The present disclosure relates to frost removal and, more particularly, to mechanical frost removal systems.
This section provides background information related to the present disclosure which is not necessarily prior art.
Frost formation on heat exchanger fins is an undesirable circumstance. Frost degrades the performance of air-source heat pumps by restricting the airflow and increasing the thermal resistance of the heat exchanger. Conventional defrosting strategies for evaporators typically employ thermal approaches. Hot-gas bypass, reverse-cycle defrosting, and embedded electric resistance heaters are the leading thermal approaches to defrosting. Conventional thermal approaches have deficiencies in the form of high energy consumption, occupant discomfort, and a low rate of defrosting.
More recently, it has been studied that ultrasonic high-frequency vibrations are more effective in defrosting than low-frequency vibrations. These vibrations can be either excited using a laboratory shaker or embedded piezoelectric actuators. However, ultrasonic vibrations have several limitations. First, ultrasonic vibrations require specialized actuators, based on piezoelectric materials that can be expensive and may rapidly fatigue. Secondly, ultrasonic vibrations induce out-of-plane vibrations on the order of a few micrometers, which are not sufficiently large to break ice crystals. Thirdly, ultrasonic vibrations diffuse and damp out rapidly away from the actuation source. This restricts the de-icing effect to the region immediately adjacent to the actuators. Furthermore, ultrasonic vibrations require relatively high power, as power is quadratically related to the frequency.
Accordingly, there is a continuing need for a frost removal system that effectively removes frost formations more efficiently than known systems, such as thermal and ultrasonic approaches.
In concordance with the instant disclosure, an energy efficient frost removal system with enhanced frost removal performance has been surprisingly discovered.
The shape-morphing fin is configured to remove an ice formation from a structure. The shape-morphing fin includes a fixed portion, a multistable portion, and a coupling portion. The multistable portion may be selectively movable between in a first position and a second position. The movement between first position and the second position may be configured to remove the ice formation from the structure. The coupling portion may couple the fixed portion to the multistable portion.
In another embodiment, the present technology may include methods of manufacturing the shape-morphing fin. For instance, a first method for manufacturing the shape-morphing fin may include providing a fixed portion, a multistable portion, a coupling portion, and a vibration source. The coupling portion may couple the fixed portion to the multistable portion. The multistable portion may be selectively movable between a first position and a second position. The movement of the multistable portion between the first position and the second position may be configured to remove the ice formations from the structure. Next, the method may include a step of forming an angle in the fixed portion. The vibration source may also be coupled to the fixed portion, the multistable portion, and/or the coupling portion.
In another embodiment, the present technology may include methods of using the shape-morphing fin. For instance, a second method for using the shape-morphing fin may include providing a fixed portion, a multistable portion, a coupling portion, and a vibration source. The coupling portion may couple the fixed portion to the metastable portion. The vibration source may be coupled to the fixed portion, the multistable portion, and/or the coupling portion. The multistable portion may be selectively movable between a first position and a second position. The movement of the multistable portion between the first position and the second position may be configured to remove the ice formations from the structure. Next, the second method may include a step of vibrating the multistable portion through the use of vibration source, thereby engaging the movement of the multistable position. Afterwards, the ice formation may be removed from the structure.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.
The following description of technology is merely exemplary in nature of the subject matter, manufacture, and use of one or more inventions, and is not intended to limit the scope, application, or uses of any specific invention claimed in this application or in such other applications as may be filed claiming priority to this application, or patents issuing therefrom. Regarding methods disclosed, the order of the steps presented is exemplary in nature unless otherwise disclosed, and thus, the order of the steps can be different in various embodiments, including where certain steps can be simultaneously performed.
Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains.
As used herein, the terms “a” and “an” indicate “at least one” of the item is present; a plurality of such items may be present, when possible. Except where otherwise expressly indicated, all numerical quantities in this description are to be understood as modified by the word “about” and all geometric and spatial descriptors are to be understood as modified by the word “substantially” in describing the broadest scope of the technology. “About” when applied to numerical values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” and/or “substantially” is not otherwise understood in the art with this ordinary meaning, then “about” and/or “substantially” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters. In the present disclosure the terms “about” and “around” may allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. Likewise, in the present disclosure the term “substantially” can allow for a degree of variability in a value or range, for example, within 90%, within 95%, or within 99% of a stated value or of a stated limit of a range.
Although the open-ended term “comprising,” as a synonym of non-restrictive terms such as including, containing, or having, is used herein to describe and claim embodiments of the present technology, embodiments may alternatively be described using more limiting terms such as “consisting of” or “consisting essentially of.” Thus, for any given embodiment reciting materials, components, or process steps, the present technology also specifically includes embodiments consisting of, or consisting essentially of, such materials, components, or process steps excluding additional materials, components or processes (for consisting of) and excluding additional materials, components or processes affecting the significant properties of the embodiment (for consisting essentially of), even though such additional materials, components or processes are not explicitly recited in this application. For example, recitation of a process reciting elements A, B and C specifically envisions embodiments consisting of, and consisting essentially of, A, B and C, excluding an element D that may be recited in the art, even though element D is not explicitly described as being excluded herein.
As referred to herein, disclosures of ranges are, unless specified otherwise, inclusive of endpoints and include all distinct values and further divided ranges within the entire range. Thus, for example, a range of “from A to B” or “from about A to about B” is inclusive of A and of B. Disclosure of values and ranges of values for specific parameters (such as amounts, weight percentages, etc.) are not exclusive of other values and ranges of values useful herein. It is envisioned that two or more specific exemplified values for a given parameter may define endpoints for a range of values that may be claimed for the parameter. For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that Parameter X may have a range of values from about A to about Z Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping, or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if Parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9,1-8,1-3,1-2,2-10,2-8,2-3,3-10,3-9, and so on.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer, or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below,” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The shape-morphing fin 100 is configured to remove an ice formation from a structure. In certain circumstances, the present disclosure may include the generation of a strain and/or the generation of resonant vibrations to engage a negative stiffness element for mechanical defrosting. As shown in
The shape-morphing fin 100 may be provided in various ways. For instance, an aperture 114 may be disposed between the fixed portion 102 and the multistable portion 104, 106. The aperture 114 may enable to the multistable portion 104, 106 move at least partially independent from the fixed portion 102. In a specific example, as shown in
In certain circumstances, the multistable portion 104, 106 may have more than one state of equilibrium. For instance, as non-limiting example, the multistable portion 104, 106 may be a bistable structure 104 and/or a metastable structure 106. The bistable structure 104 may have two statically stable states that originate from storing strain energy in the system. The strain energy of bistable structure 104 may be described by a double-well energy curve, as shown in
In certain circumstances, the shape-morphing fin 100 may include various ways to actuate the movement of the multistable portion 104, 106. For instance, the shape-morphing fin 100 may include a controller 116 communicatively coupled to at least one of the fixed portion 102, the multistable portion 104, 106, and the coupling portion 108. The controller 116 may be configured to selectively actuate the multistable portion 104, 106 between the first position 110 and the second position 112. In a specific example, the controller 116 may include a processor and a memory. The memory may include non-transitory processor-executable instructions directing the controller 116 to actuate the multistable portion 104, 106 between the first position 110 and the second position 112 at a predetermined time and/or in a predetermined sequence. The shape-morphing fin 100 may also include a vibration source 118 coupled to the controller 116. The vibration source 118 may be configured to produce a vibrational frequency. The controller 116 may selectively actuate the multistable portion 104, 106 through the use of the vibrational frequency. More particularly, the controller 116 may selectively control when the vibrational frequency may engage the multistable portion 104, 106 to transition between the first position 110 and the second position 112. In a specific example, the vibrational frequency may be between one-tenth hertz to one-thousand hertz. In another specific example, the vibrational frequency may functionally provide a dynamic loading feature to create adhesive and cohesive fractures at an ice-fin interface. The mixed-mode fracture may help to delaminate and shed the ice layer. The mechanism of defrosting may involve exciting the resonant vibrations of a frost branch and/or a frost base layer of the ice formation. Specifically, resonant vibrations generate tensile and shear stresses that may lead to a mixed-mode fracture and shedding of the frost layer.
The shape-morphing fin 100 may be manufactured from various materials and processes. In a specific example, the fixed portion 102 and the multistable portion 104, 106 may be constructed from the same material. In another specific example, the fixed portion 102 and/or the multistable portion 104, 106 may be constructed from a metallic material. In an even more specific example, the fixed portion 102 and/or the multistable portion 104, 106 may be constructed from weld steel and/or copper-coated aluminum. Advantageously, where the fixed portion 102 and/or the multistable portion 104, 106 are constructed from a metallic material, the shape-morphing fin 100 may provide an opportunity to add the defrosting functionality to heat exchangers without affecting heat exchanger performance. For instance, the shape-morphing fin 100 may be advantageously provided as a component in a heat pump.
In certain circumstances, the shape-morphing fin 100 may also be more economically manufactured due to an uncomplicated and efficient manufacturing process. As a non-limiting example, the embedded negative stiffness leading to the snap-through behavior may be achieved by introducing plastic deformation in the fixed portion 102 outer strips of the shape-morphing fin 100. High residual stresses due to plastic deformation bends may store strain energy into the multistable portion 104, 106 resulting in bistability or metastability, depending on the chosen design. The energy released from the snap-through action when jumping between the two stable shapes may be directly proportional to the magnitude of the induced residual stresses. This snap-through may lead to large strains and ensuing vibrations, which may subsequently fracture and shed the frost layer from the shape-morphing fin 100. The amount of ice fractured and shed, along with the rate of ice shedding may be dependent on the potential energy released during the snap-through. The snap-through in the bistable structure 104 or metastable structure 106 may initiate when the actuating force on the structure reaches the peak force. The bistable structure 104 or metastable structure 106 may exhibit negative stiffness behavior due to any loading beyond the peak force and undergo snap-through. The potential energy released due to the bistable structure 104 or metastable structure 106 snapping may be converted to vibrations. The compressive and shear strains in the ice formation during the snap-through may predominantly dictate the cohesive and adhesive fracturing of the ice formation. The ensuing ice shedding may be a function of the post snap-through vibrations. The dominant frequency of the vibrations may be around the resonance of the second stable state in the bistable structure 104 and may be around the resonance of the pseudo stable state in the metastable structure 106.
The combination of plastic deformation induced in the fixed portion 106 outer strips and the geometry of the shape-morphing fin 100 may allow for controlling the bistability or metastability of the multistable portion 104, 106. Specifically, residual stresses in the shape-morphing fin 100 are critical in determining whether the morphing fin will exhibit bistability, metastability, or mono stability. Advantageously, the plastic deformation in the fixed portion 106 outer strips and the induced residual stresses may be adaptable to exhibit bistability, metastability, or mono stability.
The plastic deformation and subsequent buckling of the multistable portion 104, 106 may produce various shapes. For instance, the actuation of the multistable portion 104, 106 may give rise to concave and/or convex shapes. The shape-morphing fin 100 may have curved and/or angled geometry and/or low out-of-plane stiffness. This may lead to a highly nonlinear response and/or high amplitude oscillations for both quasistatic and dynamic loading. The large strains and/or high amplitude oscillations may fracture and shed the frost layer. Advantageously, the defrosting performance of the mechanical approach in the present disclosure may be orders of magnitude more energetically efficient than the known purely thermal approaches for frost removal.
In another embodiment, the present technology may include methods of manufacturing the shape-morphing fin 100. For instance, as shown in
In another embodiment, the present technology may include methods of using the shape-morphing fin 100. For instance, as shown in
The following experimental setups, components, characteristics, and results are provided as a specific, non-limiting examples.
To investigate certain stability characteristics of the shape-morphing fin 100, compressive tests on a manufactured shape-morphing fins 100 were conducted. One set of metastable structures 106 and one set of bistable structures 104 were manufactured out of a copper-coated aluminum alloy having a thickness around 0.48 mm, and another set out of weld steel having a thickness of around 0.79 mm Both sets of morphing fins have identical base geometry in the flat configuration. The metastable structure 106 and bistable structure 104 behavior of the sets of morphing fins 100 were adjusted to different bend angles and hence varying levels of plastic deformation. The experimentally obtained force-displacement plots for a set of bistable 104 (specimen A) and metastable 106 (specimen B) fins manufactured from the copper-coated aluminum are shown in
Frost formation occurs in five stages: 1) condensation, 2) frost nucleation growth, 3) frost crystal growth, 4) frost layer growth, and 5) frost layer fully grown. Frost growth characterization is a challenging problem in refrigeration science. There are often conflicting results found in the literature. This is because the type of frost formed on evaporator fins is different for each specific case of airflow, surface temperature, and fin profile. Although there are experimental studies in the literature that classify the type of ice formed, due to the unique nature of the frost formed for each condition, it is difficult to know the mechanical properties of frost beforehand. There is no standardized experimental procedure to test the mechanical properties of the frost; hence, it is necessary to build a test setup that allows an approach for examining mechanical defrosting in situ. The experimental setup, illustrated in
Loading the shape-morphing fin 100 cyclically may lead to more ice shed from the shape-morphing fin 100. Image analysis was used to investigate the effect of the number of snap-throughs on the percentage area of the ice shed. A comparison of the percentage area of ice remaining on the surface of the shape morphing fin 100 vs the number of cycles for specimens A, B, C, and D are illustrated in
To test the energy savings potential of the shape-morphing fin 100 compared to known thermal defrosting approaches, the same setup described in
Advantageously, the shape-morphing fin 100 may provide an energy efficient frost removal system with enhanced frost removal performance. Desirably, costly thermodynamic cycle reversal and discomfort from a cold blow effect may be militated against by using shape adaptations for mechanical defrosting.
Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms, and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Equivalent changes, modifications and variations of some embodiments, materials, compositions, and methods can be made within the scope of the present technology, with substantially similar results.
This application is a Continuation of U.S. application Ser. No. 17/855,965, filed on Jul. 1, 2022, which in turn claims the benefit of U.S. Provisional Application Ser. No. 63/217,578, filed on Jul. 1, 2021. The entire disclosure of the above application is hereby incorporated herein by reference.
Number | Date | Country | |
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63217578 | Jul 2021 | US |
Number | Date | Country | |
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Parent | 17855965 | Jul 2022 | US |
Child | 18531562 | US |