Patent Application
20150271908
1. Field of the Invention
This invention relates generally to electronic devices, and more particularly to structures and methods for providing thermal management of electronic devices.
2. Description of the Related Art
Conventional schemes for thermally managing components of electronic devices normally entail placing some form of heat spreader in thermal contact with the component in question. A conventional heat spreader is typically constructed of some type of thermally conducting material and is often accompanied by some form of convective heat transfer. Some devices rely on natural convection. Others use forced convection through the usage of cooling fans. In some devices, liquid cooling schemes are used wherein a heat spreader is placed in contact with a component and a heat transfer fluid is mechanically pumped in a circuit that includes the heat spreader and some form of chiller. The chiller may simply involve a cooling fan and plurality of heat fins that are located remotely from the thermally managed component, but more complex systems may utilize refrigeration units.
Common to these conventional schemes is the treatment of the dissipated heat as a waste product. Furthermore, convective heat transfer systems quite often must pass the heated air across other components which may increase the temperatures of those components. While ducting can eliminate some of the problems of heated air increasing the temperature of surrounding components, such ducting can still exhibit air leakage. In addition, conventional water and air systems rely on the specific heats of those fluids and are thus limited by the physics of specific heat.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.
In accordance with one aspect of the present invention, an apparatus is provided that includes a computing device that has at least one heat generating component. A first container is external to and in thermal contact with the at least one heat generating component and has a first volume of a phase change material.
In accordance with another aspect of the present invention, a method of thermally managing at least one heat generating component of a computing device is provided. The method includes placing a first container that has a first volume of a phase change material in thermal contact with the at least one heat generating component. The first container is external to the at least one heat generating component.
In accordance with another aspect of the present invention, a method of manufacturing is provided that includes placing a first volume of a phase change material in a first container. The first container is adapted to be external to at least one heat generating component of a computing device. The first container has at least one member adapted to establish thermal contact with the at least one heat generating component.
The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
One or more containers of a phase change material (PCM) are used to store heat generated by a heat generating component(s) of a computing device. The containers may be swapped with other containers of PCM as necessary. The stored heat may be used to generate electrical power that may be fed back to the computing device, some other device or sent to a storage device, such as a capacitive network. Additional details will now be described.
In the drawings described below, reference numerals are generally repeated where identical elements appear in more than one figure. Turning now to the drawings, and in particular to
The usage of a PCM container 105 to provide thermal management is not dependent on the functionalities of the computing device 100 or the heat generating components 110 and 115. Thus, the computing device 100 may be a computer, a digital television, a handheld mobile device, a personal computer, a server or virtually any type of electronic device that may benefit from thermal management. The heat generating components 110 and 115 may be microprocessors, graphics processors, combined microprocessor/graphics processors sometimes known as application processing units, application specific integrated circuits, memory devices, systems on a chip, optical devices, passive components, interposers, or other devices.
Thermal contact between the heat generating component 110 and the PCM container 105 may be provided by a member 117 coupled between those features 110 and 105. The member 117 may take on a variety of configurations. In an exemplary embodiment, the member 117 may include a heat spreader plate 120 seated on the component 110. The spreader plate 120 may be thermally connected to a frame or cradle 125 by way of one or more heat pipes, and in this case one heat pipe 130. The heat pipe 130 may be directly connected to the spreader plate 120 or by way of the disclosed coupling block 135. The heat generating component 115 may be similarly thermally connected to the frame 125 by way of a member 137, which includes a spreader plate 140 and a heat pipe 145 and an optional coupling block 150. The spreader plates 120 and 140, the connector blocks 135 and 150, as well as the heat pipes 130 and 145 may be constructed of well-known thermally conducting materials, such as copper, aluminum, nickel, stainless steel, brass, laminates of these or others. Somewhat more exotic materials, such as diamond or sapphire may be used for the spreader plates 120 and 140 where extreme temperatures are anticipated. The frame 125 is designed to removably receive the PCM container 105. Here the PCM container 105 is shown in section to reveal that the container 105 includes an outer shell 155 that holds a volume of a PCM 160. The frame 125 and shell 155 are advantageously constructed of a thermally conducting material such as those just described. Connections between items, such as the spreader plates 120 and 140, the heat pipes 130 and 145, the frame 125 and the blocks 135 and 150 may be by way of soldering, brazing, friction fits, mechanical fasteners or other techniques. Optionally, the members 117 and 137 may be constructed as unitary components, stamped, punched, machined, caste or otherwise constructed.
The computing device 100 may include a circuit board 165 (or multiple boards) upon which the heat generating components 110 and 115 may be mounted. The circuit board 165 may be populated with a variety of other components, which are not numerically labeled for simplicity of illustration, but which may include passive components, integrated circuits or virtually any other type of components used in electronics. The circuit board 165 may also include large numbers of conductor lines or traces, a couple of which are illustrated and labeled 170 and 175, respectively. The circuit board 165 may be a package substrate, a circuit card, a system board or virtually any other type of printed circuit board. The enclosure 103 may be composed of well-known plastics, metals or others, and take on a variety of shapes and sizes.
As heat is generated by the heat generating components 110 and 115, that heat is conveyed by way of the spreader plates 120 and 140 and the heat pipes 130 and 145 to the frame 125 and ultimately to the PCM 160. The PCM 160 will readily absorb and store heat while undergoing a change of physical phase, say from solid to liquid or from one solid phase to another. The heat can be released later during periods of reduced power consumption by the heat generating components 110 and 115. The PCM 160 and any alternatives thereof may be so-called solid-to-liquid phase materials or solid phase-to-solid phase materials. A large variety of different types of PCMs may be used. In general, there are three varieties of PCMs: (1) organic; (2) inorganic; and (3) eutectic. These categories may be further subdivided as follows:
A variety of characteristics are desirable for the material(s) selected for the PCM 160 and any alternatives. A non-exhaustive list of the types of desired PCM characteristics includes a melting temperature Tm less than but close to the maximum anticipated chip operating temperature Tmax, a high latent heat of fusion, a high specific heat, a high thermal conductivity, small volume change and congruent melting (for solid-to-liquid), high nucleation rate to avoid supercooling, chemical stability, low or non-corrosive, low or no toxicity, nonflammability, nonexplosive and low cost/high availability. Some of these characteristics may be favored over others for a given PCM. Table 2 below illustrates some exemplary materials for the PCM 160 and any alternatives.
It should be understood that the PCM container 105 may be swapped out upon reaching its thermal limit and another PCM container 185 may be swapped in and placed in the frame 125. The changing of PCM containers 105 and 185 may be performed by robotic machines 187 or by hand. The skilled artisan will appreciate that the PCM containers 105 and 185 as well as the frame 125 may take on a large variety of different structural configurations. Examples include flat plates, cylindrical shells, cylinders or virtually any other shape. The material point is that the containers 105 and 185 are able to hold a quantity of the PCM 160 and establish satisfactory thermal contact with whatever heat conveyance apparatus are used, such as the heat pipes 130 and 145, etc.
A variety of techniques may be used to establish whether or not the thermal capacity of a given PCM container, such as the container 105, has been exhausted. For example, the thermal capacity h105 of a given PCM container 105 in a computing device 100 may be modeled using a function:
h
105
=g(Htotal,Pmeasured,Q,γ,t) (1)
where htotal is the total heat absorption capacity of the PCM 160 in the container, Pmeasured is the measured power of the heat generating components 110 and 115, Q is conductive heat transfer rate of the thermal pathway, γ is a measure of the material characteristics of the PCM 160 and t is time. Depending on the capabilities of the computing device 100, the quantity Pmeasured can be determined with onboard circuitry and sensors or by way of external measurements. The quantity Q will be typically be given by:
Q=KΔT (2)
where K is the thermal conductivity K of the thermal pathway between the computing devices 110 and 115 and the PCM 160 and ΔT is the temperature difference between the those devices 110 and 115 and the PCM 160. The quantity γ may be based on, for example, the data in Table 2 above. The solution(s) to the Equation (1) may be determined using well-known numerical methods.
In the foregoing illustrative embodiment, the PCM containers 105 and 185 are positioned within a computing device enclosure 103. However, the skilled artisan will appreciate that it may be possible and indeed advantageous to position a PCM reservoir outside of the computing device enclosure. In this regard, attention is now turned to
An alternate exemplary embodiment of a computing device 300 may be understood by referring now to
In still another alternate exemplary embodiment of a computing device 400, shown in
An exemplary control loop utilizing any of the disclosed embodiments of a computing device and a PCM container may be understood by referring now to
While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
