AU2004238898A1

AU2004238898A1 - Arrangement for air circulation by natural convection in refrigerators

Info

Publication number: AU2004238898A1
Application number: AU2004238898A
Authority: AU
Inventors: Guilherme Klitzke Giesbrecht; Luiz Antonio Diemer Lopes; Marco Eduardo Marques
Original assignee: Multibras SA
Current assignee: Whirlpool SA
Priority date: 2003-05-15
Filing date: 2004-05-13
Publication date: 2004-11-25
Also published as: WO2004102090A1; BR0301427A; CN1820170A; EP1623168A1

Description

WO 2004/102090 PCT/BR2004/000066 ARRANGEMENT FOR AIR CIRCULATION BY NATURAL CONVECTION IN REFRIGERATORS Field of the Invention The present invention refers to an arrangement for 5 providing an improved air circulation by natural convection in refrigerators, particularly in the refrigerators that comprise a cabinet defining, internally, a refrigeration compartment and, optionally, a freezer compartment, each compartment 10 being closed by a front door and provided with an evaporating plate. Prior Art The refrigerators that use the system of natural convection to promote air circulation are generally 15 provided with an evaporating plate, positioned close to a rear wall of the refrigeration compartment and which is visible to the user when he/she opens the door. There are also used the constructions in which the 20 evaporating plate is affixed behind the rear wall of the refrigeration compartment, in order to be completely hidden from view of the user upon opening the door of the refrigeration compartment. Such evaporating plate is known as the skin-type 25 evaporating plate. Independently of the particular construction of the evaporating plate, the air contained in the refrigeration compartment is submitted to a natural convection process, since by contacting the cooler 30 evaporating plate, its density is increased and it tends to flow down the rear region of the refrigeration compartment. On the other hand, the air contained in the front region of the refrigeration compartment, close to the door, is at a higher 35 temperature and thus less dense, tending to flow 2 WO 2004/102090 PCT/BR2004/000066 upwardly, as schematically illustrated by the arrows in f igure 1. These known natural convection arrangements present some disadvantages, among which we can point out the 5 temperature stratification inside the refrigeration compartment, the exudation inside the latter, and the formation of ice on the evaporating plate, when the latter is visible to the user, or on the rear wall region of the refrigeration compartment behind which 10 the skin-type evaporating plate is seated. The temperature stratification results from the absence of a system for distributing the airflow that is refrigerated in the evaporator. Since the cooler air always tends to flow down, there occurs a 15 significant difference of temperatures between the (warmer) upper region and the (cooler) lower region of the refrigeration compartment. The internal exudation occurs due to the fact that the rear mounting region of the evaporating plate, either 20 of the exposed or of the hidden (skin) type is much cooler than the regions more distant from the refrigeration compartment and which are generally adjacent to the lateral and upper walls and to the internal wall of the door. These warmer and more 25 distant regions lose a great amount of heat, by radiation, to the cooler region adjacent the evaporating plate, and thus have their temperatures reduced as a function of said heat transfer by radiation. When the user opens the refrigerator door, 30 a large amount of humid air enters the refrigeration compartment, and the lower the temperature of the internal walls of said refrigeration compartment, the higher is the amount of water contained in the humidity of the air to be condensed on said walls, 35 forming water droplets that can precipitate on the 3 WO 2004/102090 PCT/BR2004/000066 food products stored inside the refrigeration compartment, impairing the adequate preservation of said products, besides producing an unpleasant esthetic effect. 5 The formation of ice on the evaporating plate or on the rear wall of the cabinet is inevitable in the skin-type system, since the temperature in these regions is much lower than the solidification temperature of the water generated by the humidity of 10 the air admitted into the refrigeration compartment, said formation of ice considerably impairing the esthetic of the appliance, in the case of the evaporating plates of the exposed type mounted in front of the rear wall of the refrigeration 15 compartment, such as the skin-type evaporating plate seated against the rear face of the rear wall of the refrigeration compartment, causing formation of ice in the region of said rear wall being refrigerated, by conduction, by the evaporating plate. 20 Objects of the Invention By reason of the disadvantages mentioned above, it is the generic object of the present invention to provide an arrangement of the type considered herein, which allows obtaining an improved and more efficient air 25 circulation by natural convection inside the refrigeration compartment, conducting to a better distribution and homogenization of the temperatures existing in the interior of said refrigeration compartment. 30 It is a further object of the present invention to provide an arrangement for air circulation as mentioned above, which allows eliminating or at least minimizing the effects of the internal exudation on the walls of the refrigeration compartment. 35 It is still a further object of the present invention 4 WO 2004/102090 PCT/BR2004/000066 to provide an arrangement as mentioned above, which allows eliminating the negative esthetic effects of ice formation on the evaporating plate when the latter is mounted in an exposed manner in front of the rear 5 wall of the refrigeration compartment. Summary of the Invention In order to attain the above-mentioned objects, as well as other advantages resulting from the improvements introduced herein, the present invention 10 proposes an arrangement for air circulation by natural convection in a refrigerator of the type that comprises a cabinet defining, internally, a refrigeration compartment, frontally closed by a door and which is provided with an upper wall, side walls, 15 a lower wall, and a rear wall, close to which is affixed an evaporating plate. According to the invention, the present arrangement comprises a cover plate affixed in front of the evaporating plate and maintaining from the latter a 20 certain distance for allowing a downward air circulation to occur therebetween. The cover plate is configured to avoid visualization of the evaporating plate or of the rear region of the refrigeration compartment that supports the 25 evaporating plate, thus operating as a cold front face of the latter to refrigerate the air in contact therewith. The cover plate is further designed to define end and median air passages between the refrigeration compartment and the region that defines 30 the spacing between the cover plate and the evaporating plate. In a specific construction, the end air passages are defined between the upper and lower end edges of the cover plate and the adjacent portions of the upper and 35 lower walls, respectively, of the refrigeration 5 WO 2004/102090 PCT/BR2004/000066 compartment, the median air passages being defined as respective windows provided in different levels of the cover plate. The basic construction defined above allows the 5 temperature stratification inside the refrigeration compartment to be substantially improved, since the cover plate, which is maintained some millimeters from the evaporating plate, allows producing a rise in the air speed in the upper region of the refrigeration 10 compartment, which region is exactly the one presenting a highest temperature. Thus, the temperature in the upper region of the refrigeration compartment can be reduced, and consequently the temperature gradient in relation to 15 the coolest region. The median air passages provided in the cover plate can be arranged in such a way as to allow the cool airflow, which is flowing down and passing between the evaporating plate and the cover plate, to be divided 20 in multiple flows directed to the interior of the refrigeration compartment at different levels defined by the positioning of said median air passages. The median air passages can be also associated with deflecting means provided posteriorly to the cover 25 plate and which help directing a respective portion of the downward cool airflow to the interior of said median air passages. In case deflectors are provided, the cover plate can present median air passages positioned so as to allow 30 the air from the refrigeration compartment to be admitted in the region located between the evaporating plate and the cover plates, increasing the air circulation in a region of the refrigeration compartment situated between two adjacent shelves. 35 Since the cover plate is positioned in such a manner WO 2004/102090 6 PCT/BR2004/000066 as to hide the region of the evaporating plate, it actuates as a means for blocking the heat transfer by radiation, from the warmest wall portions of the refrigeration compartment to the coolest region of the 5 evaporating plate, which region can be defined by the evaporating plate itself or by the refrigerated region of the rear wall in case of the skin system. Thus, the internal walls of the compartment, which are more distant from the evaporating plate, will remain with 10 their temperatures in a little higher value, minimizing the process of internal exudation. In case of the evaporating plates being exposed in the interior of the refrigeration compartment, or presenting the skin type assembly, the ice formed on 15 the evaporating plate or on the rear wall will remain hidden behind the cover plate, preventing the refrigeration appliance from being esthetically impaired. Brief Description of the Drawings 20 The invention will be described below, with references being made to the enclosed drawings, given by way of example and in which: Figure 1 is a simplified vertical cross-sectional view of a refrigerator provided with a refrigeration 25 compartment, illustrating the air circulation by natural convection, according to the known prior art constructions; Figure 2 is a view similar to that of figure 1, but illustrating the arrangement of the present invention 30 applied to said refrigeration compartment; Figure 3 is a front view of the refrigerator illustrated in figures 1 and 2, with the door being removed to better illustrate the position of the air passages in relation to the cover plate, to the 35 evaporating plate, and to the upper and lower walls of 7 WO 2004/102090 PCT/BR2004/000066 the refrigeration compartment; Figure 4 is a partially cut perspective view of both the cover plate and the evaporating plate, illustrating a possible construction for the 5 deflectors associated with the median air passages; Figure 5 is a view similar to that of figure 2, but illustrating the present arrangement when associated with the shelves of the refrigeration compartment, and with the provision of a cover plate having a median 10 air passage for the median admission or entry of air into the region situated between the evaporating plate and the cover plate; and air directing rear fins; Figure 6 is a front view of the refrigerator of figure 5 without the door; and 15 Figure 7 is a partial rear plan view of the cover plate used in the construction of figures 5 and 6. Detailed Description of the Invention As illustrated in figures 1-7, the arrangement for air circulation by natural convection of the present 20 invention is directed to refrigerators comprising a cabinet 10, which defines, internally, a refrigeration compartment 20, frontally closed by a door 30 and which is provided with an upper wall 21, side walls 22, a lower wall 23, and a rear wall 24, it being 25 further understood that the cabinet 10 can be optionally provided with a freezer compartment (not illustrated), generally mounted above the refrigeration compartment 20 and which is separated therefrom by a dividing wall. 30 In the construction illustrated in the drawings, in front of the rear wall 24 of the refrigeration compartment 20 is affixed an evaporating plate 40, of a known construction and extended along a substantial part of the height and width of said rear wall 24. 35 In the case of the refrigerators in which the 8 WO 2004/102090 PCT/BR2004/000066 evaporating plate 40 is mounted according to the skin system, said evaporating plate 40 is positioned seated behind the rear wall 24 of the refrigeration compartment 20, being invisible to the user who opens 5 the door 30. In this case, the rear wall 24 operates as a front face of the evaporating plate 40 itself. According to the invention, the arrangement for air circulation comprises a cover plate 50, which is generally flat and constructed in a material of low 10 thermal conductivity, such as a plastic material. The cover plate 50 is dimensioned and configured to completely cover the evaporating plate 40, when the latter is mounted in an exposed manner in the refrigeration compartment 20, in front of the rear 15 wall 24 of the latter, preventing said evaporating plate 40 from being visible to the user upon opening the door 30 of the cabinet 10. In the case of the skin-type assembly, the cover plate 50 covers the region of the rear wall 24 behind which is seated the 20 evaporating plate 40 and in front of which occurs the formation of ice. The cover plate 50 defines end air passages 51, 52 and median air passages 53 between the refrigeration compartment 20 and the region defined between the 25 cover plate 50 and the evaporating plate 40. Generally, the cover plate 50 presents an upper end edge 50a and a lower end edge 50b which are respectively spaced from adjacent portions of the upper wall 21 and the lower wall 23 of the 30 refrigeration compartment 20, allowing the air to enter through the upper end of the region defined between the evaporating plate 40 and the cover plate 50, and the lower exit of the refrigerated downward airflow to the inside of the refrigeration compartment 35 20, as illustrated by the arrows in figure 2. The 9 WO 2004/102090 PCT/BR2004/000066 spacing defined between the upper end edge 50a and the lower end edge 50b of the cover plate 50 and the adjacent portions of the upper wall 21 and the lower wall 23 of the refrigeration compartment 20 defines 5 end air passages 51 and 52, in relation to said cover plate 50, which allow the air to circulate by natural convection inside the refrigeration compartment and to pass along the evaporating plate 40. Since the height of the evaporating plate 40 is 10 generally substantially lower than the height of the refrigeration compartment 20 and of its rear wall 24, the cover plate 50 can be dimensioned to adequately cover the evaporating plate 40 and, at the same time, present a height which is substantially lower than the 15 height of the refrigeration compartment 20 defined between the upper wall 21 and the lower wall 23 of the latter, in order to form the end air passages 51, 52 close to the upper end edge 50a and the lower end edge 50b of the cover plate 50. 20 The cover plate 50 is further provided with median openings 53, allowing the fluid communication to occur between different levels of the refrigeration compartment 20 and the region defined between the cover plate 50 and the evaporating plate 40. These 25 median air passages 53 are preferably defined by respective windows, provided in different levels of the cover plate 50 and each presenting a width that is substantially smaller than that of the cover plate 50. The provision of median air passages 53 allows the 30 airflow which is refrigerated by the evaporating plate 40 to be more homogenously distributed to the inside of the refrigeration compartment 20, minimizing or even eliminating the temperature stratification within the latter. The median air passages 53 for the outflow 35 of the cool air are preferably positioned in the lower 10 WO 2004/102090 PCT/BR2004/000066 region of the gap defined between two adjacent shelves, as illustrated in figures 5 and 6. In order to increase even more the distributive efficiency of the median air passages 53, the present 5 arrangement can further comprise a deflector 60, which is positioned between the evaporating plate 40 and the cover plate 50 and close to each median air passage 53, in order to direct to the latter and to the inside of the adjacent region of the refrigeration 10 compartment 20, the downward circulating airflow that reaches the deflector 60. In the illustrated embodiment, each deflector 60 comprises a small plate inclinedly projecting backwardly and upwardly from a lower edge of the 15 respective median air passage 53, said deflector maintaining a slight spacing in relation to the front face of the evaporating plate 40 and preferably presenting a curved concave upper surface. Although the deflectors 60 are illustrated as fixed 20 elements incorporated to the rear part of the cover plate 50, it should be understood that they might be mounted to the structure of the cabinet or to the cover plate 50 itself, in order to be selectively, individually or jointly displaced to different 25 operative positions, varying the quantity of cool air supplied to the respective level of the refrigeration compartment 20. However, when the deflectors 60 are provided in the rear part of the cover plate 50, the downward airflow 30 tends to deviate to both sides of each deflector, stopping to supply air to the respective median air passage 53. In this case, it is desirable to provide the cover plate 50 with fins 55 vertically disposed generally above and on both sides of the deflector 60, 35 so as to guide and direct a downward airflow toward 11 WO 2004/102090 PCT/BR2004/000066 each deflector 60, as illustrated in figures 5, 6 and 7, preventing the downward airflow from being deviated by the deflector 60 to the sides of the respective median air passage 53 through which the cool air 5 flows. The fins 55 can present a width equal to or smaller than the distance "D" that separates the evaporating plate 40 from the cover plate 50, and they can be affixed to the latter or to the structure of the 10 cabinet 10. In refrigerators provided with shelves 15 made of glass or other material defining a horizontal internal panel, it may be advantageous to increase the air circulation in one or more gaps defined between each 15 two adjacent shelves. In order to increase the air circulation in one of said gaps between the shelves 15, the cover plate 50 is provided with one or more median air passages 54 for air admission, each being positioned in the upper 20 region of a respective gap between two shelves 15, so as to allow an incoming airflow to be formed from the upper region of the gap to the interior of the region defined between the evaporating plate 40 and the cover plate 50. 25 The median air passages 54 for air admission are dimensioned and arranged so as not to interfere with the downward cool airflow, which is directed to each deflector 60. While only one exemplary embodiment of the present 30 invention has been schematically illustrated herein, it should be understood that changes in the form and relative arrangement of the components could be made without departing from the inventive concept defined in the appended claims. 35

Claims

1. An arrangement for air circulation by natural convection in refrigerators of the type comprising a cabinet (10) defining, internally, a refrigeration 5 compartment (20), frontally closed by a door (30) and which is provided with an upper wall (21), side walls (22), a lower wall (23), and a rear wall (24) close to which is affixed an evaporating plate (40), characterized in that it comprises a cover plate (50) 10 frontally affixed to the evaporating plate (40) and maintaining from the latter a certain distance (D) , in order to allow a downward air circulation to occur therebetween, said cover plate (50) being configured to avoid visualization of the evaporating plate (40) 15 and to define end air passages (51, 52) and median air passages (53, 54) between the refrigeration compartment (20) and the region defined between the cover plate (50) and the evaporating plate (40).

2. The arrangement as set forth in claim 1, 20 characterized in that the evaporating plate (40) is positioned in front of the rear wall (24) of the compartment (20), between the latter and the cover plate (50).

3. The arrangement as set forth in claim 2, 25 characterized in that the end air passages (51, 52) are defined between an upper end edge (50a) and a lower end edge (50b) of the cover plate (50) and adjacent portions of the upper wall (21) and lower wall (23), respectively, of the refrigeration 30 compartment (20).

4. The arrangement as set forth in claim 3, characterized in that the cover plate (50) presents a height that is substantially lower than the height of the refrigeration compartment (20) defined between the 35 upper wall (21) and lower wall (23). 13 WO 2004/102090 PCT/BR2004/000066

5. The arrangement as set forth in claim 1, characterized in that the median air passages (53) are defined by respective windows provided in different levels of the cover plate (50). 5

6. The arrangement as set forth in claim 5, characterized in that each median air passage (53) presents a width that is substantially smaller than the width of the cover plate (50), and it is positioned in the lower region of the gap defined 10 between two adjacent shelves (15), in order to define cool air outlets to the inside of the refrigeration compartment (20) .

7. The arrangement as set forth in claim 1, characterized in that it further comprises a deflector 15 (60), which is positioned between the evaporating plate (40) and the cover plate (50) and close to each median air passage (53) so as to direct to the latter and to the interior of the adjacent region of the refrigeration compartment (20) the downward 20 circulating airflow that reaches the deflector (60).

8. The arrangement as set forth in claim 7, characterized in that each deflector (60) comprises a small plate inclinedly projecting backwardly and upwardly from a lower edge of the respective median 25 air passage (53).

9. The arrangement as set forth in claim 8, characterized in that the deflectors (60) maintain a slight spacing in relation to the evaporating plate (40). 30

10. The arrangement as set forth in claim 8, characterized in that the deflectors (60) present a curved concave upper surface.

11. The arrangement as set forth in claim 7 characterized in that the cover plate (50) further 35 presents at least one median air passage (54) provided 14 WO 2004/102090 PCT/BR2004/000066 in the upper region with at least one gap defined between two adjacent shelves (15), in order to define a respective air inlet to the region between the evaporating plate and the cover plate (50). 5

12. The arrangement as set forth in claim 7, characterized in that the cover plate (50) is posteriorly provided with a pair of vertical fins (55) disposed above and on the opposite sides of each assembly of deflectors (60), and with a median air 10 passage (53) to direct a downward cool airflow to the respective deflector (60).

13. The arrangement as set forth in claim 12, characterized in that the fins (55) present a width at maximum equal to the distance (D) between the 15 evaporating plate (40) and the cover plate (50).

14. The arrangement as set forth in claim 1, characterized in that the evaporating plate (40) is posteriorly seated against the rear wall (24), in order to have its front face defined by the latter. 20

15. The arrangement as set forth in any one of the previous claims, characterized in that the cover plate (50) is made of a material of low thermal conductivity.