VARIABLE THERMAL RESISTANCE MOUNTING SYSTEM
A variable-thermal-resistance mounting system may include a cylinder coupled to a heat source, or heat load and a rod movably engaged to the cylinder and coupled to a remaining one of the heat source and heat load. The rod may be coupled to a heat load. The rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load such that the warm-side temperature of the heat load is initially set at a substantially optimal value.
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The present application claims priority to pending U.S. Provisional Application No. 61/728,233 filed on Nov. 19, 2013, and entitled VARIABLE THERMAL RESISTANCE MOUNTING SYSTEM, the entire contents of which is expressly incorporated herein by reference.
FIELDThe present disclosure relates generally to mounting systems for thermal platforms and, more particularly, to systems for optimizing heat flow to a heat load such as a thermoelectric generator.
BACKGROUNDThermoelectric energy harvesting systems such as thermoelectric generators convert thermal energy into electrical energy in response to a thermal gradient across the thermoelectric generator. The thermal gradient may occur as a result of heat flow from a heat source that is thermally coupled to one side of the thermoelectric generator to a heat sink that is thermally coupled to the other side of the thermoelectric generator. The thermoelectric generator may have an optimal temperature or an optimal temperature range within which the thermoelectric generator operates at maximum efficiency. The thermoelectric generator may be coupled to electronic components for conditioning the voltage produced by the thermoelectric generator prior to delivery to a device (e.g., a sensor) to be powered by the thermoelectric generator.
Electronic components typically have a maximum rated temperature up to which the electronic components may operate on a nominal basis. Approaching the maximum rated temperature of the electronic components may result in a reduction in the performance of the electronic components. Exceeding the maximum rated temperature of the electronic components may result in damage or failure of the electronic components. A failure of the electronic components may compromise the capability of the thermoelectric generator to power the device.
A thermoelectric generator may be installed in an environment where the temperature of the heat source fluctuates. For example, the thermoelectric generator may be thermally coupled to the surface of a heated pipe in an industrial facility. Process variations may result in fluctuations in the surface temperature of the heated pipe such that heat flow to the thermoelectric generator may fall outside of the range for maximum operating efficiency of the thermoelectric generator. Heat flow from the heated pipe may also result in exceeding the maximum rated temperature of the electronic components that may be coupled to the thermoelectric generator.
As can be seen, there exists a need in the art for a system and method for adjusting heat flow from a heat source such that the thermoelectric generator may operate at maximum efficiency and is thermally protected from overheating. In addition, there exists a need in the art for a system and method for adjusting heat flow from a heat source such that electronic components are maintained below their maximum rated temperature and are therefore thermally protected from overheating, and also such that the electronic components may operate at maximum efficiency.
SUMMARYThe above-described needs associated with adjusting heat flow from a heat source are specifically addressed and alleviated by the present disclosure which, in an embodiment, provides a variable-thermal-resistance mounting system. The variable-thermal-resistance mounting system may include a cylinder coupled to a heat source or a heat load. The heat source may have an optimal warm-side temperature. The variable-thermal-resistance mounting system also may include a rod movably engaged to the cylinder. The rod may be coupled to the remaining one of the heat source or heat load. The rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load in a manner such that the warm-side temperature of the heat load is set at a substantially optimal value.
In a further embodiment, disclosed is a variable-thermal-resistance mounting system including a cylinder and a rod movably engaged to the cylinder. A heat source may be mounted to an end of the cylinder. The rod may be coupled to a thermoelectric generator which may be mounted on an end of the rod. The thermoelectric generator may have an optimal warm-side temperature. The rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in thermal resistance between the heat source and the thermoelectric generator in a manner such that the warm-side temperature of the thermoelectric generator is initially set at a substantially optimal value.
Also disclosed is a method of regulating heat flow between a heat source and a heat load. The method may include coupling a rod to one of a heat source and a heat load, and coupling a cylinder to a remaining one of the heat source and the heat load. The method may additionally include axially moving the rod relative to the cylinder between a collapsed position and an extended position. Furthermore, the method may include changing a heat flow between the heat source and the heat load in response to moving the rod between the collapsed position and the extended position, and adjusting a warm-side temperature of the heat load in response to changing the heat flow.
The features, functions and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings below.
These and other features of the present disclosure will become more apparent upon reference to the drawings wherein like numbers refer to like parts throughout and wherein:
Referring now to the drawings wherein the showings are for purposes of illustrating various embodiments of the present disclosure, shown in
The thermal device 102 or heat load 106 may comprise any type of device having a desired or predetermined warm-side temperature 114 or warm-side temperature range. The heat load 106 may also have a maximum temperature such as a maximum operating temperature. For example, the thermal device 102 may include one or more temperature-sensitive components 108 such as a sensor, an imaging device, or any device having a maximum rated operating temperature. In an embodiment, the thermal device 102 may be a thermoelectric generator 110. The thermoelectric generator 110 may have an optimal temperature range within which the thermoelectric generator operates at maximum efficiency. For example, the thermoelectric generator 110 may have an optimal warm-side temperature 114 similar to the TWarm temperture of the thermal load (designated by RLoad) in the schematic diagram of
The thermoelectric generator 110 may be coupled to electronic components 112 such as conditioning electronics for conditioning the voltage produced by the thermoelectric generator 110 prior to delivery to a device (e.g., a sensor) to be powered by the thermoelectric generator 110. The efficiency of the conditioning electronics may be at a maximum at an optimal voltage generated by the thermoelectric generator 110. Due to the dependency of the thermoelectric voltage on the temperature gradient across the thermoelectric generator 110, the generated voltage may change if the temperature of the heat source 100 changes resulting in reduced conversion efficiency. In this regard, initially setting or maintaining a substantially constant optimal temperature on one side (e.g., the warm-side temperature 114) of the thermoelectric generator 110 may ensure maximum operating efficiency of the conditioning electronics (e.g., electronic components 112) for conditioning the voltage produced by the thermoelectric generator 110.
Advantageously, any one of the presently-disclosed embodiments of the variable-thermal-resistance mounting system 130 operates to adjust heat flow from a heat source 100 such that the thermoelectric generator 110 may operate at maximum efficiency by maintaining the warm-side temperature 114 at a substantially constant value or within a temperature range. In addition, the variable-thermal-resistance mounting system 130 may adjust heat flow in a manner such that the thermal load is thermally protected from overheating. In addition, the variable-thermal-resistance mounting system 130 operates to adjust heat flow from a heat source 100 such that electronic components 112 are maintained below their maximum rated temperature and are therefore thermally protected from overheating, and may operate at maximum efficiency.
Referring briefly to
Refering to
The thermal device 102 may include a thermal platform 104. The thermal platform 104 may provide a stable mechanical support for coupling the heat load 106 (e.g., thermoelectric generator) to the thermal interface 134 comprising a rod 140 slidably coupled to a cylinder 136 as described below. In addition, the thermal platform 104 may have a larger cross-sectional area than the rod 140 to distribute the heat from the rod and spread out the heat across the cross sectional area of the heat load 106 and thereby avoid temperature concentrations in localized areas of the heat load 106. In an embodiment, the thermal platform 104 may be comprised of one or more layers of materials each having individual predetermined thermal conductivity values and selected geometries (e.g., cross-sectional geometry and thicknesses). The thermal conductivity values and the geometry (e.g., thicknesses) of the one or more layers of the thermal platform 104 may be selected to provide a desired temperature range for the thermal device 102 or heat load 106. In this manner, selection of the materials for the thermal platform 104 may provide a means for tuning the system to provide a desired amount of heat to the thermal device 102 (e.g., heat load 106) within an optimum temperature range. For example, the thermal platform 104 may include one more metallic or non-metallic layers such as at least one layer of aluminum having a relatively high thermal conductivity of approximately 230 Watts/meter-Kelvin as a high end of range. On the opposite end of the thermal conductivity spectrum, the thermal platform 104 may include at least one layer of polytetrafluoroethylene (Teflon™) having a relatively low thermal conductivity of approximately 0.25 Watts/meter-Kelvin which is approximately 100 times lower than the thermal conductivity of aluminum. The thermal platform 104 may include other layers of material to provide a relatively narrow working range for the warm-side temperature of the heat load 106. In some embodiments, the thermal platform 104 may be comprised of two metallic layers having an insulting layer sandwiched therebetween. The metallic layers may provide mechanical stability to the connection of the heat load 160 to the rod 140. The thermal platform 104 may assist in spreading the heat from the rod 140 and thereby provide substantially uniform heat flow into the cross-sectional area of the thermal device 102 or heat load 106. The heat load 106 may be coupled to the thermal platform 104 using mechanical fasteners and/or adhesive or other means.
In an embodiment, the thermal device 102 may comprise an energy harvesting system such as a thermoelectric generator 110 as illustrated in
As indicated above, the variable-thermal-resistance mounting system 130 may include a thermal interface 134 comprising a rod 140 that may be slidably coupled to a generally hollow cylinder 136. The cylinder 136 may be mechanically coupled at one end to the heat source 100 via a mechanical mount 132. The mechanical mount 132 may be fastened to the cylinder 136 such as by using mechanical fasteners. The torque of the mechanical thrusters may influence the heat transfer capability between the heat source 100 and the mechanical mount 132. The mechanical mount 132 may include an arrangement of one or more materials that may be selected in consideration of the temperature range of the heat source 100 such that a desired temperature range is provided at the location where the cylinder 136 is mechanically coupled to the mechanical mount 132. In this regard, the materials of the mechanical mount 132 may be selected to provide a desired level of thermal resistance between the heat source 100 and the cylinder 136 similar to that which is described above with regard to the thermal platform 104. A heat shield 158 may be provided between the thermal device 102 and the heat source 100 to minimize radiative heat transfer to the thermal device 102. The heat shield 158 may be formed of relatively thin-gauge metal or non-metallic material and may be provided in a size that is larger (e.g., wider) than the thermal device 102 (e.g. heat load 106) and/or other components (e.g., temperature-sensitive electronics) that may be mounted adjacent to the heat load 106.
In
In certain embodiments (e.g.,
In
In some embodiments, the variable-thermal-resistance mounting system 130 may operate in a manner such that a relatively small increase in heat source 100 temperature will result in a relatively small increase in the cylinder fluid 172 temperature causing a correspondingly small extension length 156 of the rod 140 out of the cylinder 136 and a relatively small increase in thermal resistance to heat flow from the heat source 100 to the heat load 106. Conversely, a relatively large increase in the heat source 100 temperature may result in a relatively large increase in the cylinder fluid 172 temperature causing a correspondingly large extension length 156 of the rod 140 out of the cylinder 136 and a relatively large increase in thermal resistance to heat flow from the heat source 100 to the heat load 106.
As shown in
As indicated above, an increase in the extension length 156 of the rod 140 may result in a reduction in the heat resistance of the thermal interface 134 between the rod 140 and the cylinder 136. A reduction in heat resistance may result in a decrease in heat flow from the heat source 100 to the thermal device 102 and may protect heat load 106 components from over-temperature. The bellows fluid 194 may contract when cooled which may result in the bellows 192 decreasing in length and the rod 140 retracting into the cylinder 136 as shown in
Advantageously, in an embodiment, the bellows 192 may also provide structural support to the thermal device 102 on an exterior of the cylinder 136. In this regard, the bellows 192 may mechanically stabilize the connection between the thermal device 102 and the cylinder 136. The bellows material, the bellows geometry, and the bellows fluid 194 may also provide for a wide range of adjustability for altering the thermal resistance of the variable-thermal-resistance mounting system 130. The bellows fluid 194 may be provided as a liquid that boils at a predetermined temperature to increase the bellows fluid pressure 196 and cause displacement of the rod 140. Alternatively, the bellows fluid 194 may comprise an inert gas. The mechanical mount 132, the rod 140, the cylinder 136, the bellows fluid 194, and the thermal platform 104 may be selected to provide a relatively narrow working temperature range at the heat load 106.
Although not shown, the bellows 192 may be replaced with a bi-metallic spring/lever for axially displacing or extending the rod 140 out of the cylinder 136. In an embodiment, the bi-metallic spring may be comprised of two components (e.g., two different metals) fastened together and having different coefficients of thermal expansion. Heat flow from the heat source 100 may be thermally transferred along the cylinder 136 and/or rod 140 and into the bi-metallic spring result in mechanical displacement (e.g., curvature) of the bi-metallic spring due to the differences in coefficients of thermal expansion and causing the heat load 106 to be moved the axially away from the heat source 100 and thereby increasing the thermal resistance to heat flow from the heat source 100 to the head load.
In
In some embodiments disclosed herein, the arrangement of the rod 140 and cylinder 136 may be configured such that the rod 140 is connected to the heat source 100 and the cylinder 136 is connected to the thermal device 102 (e.g., heat load 106, thermoelectric generator 110, etc.). For example, in contrast to the embodiment of
Although each of the embodiments is described as having a single rod 140 sliding within a single cylinder 136, the mounting system may be provided with two or more rods 140 arranged in parallel and sliding within two or more cylinders 136. In any one of the above described embodiments, a temperature-indicating device such as a strip may be provided on an exterior of the cylinder 136 or the thermal device 102 to provide an indication of the temperature of the system. For example, a liquid crystal strip may be mounted on an exterior of the thermal platform 104 of the heat load 106 or on an exterior of a thermoelectric generator 110. The strip may change color corresponding to changes in temperature and may provide a visual indication to an observer as to whether the thermal platform 104 is in the desired temperature range.
Referring to
Step 304 of the method 300 may include axially moving the rod 140 relative to the cylinder 136 between a collapsed position 152 and an extended position 154 as shown in
Step 306 of the method 300 may include changing a heat flow between the heat source 100 and the heat load 106 in response to moving the rod 140 between the collapsed position 152 and the extended position 154. For example, when the rod 140 is extended out of the cylinder 136, the change (e.g., decrease) in contact surface area 144 may result in altering (e.g., decreasing) heat flow between the heat source 100 and the heat load 106 as a means to at least initially set or adjust the warm-side temperature 114 of the heat load 106. In some embodiments, the method 300 may optionally include mounting a heat shield 158 (
Step 308 of the method 300 may include adjusting the warm-side temperature 114 of the heat load 106 in response to changing the heat flow. In some examples, the warm-side temperature 114 may be initially adjusted to a substantially optimal value which, in the present disclosure, may be described as within a relatively small range of the optimal value. In some embodiments, the warm-side temperature 114 may be initially adjusted by manually pulling the rod 140 out of the cylinder 136 to a position that initially results in substantially achieving the optimal warm-side temperature 140 or relatively small range based on a given temperature of the heat source 100. If the heat source temperature changes, then further adjustment of the position of the rod 140 may be required to accordingly adjust the warm-side temperature 114. In an embodiment, the method may include clamping or fixing the position of the rod 140 relative to the cylinder 136 after the warm-side temperature 114 has been adjusted. For example, the rod 140 may be clamped to the cylinder 136 such as by using a mechanical clamp 146, an embodiment of which is shown in
In some embodiments, the variable-thermal-resistance mounting system 130 may be operated in a passive manner without manually or actively displacing (e.g., manually or actively pulling) the rod 140 axially outwardly from the cylinder 136 or manually or actively (e.g., with a motor—
The method 300 of varying the thermal resistance between a heat load 106 and a heat source 100 may also be implemented in a passive manner using a variable-thermal-resistance mounting system 130 having a bellows 192 containing a bellows fluid 194. The bellows 192 may be mounted between the heat load 106 and the cylinder 136 as shown in
In some embodiments, the bellows 192 may be thermally isolated from the rod 140 in a manner such that the heat flow from the heat source 100 may be conducted along the cylinder 136 and directly into the bellows fluid 194 as shown in
In some embodiments, the variable-thermal-resistance mounting system 130 may be actively operated to vary the thermal resistance between the heat source 100 and heat load 106. For example, in the embodiment shown in
In some embodiments, the method 300 may include mounting the heat load 106 within a chimney 230 as shown in
Additional modifications and improvements of the present disclosure may be apparent to those of ordinary skill in the art. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present disclosure and is not intended to serve as limitations of alternative embodiments or devices within the spirit and scope of the disclosure.
Claims
1. A variable-thermal-resistance mounting system, comprising:
- a cylinder coupled to one of a heat source and a heat load, the heat load having an optimal warm-side temperature;
- a rod movably engaged to the cylinder and being coupled to a remaining one of the heat source and heat load; and
- the rod being axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load such that the warm-side temperature of the heat load is initially set at a substantially optimal value.
2. The system of claim 1, wherein:
- the rod extending out of the cylinder by an extension length when the rod is in an extended position;
- the cylinder has a cylinder inner surface;
- the rod having a rod outer surface in contact with the cylinder inner surface along a contact surface area; and
- the contact surface area increasing and decreasing in correspondence with a respective increase and decrease in the extension length.
3. The system of claim 1, wherein:
- the heat load comprises a thermoelectric generator.
4. The system of claim 1, further comprising:
- a mechanical clamp configured to axially lock an axial position of the rod relative to the cylinder.
5. The system of claim 1, further comprising:
- a mechanical mount coupling the heat source to the rod or the cylinder and being formed of material providing a desired level of thermal resistance between the heat source and the cylinder or rod.
6. The system of claim 1, further comprising:
- a thermal platform coupling the heat load to the rod or the cylinder; and
- the thermal platform being formed of one or more thermal materials having a predetermined thermal conductivity and geometry selected to provide a desired operating temperature range of the heat load.
7. The system of claim 1, wherein:
- the cylinder contains a cylinder fluid that expands when heated causing an increase in pressure within the cylinder; and
- the increasing cylinder pressure extending the rod out of the cylinder causing an increase in a thermal resistance between the rod and cylinder and a reduction in the heat flow between the heat source and the heat load.
8. The system of claim 1, further comprising:
- a bellows located between the heat load and the cylinder, the bellows containing a bellows fluid that expands when heated causing the bellows to increase in length; and
- the increase in bellows length causing extension of the rod and a reduction in heat flow between the heat source and the heat load.
9. The system of claim 8, wherein:
- the bellows fluid contracts upon cooling causing the bellows to decrease in length; and
- the decrease in bellows length resulting in retraction of the rod and an increase in heat flow between the heat source and the heat load.
10. The system of claim 1, wherein:
- the cylinder and the rod each include at least two segmented contacts in axially slidable engagement with one another; and
- the segmented contacts being sized and configured such that axial movement of the rod causes a change in thermal resistance of the cylinder and rod.
11. The system of claim 10, wherein:
- the cylinder and rod each have at least two segmented contacts axially spaced from one another and of substantially equal length such that axial movement of the rod causes a linear change in thermal resistance of the cylinder and rod.
12. The system of claim 10, wherein:
- the cylinder and rod each have at least two segmented contacts axially spaced from one another and of unequal length such that axial movement of the rod causes a non-linear change in thermal resistance of the cylinder and rod.
13. The system of claim 1, wherein:
- a motor coupled to the rod and actively controlling axial displacement of the rod relative to the cylinder for adjusting a thermal resistance between the rod and the cylinder.
14. A variable-thermal-resistance mounting system, comprising:
- a cylinder coupled to a heat source;
- a rod movably engaged to the cylinder and being coupled to a thermoelectric generator having an optimal warm-side temperature; and
- the rod being axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in thermal resistance between the heat source and the thermoelectric generator such that the warm-side temperature of the thermoelectric generator is initially set at a substantially optimal value.
15. A method of regulating heat flow between a heat source and a heat load, comprising the steps of:
- coupling a rod to one of a heat source and a heat load, and coupling a cylinder to a remaining one of the heat source and the heat load;
- axially moving the rod relative to the cylinder between a collapsed position and an extended position;
- changing a heat flow between the heat source and the heat load in response to moving the rod between the collapsed position and the extended position; and
- adjusting a warm-side temperature of the heat load in response to changing the heat flow.
16. The method of claim 15, wherein the cylinder has a cylinder inner surface, the rod has a rod outer surface slidably engaged to the cylinder inner surface along a contact surface area, the method further comprising:
- extending the rod out of the cylinder;
- changing the contact surface area in correspondence with extending the rod; and
- altering the heat flow between the heat source and heat load in response to changing the contact surface area.
17. The method of claim 15, wherein the cylinder contains a cylinder fluid, the method further comprising:
- heating the cylinder fluid with heat from the heat source;
- expanding the cylinder fluid when heated causing an increase in pressure within the cylinder;
- extending the rod out of the cylinder in response to the increasing cylinder pressure;
- increasing a thermal resistance between the rod and cylinder in response to pushing the rod; and
- reducing the heat flow between the heat source and the heat load in response to increasing the thermal resistance.
18. The method of claim 15, wherein a bellows is mounted between the heat load and the cylinder, the bellows containing a bellows fluid, the method further comprising:
- heating the bellows fluid with heat from the heat source;
- expanding the bellows fluid when heated causing the bellows to increase in length;
- extending the rod at least partially out of the cylinder in response to increasing a bellows length;
- increasing a thermal resistance between the rod and cylinder in response to extending the rod; and
- reducing the heat flow between the heat source and the heat load in response to increasing the thermal resistance.
19. The method of claim 18, further comprising:
- allowing the bellows fluid to cool;
- contracting the bellows fluid upon cooling resulting in the bellows decreasing in length;
- retracting the rod at least partially into the cylinder in response to decreasing the bellows length;
- decreasing a thermal resistance in response to retracting the rod; and
- increasing the heat flow between the heat source and the heat load in response to decreasing the thermal resistance.
20. The method of claim 15, wherein the cylinder and the rod each include at least two axially-spaced segmented contacts of substantially equal length and in axially slidable engagement with one another, the method further comprising;
- axially moving the rod relative to the cylinder; and
- linearly changing a thermal resistance of the cylinder and rod in response to axially moving the rod.
21. The method of claim 15, wherein the cylinder and the rod each include at least two axially-spaced segmented contacts of unequal length and in axially slidable engagement with one another, the method further comprising;
- axially moving the rod relative to the cylinder; and
- non-linearly changing a thermal resistance of the cylinder and rod in response to axially moving the rod.
Type: Application
Filed: Nov 19, 2013
Publication Date: May 22, 2014
Applicant: Perpetua Power Source Technologies, Inc. (Corvallis, OR)
Inventors: Mark J. Hauck (Corvallis, OR), Ingo Stark (Corvallis, OR), Paul McClelland (Monmouth, OR)
Application Number: 14/084,587
International Classification: F28F 9/007 (20060101); F25B 21/02 (20060101);