US2163175A - Evaporator - Google Patents

Description

June 20, 1939.

w. w. HIGHAM INVENTOR. h/aL/AN h/ GHAM BY y 73W, 0 M

ATTORNEYS.

June 20, 1939. w. w. HIGHAM EVAPORATOR Filed July 5, 1955 3 Sheets-Sheet 2 MW. W H M 2 m 5 June 20, 1939. w. w, mm

EvAPoRAToR Filed July 5, 1935 5 Sheets-Sheet 3 INVENTOR. MLL/A'lf h/ HIGH/4M ATTORNEYS.

Patented June 20, 1939 EVAPORATOR William W. Hlgham, Detroit, Mich, asslgnor to Universal Cooler Corporation, Detroit, Mich., a

corporation of Michigan Application July 5, 1935, Serial No. 29,911

1 Claim.

This invention relates to an evaporatonor in other words the cooling unit of a refrigerator.

There are a number of objects of invention and a number of advantages and new results 5 attained thereby. One-of the principal objects is the provision of an evaporator so constructed as to create convection currents such that the temperature differential between the different portions of the refrigerated compartment is minimized. Ordinarily, the lowest temperature in a box, using the term box" as descriptive of a refrigerator or refrigerated compartment, such as the interior of a cabinet for household use, is in the lower portion, due to the fact that the l8 cooled air moves downwardly into the lower portion of the box, while the air displaced thereby or which moves by convection upwardly and moves into the upper portion of the box is warmer. 'Just how these convection currents minm imize this differential, whereby a substantially uniform temperature throughout the box may be maintained, will be outlined in the detailed description.

A further object is the attaining of a relatively 25 large area on the evaporator with which the air in the box contacts for heat exchange purposes without, however, providing projecting fins. To this end the invention provides the area yet has a relatively smooth finished surface appearance. A further object of the invention is to minimize frosting of the evaporator unit and particularly on certain portions thereof. This is attained by affording a relatively large surface for contact with the air in the box and by pro- 35 vidir'ig a structure wherein relatively rapidly flowing air. currents pass over certain parts of the surface. Thus localized portions of the air in the box do not assume a static condition in contact with the cooling surface, which condi- 40 tion aids or promotes chilling of the localized air below the dew point. The surface which is provided may be obtained or increased by stretching metal of certain of the parts into an irregular form as distinguished from providing 5 projecting fins.

' A still further object of the invention is the provision of a structure wherein a condition of high humidity may be attained. Certain of the surface forming structure with which the air contacts to be cooled may be associated with the fai parts retaining the refrigerant in such a way that heat exchange between such portions and theportions of the evaporator directly containing the refrigerant is not very fast, with the a result that said portions, while cooling the air,

do not chill the air to a point below freezing. Accordingly, these portions, instead of becoming frosted, merely sweat; that is to say the mois ture deposited thereon by the air currents in the box is deposited at a point above freezing. How ever, the invention may be employed for attaining the other objects of the invention, as for example such as minimizing the differential temperatures in the box, without employing this last object of operating under a high humidity con- 10 dition. In such a case the above mentioned surface forming portions which sweat may be connected in good heat exchange relation with the other portions of the evaporator so that .the

temperature thereof is below freezing.

The invention may be carried out by one form of structure shown in the accompanying drawings.

Fig. 1 is a diagrammatic view showing the inside of the box of a refrigerator and illustratingdiagrammatically the form of the convection currents.

Fig. 2 is a top plan view of the evaporator with parts in section.

Fig. 3 is a view partly in side elevation and partly in section of line 3-3 of Fig. 2.

Fig. 4 is a sectional view taken on line 4-4 of Fig. 3.

Fig. 5 is a detail view of a plate member associated with the evaporator proper and providing air fiues and cooling surface.

Fig. 6 is a sectional view taken on line 6-6 of Fig. 4.

Fig. 7 is a detailed view showing a modified form.

The refrigerator or box is illustrated at ,l

and it may have the usual door arrangement (not shown), and inside the box is the cooling unit or evaporator, as shown, and suitable shelves. The form of the evaporator shown herein comprises a shell 2 which may have a partition 3 for forming two sharp freezing chambers for the reception of ice trays or trays holding food stuffs to be frozen, as illustrated in Fig. 4. Obviously, the form of the unit may. vary 5 in this respect. The evaporator shown is of the direct expansion type or the so-called dry sys-' tem. To this end the evaporator is provided with tubing fashioned into coils. The refrigerant from .the usual compressor may enter the 5 tube at the inlet 5 through a suitable expansion valve (not shown), pass through lead 6 into a coil 1 on the bottom of the shell 2 and then pass upwardly through lead 8 to an intermediate coil 9 which may contact with the partition 3, then partment may be frozen. At the same time the I box is cooled. It is to be appreciated that the form and details of the evaporator thus far described is subject to much variation in the arrangement of coils, sharp freezing chambers, etc., and in fact the evaporator may be of the so-called flooded type as well as the direct expansion type or dry system. A drip pan is may be positioned below the evaporator and the same may be supported in any suitable manner.

The structure which is used in combination with the evaporating unit above described, in the present instance, takes the form of one or more plates which may be formed of sheet metal and suitably fashioned. Such a plate is perhaps best shown in Figs. 3 and 5. The plate is generally illustrated at and is formed with irregularities, which in the present instance are, and preferably are, of .corrugate form. In other words, the plate shown herein is corrugated. The depressions of the corrugations are illustrated at 2| in Fig. 3,

that is the depressions which appear on the outer.

surface, while the ridges (Fig. 2) are shown at 24. Two of such plates are advantageously employed and are attached to the evaporating unit. A simple manner of attachment is as follows: The opposite edges of the corrugated plates are fashioned over substantially 90 to the body of the plate, as shown at 25, and the extreme edges are turned in to form hook portions 26. These portions 26 are arrangedto hook over a run of the coils I and H, as shown in Fig. 4. Since the plates are identical, there being one on one side and one on the other, a description of one will suffice. The portions are apertured so air may pass therethrough. These apertures may take any suitable form, and are of such dimensions as to allow the desired amount of air to flow therethrough, and are shown at 21' in Fig. 2 as being of elongated form.

The portions of the corrugated plates which form the bottom of the furrows 2| may contact with the walls of the shell 2, as shown in Fig. 2, while obviously the ridges 24 are spaced from the shell. Such a contact provides for heat transfer from the plates to the shell, resulting in a lower temperature of the plates, but without such a contact there is less heat transfer to the shell. This arrangement may be varied to give the desired results. Thus flues are formed, which in the present instance extend in a vertical direction along the sides of the evaporator. The ends of the corrugated plates may be suitably fashioned to provide a finished appearance, but this is a detail which is subject to variation within the choice of mechanics or manufacturers.

' Insofar as obtaining a ilue structure is con-.

the size is to be determined to give the desired results.

In operation the air currents move somewhat as follows: Air moves downwardly through the several flues, contacting with the metal parts forming these fines, and this air beoomesconsiderably cooled. Some of this air moves in a circuit which is downwardly through the flues and upwardly in the upper portion of the box. then downwardly through the flues. This, then, tends to keep the upper part of the box cool, since cool air is locally circulated, so to speak, at this portion of the box. Also, some air currents may flow downwardly along the outside surface of the corrugated plates as shown. Some of the air moving downwardly through the flues and along the outside surface of the plates continues in a path to the bottom of the box as illustrated. This air moves downwardly over the materials in the box and then upward. This air that moves upward then may mix somewhat with the upwardly moving currents which is in a circuitous path through the flue and then upward. Thus the warm air coming from the bottom of the box mixes with and tempers the cold air which moves upward immediately after passing through the flues. Heretoforathe convection currentshave not been divided or controlled with the result that all the cool air moved downward to the bottom of the box, and thus the bottom of the box was the colder portion. This air, upon becoming warm, moved upward into the upper portion of the box and thus the upper portion of the box was warmer. By properly proportioning the ratio as between the volume of air flowing to the bottom of the box and the volume in the circuitous path in the upper portion of the box, the temperatures throughout all portions of the box may be made to be substantially uniform. One way of more or less controlling this ratio is by the simple expedient of employing a baffle which may be a drip pan is. As shown in Fig. 1 this drip pan has its edges underlying the lower outlet ends of the flues and thus serves as a baiilefor the air passing out of the flues.

This deflects the air and some moves upwardly and some moves downwardly. By simply employing a pan of the proper width the correct proportion of air may be directed upwardly and downwardly. A wider pan gives greater deflection and increases the volume of air in the local circuits in the upper portion of the box; a narrower pa'n allows more air to continue downwardly to the bottom of the box:

It will-be noted that the corrugated plates provide much additional surface for contact with the air. Both sides of the plates function from this standpoint. Accordingly, the complete evaporator has a'finished smooth appearance, considering the corrugate form has a smooth but corrugate surface as distinguished from projecting fins. The surface is increased over that afforded by the metal of the plates in flat condition by reason of the metal having been stretched into the corrugate form. It has been found that the convection currents through the flues is quite rapid and indeed the current through the flues is 'materially faster than the current of air passing contact directly with the refrigerant container only at the portions 26, and the contact of the plates with the shell 2 is only a surface to surface contact and this latter contact may be eliminated. Accordingly, the transfer of heat from the plates to the refrigerant must pass through or bridge these surface to surface contacts. This, of course, offers some resistance to the transfer of heat, with the result that the plates do not become chilled to the extent of other portions of the evaporator. For example, frost may form on the coils because the coils are chilled below the freezing point. This frosting, of course, extracts moisture from the air inside the box. The plates, however, may be so arranged that they are not chilled below the freezing point, even though they form cooling surfaces. Therefore, moisture which condenses thereon is in the form of water and is not frozen, and it may be termed that the plates sweat. The presence of this moisture facilitates a condition of high humidity, since this moisture, although once condensed and removed 'from the air, remains in the form of small globules or drops on the plates and is readily reevaporated. Obviously, if this result is not desired, the plates may be arranged to have a better heat transfer connection with the unit, and still the other results of the invention obtained, as for example, the flue structure and control of convection currents, finished appearance, etc.

As will be noted by reference to Fig. 2 the coil 'II is fashioned with an inlet run Ila which is connected by a run Hb directly with a side run He opposite that of Ila. The intermediate portions of this coil lie between the side runs Ila and H0. The reason for this structure is to have the runs Ila and He as nearly identical as possible so that when the two plates on opposite sides of the evaporator are secured to these two runs substantially like cooling efiects are obtained on the plates. The portions of the coil ll near the outlet end may be of higher temperature than portions near the inlet end and it is for this reason that the side runs Ha and He are directly connected so that their temperature condition is made more uniform. The type of connection between the hook portions 26 of the plates and the refrigerant coils may be varied to obtain the desired heat transfer to in turn control the cooling action of the plates. The hook portions may be merely clipped over the tubes forming a surface to surface contact in some instances, and to get a better heat transfer efliciency they may be united to the coils by the use of suitable solder, such as for example the so-called soft solder (a lead and tin alloy), or

silver solder or the like. The solder may run the full length of the hook portions 26 to obtain a connection of high efliciency for heat transfer, or the connections may be in the form of spots disposed in spaced relation in such number and of such spacing as to provide the desired heat transfer.

A further modified form of flue structures is shown in Fig. '7 wherein the same type of corrugated plate may be used, and the shell 2 is similarly corrugated as at 2a and the corrugations matched in such manner as to provide flues 30a, which may be generally of circular form in crosssection, although the flues need not necessarily be circular in form.

I claim: 7

In a refrigerator having a compartment to be cooled, an evaporator for refrigerant located in the upper part of the compartment and spaced relative to the opposite side walls thereof, said evaporator comprising a plurality of groups of coils of tubing for refrigerant, one group of coils being lowermost, another group being uppermost and another group of coils having an intermediate position, a shell defining a sharp freezing chamber, the lower group of coils lying below the lower wall of the shell, the upper group of coils lying above the upper wall of the shell, the intermediate group of coils lying within the shell, a partition member within the shell substantially in contact with the intermediate'group of coils, and a plate on each side of the shell, each plate having its upper and lower edges fashioned to extend inwardly and to engage over a run of tubing in the upper and lower groups of coils, the body portion of each plate extending substantially in parallel relation to a side wall of the shell and having a vertically extending corrugate formation defining substantially separate fiues for convection currents between'the side walls of the shell and each plate, the inwardly extending upper and lower edges of each plate being cut away to provide passageways for the inlet and outlet of convection currents to and from the flues.

WILLIAM W. HIGHAM.

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