Refrigeration – With indicator or tester – Position or extent of motion of movable element
Reexamination Certificate
2003-02-07
2004-04-20
Wayner, William (Department: 3744)
Refrigeration
With indicator or tester
Position or extent of motion of movable element
C062S248000, C062S186000
Reexamination Certificate
active
06722142
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a refrigerated enclosure, and more specifically to a refrigerated enclosure having a view panel and an intermittent fan for removing moisture that condenses on the view panel.
BACKGROUND OF THE INVENTION
Refrigerated enclosures (e.g., refrigerator, freezer, cooler, refrigerated display case, etc.) are used in residential settings, and also in commercial settings, for example in stores and restaurants. Commercial refrigerated enclosures often include a view panel, which may be located in a door, for viewing the contents of the refrigerated enclosure. This feature can conserve energy by minimizing the period of time the door is opened during product retrieval, selection, or location. This feature can also speed up product selection or location and, in the event the desired product is not present in the refrigerated enclosure, avoid the need to open the refrigerated enclosure at all during product selection or location.
A long standing problem with commercial refrigerators with view panels is condensation on the view panel. Condensation can occur on either the interior surface or the exterior surface of the view panel, when either of those surfaces are at a temperature below the dew point temperature of the air these surfaces are exposed to. However, condensation on the interior surface of the view panel is more commonly a problem, as explained below.
Under normal operation the air temperature inside the refrigerated enclosure is much lower than the outside air temperature. The interior surface of the view panel is exposed to the cooler inside air, while the exterior surface of the view panel is exposed to the warmer outside air. Although the view panel itself provides at least some insulation between the interior and exterior surfaces of the view panel, there will always be some heat transfer through the view panel. Thus, in normal operation the outside air is warmer than the exterior surface of the view panel, the exterior surface of the view panel is warmer the interior surface of the view panel, and the interior surface of the view panel is warmer than the air inside the refrigerated enclosure.
The difference between the temperature of the exterior surface of the view panel and the outside air depends on a number of variables, including the insulation value of the view panel itself and the temperature and circulation of the inside and outside air. If the view panel is designed to minimize heat transfer through the view panel itself, for example by using double paned glass or other material having a relatively high insulation value, the exterior surface of the view panel will be only slightly cooler than the exterior air temperature. Thus, by using a view panel with a high insulation value, as long as the exterior air temperature is well above the dew point so that the temperature of the slightly cooler exterior surface is also above the dew point, condensation on the exterior surface of the view panel can be avoided
When the door to a refrigerated enclosure remains closed, the interior air is cooled and dehumidified by the refrigeration apparatus, which lowers the dew point of the inside air. Since any view panel material will have at least some heat transfer through the view panel itself, the temperature of the interior surface of the view panel will always be at least slightly warmer than the interior air temperature. Thus, as long as the interior air temperature is above the dew point, the warmer interior surface of the view panel will also be above the dew point, and condensation on the interior surface of the view panel will be avoided.
In summary, if the view panel is designed to minimize heat transfer through the view panel itself and the interior and exterior air are not near their respective dew points, condensation on the interior and exterior surfaces of the view panel is usually not a problem as long as the door to the refrigerated enclosure remains closed.
However, when a refrigerated enclosure is opened, warm outside air is brought into the refrigerated enclosure. Since this warm outside air has not yet been cooled and dehumidified by the refrigeration apparatus, the dew point of the warm outside air may be substantially higher than the temperature of the interior surface of the view panel. When this warm outside air comes into contact with the interior surface of the view panel, condensation is likely to form. Condensation can be especially likely when the view panel is located in the door such that the warm outside air flows directly onto the much cooler view panel. Condensation on the view panel is undesirable since it destroys the utility of the view panel and detracts from the visual appearance of the refrigerated enclosure.
The problem of condensation on the interior surface of the view panel when the refrigerated enclosure is opened can be exacerbated by the use of view panel materials having a high insulation value. A view panel having a higher insulation value will keep the exterior surface of the view panel warmer, but it will also keep the interior surface of the view panel cooler. Especially if the interior air is already close to the dew point when outside humid air is introduced by opening the refrigerated enclosure, condensation on the cool interior surface of the view panel can be even more likely when view panels having a high insulation value are used.
It is known to reduce or remove condensation from a commercial refrigerated enclosure generally by applying heat to areas likely to be affected by condensation, such as door jambs and the interior and exterior surfaces of view panels. For example, an electric heater has been positioned adjacent the inside of the front face, or inside the doors, of a refrigerated cabinet, a hot gas loop has been positioned inside the front face of a refrigerated cabinet, and electrical heating elements have been concealed within the outer edges of the door or within the door frame of a refrigerated display case.
However, any heating element consumes power, and the introduction of a heating element on or near a refrigerated enclosure may be especially inefficient since heat produced by such a heating element can end up in the refrigerated enclosure, from which it must be subsequently removed, consuming additional power. It is also known to reduce or remove condensation from refrigerated enclosures used in commercial environments by operating a fan directed at clear windows. However, in commercial refrigerated enclosures such fans are run continuously during operation, consuming power and producing noise.
It is also generally known to provide a refrigerated enclosure in a residential or household environment, for example the common household refrigerator. Household refrigerators have evolved considerably over the years in response to evolving consumer preferences as well as more stringent requirements for energy efficiency. Because of differences in the commercial and residential settings, the design of a household refrigerator may differ in some respects from those of a commercial refrigerated enclosure. Most household refrigerators do not include a window or view panel on the door.
Nonetheless, for many of the same reasons that a view panel is desirable in a commercial refrigerated enclosure, it would also be desirable and advantageous to provide a household refrigerator with a view panel, for example a glass window in the door. As in a commercial setting, a view allows the contents of a household refrigerator to be viewed, which can reduce time spent perusing or searching the interior while the door is open and thereby reduce energy consumption. Further, especially in the high end consumer market, the ornamental appearance of a household refrigerator can be enhanced by a glass window in the door.
As in the commercial setting, household refrigerators with a view panel can also encounter condensation problems. However, approaches which may be adequate in the commercial environment have a number of drawbacks for household refrigerators.
For example, heating
Foley & Lardner
Sub-Zero Freezer Company Inc.
Wayner William
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