Dynamic Multi-Zone Anti-Sweat Heating System

Some embodiments consistent with the invention, as mentioned above, are directed in part to the use of a dynamic multi-zone anti-sweat heating system for inhibiting the formation of moisture on various surfaces of a refrigerator and/or to evaporate fluid collected in a refrigerator, e.g., in a dispenser recess sump, evaporative tray, or other fluid collection structure.

An anti-sweat heating system may be considered to be dynamic from the standpoint that, at least in some embodiments, the heating system is capable of dynamically activating one or more heaters in response to detection of the presence of moisture on a surface, or at least detection of conditions that are indicative of a likely presence of moisture on a surface. An anti-sweat heating system may be considered to be multi-zone from the standpoint that, at least in some embodiments, multiple individually-actuatable zones exist that can be independently monitored and activated to address potential moisture within such zones.

A zone, in particular, may include one or more heaters and one or more temperature sensors, and may cover one or more interior and/or exterior surfaces of a refrigerator cabinet (which, for the purposes of this disclosure, may include both the main case and the doors of the refrigerator, as well as any other component or structure in the refrigerator upon which it may be desirable to prevent condensation from forming and/to or evaporate any condensation or fluid that may exist). As such, in some embodiments a zone may encompass multiple surfaces, while in other embodiments one surface may have multiple zones.

The heaters in a zone may be heating elements capable of heating associated surfaces, and the temperature sensors may be surface temperature sensors capable of sensing a temperature on associated surfaces. Multiple heating elements within a zone may be supported in some embodiments, and the multiple heating elements may be disposed in the same heating assembly in some embodiments, or may be disposed in different heating assemblies. Further, in some embodiments, the heating elements may be considered to be surface heaters to the extent that the heat generated thereby provides heat to an associated surface. In addition, it will be appreciated that multiple zones may operate in a group in some embodiments, such that activities occurring within multiple zones of a group may be affect the activation of the heating elements in various zones in the group (e.g., as is the case with a dispenser recess as discussed below in connection with FIG. 7).

By utilizing multiple zones, each zone may be provided with individual temperature feedback, and the temperature feedback may be used to enable a controller to dynamically react to sensed temperature by selectively activating heaters. As such, in some embodiments zones may be monitored on an ongoing basis, with heaters activated on demand when needed, and only in zones within which moisture may be present, thereby minimizing overall energy usage.

In some embodiments, activation of a heater in a zone may be based on a dew point determined, for example, from a sensed ambient relative humidity, along with one or more surface temperature readings that detect when a surface temperature drops below a calculated dew point. In other embodiments, the temperature in each zone may be monitored to detect drops in temperature, which may be indicative of heat flux, and indicating the desirability of energizing a heater in a particular zone.

Furthermore, in some embodiments, moisture detection (and/or detection of removal of moisture) may be based in part on the evaporative cooling effect of moisture. In particular, in some embodiments moisture detection may be based at least in part on sensing the thermal load on a surface, in particular while a heater associated with the surface is active, as moisture present on a surface will generally present as a thermal mass that, when heated, will resist an increase in surface temperature as a result of the phase change occurring as the moisture evaporates. This resistance to change may be sensed, for example, by monitoring the rate of change of the sensed surface temperature, or alternatively by comparing a rate of change of the sensed surface temperature to an amount of applied current to a heater (e.g., by dividing temperature increase by applied amperage in some embodiments). Moisture may therefore be detected based upon a reduced or slower than expected rise in temperature when a heater is activated (i.e., an increased thermal load), while the evaporation of moisture may be detected based upon a transition to a faster temperature rise when a heater is activated (i.e., a decreased thermal load). Further, the detection of moisture in one zone or on one surface or portion of a surface could be used to trigger activation of heaters in other zones or associated with other surfaces, given that environmental conditions particularly suitable for condensation may have been detected.

Thus, in some embodiments consistent with the invention, a controller coupled to a heater and a temperature sensor may be able to detect moisture on a surface by activating the heater, sensing a surface temperature with the temperature sensor while the heater is activated, and determining that moisture is present on the surface in response to detecting an elevated thermal load on the surface while the surface heater is activated.

It will also be appreciated that, in addition to or in lieu of condensation formed on interior and/or exterior surfaces of a refrigerator, the techniques described herein may also be used to accelerate the evaporation of fluids collected in various receptacles in a refrigerator, e.g., a dispenser recess sump and/or an evaporative tray used to collect condensation generated by a refrigerator cooling system. In particular, heaters may be used to accelerate fluid evaporation, and monitored surface temperatures may be used to detect when fluid is present and/or when all of the fluid in a receptacle has been removed.

Now turning to FIG. 3, it will be appreciated that a dynamic multi-zone anti-sweat heating system may be used in a number of different areas and applications within a refrigerator. FIG. 3 in particular illustrates door 20 of refrigerator 10 in greater detail, along with several potential zones that may be utilized in a heating system consistent with the invention.

One potential application of such a heating system is in connection with addressing condensation on an articulating mullion of a refrigerator door. Door 20, for example, is illustrated in FIG. 3 with an articulating mullion 70 including a pair of heaters 72, 74 and associated temperature sensors 76, 78 effectively defining two different zones on the articulating mullion 70, and suitable for addressing potential moisture condensation on the mullion, e.g., when the door is open. In addition, for dispenser recess sump 30, an associated heater 80 and temperature sensor 82 are illustrated, e.g., for evaporating fluids collected in the sump 30. Furthermore, for the recess of dispenser 26 itself, an additional zone may be defined including a heater 84 formed along a back wall of the recess, and proximate to a dispenser outlet from which cold air may escape and potentially cause an increase in the likelihood of condensation. FIG. 3 also illustrates that in some embodiments, a zone may include multiple temperature sensors, e.g., temperature sensors 86 disposed at different locations in the recess. Further, FIG. 3 also illustrates that in some embodiments, a heater such as heater 84 may include multiple heating elements 88, which may be separately or collectively activated in various embodiments.

FIG. 4 illustrates an additional location for a zone in refrigerator 10, in particular, on the rear 90 of the refrigerator, where a evaporative tray 92 utilized by the cooling system may be located. A heater 94 and associated temperature sensor 96 may be used to accelerate evaporation of fluids collected in tray 92.

It will be appreciated that the various applications illustrated in FIGS. 3 and 4 are merely exemplary in nature, and that the techniques disclosed herein may be used in a wide variety of other applications, including, without limitation, interior and/or exterior surfaces of the case or doors, internal mullions, defrost heaters, duct door heaters, and compartment heaters (e.g., quick thaw compartments), among others.

Now turning to FIG. 5, an example dynamic multi-zone anti-sweat heating system 100 is illustrated in greater detail, and suitable for implementation, for example, in refrigerator 10. A controller 102 in particular is coupled to multiple zones 104, each including one or more heaters 106 and one or more temperature sensors 108. Each heater may be implemented using a number of different technologies suitable for the particular application of a zone. For example, resistive heating elements may be printed on flexible substrates or directly on or underneath a surface in some embodiments, while in other embodiments, other heating technologies, e.g., thick film heaters, resistance wire heaters, etc. may be used. Each temperature sensor 108 is generally configured to sense a surface temperature near or on a surface being monitored, and in some instances, a temperature sensor 108 may be integrated directly into a heater assembly. In other instances, however, each temperature sensor may be separate from any heater, but disposed in proximity thereto.

Controller 102 may utilize temperature sensors 108 to monitor surface temperatures for the purpose of determining when to dynamically activate and/or deactivate the associated heaters 106 in a zone 104. In addition to or in lieu of temperature sensors 108, however, various additional inputs may be used in a dynamic multi-zonal anti-sweat heating system consistent with the invention. For example, an ambient temperature sensor 110 and/or ambient humidity sensor 112 may be used to determine the temperature and/or humidity of the environment within which the refrigerator is installed. In addition, input may be provided from a cooling system 114, e.g., indicating when the cooling system is currently active. Door switches 116 may be used to determine the open/closed status of various doors in the refrigerator, while a dispensing system 118 may provide information such as whether ice and/or water is currently being dispensed, whether an ice duct door is open, etc. Further, in some embodiments, a motion sensor 120 may be used to detect occupancy in the room in which the refrigerator is installed. Still further, in some embodiments, input may be received from various external devices, e.g., from an HVAC system through a network interface 124, whereby controller 102 may receive information such as whether the HVAC is currently running, to which temperature setpoint the HVAC system is currently set, ambient temperature and/or humidity sensed by the HVAC system, etc. In still other embodiments, weather information may be received over network interface 124, e.g., from a remote service, so that controller 102 may account for upcoming changes in weather such as storms that could change ambient conditions over the near future. It will be appreciated that in some embodiments, many of the aforementioned inputs may be omitted, so the invention is not limited to the particular combination of inputs illustrated in FIG. 5.

FIG. 6 illustrates an example sequence of operations 200 for dynamically monitoring and activating zones in heating system 100 of FIG. 5. Sequence 200 may be executed for all or multiple zones, for an entire heater, an entire zone, or individual heating elements within a larger array or heater. Periodically, as illustrated in block 202, a temperature datapoint is captured for each zone, representing a surface temperature sensed by the temperature sensor(s) for that zone. A surface condensation likelihood is then predicted or calculated in block 206, e.g., using a prediction algorithm based upon the captured datapoints, and as represented by block 204, also optionally based upon ambient temperature and/or humidity sensed by sensors 110, 112. Block 206, in particular, may calculate a dew point in some embodiments, and then compare a surface temperature sensed for each zone with the calculated dew point, thereby determining whether the surface temperature of one or more zones is at or below the calculated dew point, representing conditions where condensation could occur. It will be appreciated that dew point may be calculated in a number of manners in different embodiments, and may be based on ambient temperature and/or humidity as sensed by sensors 110, 112, as provided by an HVAC system 122 or via weather data. Furthermore, the frequency at which the prediction algorithm is executed may vary in different embodiments, e.g., based upon consumer behavior, such as when ice is being retrieved (based upon dispensing system 118), whether doors are open or closed (based on door switches 116), or occupancy monitoring (based on motion sensor 120) and/or based on appliance behavior, such as when the cooling system and/or fans are running (based on cooling system 114), during sealed system cycling, when ice is being produced (based on dispensing system 118), etc.

Moreover, the prediction algorithm may calculate a likelihood (e.g., in terms of a percentage) to allow for a greater or lesser chance of activating heaters, and in some instances, an energy saving function may be used to vary the prediction algorithm based upon whether or not the energy saving function is activated, e.g., to allow a greater chance of moisture and/or a lower chance of heaters being activated. A prediction algorithm may be based on a machine learning model in some embodiments, while in other embodiments, rule-based or procedural algorithms may instead be used. In many instances, however, and regardless of how implemented the likelihood of condensation may be predicted at least in part on a surface temperature measurement of a surface, so that a heater proximate to that surface may be activated whenever condensation is determined to be likely.

Thus, after the likelihood of surface condensation is predicted in block 206, block 208 either returns control to block 202 if no surface condensation is predicted, or passes control to block 210 to energize the heaters or heating elements in any affected zones (i.e., zones where condensation is determined to be likely). Thereafter, block 212 monitors the thermal load in each energized zone, and block 214 determines if evaporation has completed in any energized zone. As noted above, based upon the evaporative cooling effect, heat applied by a heater will increase the surface temperature more slowly when moisture is present on a surface as energy is expended on the phase change from liquid to gas. Thus, by monitoring for temperature spikes during activation of a heater (e.g., based on temperature sensing and/or determining a temperature rise/amperage applied ratio), the evaporation of moisture can be detected. As such, for any zone where evaporation completion is detected, block