugo Malcolm Ullstrand, Stockholm, Sweden,

Aktiebolaget Elektrolux, Stockholm, ration of Sweden assignor to Sweden, a corpo- This invention relates to refrigeration, and more particularly concerns the cooling of a household refrigerator having a freezing section at one level and a second food storage section at a lower level.

It is an object of the invention, in a household refrigerator of this kind in which a primary cooling element effects cooling of the freezing section, to obtain better distribution of the cooling effect produced by the cooling element with the aid of a secondary refrigeration system having evaporation portions above and below the primary cooling element, respectively, one of which is arranged to effect cooling of the upper part of the freezing section and the other of which is arranged to effect cooling of the food storage section below the freezing section.

The above and other objects and advantages of the invention will be better understood from the following description taken in connection with the accompanying drawing forming a part of this specification, and in which:

'Fig. 1 is a view more or less diagrammatically illustrating an absorption refrigeration system of the inert gas type to which the invention has been applied;

Fig. 2 is a vertical sectional view of a refrigerator and a cooling arrangement therefor which embodies the invention and is associated with a refrigeration system like that shown in Fig. 1;

Fig. 3 is a fragmentary diagrammatic view of parts of the refrigeration system shown in Fig. 1 to illustrate more clearly the relative position thereof in the refrigerator shown in Fig. 2; and

Fig. 4 is a front elevation, partly broken away and in section, of the cooling arrangement shown in Fig. 2 when looking toward the rear of the storage space of the refrigerator at the front access opening thereof.

In Fig. l I have shown an absorption refrigeration system of a uniform pressure type which is well known in the art and in which an inert pressure equalizing gas is employed. Such a refrigeration system comprises a generator or boiler containing a refrigerant, such as am monia, in solution in a body of absorption liquid, such as water. Heat may be supplied to the boiler 10 from a heating tube or flue 11 thermally connected therewith, as by welding. The heating tube 11 may be heated in any suitable manner, as by a liquid or gaseous fuel burner 12, for example, which is adapted to project its flame into the lower end of the tube.

The heat supplied to the boiler 10 and its contents expels refrigerant vapor out of solution, and the vapor thus generated flows to an air-cooled condenser 14 in which it is condensed and liquefied. Liquid refrigerant flows from condenser 14 through a conduit 15 into a cooling element 16 in which it evaporates and diffuses into an inert pressure equalizing gas, such as hydrogen, which enters the upper part thereof from a gas heat exchanger 17 and a conduit 18. Due to evaporation of refrigerant fluid into inert gas, a refrigerating effect is produced and heat is abstracted from the surroundings. The rich gas mixture of refrigerant vapor and inert gas formed in cooling element 16 flows from the lower part thereof through gas heat exchanger 17, conduit 19 and absorber vessel 20 into the lower part of an absorber coil 21. In absorber coil 21 the rich gas mixture flows countercurrent to downwardly flowing absorption liquid which enters through a conduit 22. The absorption liquid absorbs refrigerant vapor from inert gas, and inert gas weak in refrigerant flows from the upper part of absorber coil 21 in a path of flow including conduit 23, gas heat exchanger 17 and conduit 18 into the upper part of cooling element 16.

The circulation of gas in the gas circuit just described is due to the difference in specific weight of the columns of gas rich and weak, respectively, in refrigerant vapor.

Since the column of gas rich in refrigerant vapor and flowing from cooling element 16 to the absorber coil 21 is heavier than the column of gas weak in refrigerant vapor and flowing from absorber coil 21 to cooling element 16, a force is produced or developed within the system for causing circulation of gas in the manner described.

Absorption solution flows downwardly through coil 21 into the absorber vessel 20, and such solution, which is enriched in refrigerant, passes from the vessel through a conduit 24 and an inner passage or pipe 25 of liquid heat exchanger 26 into the lower end of a vapor lift pipe or tube 27 which is in thermal exchange relation with the heating tube 11, as by welding. Liquid is raised by vapor-liquid lift action through pipe 27 into the upper part of boiler 10. Refrigerant vapor expelled out of solution in boiler 10, together with refrigerant vapor entering through pipe 27, flows upwardly from the boiler to the condenser 14, as previously explained.

I The outletend of condenser 14 is connected by an upper extension of conduit 15 and a conduit 28 to a part of the gas circuit, as to the upper part of conduit 19, for example, so that any inert gas which may pass through the condenser 14 can flow into the gas circuit. The absorption liquid from which refrigerant vapor has been expelled flows from the boiler 10 through a connection 29, an outer pipe or passage 30 of the. liquid heat exchanger 26 and conduit 22 into the upper part of the absorber coil 21. The circulation of absorption solution in the liquid circuit just described is effected by raising of liquid throughpipe 27.

While the cooling element 16 in Fig. 1 is diagrammatically shown in the form of a vertical looped coil, a practical form of such a cooling element may be an arrangement in which the looped coil is disposed substantially in a single horizontal plane across the space to be cooled. Such a practical embodiment is shown in Figs. 2 and 3 in which parts similar to those shown in Fig. 1 are designated by the same reference numerals.

The cooling element 16 in Figs. 2 and 3 comprises a looped coil which is disposed substantially in a single horizontal plane and adapted to extend from one lateral side to the opposite lateral side of a thermally insulated storage compartment 31 of a refrigerator cabinet 32. The thermally insulated walls defining the storage compartment 31 includes a rear insulated wall 33 having an opening 34 and a removable enclosure member 35 therefor and through which the cooling element 16 is adapted to be inserted into the insulated interior of the cabinet 32.

The gas heat exchanger 17 may be disposed lengthwise within the enclosure member 35 and retained therein within a body of insulation. In Figs. 2 and 3 inert gas weak in refrigerant flows from absorber coil 21 through conduit 23a which is disposed about conduit 19a through which inert gas rich in refrigerant flows from cooling element '16 to the absorber 21. inert gas weak in refrigerant flows from the gas heat exchanger 17 and conduit connection 18a into one end of cooling element 16, the inert gas flowing through the cooling element in the presence of liquid refrigerant which is introduced therein through the conduit 15. Inert gas rich in refrigerant flows from the opposite end 16b of the cooling element through the gas heat exchanger 17 and conduit 19a to the lower end of the absorber 21. Unevaporated refrigerant also passes from cooling element 16 at 16b and flows by gravity through the gas heat exchanger 17 to the absorber vessel 20.

As best shown in Fig. 4, the cooling element 16 is thermally connected by clamps or brackets 38 to the underside of a horizontally disposed plate 39. The plate 39 forms the bottom of a shell or casing 40 having a top 41 and rear and side vertical walls 42 adapted to be removably secured at their lower edges at 43 to the horizontally disposed plate 39. The shell 40, which may have its own closure member and is positioned closely adjacent to and at the vicinity of the ceiling 37 of the storage compartment 31, extends substantially over the entire width of the storage compartment 31 and from the rear insulated wall 33 to a region 44 at the open front which is relatively close to the rear face of a door (not shown) adapted to be hinged at the front of the cabinet. With such as arrangement, circulation of air between the shell 40 and thermally insulated walls of cabinet 32 may be restricted to a certain extent in the upper part of the storage compartment 31.

The cooling element 16, which is adapted to be perated below the freezing temperature of water, is employed to abstract heat from the bottom 39 of shell 40 which constitutes the freezing section of the refrigerator. The bottom 39 of shell 40 and cooling element 16 in thermal exchange therewith may also be employed to effect cooling of air in the part of the storage compartment 31 below shell 40 which flows in thermal exchange relation therewith. Hence, the bottom 39 of shell 40 has a limited heat transfer surface which may be employed to effect cooling of air in the bottom part of the storage compartment 31.

With the cooling element 16 positioned in the storage compartment 31 of the cabinet 32, the condenser 14 desirably is positioned at the rear of the insulated wall 33 and below the top insulated Wall 36 at an elevation sufficiently high with respect to cooling element 16 to permit liquid to flow by gravity from the condenser to the cooling element. It is for this reason that the cooling element 16 must be positioned at a level below the ceiling 37 of storage compartment 31, particularly when the top insulated wall 36 is the highest part of the cabinet 32.

In accordance with my invention, in order to abstract heat more effectively from the shell or freezing section 40 and from the part of the storage compartment 31 below the shell, I provide a hermetically sealed secondary refrigeration system 45 having a condensation portion 46 arranged in thermal exchange relation with the cooling element 16 and evaporation or vaporization portions 47 and 48 positioned below and above the cooling element, respectively. The secondary refrigeration system, which also may be referred to as a secondary heat transfer system, comprises the condenser or condensation portion 46 in the form of a looped coil having the straight portions thereof held between and in good intimate contact with the parallel arms of U-shape brackets 49 which extend lengthwise of and are fixed, as by welding, for example, to the brackets 38 which hold the cooling element 16 to the underside of the shell 40.

As best seen in Fig. 4, the condensation portion 46 extends across the bottom 39 of the shell 40 between the opposing vertical sides thereof and is connected by a vertical conduit 50 to the lower end of the vaporization portion 47 in the form of a vertically positioned looped coil to which, as by welding, for example, is fixed a plate 51. The vaporization portion 47 and plate 51 fixed thereto are closely adjacent to and at the vicinity of the r al? insulated wall 33 at a region beneath the shell 40. The upper end of the vaporization portion 47 is connected by an upwardly extending conduit 52 to one end of the vaporization portion 48 which is in the form of a looped coil and held by clamps or brackets 53 in good thermal relation with the exterior surface of the top 41 of shell 40. The opposite end of the vaporization portion 48 in turn is connected by a conduit 54 with the condensation portion 46.

The secondary condenser 46, vaporization portions 47 and 48 and connecting conduits 50, 52 and 54 form a closed fluid circuit which, after being evacuated, is partly filled with a suitable volatile fluid or heat transfer agent, such as, for example, ammonia, methyl chloride or the refrigerant fluid available under the trademark Freon, having a relatively low boiling temperature. During operation of the refrigerator, the cooling effect produced by cooling element 16 is transmitted to the condensation portion 46 which causes evaporation of volatile fluid in the vaporization portion 47, thereby taking up heat from air in the storage compartment 31. To promote such heat transfer, the vaporization portion 47 is provided with the plate 51 which serves as a heat absorber and provides a relatively extensive heat transfer surface. The vapor formed in the vaporization portion 47 is employed to raise liquid therein through the conduit 52 to the vaporization portion 48 for gravity flow in the latter, the internal diameter of the vaporization portion 47 and conduit 52 being such that vapor cannot freely pass liquid in these parts.

Volatile fluid also evaporates in the vaporization portion 48 and takes up heat, thereby transmitting cooling effect to the top 41 of shell 40 and cooling the latter. The vapor formed in both the vaporization portions 47 and 48, and also any unevaporated volatile fluid, flows from the vaporization portion 47 through conduit 54 into the condenser or condensation portion 46. The vapor is condensed and liquefied in the condensation portion 46 by the cooling element 16, which may be referred to as the primary evaporator or cooling element, the condensate then flowing by gravity through conduit 50 into the lower end of the vaporization portion 47.

The secondary refrigeration system is initially charged with the volatile heat transfer fluid so that the liquid level in conduit 50 will never rise above the level 55, as indicated in Fig. 4, and will always be located at a region below the lower end of the condensation portion 46. As best shown in Fig. 4, the conduit 50 is spaced from the plate 51 and formed with a U-shape portion 50a at its lower end. In this way, heat absorbed by the plate 51 is not readily transmitted to the conduit 50 and instead is transmitted to the vaporization portion 47 in which vaporization of volatile fluid is promoted. The conduit 50 desirably may be provided with an insulating cover (not shown) to prevent vapor forming therein.

Vapor formed in the vaporization portion 47 is effectively employed to raise liquid through conduit 52 to a higher level by vapor-lift action under the influence of a reaction head formed by the liquid column in conduit 50. Stated another way, the weight of the liquid column in conduit 50 overbalances the weight of the liquid and vapor in the vaporization portion 47 and conduit 52 to cause liquid to rise in the latter to the vaporization portion 48 at the higher level. It will be seen in Fig. 4 that both legs of the vaporization portion 47 slope upwardly to the lower end of the conduit 52 to promote upward movement of vapor in these parts.

The top 41 of the shell 40 is formed so that it is at a slight angle to the horizontal to promote downward gravity flow of liquid in the veporization portion 48 from the upper end of conduit 52 to the upper end of conduit 54. Further, the extreme right-hand end 48a of the vaporization portion 48 is arched upwardly to prevent pumping of liquid into conduit 52 from the vaporization portion 48 by vapor formed in the latter.

When the refrigerator 32 described above is assembled, the primary cooling element 16 and plate 39 fixed thereto are first inserted into the storage compartment 31 through the opening 34 which is adapted to be closed by the cover or closure member 35. Before inserting the cooling element 16 in position in the storage compartment 31, the U-shape brackets 49 are also secured to the clamps 38 which hold the cooling element 16 against the underside of the horizontally disposed plate 39.

The secondary refrigeration system and all parts of shell 40, except the bottom wall 39 thereof, are inserted into the storage compartment 31 through the front access opening of the refrigerator cabinet 32. Before this is done, the vaporization portion 47 is fixed to the vertical plate 51 and the vaporization portion 48 is fixed by the clamps 53 to the top wall 41 of the shell part forming such top Wall and the rear and side walls of the shell 40. When the secondary refrigeration system and parts fixed thereto are inserted into the storage compartment 31, the straight portions of the looped coil forming the condensation portion 46 are moved rearwardly in the U-shape brackets 49 which form channels or grooves to receive and hold the secondary refrigeration system in place in the interior of the cabinet 32. The bottom 'horizontally disposed plate 39 is then secured at 43 to the lower edges of the rear and side walls 42 to form the shell or freezing section 40.

In view of the foregoing, it will now be understood that the primary cooling element 16 not only effectively transmits cooling effect at a low temperature directly to the bottom 39 of the shell 40 which is employed as the freezing section in which frozen food packages may be stored, as well as trays containing Water adapted to be frozen for producing ice cubes, but also, with the aid of the secondary refrigeration system 45, is advantageously employed to transmit cooling effect to the region of the compartment 31 below the shell 40 as well as to the upper part of the freezing section 40. As a result, the freezing section 40, which extends horizontally across the top of the storage compartment 31, is located between the horizontally disposed regions at which the cooling effects are produced by the coils 16 and 48. The vaporization portion 47 desirably is provided with the plate 51 to provide a relatively extensive heat transfer surface to promote cooling of air in the part of the storage compartment 31 beneath the shell 40.

While it has been stated above that the internal diameter of the vaporization portion 47 and conduit 52 should be of such size that vapor cannot freely pass liquid in these parts, it may be desirable in certain instances to employ in all parts of the hermetically closed refrigeration system, except in the case of the connecting conduit 50, looped coils and conduits which are of such size that vapor cannot freely pass liquid therein.

While a particular embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that modifications and changes may be made without departing from the spirit and scope of the invention, as pointed out in the following claims.

What is claimed is:

1. A refrigerator comprising a cabinet having thermally insulated walls defining a storage compartment having a front access opening, one of said walls having an opening and a thermally insulated closure therefor, refrigeration apparatus including a cooling element disposed in said storage compartment and removable therefrom through said wall opening, structure providing a freezing section in the upper part of said compartment, said cooling element being arranged to effect cooling of said freezing section, a secondary refrigeration system containing a volatile fluid and having a condensation portion in thermal exchange relation with said cooling element and evaporation portions above and below said cooling element, respectively, said secondary refrigeration system being removable from said compartment through the front acces's' opening, said evaporation portion above said cooling element being arranged to abstract heat from the upper part of said freezing section and said evaporation portion belo-wtsaid cooling element being arranged to abstract heat from a region of the storage compartment below said freezing section, said evaporation portion below said cooling element being connected to receive volatile fluid by gravity from said condensation portion, and means for raising volatile fluid in liquid phase 'by vapor-lift action from said evaporation portion below said cooling element to said evaporation portion above said cooling element.

2. A refrigerator comprising a cabinet having thermally insulated walls defining a storage compartment having a front access opening, one of said walls having an opening and a thermally insulated closure therefor, refrigeration apparatus including a cooling element disposed in said storage compartment and removable therefrom through said wall opening, structure providing an across-the-top freezing section of the horizontal type in the upper part of said compartment, said freezing section comprising wall means defining a space having top and bottom horizontal members formed of heat conducting material, said cooling element being in heat conductive relation with the bottom horizontal member to effect cooling of said freezing section, a secondary refrigeration system containing a volatile fluid and having a condensation portion in thermal exchange relation with said cooling element and evaporation portions above and below said cooling element, respectively, said secondary refrigeration system being removable from said compartment through the front access opening, said evaporation portion above said cooling element being in heat conductive relation with the top horizontal member to abstract heat from the upper part of said freezing section, and said evaporation portion below said cooling element being arranged to abstract heat from a region of the storage compartment below said freezing section, said evaporation portion below said cooling element being connected to receive volatile fluid by gravity from said condensation portion, and said secondary refrigeration system including means for raising volatile fluid by vapor-lift action from said evaporation portion below said cooling element to said evaporation portion above said cooling element.

3. A refrigerator comprising a cabinet having thermally insulated walls defining a storage compartment having a front access opening, said thermally insulated walls including top, bottom, rear and lateral sides of said cabinet, said rear wall having an opening and a thermally insulated closure therefor, refrigeration apparatus including a cooling element disposed in said storage compartment and removable therefrom through said rear wall opening, structure providing an across-the-top freezing section of the horizontal type in the upper part of said compartment, said freezing section comprising wall means defining a space having top and bottom horizontal members formed of heat conducting material, said cooling element comprising a looped coil which is disposed essentially in a horizontal plane and along its length is in heat conductive relation with the outer surface of said bottom horizontal member to effect cooling of said freezing section, a secondary refrigeration system containing a volatile fluid and having a condensation portion in thermal exchange relation with said cooling element and evaporation portions above and below said cooling element, respectively, said secondary refrigeration system being removable from said compartment through the front access opening, said evaporation portion above said cooling element comprising a looped coil which is disposed essentially in a horizontal plane and along its length being in heat conductive relation with the outer surface of said top horizontal member to abstract heat from the upper part of said freezing section, and said evaporation portion below said cooling element being arranged to abstract heat from a region of the storage compartment below said freezing section, said evaporation portion below said cool.- ing element being connected to receive volatile fluid by gravity from said condensation portion, and said secondary refrigeration system including means for raising volatile fluid by vapor-lift action from said evaporation portion below said cooling element to said evaporation portion above said cooling element.

4. Apparatus as set forth in claim 3 in which said bottom horizontal member of said freezing section and looped coil of said cooling element are removable as a,

unitary body through said rear wall opening, and the top horizontal member of said freezing section and looped coil of said evaporation portion above said cooling element are removable as a unitary body from said compartment through the front access opening of the cabinet.

5. Apparatus as set forth in claim 4 in which the top horizontal member of said wall means of said freezing section forms the closed end of an inverted U-shape part having downwardly extending portions forming the lateral walls of said wall means which define the freezing section space.

6. Apparatus as set forth in claim 5 which includes means for detachably connecting the bottoms of the lateral walls and the bottom horizontal member of said wall means.

7. Apparatus as set forth in claim 3 in which said condensation portion comprises a looped coil disposed essentially in a horizontal plane, said last-mentioned looped coil and the looped coil of said cooling element being in heat conductive relation along their lengths with the looped coil of said cooling element being disposed between the bottom horizontal member of said freezing section and the looped coil of said condensation portion.

, 8. Apparatus as set forth in claim 7 in which said looped coils of said cooling element and condensation portion each comprises a plurality of U-shape loops adjacent to one another, each of said loops including a pair of spaced arms and a connecting bend, U-shape channels disposed lengthwise of the arms of the loops of said cooling element coil and in heat conductive connection therewith, said U-shape channels being formed and arranged to slidably receive and hold the arms of the loops of said condensation coil.

9. Apparatus as. set forth in claim 3 in which said evaporationportion below said cooling element comprises a looped coil disposed essentially in a vertical plane substantially parallel to the rear thermally insulated wall of the storage compartment and adjacent thereto.

10. Apparatus as set forth in claim 9'which includes a plate fixed to the looped coil of said evaporation portion below said condensation portion, said plate extending be tween the lateral side walls of the cabinet and concealing from view a major portion of the aforementioned looped coil.

References Cited in the file of this patent UNITED STATES PATENTS

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