Patent Application
20170328646
Embodiments described herein generally relate to a heat flux rectifier and, more specifically, to embodiments related to a heat pipe that provides unidirectional heat flux.
Many devices, such as electronic devices perform more optimally with a quick warm-up when started cold, but continue to operate more optimally the operation temperatures is within a predetermined range. These components include battery pack, engine, fuel cell stack, catalyst converter, to name a few. As a consequence, these types of devices often benefit from use of a device that may allow heat to flow in only one direction. As an example, some of these devices benefit from heat only being expelled from the device, while others may benefit from heat being absorbed by the device. Thus, a need exists in the industry.
Embodiments for a heat pipe heat flux rectifier are provided. One embodiment includes a first curved diode heat pipe that includes an adiabatic section that includes a curved portion, an evaporator section that is coupled to the adiabatic section, and a condenser section that is coupled to the adiabatic section. In some embodiments, the first curved diode heat pipe includes a non-condensable gas reservoir that is coupled to the condenser section for storing non-condensable gas, where the first curved diode heat pipe stores a fluid and a wicking material. In some embodiments, the first curved diode heat pipe operates as a thermal conductor when heat is applied to the evaporator section and as a thermal insulator when heat is applied to the condenser section.
In another embodiment, a first curved heat pipe includes an adiabatic section that includes a curved portion that defines a curve, an evaporator section that is coupled to the adiabatic section, a condenser section that is coupled to the adiabatic section, and a non-condensable gas reservoir that is coupled to the condenser section for storing non-condensable gas. In some embodiments, the first curved diode heat pipe stores a fluid and a wicking material. Similarly, some embodiments may be configured with the first curved diode heat pipe operating as a thermal conductor when heat is applied to the evaporator section.
In yet another embodiment, a heat pipe heat flux rectifier includes a first conductor layer and a first curved diode heat pipe. The curved diode heat pipe may include an adiabatic section that includes a curved portion, an evaporator section that is coupled to the adiabatic section and disposed in the first conductor layer, a condenser section that is coupled to the adiabatic section, and a non-condensable gas reservoir that is coupled to the condenser section for storing non-condensable gas. Additionally, the heat pipe heat flux rectifier may include a second curved diode heat pipe disposed in a substantially parallel configuration with the first curved diode heat pipe, where at least a portion of the second curved diode heat pipe is disposed within the first conductor layer. In some embodiments, the heat pipe heat flux rectifier operates as a thermal insulator when heat is applied to the first conductor layer.
These and additional features provided by the embodiments of the present disclosure will be more fully understood in view of the following detailed description, in conjunction with the drawings.
The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the disclosure. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
Embodiments disclosed herein include a heat pipe heat rectifier. Some embodiments are directed to a heat flux rectifier that includes a bended diode heat pipe. Accordingly, embodiments of the present disclosure apply a vapor trap from a diode heat pipe to develop a plane heat flux rectifier with thin profile. The heat flux rectifier may be configured to insulate heat at “low” temperature. In some embodiments, the heat flux rectifier dissipates heat at “high” temperature. Similarly, some embodiments are configured to provide a controlled boiling point. Embodiments may also provide high thermal conductivity from evaporator side to condenser side. Still some embodiments provide low thermal conductivity from condenser side to evaporator side. Embodiments providing the same will be described in more detail, below.
Referring now to the drawings,
Additionally, embodiments described herein may be configured to store a fluid within the curved diode heat pipe 100. Depending on the particular embodiment, the fluid may include water, coolant, and/or other material for providing the functionality described herein. Additionally, a non-condensable gas may be stored within the non-condensable gas reservoir 108. The non-condensable gas may include nitrogen, light hydrocarbons, carbon dioxide, and/or other non-condensable gaseous materials.
Within the evaporator section 102, the condenser section 104, and the adiabatic section 106 is a wicking material. The wicking material may be constructed of a high thermal-conductivity porous material for facilitating wicking of the fluid between the sections 102, 104, 106. In some embodiments, the wicking material may include a substantially uniform wick, while other embodiments may utilize different wicking materials or structures for each section. Regardless, the wicking material may include a porous media, such as monoporous wick, biporous wick, mono/biporous hybrid wick made of copper, graphite, etc., by using metal particle sintering process or by using copper inverse opal (CIO) technology, etc.
The heat flux rectifier 200 includes a plurality of different layers. A first conductor layer 210a and a second conductor layer 210b may be made of high-thermal conductivity material with the evaporator section 102 and the condenser section 104 of heat pipe being embedded therein. The high thermal conductivity material of the first conductor layer 210a and the second conductor layer 210b functions as heat spreader. A first insulator layer 210c is disposed between the first conductor layer 210a and the second conductor layer 210b and may be constructed of a thermal insulator to cut off the heat flow path between the first conductor layer 210a and the second conductor layer 210b. The first insulator layer 210c can be made of low thermal conductivity material or vacuumed chamber.
The first insulator layer 210c may be configured to ensure that most of the heat transfer between the first conductor layer 210a and the second conductor layer 210b is through the curved diode heat pipe 100. The adiabatic section 106 of the curved diode heat pipe 100 may be embedded in a second insulator layer 210d, which may be constructed of a low thermal conductivity material. The adiabatic section 106 may include an exterior material and a wicking material. The wicking structure of the adiabatic section 106 may be constructed of any material with low thermal conductivity that bonds to the condenser section 104 and evaporator section 102, which may both be constructed of materials with high thermal conductivity (e.g. copper, aluminum, silicon, silicon carbide, graphite, etc.). In some embodiments, the wicking structure of the adiabatic section 106 can be made of the same material as the wicking structures of the evaporator section 102 and/or the condenser section 104.
Since the heat flux rectifier 200 has a thin profile, it can be used as a cover of a device, only allowing heat to be dissipated from the device but shielding the external heat. Additionally, some embodiments may be coupled to a device to become a heat absorber, only allowing heat to enter, but not easy to be released. When the heat flux rectifier 200 is operating in forward mode, if the liquid in the wicking material of the evaporator section 102 is heated to the liquid boiling point, heat may be transferred from the evaporator section 102 to the condenser section 104. When the evaporator temperature is lower than the boiling point, heat is transferred through pure conduction. The evaporating temperature of the liquid can be tuned by controlling the partial vapor pressure (amount of non-condensable gas) inside the curved diode heat pipe 100 during the manufacturing. Additionally, different liquids can be used for different applications, as described above.
By tuning the boiling point of the liquid within the curved diode heat pipe 100 during manufacturing, a switch point may be set up. For example, if the pressure is tuned such that the liquid boils at 35 C, then in the forward mode, when the evaporator temperature is lower than 35 C, the curved diode heat pipe 100 still functions as a thermal insulator. When the curved diode heat pipe 100 is operating in forward mode and the evaporator temperature is higher than 35 C, the curved diode heat pipe 100 operates as a thermal conductor. This thermal switching function may be utilized for cold starting some systems. For example, if a battery pack is covered with the heat flux rectifier 200, then thermal energy can be stored within the battery pack overnight, so that the battery pack is still warm when the system is started the next morning. This thermal switch function may also be utilized for other systems (such as an engine) but the boiling point might be tuned to a higher or lower temperature, depending on the embodiment.
While the embodiments of
Similar to the heat flux rectifier 200 of
In operation, the heat flux rectifier 500 may react similarly as the heat flux rectifier 200 from
In the reverse mode, heat is applied to the condenser section 404. The non-condensable gas may leave the perpendicular non-condensable gas reservoir 408 into the condenser section 404. The non-condensable gas may thus act as a thermal insulator, thereby reducing the transfer of heat out of the heat flux rectifier 500.
As illustrated above, various embodiments heat pipe heat flux rectifier are disclosed. These embodiments may be configured to operate as a thermal diode and/or thermal switch. The thermal diode operates to transfer heat in one direction, but to act as a thermal insulator when heat is applied to anther side of the heat pipe heat flux rectifier.
While particular embodiments and aspects of the present disclosure have been illustrated and described herein, various other changes and modifications can be made without departing from the spirit and scope of the disclosure. Moreover, although various aspects have been described herein, such aspects need not be utilized in combination. Accordingly, it is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the embodiments shown and described herein. It should also be understood that these embodiments are merely exemplary and are not intended to limit the scope of this disclosure.
