US2449824A - Controlled humidity refrigerator - Google Patents

Description

P 1948. M. e. SHOEMAKER CONTROLLED HUMIDITY REFRIGERATOR 2 Sheets-Sheet 1 Filed Feb. 28, 1945 M. G. SHOEMAKER CONTROLLED HUMIDITY REFRIGERATOR Sept. 21, 1948.

2 Sheets-Sheet 2,

Filed Feb. 28, 1945 Patented Sept. 21, 1948 CONTROLLED HUMIDITY REFRIGERATOR Malcolm G. Shoemaker, Abington,

by mcsne assignments, to Philco Philadelphia, Pa., a corporation vania Pa" assignor, Corporation, of Pennsyl- Application February 28, 1945, Serial No. 580,109

Claims.

This invention has to do with refrigeration apparatus and, more particularly, is concerned with controlling the moisture content of air within the food storage compartment of a refrigerator.

With reference to the present invention, it should be borne in mind that it is desirable to provide a so-called moist-cold compartment in which the average relative humidity of the compartment air is maintained at a value sufliciently high to properly preserve exposed foodstuffs, without dehydration. However, in refrigerators embodying such high humidity compartments, it has provendiflicult to insure the desired degree of compartment humidity throughout the varying seasons of the year, while still preventing the moisture-content from reaching undesirably high values at certain times. This difficulty may arise under various operating conditions, but be comes particularly troublesome in more damp climates. As is well known, excessive box humidity results in undesirable condensation upon the walls of the compartment. The primary reason for this will be more apparent hereinafter when further reference is made to prior construction, but it is to be understood that it has become common to effect cooling of the moist-cold compartment through its walls and, as a consequence, such walls frequently assume temperature values below the dew-point temperature of the compartment air, when the relative humidity in the compartment has reached the undesirably high Values mentioned. above.

It is a primary object of the present invention to provide an improved refrigerator incorporating humidity control apparatus which is not only highly effective, but is characterized by unusual simplicity and low cost.

More particularly, my invention has as an object the provision of a refrigerator of the aforesaid moist-cold type, in which the maximum relative humidity of the compartment air may be positively limited to a predetermined value below 100%, whereby to prevent the undesired accumulation of moisture upon the walls of said compartment.

In accordance with one embodiment of the invention, it is also an object to provide humidity control apparatus of such a character as to ob viate the necessity for humidity-responsive switching devices, blowers, and like apparatus.

The present invention further contemplates the provision of a refrigerator including an air dehumidifying zone which, while effective to prevent excessively high compartment humidity, may

be utilized under temperature conditions such as to completely eliminate the possibility of frost accumulation in said zone, if such operation is desired.

To the above general ends, and in the broad aspect, my invention contemplates locating within the food storage compartment a portion of that relatively high temperature evaporator which cools the walls of said compartment, and utilizing said portion to effect condensation and consequent removal of excess moisture from the compartment air. While this evaporator may form a part of a refrigerating system of any desired type, I prefer to employ a secondary refrigeration system secured in the usual convoluted arrangement about the exterior walls of the food compartment inner liner, one or more passes" of tubing being arranged within said compartment, as aforesaid.

The invention extends further to certain novel and advantageous constructional features and arrangements hereinafter described, and illus-- trated in the accompanying drawings, in which:

Figure 1 is a view in perspective of a refrigerator embodying the invention;

Figure 2 is a view similar to Figure l, and illustrating a modified form of the present invention;

Figure 3 is an enlarged sectional view taken in the direction indicated by line 3-3 of Figure 2; and

Figure 4 is an enlarged sectional view taken through the vertical mid-plane of a portion of the apparatus shown in Figure 2 and in the direction indicated by line 4-4, applied to Figure 3.

First making detailed reference to Figure 1, there is shown a refrigerator which includes an outer shell 2 and an inner shell or liner member 3 defining a so-called moist-cold food storage compartment 4, which compartment may be fitted with a plurality of shelves of any desired type. The cabinet would, of course, be provided with a door (not shown) said door being adapted to seat thereagainst in the plane defined by vertical and horizontal breaker- strips 5 and 6, respectively. In the embodiment illustrated, the refrigerator further includes ice-freezing and low-temperature storage compartments to which access may be had through doors shown at 1'l. It will be understood that the compartment 4 is thermally isolated from the low-temperature storage sec-. tions (which, per se, need not be further described) in order that it may be possible to operate compartment 4 at relatively high temperatures as compared with the temperature of said sections, such isolation also serving to prevent said compartment 4.

'iently be accomplished by the use of a double 3 the undesired frosting-out of moisture present in These ends may conventhickness partition of glass or some other suitable insulating material. T his partition is shown at 8 and appears to best advantage in Figure 4.

Although the refrigerant circuits may take any one of several forms, there is illustrated an arrangement in which the main compartment 4 is cooled by means of refrigerant tubing 9 secured in convoluted arrangement about the exterior side and rear surfaces of the inner liner and, as shown, constituting the evaporator portion of a secondary refrigerant circuit of known type. It will be appreciated that this tubing 9 is located within the insulation M which fills the space between the outer shell and inner liner.

' in the circuit utilized to refrigerate the storage sections aforesaid and, as fragmentarlly illustrated in Figure 1, said evaporator is fed by a liquid line l3 extending upwardly from the vicinity of said low-temperature storage sections, a portion of the suction line returning to the main condensing unit (not shown) being illustrated at H. heat exchange association is well known, further and more detailed description is unnecessary.

As thus far described, the structure corresponds substantially to that commonly utilized in multi-temperature refrigerators and is designed; for example, to maintain the surface of said liner 3, defining the-compartment 4, at a temperature of approximately 38 F. There is, of course, a gradient between this temperature and the temperature of the tubing 9, the value of which will be dependent upon certain design factors, including the length of tubing convoluted about the liner. as well as the thickness of the said liner and the nature of the primarysecondary connection. In the embodiment illustrated, the temperature of the tubing 9 may be in the neighborhood of 34 F.

It should be borne in mind that the invention is concerned with the elimination of excessive moisture from the air within the compartment l, primarily to prevent the undesired deposition of condensate on the walls of the inner liner through which walls the compartment 4 is refrigerated.

As such primary-secondary.

4 through the walls of the compartment by arranging an evaporator in thermal transfer relation therewith. In such constructions, ,as

brought out above, the compartment walls being g cooler than the air within said compartment were subject to accumulation of an undesirable coating of moisture, whenever the relative humidity of the air had risen substantially. Various arrangements for eliminating this difficulty have been devised, some of which are effective and advantageous.

As far as I am aware, however, it has not been previously recognized that the problem is susceptible of extremely simple solution by locating a small portion of the evaporator system directly within the space defined by the cooled walls.

In the apparatus illustrated in Figure 1, provision is made for the effective removal of undesired moisture in this novel and unusually simple manner, as will now appear.

After the secondary refrigerant has been returned to the liquid phase in the condenser II,

it is delivered downwardly through a section of as tubing 90, which tubing is arranged within the food compartment 4, and is exposed to the circulating air therein. As pointed out hereinafter, some of the liquid refrigerant is volatilized in section 9a. At the point of introduction into 30 the food space, the tubing passes through a mounting grommet l5, while the lower extremity of the section 80. passes through an aperture l6 provided in the partition 8. From this point, as will be clear from the drawing, liquid refrigerant is delivered to the convoluted passages 9 within which the volatilization is completed.

The secondary circuit is closed by re-introduction of the vaporized refrigerant, into the condensing header l2, as indicated at H. In order to promote the free circulation of air about the tubing portion So, for a purpose which will become apparent hereinafter, said portion preferably extends along the wall of the liner in spaced relation thereto. 7

In view of the fact that the secondary system constitutes a single closed circuit, all portions of which are at substantially the same pressure,

tubing portion So will 'be maintained at substanis preferably maintained substantially constant.

the exposed portion always being somewhat cooler than the wall surfaces, a 4 differential having been given by way of example. As a result of this temperature differential, the area immediately surrounding said portion So, will be maintained at a low vapor pressure, with respect to the vapor pressure existing in the vicinity of the higher temperature walls. Consequently, the moisture present within the compartment 4 will be deposited upon the.exposed secondary tubing, rather than upon the refrigerator walls, such deposition taking place whenever the relative humidity of the box air has risen to such a pointthat contact of said ,air'with the cooler tubing reduces the temperature of the air below the dew-point. As shown in Figure 1, the tubing 8a is provided with 75 a flu I8 to faciliate the transfer of latent heat necessary to efiect the moisture condensation and, as mentioned above, the tube is spaced slightly from the liner wall to increase contact of the airtherewith. The moisture condensed passes downwardly along the exterior surface of the tubing and is delivered to the passage I!) through which it may be removed from the refrigerator.

'It will be evident that the apparatus of the present invention will effectively prevent any undesirable accumulation of condensate upon the walls of the inner liner. Although moisture, when first introduced, may tend to deposit upon the wall surfaces, a stabilized condition is reached quickly when the main door is closed, and any small amounts of moisture so deposited will then migrate to and be deposited upon the tube So, as a'result of the above mentioned vapor pressure differential.

There is no possibility of reducing the moisture content of the box air below a predetermined value of percent relative humidity, provided the proper temperature relations are maintained. The reason for this will be understood'by refer ence to a psychrometric chart, from which it will be clear that operation of the tube portion 9a at 34 F. could not reduce the percent relative humidity of box air at, for example, 40 F. to a value below 80%. Below such a percentage, under the temperature conditions assumed for exemplary purposes, the air in the vicinity of the exposed tubing would not be reduced below the dew-point temperature, and no moisture removal will take place. Tests have indicated that the system as thus far described is unusually effective in preventing undesirable increases of box humidity and consequent moisture collection upon the interior walls.

While it is preferred that the secondary system be operated at a temperature slightly above freezing, to prevent the accumulation of frost upon the moisture-condensing portion 8a, other modes of operation may be followed, if desired. A reduction of the secondary temperature to a value slightly below freezing results in a. somewhat more rapid response to the introduction into the box of unusually high quantities of free moisture and, for this reason, operation at sub-freezing temperatures may be desirable under certain conditions.

For best operational results, it has been found desirable to stabilize the temperature of the secondary system to a degree greater than that possible with the system as thus far described. and for this purpose a valve responsive to the vapor pressure within the secondary tubing may be employed. Such a valve is indicated at 20 in the drawings, and is well known in this art. If

the refrigerating capacity of the primary system is very high, or the primary temperature fluctuates considerably, undesirable temperature fluctuations may be reflected in the secondary systern. In addition to overcoming this disadvantage, a valve responsive to the secondary pressure has a tendency to insure unidirectional flow of the refrigerant through the secondary system, thereby increasing the capacity of the system.

There has been illustrated in Figures 2 to 4 a second embodiment of the invention, which while essentially similar to that already described, is particularly well adapted for use in extremely humid climates, or when very frequent access is had to the refrigerator. Under such conditions, it may be desirable to accelerate the response of the moisture control apparatus.

In this second embodiment, the refrigerator and the associated primary and secondary systems are similar to those already described and, accordingly, further description of those portions will be omitted in the following description.

This form of the invention, is concerned with an arrangement in which undesired humidity in the main food storage compartment is eliminated by effecting periodic circulation of the compartment air through a duct surrounding the secondary tubing 9a, and thereby in heat exchange relation with said tubing. In this system, the transfer of latent heat from the moisture laden air and consequent moisture condensation may be effected very rapidly when the need for moisture removal arises.

In the apparatus depicted in Figures 2 to 4 this air circulation is effected, as and when required, by means of a motor 2! and an associated blower 22, operable periodically in response to the humidity conditions existing in-the compartment 4, as will be set forth in detail hereinafter. As shown at 23 in the drawings, the rear wall of the inner liner is provided with an aperture in registry with the inflow portion of blower 22, said blower being mounted upon the exterior surface of the liner in any convenient manner. The outflow passage 24 extends horizontally across the back of the liner, and is provided with an opening in registry with an outflow aperture 25 formed in the liner wall immediately above the secondary portion 9a. A cap member 28 directs the air downwardly through the duct 2] surrounding the moisture condensing tube, said duct being provided with outwardly extending flanges 28--28 adapted to be resiliently'received within the undercut portions of a pair of mounting channels 29 fixed to the inner wall of the liner (see Figure 3). As shown at 30, the lower portion of the duct 21 communicates with a generally C-shaped air injection duct'3l extending about the side and rear walls of the liner 3, directly above the insulating partition 8. This duct is provided with a plurality of apertures 32 to permit passage of air from said duct and reinjection into the food compartment 4. As designated by arrows appearing in the drawings it will be apparent that air is initially withdrawn from the compartment through aperture 23, passes through the blower out-flow passage 24 and thence downwardly through duct 21 in heat exchange association with the tubing 9a. The circuit is, of course, completed by reinjection of the air into compartment 4 through apertures 32, as above described.

This controlled circulation may conveniently be initiated by means of a humidostat 33 which, while it may be of any desired type, is preferably of the type disclosed and claimed in the copending application of John J. Bauman, Serial No. 537,701, filed May 2'7, 1944. Description of the humidostat is unnecessary herein, beyond mentioning that it is adapted to initiate operation of the motor 2| when the relative humidity in the compartment 4 has risen just above a predetermined value. Further, it will be evident that while humidostat control is preferable, it would be possible to effect periodic actuation of the air circulation blower by other means. For example, the motor 2| could be energized at periodic, timed intervals, in accordance with the average humidity conditions encountered in practice in any particular locality. Further, in the broad aspect, certain advantages of the instant embodiment could be realized by a slow continuous circulation oi. the compartment air under the influence of the blower 22.

In all essential respects, the operation and advantages of this second form of the present invention are similar to those already set forth in connection with the first embodiment. As indicated above, more rapid response to excessive humidity conditionsmay be realized with the blower operated system. Again, the question of operating temperatures for the secondary system, and hence for the moisture condensing por-' tion Ia, are determined bythe maximum permissible average relativehumidity value of the compartment air, and the determination of whether or not some frost collection on the exposed tube is objectionable.

From the foregoing, it will be evident that the present invention provides an extremely simple and eil'ective apparatus for eliminating excessive moisture frequently present in refrigerators of the type referred to. The importance of the resultant prevention :of condensate accumulations within the box, will be readily appreciated.

I claim:

1. In a refrigerator, a storage compartment, evaporator means adapted to maintain wall portions of said compartment at a refrigerating temperature whereby to cool the compartment, evaporator means within said compartment affording a surface maintained at a temperature lower than the temperature at which said wall portions are maintained and upon which surface the deposition of moisture is substantially localized, means normally preventing contact of compartment air with said surface, and humidity-responsive means for-eflecting intermittent circulation of the compartment air in heat exchange relation with said surface.

2. A construction in accordance with claim 1, wherein said last meansis responsive to an increase in relative humidity above a predeterminedvalue and is adapted to maintain said circulation until the relative humidity is reduced to said predetermined value.

3. In a refrigerator, 9. storage compartment, evaporator means adapted to maintain wall portions of said compartment at a refrigerating temperature whereby to coolthe compartment, evaporator means within said compartment affording a surface maintained at a temperature lower than the temperature at which said wallportions are maintained and upon which surface the deposition of moisture is substantially localized. a housing normally preventing contact of compartment air with said surface, a blower located exteriorly of said compartment and having inflow and outflow passages communicating with said compartment and said housing, respectively, and means for initiating operation of said blower in response to an increase in relative humidity above a predetermined value, whereby to effect circulation of the compartment air in heat exchange relationwith said surface.

4. In a refrigerator, a storage compartment, a relatively large refrigerant evaporator arranged in high heat transfer relation with exterior surfaces of the walls of said compartment and effective to maintain interior wall portions at a temperature higher than the temperature of said exterior surfaces, and a relatively small refrigerant evaporator within said compartment, both said evaporators being maintained at substantially the same pressure to insure that said second-mentioned evaporator will be maintained .vailing in said first-mentioned evaporator and somewhat 'lower than the temperature ofsaid interior wall portions. e

5. In a refrigerator, a storage compartment, a relatively large refrigerant evaporator arranged in high heat transfer relation with exterior surbe maintained at a temperature substantially equal to that prevailing in' said first-mentioned evaporator and somewhat lower than the temperature 'of said interior wall portions.

6. In a refrigerator, a high humidity storage compartment, cooling means for said compartment, said cooling means having relatively large heat exchange capacity and being effective to cool the compartment air by maintaining exposed surfaces within said compartment at a predetermined temperature somewhat above the freezing point of water and below that of the air within' said compartment whereby, under high humidity conditions, said exposed surfaces are subject to undesirable moisture condensation thereon, and means forpreventing such condensation without reducing the moisture content of the compartment air below a desired predetermined lower value of percent relative humidity, said means comprising; a relatively small cooling element located within the compartment and maintained at a temperature slightly below the temperature of said exposed cooling surfaces, means normally preventing contact of compartment air with said element, and means for effecting intermittant circulation of the compartment air in heat exchange relation with said element.

"I. In a refrigerator, a metallic liner defining a refrigerated space, and a refrigerant evaporator comprisin tubing the major portion of which extends about exterior wall surfaces of said liner in high heat exchange relation therewith, whereby to refrigerate said space through the walls of said liner, a minor portion of said evaporator tubing being disposed in said space, said evaporator tubing being at substantially the same temperature throughout, and the temperature gradient through said cooled walls being such that interior surfaces of said cooled walls are maintained at a temperature slightly higher than the temperature of said minor portion.

8. In a refrigerator, a liner defining a refrigerated space, and a refrigerant evaporator comprising tubing the major portion of which extends about exterior wall surfaces of said liner in 'high heat exchange relation therewith, whereby to refrigerate said space through the walls of said liner, a minor portion of said evaporator tubing being disposed within said space along an interior wall surface of the liner and constituting a condensate-localizing surface,

9. In a refrigerator, a liner defining a refrigerated space, a refrigerant evaporator comprising tubing the major portion of which extends about exterior wall surfaces of said liner in high heat exchange relation therewith, whereby to refrigerate said space through the walls of said liner, a minor portion of said evaporator tubing being disposed within said space along an interior wall at a temperature substantially equal to that pre- '76 surface of the liner and constituting a conden- 9 sate-localizing surface, and means providing for removal of condensate from'saidrefrigerated space. V v

10. In a refrigerator, a high humidity storage compartment, cooling means arranged in heat exchange relation with exterior surfaces of the walls of said, compartment. saidcooling means having relatively large heat exchange capacity being effective to cool the compartment air by maintaining exposed surfaces within said compertinent at a predetermined temperature somewhat above the freezing point of water and below that of the air within said compartment whereby, under high humimty conditions, said exposed surfaces are subject to undesirable moisture condensation thereon, and means for preventing such eondensation without reducing the moisture small cooling element content of the compartment air below a desired predetermined lower value of percent relative humidity, said means comprising a relatively REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,133,958 Kalischer Oct. 25, 1938 2,261,681 Ullstrand Nov. 4, 1941 2,292,015 Schweller Aug. 4, 1942 2,361,792 Philipp Oct. 31, 1944 2,370,267 Starr Feb. 27, 1945

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