Claims:WE CLAIM:
1. A method of evaluating the performance of Thermal Interface Material (TIM) using open circuit voltage of a Thermo-Electric Generator (TEG) (15), the method comprising:
measuring the open circuit voltage of the TEG (15) by a direct 5 current (DC) voltmeter (19); and
evaluating the performance of the TIM for ascertaining optimum value of thermal conductivity of the TIM based on the measured open circuit voltage of the TEG (15).
2. The method as claimed in claim 1, wherein based on the evaluation, the 10 TIM having a thermal conductivity of 0.6 W/mK is ascertained optimum for the TEG (15) up to operational temperature of 400 °C.
3. The method as claimed in claim 1, further comprising measuring contact pressure of interfaces using torque wrench at bolts and nuts (20) used in four corners of the TEG (15). 15
4. The method as claimed in claim 3, wherein parameters of the contact pressure remain unaffected when the TIM having optimum value of thermal conductivity is used in the interfaces for low surface roughness.
5. The method as claimed in claim 4, wherein the contact pressure of 500 kPa is measured for higher surface roughness of 6.14 µm. , Description:METHOD OF EVALUATING THE PERFORMANCE OF THERMAL INTERFACE MATERIAL
TECHNICAL FIELD
[0001] The present disclosure, in general, relates to enhance power output of 5 Thermo-Electric Generator (TEG) for waste heat recovery systems. Further, the present disclosure relates to ae method for evaluating the thermal interface effect for TEG application.
[0002] In particular, the present disclosure relates to a method of evaluating the performance of Thermal Interface Material (TIM) using open circuit voltage of a 10 Thermo-Electric Generator (TEG).
BACKGROUND
[0003] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information 15 provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0004] Thermo-Electric Generator (TEG) is a solid state device which requires thermal contact with hot source and heat sink. The performance of TEG depends upon the heat source temperature (hot side of TEG) and heat sink temperature (cold 20 side of TEG). In convention, thermally contacting surface experience a thermal resistance layer of air molecules which increases the thermal resistance. This resistance has a direct impact on power generation. Therefore, in order to reduce thermal resistance, a suitable Thermal Interface Material (TIM) parameter is to be identified to reduce the thermal resistance based on the selected operational 25 temperature of TEG. The application of TIM increases the heat transfer across the
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thermal contact layers. The TIM plays an important role in increasing the efficiency of the TEG system by maximizing the heat conduction between the source and the sink. Also, the alternate method is required to measure thermal resistance effect in TEG interfaces due to conventional method is not suitable.
[0005] Further, in US 9741636 ?1, a thermal interface material (TIM) using high 5 thermal conductivity nanoparticles, particularly one with large aspect ratios, for enhancing thermal transport across boundary or interfacial layers that exist at bulk material interfaces is disclosed. The nanoparticles do not need to be used in a fluid carrier or as filler material within a bonding adhesive to enhance thermal transport, but simply in a dry solid state. The nanoparticles may be equiaxed or acicular in 10 shape with large aspect ratios like nanorods and nanowires.
[0006] Thus, the patent US 9741636 ?1 is describing only about development of nano based thermal interface material for reducing thermal interface resistance.
OBJECTS OF THE DISCLOSURE 15
[0007] In view of the foregoing limitations inherent in the state of the art, some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0008] It is a general object of the present disclosure to optimize the influencing parameters of thermal interface material for Thermo-Electric Generator (TEG) 20 applications such as thermal conductivity of thermal interface material (TIM), contact pressure, surface roughness.
[0009] It is an object of the present disclosure to evaluate the performance of TIM using TEG modules is presented as the TEG module produces the output voltage as a function of temperature difference. 25
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[0010] It is an object of the present disclosure to propose an alternate method for assessing the thermal interface effect is evaluated for TEG application.
[0011] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a 5 preferred form of the present invention is illustrated.
SUMMARY
[0012] This summary is provided to introduce concepts related to a method of evaluating the performance of Thermal Interface Material (TIM) using open circuit 10 voltage of a Thermo-Electric Generator (TEG). The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0013] In an embodiment, the present disclosure relates to a method of evaluating 15 the performance of Thermal Interface Material (TIM) using open circuit voltage of a Thermo-Electric Generator (TEG). The method includes measuring the open circuit voltage of the TEG by a direct current (DC) voltmeter; and evaluating the performance of the TIM for ascertaining optimum value of thermal conductivity of the TIM based on the measured open circuit voltage of the TEG. 20
[0014] In an aspect, based on the evaluation, the TIM having a thermal conductivity of 0.6 W/mK is ascertained optimum for the TEG up to operational temperature of 400 °C.
[0015] In an aspect, the method further includes a step of measuring contact pressure of interfaces using torque wrench at bolts and nuts used in four corners of 25 the TEG.
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[0016] In an aspect, parameters of the contact pressure remain unaffected when the TIM having optimum value of thermal conductivity is used in the interfaces for low surface roughness.
[0017] In as aspect, the contact pressure of 500 kPa is measured for higher surface roughness of 6.14 µm. 5
[0018] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
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BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
[0019] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that 15 are consistent with the subject matter as claimed herein, wherein:
[0020] FIG. 1 illustrates a conventional method for measuring thermal interface resistance for central processing unit (CPU) and microelctronics heat sink application in accordance with the state of the art;
[0021] FIG. 2 illustrates an alternate method for measuring thermal interface 20 resistance for Thermo-Electric Generator TEG system in accordance with the state of the art;
[0022] FIG. 3 illustrates a front view of an apparatus for measuring thermal interface effect in TEG application, in accordance with an embodiment of the present disclosure; 25
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[0023] FIG. 4 illustrates a top view of apparatus for measuring thermal interface effect in TEG application, in accordance with an embodiment of the present disclosure; and
[0024] FIG. 5 illustrates a method of evaluating the performance of Thermal Interface Material (TIM) using open circuit voltage of a Thermo-Electric Generator 5 (TEG), in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0025] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should 10 be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. 15
[0026] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof. 20
[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, “consisting” and/or 25 “including” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition
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of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0028] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes 5 be executed in the reverse order, depending upon the functionality/acts involved.
[0029] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be 10 interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0030] Embodiments explained herein pertain to the effect of thermal interface material (TIM) present on hot and cold side of Thermo-Electric Generator (TEG) on 15 the performance of the thermoelectric system. The effect of contact pressure, surface roughness and thermal conductivity on the temperature drop in TIM were evaluated towards optimisation of each factor for TIM application. A TIM material having a thermal conductivity of 0.6 W/mK is found optimum for thermal system up to operational temperature of 400 °C. The application of TIM in the interface does not 20 affect the parameter of contact pressure when the optimized TIM is used in the interface for low surface roughness. However, the contact pressure of 500 kPa and optimized TIM are required for higher surface roughness of 6.14 µm. In addition, an alternate approach to evaluate the performance of TIM using TEG modules is developed as the TEG modules is a direct measure of the open circuit voltage instead 25 of TEG interface thermal resistance.
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[0031] Conventionally, the thermal interface resistance was evaluated to discuss about thermal interface effect for CPU and microelctronics heat sink application as shown in FIG. 1. The case of a single copper plate and two stacked copper plates. As per the conventional method for measuring TIM effect, the thermocouples (6 and 7) are placed in bottom copper plates (1) and top copper plates (2) to measure the 5 temperature drop (10) at interface (3) for evaluating thermal interface resistance as shown FIG. 2 and heat is supplied by heat source (4) and rejected by heat sink (5). Here the temperature of bottom (8) and top (9) of the interface (3) is to be measured. But the TEG system is having hot side thermal interface (14) and cold side thermal interface (15) at a thickness of approximately 4 mm and heat input (12) of TEG is not 10 equal to heat rejection (19) of TEG due to the generation of electrical power output. In addition, the thermocouples cannot be placed inside the TEG (15) to measure the temperature. Therefore, this invention relates an alternate method for assessing the thermal interface effect for TEG (15) application only. The TEG hot and cold side temperatures are strongly influnced by TEG thermal interface resistance. At the same 15 time, TEG voltage and electrical power output is dependent on temperature difference across the TEG. Hence, the performance of TIM is evaluated using TEG open circuit voltage (20) as shown in FIG. 3.
[0032] The present disclosure can be explained with the help of accompanying drawings in which FIG. 3 shows the evaluation of TIM using TEG open circuit 20 voltage. The holding plate (11) is used for holding the heat source (12) at a constant position. A heat spreader plate (13) is used for uniform heat distribution to TEG (15). The TIM for TEG hot side (14) is applied between the heat spreader plate (13) and TEG (15). The TIM for TEG cold side (16) is applied between TEG (15) and aluminium plate (17) and heat is rejected by using heat sink (18). The open circuit 25 voltage of TEG is measured by dc voltmeter (19). FIG. 3 and FIG. 4 show the bolts and nuts (20) used in all four corner of the set up for measuring contact pressure of
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interfaces by using torque wrench. In addition, the TIM parameter is to be optimised for TEG system in boiler application
[0033] The optimised value of thermal conductivity of thermal interface material is 0.6 W/mK up to operational temperature of 400 °C. The use of TIM lessens the thermal resistance at surface texture as convention air fills up the texture whereas 5 when TIM is applied, TIM fills up the surface texture. Thus, the thermal contact surface experience better connectivity and conductivity and thus improves the performance of TEG.
[0034] The application of TIM in the interface does not affect the parameter of contact pressure when the optimized TIM is used in the interface for low surface 10 roughness. However, a contact pressure of 500 kPa required for higher surface roughness of 6.14 µm. Thus, the contact pressure predominantly decreases the air gap at the macroscopical level, but on a microscopic level, the mating surface has still some air gaps which offers thermal resistance. This is reduced by application of TIM at the interface. 15
[0035] FIG. 5 illustrates example method 500 of evaluating the performance of Thermal Interface Material (TIM) using open circuit voltage of a Thermo-Electric Generator (TEG), in accordance with an embodiment of the present disclosure. The order in which the method 500 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any 20 order to implement the method 500, or an alternative method.
[0036] At block 502, the method 500 includes measuring the open circuit voltage of the TEG (15) by a direct current (DC) voltmeter (19).
[0037] At block 504, the method 500 includes evaluating the performance of the TIM for ascertaining optimum value of thermal conductivity of the TIM based on the 25 measured open circuit voltage of the TEG (15).
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[0038] In an aspect, based on the evaluation, the TIM having a thermal conductivity of 0.6 W/mK is ascertained optimum for the TEG (15) up to operational temperature of 400 °C.
[0039] In an aspect, the method further includes a step of measuring contact pressure of interfaces using torque wrench at bolts and nuts (20) used in four corners 5 of the TEG.
[0040] In an aspect, parameters of the contact pressure remain unaffected when the TIM having optimum value of thermal conductivity is used in the interfaces for low surface roughness.
[0041] In as aspect, the contact pressure of 500 kPa is measured for higher 10 surface roughness of 6.14 µm.
[0042] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In 15 other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0043] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the 20 group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims. 25
[0044] Furthermore, those skilled in the art can appreciate that the terminology used herein is for the purpose of describing particular embodiments only and is not
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intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of 5 the present disclosure as encompassed by the following claims.
[0045] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise 10 from applicants/patentees and others.
[0046] While the foregoing describes various embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof. The scope of the present disclosure is determined by the claims that follow. The present disclosure is not limited to the 15 described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
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