System and method for heating a heat exchanger for frost removal and frost prevention

Abstract

There are provided systems and methods for heating a heat exchanger. A system includes a heat exchanger configured to be placed inside a magnetic field created by a pair of electromagnetic coils. The system further includes the electromagnetic coils configured to control a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils. A method includes placing the heat exchanger inside a magnetic field created by a pair of electromagnetic coils. The method further includes controlling a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils.

Description

TECHNICAL FIELD

[0001] The embodiments disclosed herein relate to heat exchangers, and, in particular to heating a heat exchanger for frost removal and prevention.INTRODUCTION

[0002] Frost buildup on surfaces can pose several problems in various applications, including the creation of hazardous conditions. Therefore, it is important to ensure that components exposed to the elements are free of frost buildup.

[0003] One technique for frost removal is manual removal. However, not all areas where frost has built up may be easily accessible for manual removal. This can increase at least the time and cost required to remove the frost. Further, manual removal may not offer any techniques for preventing frost in the first place.

[0004] Other techniques used to flood heat exchangers with heat include using external space heaters which heat the heat exchanger from the outside, and hot gas reverse cycle techniques which heat the heat exchanger from the inside. However, such techniques are generally costly, complex and difficult to implement.

[0005] Accordingly, there is a need for techniques for frost removal and prevention that are not subject to one or more limitations of the prior art.

[0006] This background information is provided to reveal information believed by the applicant to be of possible relevance to the present disclosure. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present disclosure.SUMMARY

[0007] A system for heating a heat exchanger is provided. The system includes a heat exchanger configured to be placed inside a magnetic field created by a pair of electromagnetic coils. The system further includes the electromagnetic coils configured to control a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils.

[0008] In an embodiment, a wire is attached in direct contact to the heat exchanger to increase heat generation by concentrating a high power signal in the wire at an outside surface of the wire.

[0009] In an embodiment, the aspect of the magnetic coupling includes at least one of: an amount of power of the magnetic coupling; an amplitude of the magnetic coupling; a frequency of the magnetic coupling; a phase of the magnetic coupling; and an alignment of the magnetic coupling.

[0010] In an embodiment, there is direct contact between wires of the electromagnetic coils and a surface of the heat exchanger.

[0011] In an embodiment, a layer of metallic paint is applied to a surface of the heat exchanger to improve heating of the heat exchanger.

[0012] In an embodiment, improving heating of the heat exchanger includes at least one of improving a depth of an eddy current, improving a resistivity of an eddy current, and improving a magnetic permeability of an eddy current.

[0013] In an embodiment, a metal implant is inserted inside of the heat exchanger to improve heating of the heat exchanger.

[0014] In an embodiment, a thin layer of an electrical insulator is applied between the metal implant and the heat exchanger.

[0015] In an embodiment, a conductive layer may be insulated by a layer of insulator and attached to the heat exchanger to improve heating of the heat exchanger.

[0016] In an embodiment, a resistance measurement of a heated wire or a conductive material is used as a temperature sensor for temperature control and energy optimization.

[0017] A method of heating a heat exchanger is provided. The method includes placing the heat exchanger inside a magnetic field created by a pair of electromagnetic coils. The method further includes controlling a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils.

[0018] In an embodiment, a wire is attached in direct contact to the heat exchanger to increase heat generation by concentrating a high power signal in the wire at an outside surface of the wire.

[0019] In an embodiment, the aspect of the magnetic coupling includes at least one of: an amount of power of the magnetic coupling; an amplitude of the magnetic coupling; a frequency of the magnetic coupling; a phase of the magnetic coupling; and an alignment of the magnetic coupling.

[0020] In an embodiment, there is direct contact between wires of the electromagnetic coils and a surface of the heat exchanger.

[0021] In an embodiment, a layer of metallic paint is applied to a surface of the heat exchanger to improve heating of the heat exchanger.

[0022] In an embodiment, improving heating of the heat exchanger includes at least one of improving a depth of an eddy current, improving a resistivity of an eddy current, and improving a magnetic permeability of an eddy current.

[0023] In an embodiment, a metal implant is inserted inside of the heat exchanger to improve heating of the heat exchanger.

[0024] In an embodiment, a thin layer of an electrical insulator is applied between the metal implant and the heat exchanger.

[0025] In an embodiment, a conductive layer is insulated by a layer of insulator and attached to the heat exchanger to improve heating of the heat exchanger.

[0026] In an embodiment, a resistance measurement of a heated wire or a conductive material is used as a temperature sensor for temperature control and energy optimization.

[0027] Other aspects and features will become apparent, to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0029] FIG. 1 depicts a block diagram of an example system for heating a heat exchanger, according to an embodiment of the present disclosure.

[0030] FIG. 2 depicts an example method flow of operating the system of FIG. 1, according to an embodiment.DETAILED DESCRIPTION

[0031] Various apparatuses or processes will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover processes or apparatuses that differ from those described below. The claimed embodiments are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below.

[0032] As used herein, the term “about” should be read as including variation from the nominal value, for example, a + / −10% variation from the nominal value. It is to be understood that such a variation is always included in a given value provided herein, whether or not it is specifically referred to.

[0033] A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the present disclosure.

[0034] Further, although process steps, method steps, algorithms or the like may be described (in the disclosure and / or in the claims) in a sequential order, such processes, methods and algorithms may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of processes described herein may be performed in any order that is practical. Further, some steps may be performed simultaneously.

[0035] When a single device or article is described herein, it will be readily apparent that more than one device / article (whether or not they cooperate) may be used in place of a single device / article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device / article may be used in place of the more than one device or article.

[0036] The following relates generally to heat exchangers, and more particularly to a heating a heat exchanger for frost removal and prevention.

[0037] Techniques are disclosed herein for heating a heat exchanger that is configured to be placed inside a magnetic field created by a pair of electromagnetic coils. The electromagnetic coils are configured to control a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils. By heating the surface temperature of the heat exchanger, frost may be removed. Similarly, by maintaining a warm surface temperature of the heat exchanger, further frost build up may be prevented.

[0038] Advantageously, the techniques disclosed herein may be used in a variety of applications requiring the removal and / or prevention of frost. Techniques disclosed herein may be used to provide uniform heat distribution in different structures, such that frost may be removed evenly from said structures.

[0039] Referring to FIG. 1, depicted therein is an example system 100 for heating a heat exchanger, according to an embodiment of the present disclosure. The system 100 includes a heat exchanger 115 that is configured to be placed inside a magnetic field 110 created by a pair of electromagnetic coils 105. The system 100 further includes the electromagnetic coils 105 configured to control a surface temperature of the heat exchanger 115 by varying an aspect of a magnetic coupling between the heat exchanger 115 and the electromagnetic coils 105.

[0040] For clarity of illustration, only a single pair of electromagnetic coils 105 is shown, but it will be appreciated that the system 100 may include any number of the electromagnetic coils 105, e.g., a plurality of electromagnetic coils 105.

[0041] By placing the heat exchanger 115 inside of electromagnetic coils 105 where an alternating current is passed, the heat exchanger 115 surface temperature will rise due to the induced eddy current and joule heating effect.

[0042] The depth to which the eddy currents penetrate, and therefore the distribution of heat within the heat exchanger depends on the amplitude and the frequency of the alternating current / voltage, the magnetic permeability, the resistivity of the heat exchanger 115 material, as well as the distance between the surface and the heating coil.

[0043] In an embodiment, at least one wire may be attached in direct contact to the heat exchanger to increase heat generation by concentrating a high power signal in the wire at an outside surface of the wire.

[0044] The high frequency high power signal passing through the wire(s) will be concentrated close to the wire outside surface which increases its effective resistance. The increase in resistance increases the power losses in the wire. Which is translated into heat generation, which is transferred to the heat exchanger by the direct contact.

[0045] In an embodiment, the aspect of the magnetic coupling includes at least one of an amount of power of the magnetic coupling, an amplitude of the magnetic coupling, a frequency of the magnetic coupling, a phase of the magnetic coupling, and an alignment of the magnetic coupling.

[0046] In an embodiment, there is direct contact between wires of the electromagnetic coils 105 and a surface of the heat exchanger 115.

[0047] Direct contact between an electromagnetic coil wire and the heat exchanger 115 surface provides an improvement to the heating process. Given that the heat exchanger 115 is electrically insulated by a thin non-electrically conductive layer, this will allow for heat transfer using both induction heating and convection heating.

[0048] In an embodiment, a layer of metallic paint is applied to a surface of the heat exchanger 115 to improve a depth of an eddy current.

[0049] Applying a layer of metallic paint to the heat exchanger 115 surface provides an improvement to the heating process, as this improves the depth of the eddy current, its resistivity (DC and AC), and its magnetic permeability. A thin layer of electrical insulator can also be applied in between if needed.

[0050] In an embodiment, a metal implant is inserted inside of the heat exchanger 115 to improve a depth of an eddy current.

[0051] Inserting metal implants within a strategic region or area inside of the heat exchanger 115 can improve the depth of eddy current, its resistivity (DC and AC), and its magnetic permeability. A thin layer of electrical insulator can also be applied in between if needed.

[0052] Direct contact can be achieved between an electrically isolated piece of metal such as a wire, rod, tube, or the like, and the surface of the heat exchanger 115 using thermally conductive and electrically insulated adhesive.

[0053] An alternative current / voltage is applied to the piece of metal at a frequency high enough to force the electrical current to pass only on the outside surface of the conductor (i.e., controlling the skin depth). Such a conductor will examine an effective dominant AC resistance that is much higher than its DC resistance.

[0054] The heating power is controlled by either controlling the amplitude or the frequency of the applied electrical power to the conductive material. The heat is then transferred between the heat exchanger 115 by conduction. The length and placement of the conductive material is to be designed to guarantee uniform heat distribution.

[0055] Where the heat exchanger 115 is a fin and tube heat exchanger, the direct contact between an electrically isolated piece of metal (such as a wire or a coating) and the surface of the tubes and / or the plate fins is achieved using a thermally conductive and electrically insulated adhesive.

[0056] An alternative current / voltage is applied to the piece of metal at a frequency high enough to force the electrical current to pass only on the outside surface of the conductor (i.e., controlling skin depth). Such a conductor will examine an effective dominant AC resistance that is much higher than its DC resistance.

[0057] The heating power is controlled by either controlling the amplitude or the frequency of the applied electrical power to the conductive material. The heat is then transferred between the heat exchanger by conduction. The length and placement of the conductive material is to be designed to guarantee uniform heat distribution.

[0058] In an embodiment, if the plate fins are coated and the DC resistance is high enough, the alternating current is applied at normal frequency (about 50 or 60 Hz).

[0059] In an embodiment, the plate fins connect directly to the alternating current after making sure that the plate fins are electrically insulated from the tubes but thermally connected.

[0060] This may be achieved by adding a special material at the collars of the plate fins to electrically isolate such fins from the tubes.

[0061] In an embodiment, a thin conductive layer (such as fluorine-doped tin oxide (FTO) or indium-tin oxide (ITO)) may be insulated by a thin layer of insulator and attached to the heat exchanger.

[0062] A constant or time varying power signal may be used to energize such a layer. The generated heat inside of this layer due to the ohmic losses will be transferred to the heat exchanger for defrosting / frost prevention. Such conductive layers may be constructed with different thickness and patterns to cover completely or partially the heat exchanger.

[0063] In an embodiment, a resistance measurement of a heated wire or a conductive material is used as a temperature sensor for temperature control and energy optimization.

[0064] Benefits of the present disclosure include potentially faster heating times of the heat exchanger, which result in faster removal of frost build up.

[0065] Moreover, as frost buildup on a heat exchanger blocks the air flow, this eventually significantly reduces the heat transfer which is the main function of the heat exchanger. However, existing methods require a lot of heat to melt frost buildup. Advantages of the present disclosure include energy efficient defrosting and maintaining the efficient operation of a heat exchanger. An additional benefit is a reduction in temperature fluctuations due to the use of existing methods of defrosting heat exchangers.

[0066] Referring now to FIG. 2, depicted therein is a method 200 of heating a heat exchanger. The method 200 includes at 205 placing the heat exchanger inside a magnetic field created by a pair of electromagnetic coils. The method 200 further includes at 210 controlling a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils.

[0067] By placing the heat exchanger inside of a magnetic field created by one or more pairs of electromagnetic coils, the power transferred between the sending coil of each pair and the receiving coil experiences power loss which is consumed by the heat exchanger and causes the surface temperature of the heat exchanger to rise.

[0068] The heat exchanger surface temperature can be controlled by controlling the amount of power transferred though the magnetic coupling, its frequency, phase, and alignment.

[0069] Placing the heat exchanger inside of an electromagnetic coil (or more than one) where an alternating current / voltage is provided causes the surface temperature of the heat exchanger to rise due to the induced eddy current and the joule heating effect.

[0070] The depth to which the eddy currents penetrate, and the distribution of heat within the heat exchanger, depends on the amplitude and the frequency of the alternating current / voltage, the magnetic permeability, the resistivity of the heat exchanger material, as well as the distance between the heat exchanger surface and the heating coil.

[0071] In an embodiment, at least one wire may be attached in direct contact to the heat exchanger to increase heat generation by concentrating a high power signal in the wire at an outside surface of the wire.

[0072] The high frequency high power signal passing through the wire(s) will be concentrated close to the wire outside surface which increases its effective resistance. The increase in resistance increases the power losses in the wire. Which is translated into heat generation, which is transferred to the heat exchanger by the direct contact.

[0073] In an embodiment, the aspect of the magnetic coupling includes at least one of an amount of power of the magnetic coupling, an amplitude of the magnetic coupling, a frequency of the magnetic coupling, a phase of the magnetic coupling, and an alignment of the magnetic coupling.

[0074] In an embodiment, there is direct contact between wires of the electromagnetic coils and a surface of the heat exchanger.

[0075] Direct contact between an electromagnetic coil wire and the heat exchanger surface provides an improvement to the heating process. Given that the heat exchanger is electrically insulated by a thin non-electrically conductive layer, this will allow for heat transfer using both induction heating and convection heating.

[0076] In an embodiment, a layer of metallic paint is applied to a surface of the heat exchanger to improve a depth of an eddy current.

[0077] Applying a layer of metallic paint to the heat exchanger surface provides an improvement to the heating process, as this improves the depth of the eddy current, its resistivity (DC and AC), and its magnetic permeability. A thin layer of electrical insulator can also be applied in between if needed.

[0078] In an embodiment, a metal implant is inserted inside of the heat exchanger to improve a depth of an eddy current.

[0079] Inserting metal implants within a strategic region or area inside of the heat exchanger can improve the depth of eddy current, its resistivity (DC and AC), and its magnetic permeability. A thin layer of electrical insulator can also be applied in between if needed.

[0080] Direct contact can be achieved between an electrically isolated piece of metal such as a wire, rod, tube, or the like, and the surface of the heat exchanger using thermally conductive and electrically insulated adhesive.

[0081] An alternative current / voltage is applied to the piece of metal at a frequency high enough to force the electrical current to pass only on the outside surface of the conductor (i.e., controlling the skin depth). Such a conductor will examine an effective dominant AC resistance that is much higher than its DC resistance.

[0082] The heating power is controlled by either controlling the amplitude or the frequency of the applied electrical power to the conductive material. The heat is then transferred between the heat exchanger by conduction. The length and placement of the conductive material is to be designed to guarantee uniform heat distribution.

[0083] Where the heat exchanger is a fin and tube heat exchanger, the direct contact between an electrically isolated piece of metal (such as a wire or a coating) and the surface of the tubes and / or the plate fins is achieved using a thermally conductive and electrically insulated adhesive.

[0084] An alternative current / voltage is applied to the piece of metal at a frequency high enough to force the electrical current to pass only on the outside surface of the conductor (i.e., controlling skin depth). Such a conductor will examine an effective dominant AC resistance that is much higher than its DC resistance.

[0085] The heating power is controlled by either controlling the amplitude or the frequency of the applied electrical power to the conductive material. The heat is then transferred between the heat exchanger by conduction. The length and placement of the conductive material is to be designed to guarantee uniform heat distribution.

[0086] In an embodiment, if the plate fins are coated and the DC resistance is high enough, the alternating current is applied at normal frequency (about 50 or 60 Hz).

[0087] In an embodiment, the plate fins connect directly to the alternating current after making sure that the plate fins are electrically insulated from the tubes but thermally connected.

[0088] This may be achieved by adding a special material at the collars of the plate fins to electrically isolate such fins from the tubes.

[0089] In an embodiment, a thin conductive layer (such as fluorine-doped tin oxide (FTO) or indium-tin oxide (ITO)) may be insulated by a thin layer of insulator and attached to the heat exchanger.

[0090] A constant or time varying power signal may be used to energize such a layer. The generated heat inside of this layer due to the ohmic losses will be transferred to the heat exchanger for defrosting / frost prevention. Such conductive layers may be constructed with different thickness and patterns to cover completely or partially the heat exchanger.

[0091] In an embodiment, a resistance measurement of a heated wire or a conductive material is used as a temperature sensor for temperature control and energy optimization.

[0092] While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art. Elements of each embodiment may be incorporated into other embodiments, for example, configurations or components discussed in relation to one embodiment, may be applied to other embodiments disclosed herein. Further, it is evident that various modifications and combinations can be made without departing from the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.

Claims

1. A system for heating a heat exchanger, the system comprising:a heat exchanger configured to be placed inside a magnetic field created by a pair of electromagnetic coils;the electromagnetic coils configured to control a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils.

2. The system of claim 1, wherein a wire is attached in direct contact to the heat exchanger to increase heat generation by concentrating a high power signal in the wire at an outside surface of the wire.

3. The system of claim 1, wherein the aspect of the magnetic coupling includes at least one of: an amount of power of the magnetic coupling; an amplitude of the magnetic coupling; a frequency of the magnetic coupling; a phase of the magnetic coupling; and an alignment of the magnetic coupling.

4. The system of claim 1, wherein there is direct contact between wires of the electromagnetic coils and a surface of the heat exchanger.

5. The system of claim 1, wherein a layer of metallic paint is applied to a surface of the heat exchanger to improve heating of the heat exchanger.

6. The system of claim 5, wherein improving heating of the heat exchanger includes at least one of: improving a depth of an eddy current; improving a resistivity of an eddy current; and improving a magnetic permeability of an eddy current.

7. The system of claim 1, wherein a metal implant is inserted inside of the heat exchanger to improve heating of the heat exchanger.

8. The system of claim 7, further including applying a thin layer of an electrical insulator between the metal implant and the heat exchanger.

9. The system of claim 1, wherein a conductive layer is insulated by a layer of insulator and attached to the heat exchanger to improve heating of the heat exchanger.

10. The system of claim 1, wherein a resistance measurement of a heated wire or a conductive material is used as a temperature sensor for temperature control and energy optimization.

11. A method of heating a heat exchanger, the method comprising:placing the heat exchanger inside a magnetic field created by a pair of electromagnetic coils;controlling a surface temperature of the heat exchanger by varying an aspect of a magnetic coupling between the heat exchanger and the electromagnetic coils.

12. The method of claim 11, wherein a wire is attached in direct contact to the heat exchanger to increase heat generation by concentrating a high power signal in the wire at an outside surface of the wire.

13. The method of claim 11, wherein the aspect of the magnetic coupling includes at least one of: an amount of power of the magnetic coupling; an amplitude of the magnetic coupling; a frequency of the magnetic coupling; a phase of the magnetic coupling; and an alignment of the magnetic coupling.

14. The method of claim 11, wherein there is direct contact between wires of the electromagnetic coils and a surface of the heat exchanger.

15. The method of claim 11, wherein a layer of metallic paint is applied to a surface of the heat exchanger to improve heating of the heat exchanger.

16. The system of claim 15, wherein improving heating of the heat exchanger includes at least one of: improving a depth of an eddy current; improving a resistivity of an eddy current; and improving a magnetic permeability of an eddy current.

17. The method of claim 11, wherein a metal implant is inserted inside of the heat exchanger to improve heating of the heat exchanger.

18. The system of claim 17, further including applying a thin layer of an electrical insulator between the metal implant and the heat exchanger.

19. The method of claim 11, wherein a conductive layer is insulated by a layer of insulator and attached to the heat exchanger to improve heating of the heat exchanger.

20. The method of claim 11, wherein a resistance measurement of a heated wire or a conductive material is used as a temperature sensor for temperature control and energy optimization.

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