Patent Description:
A method of measuring pressure within a vacuum insulated cabinet structure according to claim <NUM> includes the steps of (i) providing a vacuum insulated cabinet structure having a storage compartment, a first temperature sensor positioned on an interior wall of the storage compartment, a second temperature sensor positioned on an exterior wall of the vacuum insulated cabinet structure, a third temperature sensor positioned to sense an ambient temperature level, (ii) sensing a first temperature level of the interior wall of the storage compartment using the first temperature sensor; (iii) sensing a second temperature level of the exterior wall of the storage compartment using the second temperature sensor; (iv) calculating a first temperature differential between the second temperature level and the first temperature level; (v) sensing an ambient temperature level using the third temperature sensor; (vi) calculating an overall heat transfer coefficient (Q) using the ambient temperature level, the first temperature level, and a convective heat transfer coefficient for the exterior wall of the storage compartment; (vii) determining a first conductivity level (K) using the first temperature differential, the overall heat transfer coefficient (Q) and a thickness of the insulating space; and (viii) determining a first pressure level (P) within the insulating space using the first conductivity level (K).

These and other features, advantages, and objects of the present method will be further understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

<FIG> show embodiments being useful for understanding the invention, which are outside the subject-matter of the claims. <FIG> shows an embodiment according to the present invention, which discloses a method according to claim <NUM>.

The present illustrated embodiments reside primarily in combinations of method steps and apparatus components related to an anti-condensation feature for an appliance. Accordingly, the apparatus components and method steps have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Further, like numerals in the description and drawings represent like elements.

The terms "including," "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises a. " does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

The terms "substantial," "substantially," and variations thereof, as used herein, are intended to note that a described feature is equal or approximately equal to a value or description. For example, a "substantially planar" surface is intended to denote a surface that is planar or approximately planar. Moreover, "substantially" is intended to denote that two values are equal or approximately equal. In some embodiments, "substantially" may denote values within about <NUM>% of each other, such as within about <NUM>% of each other, or within about <NUM>% of each other.

With reference to <FIG>, an appliance is shown in the form of a refrigerator <NUM>. The refrigerator <NUM> includes a cabinet structure <NUM> which, in the embodiment of <FIG>, further includes a refrigerator compartment <NUM> positioned above a freezer compartment <NUM>. The refrigerator compartment <NUM> and the freezer compartment <NUM> may be referred to herein as compartments <NUM>, <NUM> and may also be referred to herein on an individual basis as a storage compartment. Doors <NUM> and <NUM> are provided to selectively provide access to the refrigerator compartment <NUM>, while a drawer <NUM> is used to provide access to the freezer compartment <NUM>. The cabinet structure <NUM> is surrounded by an exterior wrapper <NUM>. The cabinet structure <NUM> of the refrigerator <NUM> may be a vacuum insulated cabinet structure and may be referred to herein as such. The configuration of the refrigerator <NUM> as shown in <FIG> is exemplary only and the present concept is contemplated for use in all refrigerator styles including, but not limited to, side-by-side refrigerators, whole refrigerator and freezers, and refrigerators with upper freezer compartments.

Referring now to <FIG>, the cabinet structure <NUM> generally includes a trim breaker <NUM>. In the embodiment shown in <FIG>, the trim breaker <NUM>, or thermal bridge, includes a frame <NUM> having an upper opening 12A and a lower opening 12B with a mullion portion <NUM> disposed therebetween. The trim breaker <NUM> further includes an upper portion 10A, a middle portion 10B and a lower portion 10C.

As further shown in the embodiment of <FIG>, the cabinet structure <NUM> further includes a refrigerator liner <NUM> having a top wall <NUM>, a bottom wall <NUM>, opposed sidewalls <NUM>, <NUM>, and a rear wall <NUM>. Together, the walls <NUM>, <NUM>, <NUM>, and <NUM> of the refrigerator liner <NUM> cooperate to define the refrigerator compartment <NUM> when the cabinet structure <NUM> is assembled. The refrigerator liner <NUM> further includes a front edge <NUM> disposed on a front portion thereof. The front edge <NUM> is disposed along the top wall <NUM>, the bottom wall <NUM> and the opposed sidewalls <NUM>, <NUM> in a quadrilateral ring configuration.

As further shown in the embodiment of <FIG>, a freezer liner <NUM> is provided and includes a top wall <NUM>, a bottom wall <NUM>, opposed sidewalls <NUM>, <NUM>, and a rear wall <NUM>. Together, the walls <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of the freezer liner <NUM> cooperate to define the freezer compartment <NUM>. The rear wall <NUM> is shown in <FIG> as being a contoured rear wall that provides a spacing S for housing mechanical equipment <NUM> (<FIG>) for cooling both the refrigerator compartment <NUM> and freezer compartment <NUM>. Such equipment may include a compressor, a condenser, an expansion valve, an evaporator, a plurality of conduits, and other related components used for cooling the refrigerator and freezer compartments <NUM>, <NUM>, as further described below with specific reference to <FIG>. As further shown in the embodiment of <FIG>, the freezer liner <NUM> includes a front edge <NUM> disposed on a front portion thereof. The front edge <NUM> is disposed along the top wall <NUM>, the bottom wall <NUM> and the opposed sidewalls <NUM>, <NUM> in a quadrilateral ring configuration. In assembly, the front edge <NUM> of the refrigerator liner <NUM> and the front edge <NUM> of the freezer liner <NUM> are configured to couple with coupling portions disposed about the upper and lower openings 12A, 12B of the trim breaker <NUM>.

As further shown in <FIG>, the cabinet structure <NUM> also includes the exterior wrapper <NUM>. In the embodiment of <FIG>, the exterior wrapper <NUM> includes a top wall <NUM>, a bottom wall <NUM>, opposed sidewalls <NUM>, <NUM>, and a rear wall <NUM> which cooperate to define a cavity <NUM>. The exterior wrapper <NUM> further includes a front edge <NUM> which is disposed along the top wall <NUM>, the bottom wall <NUM>, and the opposed sidewalls <NUM>, <NUM> in a quadrilateral ring configuration. In assembly, the front edge <NUM> of the exterior wrapper <NUM> is coupled to coupling portions of the trim breaker <NUM> around the refrigerator liner <NUM> and the freezer liner <NUM>. In this way, the trim breaker <NUM> interconnects the exterior wrapper <NUM> and the refrigerator liner <NUM> and the freezer liner <NUM> when assembled. Further, the refrigerator liner <NUM> and the freezer liner <NUM> are received within the cavity <NUM> of the exterior wrapper <NUM> when assembled, such that an insulating space <NUM> (<FIG>) is defined between the outer surfaces of the refrigerator liner <NUM> and the freezer liner <NUM> relative to the inner surfaces of the exterior wrapper <NUM>. The insulating space <NUM> can be used to create a vacuum insulated cavity provided at a negative pressure, or can be used to receive an insulation material to insulate the refrigerator compartment <NUM> and the freezer compartment <NUM>, or both. For example, the insulating space <NUM> may be evacuated to a negative pressure and also contain an insulation material, such as a polyurethane foam insulation material disposed therein. In assembly, the insulating space <NUM> surrounds the refrigerator liner <NUM> and the freezer liner <NUM> to insulate the same, with the exception of the front portions thereof, which are accessible via doors <NUM>, <NUM> and drawer <NUM>.

When the cabinet structure <NUM> is contemplated to be a vacuum insulated cabinet structure, the trim breaker <NUM> may be configured to provide an air-tight connection between the exterior wrapper <NUM> and the liners <NUM>, <NUM> which allows for a vacuum to be held between the trim breaker <NUM>, the exterior wrapper <NUM> and the liners <NUM>, <NUM> in the insulating space <NUM> (<FIG>). The trim breaker <NUM> may also be formed from any suitable material that is substantially impervious to gasses to maintain a vacuum in the insulating space <NUM>, if so desired.

Referring now to <FIG>, when the cabinet structure <NUM> is assembled, the trim breaker <NUM> connects to the front edge <NUM> (<FIG>) of the exterior wrapper <NUM>, and further connects to the front edge <NUM> (<FIG>) of the refrigerator liner <NUM>, and to the front edge <NUM> (<FIG>) of the freezer liner <NUM>. In this way, the trim breaker <NUM> interconnects the exterior wrapper <NUM> and the liners <NUM>, <NUM>. When the refrigerator <NUM> (<FIG>) is in use, the exterior wrapper <NUM> is typically exposed to ambient room temperature air, whereas the liners <NUM>, <NUM> are generally exposed to refrigerated air in the refrigerator compartment <NUM> or the freezer compartment <NUM>. With the trim breaker <NUM> being made of a material that is substantially non-conductive with respect to heat, the trim breaker <NUM> reduces transfer of heat from the exterior wrapper <NUM> to the liners <NUM>, <NUM>. As shown in <FIG>, the insulating space <NUM> substantially surrounds the refrigerator compartment <NUM> and the freezer compartment <NUM>.

Referring now to <FIG>, the refrigerator <NUM> is shown in a cross-sectional view having the refrigerator liner <NUM> and the freezer liner <NUM> coupled to the trim breaker <NUM> at upper and lower openings 12A, 12B, respectively. Further, the exterior wrapper <NUM> is also coupled to the trim breaker <NUM>, such that the trim breaker <NUM> interconnects the exterior wrapper <NUM> with the refrigerator liner <NUM> and the freezer liner <NUM>. Specifically, the trim breaker <NUM> of the present concept is coupled to the liners <NUM>, <NUM> and the exterior wrapper <NUM> to hermetically seal the components together as a unitary whole as shown in <FIG>. As further shown in <FIG>, the refrigerator <NUM> includes a sensor <NUM> positioned within the refrigerator compartment <NUM> and a sensor <NUM> positioned within the freezer compartment <NUM>. The refrigerator <NUM> further includes a sensor <NUM> positioned on the wrapper <NUM>. Specifically, in the embodiment shown in <FIG>, the sensor <NUM> is positioned on the rear wall <NUM> of the exterior wrapper <NUM>. As such, the sensors <NUM> and <NUM> are positioned on opposite sides of the insulating space <NUM> adjacent the refrigerator compartment <NUM>. Similarly, the sensors <NUM> and <NUM> are positioned on opposite sides of the insulating space <NUM> with sensor <NUM> positioned in the freezer compartment <NUM>. As further shown in <FIG>, the refrigerator <NUM> further includes a sensor <NUM> positioned on the wrapper <NUM>. Specifically, in the embodiment shown in <FIG>, the sensor <NUM> is positioned on the rear wall <NUM> of the exterior wrapper <NUM>. It is contemplated that the sensors <NUM> and <NUM> may be positioned on other walls of the exterior wrapper <NUM>, the sensor <NUM> can be positioned on other walls of the refrigerator liner <NUM> within the refrigerator compartment <NUM>, and the sensor <NUM> may be positioned on other walls of the freezer liner <NUM> within the freezer compartment <NUM>. It is further contemplated that the sensor <NUM> may be positioned in a remote location for measuring ambient temperature levels, as further described below. As further shown in <FIG>, the refrigerator <NUM> further includes a sensor <NUM> positioned on a sidewall of the refrigerator liner <NUM>. Specifically, in the embodiment shown in <FIG>, the sensor <NUM> is positioned on the sidewall <NUM> of the refrigerator liner <NUM>. As further shown in <FIG>, the refrigerator <NUM> further includes a sensor <NUM> positioned on a sidewall of the freezer liner <NUM>. Specifically, in the embodiment shown in <FIG>, the sensor <NUM> is positioned on the sidewall <NUM> of the freezer liner <NUM>. Thermistors, thermocouples, and other types of temperature sensors known in the art are suitable for use as the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>.

Referring now to <FIG>, a schematic illustration of refrigerator <NUM> and its component parts is provided. In <FIG>, the refrigerator <NUM> is shown having a refrigerant circuit <NUM> for circulating refrigerant <NUM>, a compressor <NUM>, a condenser <NUM>, a heat loop <NUM>, a pressure reduction device <NUM>, an evaporator <NUM>, a compressor outlet line <NUM>, a check valve <NUM>, fans <NUM>, <NUM>, <NUM>, <NUM> and a compressor inlet line <NUM>. As further shown in <FIG>, a controller <NUM> is provided. The controller <NUM> is contemplated to control the general operations of the refrigerator <NUM>. In general, the controller <NUM> operates the compressor <NUM>, for example, to maintain the refrigerator compartment <NUM> and the freezer compartment <NUM> at various temperatures desired by the user during a duty cycle of the compressor <NUM>. A duty cycle of the compressor <NUM> can run for various time intervals as needed to reach desired temperature levels within the refrigerator compartment <NUM> (as measured by sensor <NUM>) and the freezer compartment <NUM> (as measured by sensor <NUM>).

The controller <NUM> is configured to receive and generate control signals via interconnecting wires provided in the form of leads arranged between and coupled to the refrigerator mechanical equipment <NUM>. In particular, a lead 122a is arranged to couple the controller <NUM> with the compressor <NUM>. Lead 134a is arranged to couple the controller <NUM> with the check valve <NUM>. Lead 135a is arranged to couple the controller <NUM> with the condenser fan <NUM>. Further, leads 142a, 144a, and 146a are arranged to couple the controller <NUM> with the evaporator fan <NUM>, the freezer compartment fan <NUM>, and the refrigerator compartment fan <NUM>, respectively.

In the embodiment illustrated in <FIG>, the controller <NUM> also relies on compartment temperature sensors to perform its intended function within the refrigerator <NUM>. In particular, controller <NUM> is operably coupled to sensors <NUM> and <NUM> via leads 23a and 25a, respectively. As shown in <FIG> and <FIG>, the sensors <NUM> and <NUM> are arranged in the refrigerator compartment <NUM> and the freezer compartment <NUM>, respectively. The sensors <NUM> and <NUM> are configured to generate signals indicative of temperature levels of the walls of the respective compartments <NUM> and <NUM> in which they are disposed, and send this data to the controller <NUM> for processing. Further, the sensor <NUM> is shown in <FIG> as provided on an exterior surface of the refrigerator <NUM>, and is configured to provide temperature information for a particular exterior surface of the refrigerator <NUM>. Information provided from the sensor <NUM> is delivered to the controller <NUM> via lead 21a. It is further contemplated that the sensors <NUM>, <NUM> and <NUM> may be wirelessly coupled to the controller <NUM> for collecting and delivering signal information thereto. Further, the sensor <NUM> is shown in <FIG> as provided on an exterior surface of the refrigerator <NUM>, and is configured to generate signals indicative of an ambient air temperature level from the environment in which the refrigerator <NUM> is disposed. It is contemplated that the sensor <NUM> can be a remote sensor that is spaced away from the refrigerator <NUM> and wirelessly connected to the controller <NUM>. As such, the sensor <NUM> is configured to provide ambient temperature levels of a room in which the refrigerator <NUM> is disposed and forward the ambient temperature level sensed to the controller <NUM> by wired or wireless means for processing.

Further, the sensor <NUM> is shown in <FIG> as provided within the refrigerator compartment <NUM>. As such, the sensor <NUM> is configured to provide ambient temperatures levels within the refrigerator compartment <NUM>. Similarly, the sensor <NUM> is shown in <FIG> as provided within the freezer compartment <NUM>. As such, the sensor <NUM> is configured to provide ambient temperatures levels within the freezer compartment <NUM>. Both sensors <NUM> and <NUM> are contemplated to be in electrical communication with the controller <NUM> for providing ambient compartment temperature information thereto via wired or wireless means for processing.

The data received from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be used in controlling the duty cycle of the compressor <NUM>, such as runtime, duration, modulated power level, and other like parameters of the compressor <NUM> to cool the compartments <NUM>, <NUM> of the refrigerator <NUM>. The run time of the compressor <NUM> can be used to predict absolute vacuum. Here, the idea is to generate a graph of compressor run time for a particular product with respect to absolute vacuum pressure, and then use this data to predict pressure from compressor run time. Compressor run time changes as the vacuum pressure changes. For example, an increase in vacuum pressure causes the insulation quality to degrade, which will put more load on compressor, and lead to longer compressor run time intervals. Compressor run time can be combined with an external air temperature sensor (such as sensor <NUM>) to compare the compressor run time with the external temperature sensed by sensor <NUM>. If the external temperature is stable and the compressor run time is increasing over time, then it is an indication that the vacuum insulated cabinet structure is losing vacuum. If the compressor run time increases while the room temperature also increases, it is likely because of the increased heat load.

Using the information collected from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, the controller <NUM> of the present concept is configured to provide data that can be used to measure the performance of the insulation of the insulating space <NUM> of the vacuum insulated cabinet structure <NUM>. The performance of the insulating space <NUM> to insulate the compartments <NUM>, <NUM> is related to the pressure maintained in the insulating space <NUM>. Said differently, in the vacuum insulated cabinet structure <NUM>, the pressure can be an initial negative pressure that gradually increases over the life of the refrigerator <NUM>. Pressure increase in the vacuum insulated cabinet structure <NUM> of the refrigerator <NUM> can result in decreased insulation performance across the insulating space <NUM>. This will result in the need for the compressor <NUM> to run more often, for longer time intervals per duty cycle, or both, in order to maintain desired temperatures in the compartments <NUM>, <NUM>.

The sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may, either alone or in combination, include temperature sensors configured to provide temperature values for the ambient air temperature from the environment in which the refrigerator <NUM> is located, the ambient refrigerator compartment temperature, the ambient freezer compartment temperature, and the temperature levels of the inner and outer walls of the vacuum insulated cabinet structure <NUM>, as further described below. As used herein, the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be described as monitoring, sensing, detecting and providing data regarding the refrigerator compartments <NUM>, <NUM>, the ambient air around the refrigerator <NUM>, or the exterior surfaces of the refrigerator <NUM>. All such terms, and other like terms, are contemplated to indicate that the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are configured to gather temperature level data and send the data to the controller <NUM> for processing.

The present concept seeks to measure the performance of the insulation of a vacuum insulated structure over time. Insulation quality of a vacuum insulated structure, such as the vacuum insulated cabinet structure <NUM> described above, depends upon the level of vacuum pressure maintained inside the vacuum insulated cabinet structure <NUM>. Achieving target pressure during evacuation and monitoring vacuum pressure during product operation (i.e. the product life) is important. The present concept provides a solution on how to predict or calculate inside vacuum pressure by measuring wall temperatures on an appliance, such as the refrigerator <NUM> described above.

A common way to measure vacuum pressure inside a vacuum insulated cabinet structure is by using actual pressure sensors that are mounted on a vacuum insulated cabinet structure. There are multiple challenges in having an actual sensor mounted on the product. As stated above, the quality of insulation or the overall insulation performance depends upon the level of vacuum achieved inside an insulating space. Also we know that the temperature difference between the walls of the refrigerator <NUM> (inside and outside) depends upon quality of insulation. As such, vacuum pressure can be correlated with insulation quality or conductivity, and vacuum pressure can further be correlated with temperature differentials determined in and around the refrigerator <NUM>.

Referring now to <FIG>, a portion of the vacuum insulated cabinet structure <NUM> of the refrigerator <NUM> is shown, as taken from <FIG>. The vacuum insulated cabinet structure <NUM> is shown in <FIG> as a double-walled structure. Specific to the view of <FIG>, the insulating space <NUM> of the vacuum insulated cabinet structure <NUM> is shown positioned between the rear wall <NUM> of the refrigerator liner <NUM> and the rear wall <NUM> of the exterior wrapper <NUM>. As noted above, the rear wall <NUM> of the refrigerator liner <NUM> includes a sensor <NUM> positioned thereon, such that the sensor <NUM> is disposed within refrigerator compartment <NUM> for measuring a temperature level of the rear wall <NUM> of the refrigerator liner <NUM>. Also noted above, the rear wall <NUM> of the exterior wrapper <NUM> includes the sensor <NUM> disposed thereon. Being disposed on the rear wall <NUM> of the exterior wrapper <NUM>, the sensor <NUM> is positioned to sense a temperature level of an exterior wall of the vacuum insulated structure <NUM>. Also noted above, the rear wall <NUM> of the exterior wrapper <NUM> includes the sensor <NUM> disposed thereon. In this way, the sensor <NUM> is positioned to sense ambient temperature levels for the environment in which the vacuum insulated cabinet structure <NUM> is disposed. Also noted above, the refrigerator liner <NUM> includes a sensor <NUM> disposed thereon. The sensor <NUM> is positioned to sense ambient temperature levels of the refrigerator compartment <NUM>.

The sensors <NUM>, <NUM>, <NUM> and <NUM> are configured such that a first temperature sensor (sensor <NUM>) is positioned on a first side (rear wall <NUM> of refrigerator liner <NUM>) of the insulating space <NUM>, and a second temperature sensor (sensor <NUM>) is positioned on a second side (rear wall <NUM> of the exterior wrapper <NUM>) of the insulating space <NUM>. Thus, the first side of the insulating space <NUM> is spaced-apart from and opposed to the second side of the insulating space <NUM>. The insulating space <NUM> is shown as having a distance D provided between the rear walls <NUM>, <NUM> of the refrigerator liner <NUM> and the exterior wrapper <NUM>, respectively.

As further shown in <FIG>, the sensor <NUM> is configured to measure an ambient temperature level of the refrigerated air of the refrigerator compartment <NUM>, which is expressed herein as temperature level (Ti). The sensor <NUM> is configured to measure the temperature level of the interior wall <NUM> of the insulating space <NUM>, which is expressed herein as temperature level (Twi). The temperature levels from (Ti) to (Twi) is typically an increase in temperature, which is related to a convective heat transfer coefficient (hi). As further shown in <FIG>, the sensor <NUM> is configured to measure the temperature level of the outer wall <NUM> of the insulating space <NUM>, which is expressed herein as temperature level (Two). The temperature levels from (Twi) to (Two) is typically an increase in temperature, which is related to conductivity (K) of the insulating space <NUM>. As further shown in <FIG>, the sensor <NUM> is configured to measure an ambient temperature level of the room in which the refrigerator <NUM> is disposed, which is expressed herein as temperature level (To). The temperature levels from (Two) to (To) is typically an increase in temperature, which is related to a convective heat transfer coefficient (ho). Thus, Q is a constant number showing an overall heat transfer coefficient from the ambient temperature (Ti) of the refrigerator compartment <NUM> to the ambient temperature level (To) of the room in which the refrigerator <NUM> is disposed.

As further noted above, the insulating space <NUM> is provided at a negative pressure in the vacuum insulated cabinet structure <NUM> in order to provide insulating properties for the refrigerator compartment <NUM>. As vacuum pressure inside the insulating space <NUM> increases over the life of the refrigerator <NUM> from its initial evacuation, the thermal conductivity through the insulating space <NUM> also increases. As a corollary, a temperature differential between temperature levels sensed by the sensors <NUM>, <NUM> at the inner and outer walls of the refrigerator compartment <NUM> drops as thermal conductivity and vacuum pressure increase within the insulating space <NUM>. Thus, vacuum pressure (P) within the insulating space <NUM> is related to a thermal conductivity level (K) provided within the insulating space <NUM>. The vacuum pressure (P) and the thermal conductivity level (K) provided within the insulating space <NUM> are related to a temperature differential calculated between the temperature levels sensed by the sensors <NUM>, <NUM> at the inner and outer walls of the refrigerator compartment <NUM>. The temperature differential is provided by the sensor <NUM> measuring the temperature level (Two) of the exterior wall of the refrigerator compartment <NUM>, and the sensor <NUM> measuring the temperature level (Twi) of the interior wall of the refrigerator compartment <NUM>. The temperature level (Two) sensed by the sensor <NUM> is compared to the temperature level (Twi) sensed by the sensor <NUM> disposed within the refrigerator compartment <NUM>. As such, a temperature differential level (ΔT) is calculated by subtracting the temperature level (Twi) sensed by the sensor <NUM> (temperature level of the interior wall of the refrigerator compartment <NUM>) from the temperature level (Two) sensed by the sensor <NUM> (temperature level of the exterior wall of the refrigerator compartment <NUM>).

As thermal conductivity (K) increases within the insulating space <NUM>, the difference between the interior wall temperature level (Twi) sensed in the refrigerator compartment <NUM> and the exterior wall temperature level (Two) sensed on the exterior wall of the vacuum insulated cabinet structure <NUM> will lessen. Said differently, the ability of the refrigerator <NUM> to keep the refrigerator compartment <NUM> at a refrigerated level will decrease as the performance of the insulating space <NUM> decreases. The performance of the insulating space <NUM> decreases as the vacuum pressure (P) within the insulating space <NUM> increases along with the thermal conductivity (K). As such, the vacuum pressure (P) and the thermal conductivity level (K) provided within the insulating space <NUM> are related to the calculated temperature differential (ΔT).

For example, if the refrigerator <NUM> is disposed within an environment in which the ambient temperature is <NUM>° C, then this ambient temperature level (To) will be sensed by the sensor <NUM> which is configured to sense the ambient temperature of the environment in which the refrigerator <NUM> is disposed (e.g. a kitchen). If the refrigerator compartment <NUM> of the refrigerator <NUM> is refrigerated to <NUM>° C, then this refrigerated temperature level (Ti) will be sensed by the sensor <NUM> positioned within the refrigerator compartment <NUM>. For this example, the resulting temperature differential (ΔT) is <NUM>° C. Thus, the resulting temperature differential (ΔT) can be calculated by the following formula: <MAT>.

For the example given above, the resulting temperature differential (ΔT) of <NUM>° C may be described as a data point "Delta T1" that is provided by a temperature differential sensed between the sensors <NUM>, <NUM> at a first point in time. If the resulting temperature differential (ΔT) is equal to Delta T1, then the vacuum pressure (P) is provided by the data point "P1" which correlates to the vacuum pressure (P) within the insulating space <NUM> of the vacuum insulated cabinet structure <NUM> at the first point in time. If the resulting temperature differential (ΔT) is equal to Delta T1, then the thermal conductivity (K) is provided by the data point "K1" which correlates to the thermal conductivity (K) within the insulating space <NUM> of the vacuum insulated cabinet structure <NUM> at the first point in time.

At a second point in time, over the life of the refrigerator <NUM>, the resulting temperature differential will likely be a lower number than <NUM>° C as the vacuum pressure (P) within the vacuum insulated cabinet structure <NUM> rises along with the thermal conductivity (K). This second temperature differential can be provided as a data point "Delta T2" which correlates to a vacuum pressure data point of "P2" for the vacuum pressure of the vacuum insulated cabinet structure <NUM> at the second point in time. Similarly, if the resulting temperature differential (ΔT) is equal to Delta T2, then the thermal conductivity (K) is provided by the data point "K2" which correlates to the thermal conductivity (K) within the insulating space <NUM> of the vacuum insulated cabinet structure <NUM> at the second point in time.

The steps described above can be repeated multiple times to provide a plurality of temperature differential levels, a plurality of vacuum pressure levels, and a plurality of thermal conductivity levels over time. With this information, a curve can be derived mathematically using vacuum pressure levels (P1, P2, etc.) vs. thermal conductivity levels (K1, K2 etc.) and the conductivity equation and later can be validated through testing.

It is further contemplated that a series of temperature levels can be compiled by taking multiple temperature readings by the sensors <NUM>, <NUM> at the first period in time to provide multiple temperature differentials that can be calculated by the controller <NUM> (<FIG>). The controller <NUM> can further calculate an average temperature differential using data from the series of temperature levels sensed during an off-duty cycle of the compressor <NUM>. This process can be repeated for multiple periods in time to provide vacuum pressure levels and thermal conductivity levels that are averaged at those periods in time.

With further reference to the example given above, and with further reference to <FIG>, we have the following conditions: <NUM>) the sensor <NUM> has measured the inside ambient temperature level (Ti) of the refrigerator compartment <NUM> at <NUM>° C; <NUM>) the sensor <NUM> has measured the outside ambient temperature level (To) of the space in which the refrigerator <NUM> is disposed at <NUM>° C; <NUM>) the thickness (D) of the insulating space <NUM> or the distance between interior wall <NUM> and exterior wall <NUM> is <NUM>; <NUM>) the conductivity of the insulation (K) is <NUM> mw/mk; <NUM>) the convective heat transfer coefficient (hi) from the ambient temperature (Ti) of the refrigerator compartment <NUM> to the temperature level (Twi) of the rear wall <NUM> of the liner <NUM> of the refrigerator compartment <NUM> is <NUM> W/(m<NUM> K); and <NUM>) the convective heat transfer coefficient (ho) from the temperature level (Two) of the rear wall <NUM> of the exterior wrapper <NUM> to the ambient air temperature (To) is <NUM> W/(m<NUM> K). With this information, we can calculate the overall heat transfer coefficient (Q) using the following formula: <MAT>.

The overall heat transfer coefficient (Q) demonstrates how heat is conducted through a series of resistant mediums, as shown in <FIG>.

In the above equation, using the parameters set forth in this example, Q = <NUM> W/m<NUM>. With Q calculated, we can now determine the temperatures of the interior wall (Twi) and the outer wall (Two) using the following formulas, respectively: <MAT>.

In the first equation, ΔT = Twi-Ti. As such, for the first equation, <NUM> W/m<NUM> / <NUM> W/(m<NUM> K) =. Therefore, with the ambient temperature level (Ti) inside the refrigerator compartment <NUM> being known as <NUM>° C, we can deduce that the temperature level (Twi) of the wall inside the refrigerator compartment <NUM> is <NUM>° C. In the second equation, ΔT = Two-To. As such, for the second equation, <NUM> W/m<NUM> / <NUM> W/(m<NUM> K) =. Therefore, with the ambient temperature level (To) of the environment in which the refrigerator <NUM> is disposed being known as <NUM>° C, we can deduce that the temperature level (Two) of the exterior wall outside the refrigerator compartment <NUM> is <NUM>° C. Thus, for any refrigerated system, the present concept can calculate an overall heat transfer coefficient (Q) if we are provided with: <NUM>) two temperature levels selected from the group consisting of an ambient temperature of a refrigerator compartment (Ti), an interior wall temperature level (Twi) of an insulating space, an exterior wall temperature level (Two) of an insulating space, and an outside ambient temperature level (To); and the resistance (hi, K or ho) between the known temperature levels. For example, we can determine (Q) if we have the ambient temperature (Ti) of the refrigerator compartment <NUM> and the temperature level (Twi) of the rear wall <NUM> of the liner <NUM> of the refrigerator compartment <NUM>, and the resistance between them (hi). Similarly, we can determine (Q) if we have the temperature level (Twi) of the rear wall <NUM> of the liner <NUM> of the refrigerator compartment <NUM> and the temperature level (Two) of the rear wall <NUM> of the exterior wrapper <NUM> of the refrigerator <NUM>, and the resistance between them (K). Still further, we can determine (Q) if we have the temperature level (Two) of the rear wall <NUM> of the exterior wrapper <NUM> of the refrigerator <NUM> and the outside ambient temperature level (To), and the resistance between them (ho).

With Q calculated, we can use either of the formulas noted below to determine unknown variables: <MAT>.

Further, if (K) is unknown and the interior wall temperature level (Twi) of an insulating space, the exterior wall temperature level (Two) of an insulating space, and (Q) are known, we can use the following formula to calculate unknowns: <MAT>.

In the above example, the temperature level (Twi) of the wall <NUM> inside the refrigerator compartment <NUM> was calculated to be <NUM>° C. Further, the temperature level (Two) of the exterior wall <NUM> outside the refrigerator compartment <NUM> was calculated to be <NUM>° C. With this information, along with the thickness of the insulating space <NUM> and knowing Q to be <NUM> W/m<NUM>, we can calculate the conductivity (K) of the insulating space <NUM> using the equation below, wherein: <MAT> so K = <NUM> mW/mK.

Thus, as noted above, Delta T (ΔT) of the interior and exterior walls (<NUM>, <NUM>) of the insulating space <NUM> is correlated to the conductivity (K) of the insulating space <NUM>. The conductivity (K) of the insulating space <NUM> is further correlated to the absolute vacuum pressure P inside the vacuum insulated cabinet structure <NUM>. The relationship between the conductivity (K) of the insulating space <NUM> and the vacuum pressure P inside the vacuum insulated cabinet structure <NUM> is illustrated in the reference chart <NUM> shown in <FIG> presenting an embodiment according to the present invention, which discloses a method according to claim <NUM>. As shown in the reference chart <NUM> of <FIG>, the relationship between the conductivity (K) of the insulating space <NUM> and the vacuum pressure P inside the insulating space <NUM> of the vacuum insulated cabinet structure <NUM> is plotted as an S-curve. The reference chart <NUM> of <FIG> includes the conductivity of an insulating space as provided with various types of insulation (fumed silica, precipitated silica, polystyrene foam, polyurethane foam, and glass fibers). In this way, the reference chart <NUM> of <FIG> plots the conductivity of an insulating space through a plurality of resistive mediums (fumed silica, precipitated silica, polystyrene foam, polyurethane foam, and glass fibers) as a function of vacuum pressure P inside the insulating space. The S-curve of the reference chart <NUM> of <FIG> forms its S-curve shape because the thermal conductivity is relatively slow to change in the initial stages of pressure increase within the insulating space <NUM>. As pressure begins to increase from 1mbar to 10mbar within the insulating space <NUM>, the conductivity increases rapidly, thereby creating an upward slope that forms the middle part of the "s" in the S-curve of the reference chart <NUM>. This point of increased conductivity may be referred to herein as the point of inflection. After the point of inflection, the conductivity begins to plateau, forming the upper part of the "s" of the S-curve of the reference chart <NUM>, which may be referred to herein as the upper asymptote. At this point, the insulation performance has significantly degraded. Thus, as shown in the reference chart <NUM> of <FIG>, the conductivity of insulation is proportional to vacuum pressure, and the relationship is nonlinear. Using the information provided in the reference chart <NUM> of <FIG>, a model is provided from which we can estimate vacuum pressure P within the insulating space <NUM> once we have determined the conductivity (K) within the insulating space <NUM>. So, the present concept involves finding the conductivity (K) of the insulating space using Delta T (Two- Twi), and then finding Pressure (P) from the calculated conductivity (K) using the reference chart <NUM> provided in <FIG>. It is contemplated that the values of the reference chart <NUM> can be stored in the controller <NUM> for estimating pressure in an insulating space.

Claim 1:
A method of measuring pressure within a vacuum insulated cabinet structure (<NUM>), the method comprising the steps of:
(i) providing a vacuum insulated cabinet structure (<NUM>) having a storage compartment (<NUM>) and an insulating space (<NUM>) positioned between an interior wall (<NUM>) of the storage compartment (<NUM>) and an exterior wall (<NUM>) of the storage compartment (<NUM>), a first temperature sensor (<NUM>) positioned on the interior wall (<NUM>) of the storage compartment (<NUM>), a second temperature sensor (<NUM>) positioned on the exterior wall (<NUM>) of the storage compartment (<NUM>), a third temperature sensor (<NUM>, <NUM>) positioned to sense an ambient temperature level (Ti, To);
(ii) sensing a first temperature level (Twi) of the interior wall (<NUM>) of the storage compartment (<NUM>) using the first temperature sensor (<NUM>);
(iii) sensing a second temperature level (Two) of the exterior wall (<NUM>) of the storage compartment (<NUM>) using the second temperature sensor (<NUM>);
(iv) calculating a first temperature differential (ΔT) between the second temperature level (Two) and the first temperature level (Twi);
(v) sensing an ambient temperature level (Ti, To) using the third temperature sensor (<NUM>, <NUM>);
(vi) calculating an overall heat transfer coefficient (Q) using the ambient temperature level (Ti, To), the first temperature level (Twi), and a convective heat transfer coefficient for the exterior wall of the storage compartment;
(vii) determining a first conductivity level (K) using the first temperature differential (ΔT), the overall heat transfer coefficient (Q) and a thickness (D) of the insulating space (<NUM>); and
(viii) determining a first pressure level (P) within the insulating space (<NUM>) using the first conductivity level (K).