US20080115514A1

US20080115514A1 - Condensation prevention apparatus and method

Info

Publication number: US20080115514A1
Application number: US11/561,714
Authority: US
Inventors: John C. Steimel
Original assignee: PHILIP J HOFFMANN; General Electric Co
Current assignee: General Electric Co
Priority date: 2006-11-20
Filing date: 2006-11-20
Publication date: 2008-05-22
Also published as: CA2609081A1

Abstract

A refrigerator includes a housing with an interior space defined by an exterior surface. A heater is configured to heat a portion of the exterior surface. A processor is configured to control the heater based on a dew point temperature outside the housing.

Description

BACKGROUND OF THE INVENTION

The described technology relates to a condensation prevention apparatus, such as for a refrigerator, and more particularly such as for an exterior surface of a freezer compartment of the refrigerator, and a corresponding method.
FIG. 1 is a block diagram of a known refrigerator. The refrigerator 10 includes fresh food and freezer sections 20 and 30 cooled by a cooling system (40, 50, 60 and 70), each of which is known. Specifically, a compressor 40, which is disposed outside of the fresh food and freezer sections 20 and 30, compresses an ammonia gas. The compressed ammonia gas flows from the compressor 40, through a heat exchanger 50, to an expansion valve 60. Heat is radiated from the compressed ammonia gas while flowing through the heat exchanger 50. As a result of this cooling, the ammonia gas condenses to an ammonia liquid.
The ammonia liquid expands while flowing through the expansion valve 60, the ammonia liquid going from a high pressure area on an upstream side of the expansion valve 60 to a low pressure area on a downstream side of the expansion valve 60. On the downstream side of the expansion valve 60, the low-pressure liquid ammonia evaporates and absorbs heat.
The ammonia gas travels from the expansion valve 60, through a heat exchanger 70 disposed in an interior space of the freezer section 30, back to the compressor 40. Heat continues to be absorbed by the ammonia gas while flowing through the heat exchanger 70, such that the ammonia gas increases in temperature. Thus, air in the interior space of the freezer section 30 is cooled. The cooled air from the freezer section 30 flows to the fresh food section 20. The above-described cycle is repeated when the heated ammonia gas flows to, and is compressed by, the compressor 40.
During the cooling of the air in the interior space of the freezer section 30, a temperature of an exterior surface of the freezer section 30 can decrease below a temperature of a room in which the refrigerator 10 is housed. When the temperature of the exterior surface of the freezer section 30 decreases below a dew point temperature of the room, condensation forms on the exterior surface. Condensation can result in oxidation of an exterior surface of the refrigerator 10, can be misinterpreted as an indication of a problem with operation of the refrigerator 10, and is undesirable from an aesthetic viewpoint.
To prevent the formation of this condensation, it is known to use a heater 80 to heat the exterior surface of the freezer section 30 to a temperature at or above a predicted dew point temperature of the room. The known use of the heater 80 suffers from numerous disadvantages, however. In some instances, the heater 80 operates continuously. In other instances, to reduce an amount of energy consumed by the heater 80, the heater 80 operates only when the cooling system operates or when a temperature within or outside of the fresh food section 20 and/or freezer section 30 is above or below predetermined temperatures. In each case, operation of the heater 80 results in unnecessarily high energy consumption, as the heater 80 invariably operates under some conditions where condensation would not otherwise form on the exterior surface of the freezer section 30. Attempts to decrease the energy consumption of the heater 80, such as by changing assumptions on which the predicted dew point temperature is based, may result in the formation of condensation on the exterior surface of the freezer section 30 under some conditions under which the refrigerator 10 operates.

BRIEF DESCRIPTION OF THE INVENTION

As described herein, embodiments of the invention overcome one or more of the above or other disadvantages known in the art.
In an embodiment, a refrigerator includes a housing with an interior space defined by an exterior surface. A heater is configured to heat a portion of the exterior surface. A processor is configured to control the heater based on a dew point temperature outside the housing.
In another embodiment, an apparatus for preventing condensation on an exterior surface of a refrigerator includes a heater configured to heat a portion of the exterior surface, and a processor configured to control the heater based on a dew point temperature outside the refrigerator.
In another embodiment, a method of heating an exterior surface of a refrigerator to prevent condensation thereon includes determining a dew point temperature outside of the refrigerator, and heating the exterior surface of the refrigerator in response to the determined dew point temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures illustrate examples of embodiments of the invention. The figures are described in detail below.

FIG. 1 is a block diagram of a known refrigerator.

FIG. 2 is a block diagram of a refrigerator including a condensation prevention apparatus.

FIG. 3 is a flow chart of a method of using the condensation prevention apparatus of FIG. 2.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention are described below, with reference to the figures. Throughout the figures, like reference numbers indicate the same or similar components.
FIG. 2 is a block diagram of a refrigerator including a condensation prevention apparatus, and FIG. 3 is a flow chart of a method of using the condensation prevention apparatus of FIG. 2. As shown in the figures, the refrigerator 100 includes fresh food and freezer compartments 200 and 300 cooled by a cooling system including a compressor 400, a heat exchanger 500, an expansion valve 600 and a heat exchanger 700. Further, a heater 800 is used to prevent the formation of condensation on a portion of an exterior surface of the refrigerator 100. These components are similar to the above-described components of the fresh food section 20, the freezer section 30, the compressor 40, the heat exchanger 50, the expansion valve 60, the heat exchanger 70 and the heater 80, and therefore components 200, 300, 400, 500, 600, 700 and 800 will not be further described, except with respect to the condensation prevention apparatus.
In accordance with an embodiment of the invention, the condensation prevention apparatus is configured to determine an actual dew point temperature of a room in which the refrigerator 100 is housed. Because the actual room dew point temperature is determined, a portion of the exterior surface of the refrigerator 100 can be heated to a predetermined temperature equal to or greater than the determined dew point temperature, such that condensation is prevented from forming on the portion of the exterior surface of the refrigerator 100. It is contemplated that the condensation prevention apparatus is used to determine the actual room dew point temperature such than an exterior surface of the freezer compartment 300, in particular, is heated to the predetermined temperature, and condensation is therefore prevented from being formed on this exterior surface. It is understood, however, that the condensation prevention apparatus is not limited to preventing condensation only on the exterior surface of the freezer compartment 300, but can be used to prevent condensation on other portions of the exterior surface of the refrigerator 100, such as but not limited to an exterior surface of the fresh food compartment 200. Further, it is understood that the condensation prevention apparatus can be used to prevent condensation on one or more sides of the exterior surface of the refrigerator 100, including top, bottom, left, right, front and/or back sides.
Still further, it is understood that the condensation prevention apparatus is not limited to preventing the formation of condensation only on the exterior surface of the refrigerator 100, but can be used to prevent condensation formation in an interior space of the refrigerator 100. It is also understood that the condensation prevention apparatus is not limited to preventing condensation formation with respect to the refrigerator 100, but can be used in other contexts where a heater is used to heat a component to a temperature above an actual dew point temperature of a volume in which the component is disposed, to prevent the formation of condensation on that component.
In accordance with an embodiment of the invention, the condensation prevention apparatus 900 determines an actual dew point temperature of the room in which the refrigerator 100 is housed, such as based on a temperature of the room and a relative humidity of the room. As shown in the drawings, the condensation prevention apparatus 900 includes a temperature sensor 910 configured to sense the temperature of the room, and a relative humidity sensor 920 configured to sense the relative humidity of the room. Details of each of the sensors 910 and 920 are known to those or ordinary skill in the art, and therefore features of these components will not be further described.
Based on outputs from the room temperature sensor 910 and the room relative humidity sensor 920, a processor, referred to as a dew point temperature calculator 930, calculates the actual dew point temperature of the room. The calculation of the actual dew point temperature based on the room temperature and the room relative humidity can be accomplished in a variety of ways, through a variety of different formulas, known to those of ordinary skill in the art. Thus, further specific details of such calculations are not necessary to completely enable those of ordinary skill in the art to make and use the invention, or to fully describe the condensation prevention apparatus 900.
Nonetheless, following is an example of a formula that can be used to calculate the actual room dew point temperature based on the room temperature and the room relative humidity. In the formula,
T=the temperature of the room, expressed in degrees Celsius,
RH=the relative humidity of the room, expressed in decimal form, and
T_d=the actual dew point temperature of the room which is to be calculated, expressed in degrees Celsius.
The formula is:
T _d =bγ(T,RH)/a−γ(T,RH)
where

- γ(T,RH)=((a T)/(b+T))+1n(RH)
- a=17.27,
- b=237.7° C.

It has been determined that this formula provides the actual room dew point temperature in degrees Celsius to within ±0.4° C. under the following conditions:
0° C.<T<100° C.,
0.01<RH<1.0, and
0° C.<T_d<50° C.
As stated above, the condensation prevention apparatus 900 determines the actual dew point temperature of the room in which the refrigerator 100 is housed. The heater 800 can then be operated only when the actual (e.g., measured) temperature or the expected (e.g., calculated) temperature of the portion of the exterior surface of the refrigerator 100, on which condensation is to be prevented from forming, is near, at and/or below the actual dew point temperature.
In an embodiment of the invention shown in the drawings, the condensation prevention apparatus 900 includes a surface temperature sensor 960 configured to measure the actual temperature of the portion of the exterior surface of the refrigerator 100 on which condensation is to be prevented. In accordance with the above-described embodiment in which it is desired to prevent condensation formation on the exterior surface of the freezer compartment 300, it is contemplated that the surface temperature sensor 960 measure the actual surface temperature of that portion of the exterior surface. The heater 800 can be operated, as previously described, when that portion of the exterior surface is near, at and/or below the actual room dew point temperature. In an alternate embodiment, the expected temperature of the portion of the exterior surface on which condensation is to be prevented can be calculated, such as by mathematical algorithm. This algorithm can be based on various characteristics of the refrigerator 100 and/or an environment in which the refrigerator 100 is disposed, including but not limited to one or more of a temperature within the freezer compartment 300 and/or the fresh food compartment 200, the room temperature, an expected heat transfer through one or more components of the refrigerator 100, and characteristics of the operation of the heater 800.
Based on the foregoing, it is understood that the use of the condensation prevention apparatus 900 to control the heater 800 provides numerous advantages that are not provided by known uses of the heater. As discussed, the known use of the heater includes continuous operation of the heater, or operation of the heater only when the cooling system is operating or when the temperature within or outside of the fresh food compartment and/or freezer compartment is above or below predetermined temperatures. This results in unnecessarily high energy consumption, as the heater is invariably operated under some conditions where condensation would not otherwise form. Further, with respect to known heater operations, attempts to decrease the energy consumption of the heater, such as by changing assumptions on which the predicted dew point temperature is based, may result in the formation of condensation under some conditions under which the refrigerator is operated. These disadvantages are avoided by the use of the condensation prevention apparatus 900, as the condensation prevention apparatus 900 is capable of operating the heater 800 based on the actual, determined dew point temperature of the room in which the refrigerator 100 is housed. Thus, unlike known heater uses, the condensation prevention apparatus 900 can restrict operation of the heater 800 to one or more specific instances, such as when the surface temperature of the portion of the exterior surface on which condensation is to prevented is near, at and/or below the actual, determined dew point temperature, and can preclude operation of the heater 800 under all other circumstances. Thus, energy consumption of the heater 800 is minimized, and condensation formation can be prevented under all circumstances, such that any or all of the disadvantages suffered from condensation formation are avoided.
In an alternative embodiment, the condensation prevention apparatus 900 can include a sensor that senses an actual wet bulb temperature of the room in which the refrigerator 100 is housed. The dew point temperature calculator 930 can then calculate the actual room dew point temperature based on the room wet bulb temperature and the room dry bulb temperature (previously referred to as the room temperature). This calculated, actual room dew point temperature can be used in the control of the heater 800 in a manner similar to that discussed in detail above. Thus, it is understood that the use of wet and dry bulb temperatures to calculate the actual room dew point temperature is within the scope of the invention. It is further understood that the calculation of the actual room dew point temperature based on the room (dry bulb) temperature and the room wet bulb temperature can be accomplished in a variety of ways, through a variety of different formulas, known to those of ordinary skill in the art. Thus, further specific details of such calculations are not necessary to completely enable those of ordinary skill in the art to make and use the invention, or to fully describe the condensation prevention apparatus 900.
FIG. 3 illustrates an embodiment of the method of using the condensation prevention apparatus 900. The method 2000 includes step 2010, in which an actual dew point temperature is calculated for the room in which the refrigerator 100 is housed. Calculation of the actual room dew point temperature can be performed as discussed in detail above.
In step 2020, the actual room dew point temperature is compared to a surface temperature of a portion of the refrigerator 100 on which condensation is to be prevented from forming. As discussed above, the surface temperature can be an actual, measured temperature of this portion of the refrigerator 100, or can be the expected, calculated temperature of this portion.
In step 2030, the heater 800 is energized when the surface temperature is within a predetermined range of the actual room dew point temperature, to heat the portion of the refrigerator 100 to a predetermined temperature. For example, the heater 800 can be energized when the surface temperature is (i) less than the actual room dew point temperature, (ii) less than or equal to the actual room dew point temperature, or (iii) within some range of temperatures greater than or is less than or equal to the actual room dew point temperature. By way of further example, the condensation prevention apparatus 900 can be used to heat the portion of the refrigerator 100 to the predetermined temperature that is equal to the actual room dew point temperature or within some range of temperatures greater than the actual room dew point temperature.
The above description discusses embodiments of the present invention in relation to the room in which the refrigerator 100 is housed. It is understood that the term “room” and variations thereof can refer to a volume immediately adjacent the refrigerator 100, such that regardless of whether temperature variations exist within a larger room in which the refrigerator 100 is housed, control of the heater 800 by the condensation prevention apparatus 900 can be accomplished based, for example, on the temperature and/or relative humidity of the volume of the room that is immediately adjacent the refrigerator 100.
It is understood that the various sensors described above can be disposed on or near various surfaces of the refrigerator 100, such as but not limited to one or more of the exterior surfaces of the freezer compartment 300 and the fresh food compartment 200, or separate from the refrigerator 100.
Specifically, it is contemplated that in embodiments of the invention, the refrigerator 100 may have one or more recessed areas, such as dispenser areas, gaps between doors, and the like. The dew point temperature in these recessed areas may be different from the general dew point temperature of the room. In some embodiments, one or more of each of the room temperature sensor 910, the room relative humidity sensor 920, the dew point temperature calculator 930 and the surface temperature sensor 960 are disposed within at least one of the recessed areas of the refrigerator. Thus the dew point temperature calculator 930 would calculate a localized dew point temperature of the recessed area, rather than the general dew point temperature of the room. In these embodiments, the calculation of the localized dew point temperature and/or control of the heater 800 for the recessed area, is accomplished in a manner similar to that discussed in detail above.
This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable a person of ordinary skill in the art to make and use embodiments of the invention. It is understood that the patentable scope of embodiments of the invention is defined by the claims, and can include additional components occurring to those skilled in the art. Such other arrangements are understood to be within the scope of the claims.

Claims

1. A refrigerator, comprising:

a housing including an interior space defined by an exterior surface;

a heater configured to heat a portion of the exterior surface; and

a processor configured to control the heater based on a dew point temperature outside the housing.

2. The refrigerator of claim 1, wherein the processor comprises a dew point temperature calculator configured to calculate the dew point temperature outside the housing based on a relative humidity outside the housing.

3. The refrigerator of claim 1, further comprising:

a temperature sensor configured to measure a temperature outside the housing,

wherein the processor is configured to calculate the dew point temperature outside the housing based on the temperature outside the housing.

4. The refrigerator of claim 3, further comprising:

a relative humidity sensor configured to measure a relative humidity outside the housing,

wherein the processor is configured to calculate the dew point temperature outside the housing based on the relative humidity outside the housing.

5. The refrigerator of claim 4, further comprising:

a surface temperature sensor configured to measure a temperature of the portion of the exterior surface heated by the heater,

wherein the processor is configured to control the operation of the heater based on the temperature of the portion of the exterior surface heated by the heater.

6. The refrigerator of claim 1, further comprising:

a temperature sensor configured to measure a temperature outside the housing adjacent the refrigerator; and

a relative humidity sensor configured to measure a relative humidity outside the housing adjacent the refrigerator;

wherein each of the sensors is disposed on the exterior surface of the refrigerator, and

wherein the processor is configured to calculate the dew point temperature outside the housing based on the measured temperature and the measured relative humidity.

7. The refrigerator of claim 6, further comprising:

a second temperature sensor configured to measure a temperature of the portion of the exterior surface heated by the heater,

wherein the processor is configured to control the heater based on the measured temperature of the portion of the exterior surface heated by the heater.

8. The refrigerator of claim 1, further comprising:

a temperature sensor configured to measure a temperature of the portion of the exterior surface heated by the heater,

9. The refrigerator of claim 1, further comprising:

a cooling system configured to cool the interior of the housing,

wherein the housing comprises a freezer compartment, the cooling system configured to cool an interior of the freezer compartment, and

wherein the heater is disposed to heat the exterior surface of the refrigerator that is exterior to the freezer compartment.

10. The refrigerator of claim 9, wherein the processor comprises a dew point temperature calculator configured to calculate the dew point temperature outside the housing based on a relative humidity outside the housing.

11. The refrigerator of claim 10, further comprising:

a temperature sensor configured to measure a temperature outside the housing,

12. The refrigerator of claim 11, further comprising:

13. The refrigerator of claim 12, further comprising:

14. An apparatus for preventing condensation on an exterior surface of a refrigerator comprising:

a heater configured to heat a portion of the exterior surface; and

a processor configured to control the heater based on a dew point temperature outside the refrigerator.

15. The apparatus of claim 14, further comprising:

a temperature sensor configured to measure a temperature outside the refrigerator; and

a relative humidity sensor configured to measure a relative humidity outside the refrigerator;

wherein the processor is configured to calculate the dew point temperature outside the refrigerator based on the measured temperature and the measured relative humidity.

16. A method of heating an exterior surface of a refrigerator to prevent condensation thereon, the method comprising:

determining a dew point temperature outside of the refrigerator; and

heating the exterior surface of the refrigerator in response to the determined dew point temperature.

17. The method of claim 16, wherein heating comprises heating the exterior surface of the refrigerator when a temperature of the exterior surface is below the dew point temperature.

18. The method of claim 16, wherein heating comprises heating the exterior surface of the refrigerator when a temperature of the exterior surface is one of below the dew point temperature, at the dew point temperature, and within a predetermined temperature range of the dew point temperature.

19. The method of claim 16, further comprising:

preventing further heating of the exterior surface of the refrigerator when the exterior surface reaches a predetermined temperature.

20. The method of claim 19, wherein preventing comprises preventing further heating when the exterior surface reaches the predetermined temperature that is greater than the dew point temperature.