The following description relates to an improvement in realizing a ferroic response and, more particularly, to an improvement in realizing a ferroic response through the application of a conjugate field.
A wide variety of technologies exist for cooling applications. These include, but are not limited to, technologies that make use of evaporative cooling, technologies that make use of convective cooling and technologies that make use of solid state cooling (e.g., thermoelectric cooling technologies). With this in mind, one of the most prevalent technologies in use for residential and commercial refrigeration and air conditioning is the vapor compression refrigerant heat transfer loop. These loops typically circulate a refrigerant having appropriate thermodynamic properties through a loop that includes a compressor, a heat rejection heat exchanger (i.e., heat exchanger condenser), an expansion device and a heat absorption heat exchanger (i.e., heat exchanger evaporator). Vapor compression refrigerant loops effectively provide cooling and refrigeration in a variety of settings and in some situations can be run in reverse as a heat pump.
Many of the refrigerants used in vapor compression refrigerant loops can present environmental hazards such as ozone depletion potential (ODP) or global warming potential (GWP) or can be toxic or flammable. Additionally, vapor compression refrigerant loops can be impractical or disadvantageous in environments lacking a ready source of power sufficient to drive the compressor. For example, in an electric vehicle, the power demand of an air conditioning compressor can result in a significantly shortened vehicle battery life or driving range. Similarly, the weight and power requirements of the compressor can be problematic in various portable cooling applications.
Accordingly, there has been interest in developing cooling technologies as alternatives to vapor compression refrigerant loops.
According to one aspect of the disclosure, a method of realizing a ferroic response is provided. The method includes applying a first conjugate field to a ferroic material in a non-singular-stepwise manner and applying a second conjugate field to the ferroic material in a non-singular-stepwise manner.
In accordance with additional or alternative embodiments, the ferroic material includes at least a magneto-caloric material and the first and second conjugate fields includes at least magnetic fields.
In accordance with additional or alternative embodiments, the ferroic material includes at least an electro-caloric material and the first and second conjugate fields include at least electric fields.
In accordance with additional or alternative embodiments, the ferroic material includes at least an elasto-caloric material and the first and second conjugate fields include at least stress fields.
In accordance with additional or alternative embodiments, the non-singular-stepwise manner includes one or more of a non-linear or linear ramping of the first and second conjugate fields, an application of the first and second conjugate fields in a sine wave or a flattened sine wave pattern, an application of the first and second conjugate fields in multiple steps and an application of the first and second conjugate fields in an alternating pattern.
In accordance with additional or alternative embodiments, the applying of the first conjugate field includes applying multiple first conjugate fields in the non-singular-stepwise manner and the applying of the second conjugate field includes applying multiple second conjugate fields in the non-singular-stepwise manner.
According to another aspect of the disclosure, a method of realizing a ferroic response is provided. The method includes applying a first conjugate field to a ferroic material in a non-singular-stepwise manner, applying a second conjugate field to the ferroic material in a non-singular-stepwise manner, applying a third conjugate field to the ferroic material in a non-singular-stepwise manner and applying a fourth conjugate field to the ferroic material in a non-singular-stepwise manner.
In accordance with additional or alternative embodiments, the ferroic material includes at least a magneto-caloric material and the first, second, third and fourth conjugate fields include at least magnetic fields.
In accordance with additional or alternative embodiments, the ferroic material includes at least an electro-caloric material and the first, second, third and fourth conjugate fields include at least electric fields.
In accordance with additional or alternative embodiments, the ferroic material includes at least an elasto-caloric material and the first, second, third and fourth conjugate fields include at least stress fields.
In accordance with additional or alternative embodiments, the ferroic material includes a multi-ferroic material as a combination, composite, layered structure or alloy and one or more of the first, second, third and fourth conjugate fields pertains to constituents of the multi-ferroic material.
In accordance with additional or alternative embodiments, the applying of the first, second, third and fourth conjugate fields includes one or more of a non-linear or linear ramping of the first, second, third and fourth conjugate fields, an application of the first, second, third and fourth conjugate fields in a sine wave or a flattened sine wave pattern, an application of the first, second, third and fourth conjugate fields in multiple steps and an application of the first, second, third and fourth conjugate fields in an alternating pattern.
In accordance with additional or alternative embodiments, the applying of the first and third conjugate fields includes applying multiple first and multiple third conjugate fields in the non-singular-stepwise manner and the applying of the second and fourth conjugate fields includes applying multiple second and multiple fourth conjugate fields in the non-singular-stepwise manner.
According to yet another aspect of the disclosure, a ferroic response system is provided. The ferroic response system includes a ferroic response element and a controller. The ferroic response element is thermally interposed between a heat source and a heat sink and includes a ferroic material and devices disposed to apply first, second, third and fourth conjugate fields to the ferroic material. The controller is configured to control the devices to apply the first or third conjugate field in a non-singular-stepwise manner to the ferroic material to enable heat transfer between the ferroic response element and the heat sink or to control the devices to apply the second or fourth conjugate field in the non-singular-stepwise manner to the ferroic material to enable heat transfer between the ferroic response element and the heat source.
In accordance with additional or alternative embodiments, the ferroic response system further includes the heat sink, the heat source, a first valve, which is thermally interposed between the ferroic response element and the heat sink and which is controllable by the controller to enable the heat transfer between the ferroic response element and the heat sink and a second valve, which is thermally interposed between the ferroic response element and the heat source and which is controllable by the controller to enable the heat transfer between the ferroic response element and the heat source.
In accordance with additional or alternative embodiments, the ferroic material includes at least a magneto-caloric material and the first or the third and the second or the fourth conjugate fields include at least magnetic fields.
In accordance with additional or alternative embodiments, the ferroic material includes at least an electro-caloric material and the first or the third and the second or the fourth conjugate fields include at least electric fields.
In accordance with additional or alternative embodiments, the ferroic material includes at least an elasto-caloric material and the first or the third and the second or the fourth conjugate fields include at least stress fields.
In accordance with additional or alternative embodiments, the controller controls the devices to apply the first or the third and the second or the fourth conjugate fields along one or more of non-linear or linear ramping, sine wave or flattened sine wave pattern, multiple step schedules and an alternating pattern.
In accordance with additional or alternative embodiments, the devices are disposed to apply multiple first or multiple third conjugate fields and multiple second or multiple fourth conjugate fields.
In accordance with additional or alternative embodiments, the controller is configured to control the devices to apply the first conjugate field in the non-singular-stepwise manner to the ferroic material to enable heat transfer between the ferroic response element and the heat sink, control the devices to apply the second conjugate field in the non-singular-stepwise manner to the ferroic material to enable heat transfer between the ferroic response element and the heat source, control the devices to apply the third field to the ferroic material in the non-singular-stepwise manner to enable heat transfer between the ferroic response element and the heat sink, and control the devices to apply the fourth conjugate field in the non-singular-stepwise manner to the ferroic material to enable heat transfer between the ferroic response element and the heat source.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
With reference to
With continued reference to
In addition, it is seen that an application of unidirectional conjugate fields may exhibit additional adverse effects related to ferroic-based cooling systems. These include the fact that a unidirectional field may lead to a progressively more poled ferroic due to repeated cycling in one direction such that over time the ferroic “locks” in entropy that cannot be freed up to provide cooling and the cooling module consequently degrades in performance. Another adverse effect is seen is that an application of a unidirectional field often drives an accumulation of: point, line or other microstructural defects toward accumulation points where they coalesce and eventually result in local material breakdown and sometimes complete material and module destruction. Unidirectional electric fields can also drive the accumulation of ionized impurity atoms (free Na+ ions being especially notorious) toward the high potential electrode where they cause dielectric breakdown.
Such performance reductions have been noted in all the caloric systems. Thus, as will be described below, a ferroic-based cooling method and system are provided which employ an application of a negative or slightly negative (or a positive or slightly positive) conjugate field to maximize entropy of a ferroic material at a given temperature and, in some cases, to disperse local defects throughout the body of the ferroic material to thereby provide for longer life modules in additional to improved performance.
With reference to
As used herein, the substantially minimized entropy of the ferroic material may represent about 80-99% or 99-99.99% of the minimized entropy of the ferroic material (i.e., a degree of minimized entropy that would be associated with a non-zeroed field). Similarly, the substantially maximized entropy of the ferroic material may represent about 80-99% or 99-99.99% of the maximized entropy of the ferroic material (i.e., a degree of maximized entropy that would be associated with a non-zeroed field). For purposes of clarity and brevity, however, the following description will refer only to the minimized and maximized entropy but it is to be understood that such references also include the possibility of obtaining substantially minimized or substantially maximized entropy.
That is, for an electro-caloric material for example, a positive or negative conjugate field is applied to drive electric displacement of the electro-caloric material toward minimized entropy to thereby minimize entropy of the electro-caloric material and to generate heat that can be given off to the surrounding environment. Meanwhile, a non-zero negative or positive conjugate field is applied to drive electric displacement of the electro-caloric material to zero to thereby maximize entropy of the electro-caloric material and to absorb heat from the surrounding environment.
The application of conjugate fields can be realized in a variety of ways including, but not limited to, the application of subsystem components rather than fixed field components. Alternatively, where dielectric permittivity is strongly coupled to an electric field (i.e., where ε=ε(E), the shape and the slope of the hysteresis loop can vary with the applied conjugate field.
Here, it is noted that
The illustrations of
In accordance with embodiments, the ferroic material to which the positive and the slightly negative conjugate fields are applied may include magneto-caloric materials while the positive and the slightly negative conjugate fields may include magnetic fields, electro-caloric materials while the positive and the slightly negative conjugate fields may include electric fields and elasto-caloric materials while the positive and the slightly negative conjugate fields include stress fields. In addition, any other ferroic transition state other than these mentioned, as well as multi-ferroics that combine various ferroic elements may also be represented by this analysis. In accordance with further embodiments, and with reference to
The non-linear and linear ramping of the conjugate field of
While
As a general matter, the phrase “non-singular-stepwise manner”, as used herein, refers to any application of a conjugate field that is not a single instantaneous step from a “starting potential” to an “end potential.”
In accordance with still further embodiments, where the ferroic material exhibits ferroic behavior in response to multiple types of conjugate field applications, the applying of the positive conjugate field may include applying multiple positive conjugate fields to the ferroic material to obtain a minimized multi-dimensional entropy of the ferroic material and the applying of the slightly negative conjugate field may include applying multiple slightly negative conjugate fields to the ferroic material to obtain maximized multi-dimensional entropy of the ferroic material. That is, where the ferroic material is magneto-caloric and electro-caloric, the multiple positive and the multiple slightly negative conjugate fields may include magnetic fields as well as electric fields.
With reference to
As such, it is to be understood that the method of
With reference to
The ferroic element 611 is disposed in thermal communication with a heat sink 617 through a first thermal flow path 618 and with a heat source 620 through a second thermal flow path 622. The first and second thermal flow paths 618 and 620 provide for thermal transfer of fluid through valves 626 and 628 and also permit conductive heat transfer through a transfer fluid (e.g., air, oil, dielectric), a solid state or thermomechanical set of switches that are disposable in thermally conductive contact with the electro-caloric element and either the heat sink 617 or the heat source 620. A controller 624 serves as an electrical power source and is configured to control power to selectively activate the conjugate field application devices 614 and 616. The controller 324 is also configured to open and close the valves 626 and 628 to selectively direct the heat transfer along the first and second flow paths 618 and 622.
In operation, in an exemplary case in which the ferroic element 611 is an electro-caloric element, the heat transfer system 610 can be operated by the controller 624 initially controlling the conjugate field application devices 614 and 616 to apply an electric field as a voltage differential across the ferroic material film 612 (i.e., the electro-caloric film) to thereby cause a decrease in entropy or to obtain a minimization of entropy in the ferroic element 611 and to thus obtain a corresponding release of heat energy by the ferroic element 611. At this point, the controller 624 opens the valve 626 to transfer at least a portion of the released heat energy along the first flow path 618 to the heat sink 617. This transfer of heat can occur after the temperature of the ferroic element 611 has risen to a threshold temperature. In some embodiments, heat transfer to the heat sink 617 is begun as soon as the temperature of the ferroic element 611 increases to be about equal to the temperature of the heat sink 617. In either case, after application of the electric field for a time to induce a desired release and transfer of heat energy from the ferroic element 611 to the heat sink 617, the electric field can be removed by the controller 624. Such removal causes an increase in entropy or a maximization of entropy in the ferroic element 611 and a corresponding decrease in heat energy of the ferroic element 611. This decrease in heat energy manifests as a reduction in temperature of the ferroic element 611 to a temperature below that of the heat source 320. The controller 624 thus closes valve 626 to terminate flow along the first flow path 618 and opens valve 628 to transfer heat energy from the heat source 620 to the colder ferroic element 611 in order to regenerate the ferroic element 611 for another cycle.
At this point, the controller 624 can either re-apply the originally applied electric field to the ferroic element 611 so that the ferroic element 611 follows the “minor loop” of the hysteresis curve of
In some embodiments, for example where a heat transfer system is utilized to maintain a temperature in a conditioned space or thermal target, the electric field can be applied to the ferroic element 611 to increase its temperature to a first threshold. After this first threshold is reached, the controller 624 opens valve 626 to transfer heat from the ferroic element 611 to the heat sink 617 until a second threshold is reached. The electric field can continue to be applied during all or a portion of the time period between the first and second thresholds being reached and can then be removed to reduce the temperature of the ferroic element 611 until a third threshold is reached. The controller 624 can then close the valve 626 to terminate heat transfer along the first flow path 618 and open the valve 628 to transfer heat from the heat source 320 to the ferroic element 611. These operations can be optionally repeated until a target temperature of the conditioned space or thermal target (which can be either the heat source or the heat sink) is reached.
While the disclosure is provided in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that the exemplary embodiment(s) may include only some of the described exemplary aspects. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/037583 | 6/14/2018 | WO | 00 |
Number | Date | Country | |
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62520913 | Jun 2017 | US |