Showing papers on "Heat pipe published in 2002"

System for monitoring health, wellness and fitness having a method and apparatus for improved measurement of heat flow

Abstract: Means and methods for measuring heat flux between a living body and an ambient atmosphere and for generating information related thereto. Means include a heat pipe configuration comprising at least one heat conduit in thermal communication with a heat flux sensor and a surface of a living body. Methods include employing such a heat pipe configuration. Heat pipe configuration may be used in a device included in a system for detecting, monitoring and reporting human physiological information.

Reversible quantum Brownian heat engines for electrons

Abstract: Brownian heat engines use local temperature gradients in asymmetric potentials to move particles against an external force. The energy efficiency of such machines is generally limited by irreversible heat flow carried by particles that make contact with different heat baths. Here we show that, by using a suitably chosen energy filter, electrons can be transferred reversibly between reservoirs that have different temperatures and electrochemical potentials. We apply this result to propose heat engines based on mesoscopic semiconductor ratchets, which can quasistatically operate arbitrarily close to Carnot efficiency.

Analysis of heat transfer in unlooped and looped pulsating heat pipes

Abstract: An advanced heat transfer model for both unlooped and looped Pulsating Heat Pipes (PHPs) with multiple liquid slugs and vapor plugs has been developed. The thin film evaporation and condensation models have been incorporated with the model to predict the behavior of vapor plugs and liquid slugs in the PHP. The results show that heat transfer in both looped and unlooped PHPs is due mainly to the exchange of sensible heat. Higher surface tension results in a slight increase in the total heat transfer. The diameter, heating wall temperature, and charging ratio have significant effects on the performance of the PHP. Total heat transfer significantly decreased with a decrease in the heating wall temperature. Increasing the diameter of the tube resulted in higher total heat transfer. The results also showed that the PHP could not operate for higher charge ratios.

Thermal management of microelectronic equipment : heat transfer theory, analysis methods, and design practices

Abstract: With this systematic examination of the factors that govern the thermal performance of electronics, the authors solve design problems encountered in developing and analyzing very-high-performance and high-heat-dissipation devices, as well as intermediate and lower-power devices. They explore a wide range of heat transfer technologies and consider their options when employing several different heat transfer modes simultaneously in a system. This important reference provides: Data and correlation's for the analysis and design of electronic equipment; Latest updates on thermal control technology; Review of the fundamentals of heat transfer; Approaches to solving real-world problems of vast complexity. While emphasizing the physics of each subject, the book keeps high-level mathematics to a minimum. Two chapters on conduction and extended surfaces deal with the fundamentals of various heat transfer modes; the other fifteen chapters focus on specific subjects of practical importance to the design of electronic systems. The nine appendices provide useful material, such as property tables for solids and sixteen types of fluids, as well as a comprehensive catalog of topics in connective heat transfer that includes heat transfer correlation's for various physical configurations and thermal boundary conditions. Contents: Introduction; Conduction; Convection; Radiation; Pool Boiling; Flow Boiling; Condensation; Extended Surfaces; Thermal Interface Resistance; Components and Printed Circuit Boards; Direct Air Cooling and Fans; Natural and Mixed Convection; Heat Exchangers and Cold Plates; Advanced Cooling Technologies; Heat Pipes; Thermoelectric Coolers. Appendices: Material Thermal Properties; Thermal Conductivity of Silicon and Gallium Arsenide; Properties of Air, Water, and Dielectric Fluids; Typical Emissivities of Common Surfaces; Properties of Phase-Change Materials; Friction Factor Correlation's; Heat Transfer Correlation's; Units Conversion Table.

Heat sink with heat pipes and fan

Abstract: A heat sink provides efficient heat transfer from a heat-producing semiconductor device. Heat pipes project from a spreader plate in contact with the device and distribute heat to multiple cooling fins. The fins are arranged for maximum contact with the ambient air. An active fan is internally disposed within the fins, for further cooling efficiency. The heat sink may be permanently affixed to a printed circuit board holding the semiconductor device or the heat sink may be attached and released thereto without need of tools. A base plate maintains spring-like compliance of the printed circuit board while allowing sufficient clamping force on the heat sink to sustain thermal contact with the heat-producing surface during shock-loading.

Investigation of heat pipe cooling in drilling applications. Part I: preliminary numerical analysis and verification

Abstract: A combined numerical and experimental study is performed to analyze the feasibility of using heat pipe cooling in drilling applications. A parametric study is conducted to analyze the effect of different geometrical parameters expected for a heat pipe drill configuration, such as depth of the heat pipe within the drill, heat pipe diameter, heat flux input magnitude and length of the heat input zone. In this model, it is assumed that the drill is subjected to a static heat source which verifies the analysis and feasibility of using heat pipe cooling in drilling operations. The performance of the heat pipe drill model is approximated using a solid cylinder model of pure conduction. To validate the assumptions, numerical results are compared with experimental data that are based on the solid cylinder model. Both the numerical and experimental studies show that the use of a heat pipe in a drill can reduce the temperature field significantly. The results of this study can be used to define geometrical parameters for ‘optimal’ design and the setup for further analysis.

Oscillatory Flow in Pulsating Heat Pipes with Arbitrary Numbers of Turns

Abstract: Oscillatory flow in pulsating heat pipes (PHPs) with arbitrary numbers of turns is investigated numerically. The PHP is placed vertically with the evaporator sections at the top and the condenser sections at the bottom. The governing equations, obtained by analysis of the conservation of mass, momentum, and energy of the liquid and vapor plugs, are nondimensionalized, and the problem is described by eight nondimensional parameters. The numerical solution is obtained by employment of an implicit scheme. The effects of the number of turns, length of the heating and cooling sections, and charge ratio on the performance of the PHP were also investigated.

Biomass heating system

Abstract: Improved systems, methods, apparatus and compositions for generating, extracting and distributing the renewable heat energy produced by microbial decomposition of organic biomass within a contained and controlled environment. This heat energy is preferably transferred and distributed, preferably by the use of heat pipes, to the interior of a greenhouse or other structure to be heated, either directly or via heat exchange apparatus such as hot water heating systems. In one embodiment heat transfer and distribution mechanism customized to the application requirements of a greenhouse heating batch-type process is disclosed, along with a recipe for a readily available biomass material composition that will slowly decompose while it generates a substantial quantity of usable heat energy to be consumed in the elevation of temperature in a separated greenhouse basement confinement area. Additional continuous and batch process embodiments of biomass heating systems are also disclosed that extract heat energy from decomposing biomass for heating uses. In some embodiments gaseous products generated in a biological decomposition process, primarily CO 2 , are utilized to enhance plant growth in the greenhouse environment.

Heat pipe and method for processing the same

Abstract: A heat pipe comprising a flat container, and a member selected from a rod, a plate and a mesh, the member being fixedly arranged between narrow walls of the container so that space is provided in the inner circumference of the container both in the direction of width and length of the container.

Spreading in the heat sink base: phase change systems or solid metals??

Abstract: Presently, the microelectronics industry needs thermal solutions that are able to dissipate high heat fluxes at low thermal resistance. The majority of original equipment manufacturers (OEMs) within the microelectronics industry would like to achieve this by extending the application of air-cooling technologies since it implies minimal impact to the design of computer systems and is known to be a cost effective solution space. Spreading resistance through the base of the heat sink is one major component of the total thermal resistance from the silicon junction to the local ambient, especially if larger volume heat sinks are to be used. Until now, most of the research has focused on using phase change systems (i.e., vapor chambers) for reducing the spreading resistance of the heat sink base. Since no significant improvements have been achieved, there is a need to determine the envelope of the limitations for phase change-heat spreaders used in processor cooling, and to compare their performance against high thermal conductivity solid metals. Two simple models are presented to address the heat transfer limitations in phase change systems. Using these models, the ratio of phase change spreading resistance over solid metal spreading can be estimated.

Method of action of the pulsating heat pipe, its construction and the devices on its base

Abstract: By construction of heat pipes with two phase heat carrying fluid, an efficient heat transfer system is available. The heating section is used to create, within the heat pipe, build up of vapor pressure which causes the heat carrying fluid to move which then allows for dissipations of the heat into the cooling section. Additions to the system allow for storage of kinetic energy to enhance or regulate the flow, and by introduction of heating elements or porous surfaces, the mechanic can be improved or regulated.

High performance cold plate

Abstract: A cold plate assembly for cooling a heat source is disclosed. The cold plate assembly includes a thermally conductive base having an inner surface for thermally interfacing with the heat source. Machining, casting, or molding a contour to interface with the heat source forms the base. Heat pipe thermal plane or individual heat pipes are selected to conform to the thermal cooling capacity of the cold plate assembly. One or two compact heat exchangers are selected to remove the heat conducted through the base to the cooling liquid is used in the compact heat exchanger. The three modules are bonded together to form the cold plate assembly.

Fabrication of star grooves and rhombus grooves micro heat pipe

Abstract: With the development of miniaturized and high power electronic devices in recent years, electronic heat dissipating apparatus has become important. The concept of micro heat pipe (MHP) was first proposed in 1984 with the application background of electronic cooling. Since that time, numerous theoretical analyses and experimental tests were proposed, and the cross section of the MHP is either rectangular or triangular. But the capillarity of these grooves is low and restricts heat transfer limitation. In this study, star grooves MHP and rhombus grooves MHP were fabricated. Heat transfer performance of the MHP was enhanced due to better capillarity provided by more acute angles and micro gaps. Star grooves MHP and rhombus grooves MHP were fabricated by bulk micro machining on 4 inch (100) silicon wafers. Finally, the MHP structure was bonded by employing eutectic bonding technique. Testing has been conducted to evaluate the performance over a range of working fluid volumes and heat fluxes. We glue the heater on the evaporator section of the heat pipe, infuse cold water through a copper pipe in the condenser section and paste K-type thermocouples on the MHP in the direction of the length. Then we join the thermocouples to a data acquisition system and adopt Fourier's law to calculate effective thermal conductivity. The best thermal conductivities of star grooves MHP and rhombus grooves MHP are 277.9 W m−1K−1 and 289.4 W m−1K−1, respectively.

Thermal module with temporary heat storage

Abstract: A thermal module with temporary heat storage. The thermal module includes a heat storage, a heat absorber, a heat dissipater, and a heat pipe for rapidly transferring heat from the heat absorber to the heat dissipater. The heat storage includes a phase change material and is in contact with the heat pipe. When heat quantities generated by the system are greater than a predefined reasonable thermal target, heat in excess of the thermal target is temporarily absorbed into the heat storage through the melting of the PCM. When the heat quantities generated by the system are again less than the thermal target, the PCM re-freezes, releasing the stored heat to be dissipated normally.

Heat dissipation structure for electronic apparatus component

Abstract: A computer microprocessor has a housing portion with a recess formed in a top side wall thereof, and a die portion inset within the recess. Operating heat from the die is removed by heat dissipation apparatus which automatically adapts to variations in the microprocessor bond line thickness and includes a sheet metal EMI shield wall overlying the microprocessor and having a condensing end portion of a thermosyphoning heat pipe secured to its bottom side, with an evaporating end portion of the heat pipe overlying the die recess and being resiliently deflectable toward a phase change thermal pad mounted on the top side of the die and inset into the housing die recess. A metal heat sink member is rotatably mounted on the heat pipe evaporating end portion and has a flat bottom side and an arcuate top side. The heat sink member is resiliently deflected into the die recess, and has its flat bottom side resiliently pressed against the thermal interface pad, by a spring plate portion of a clamping structure downwardly engaging the arcuate top side of the heat sink member. During operation of the microprocessor, die heat is transferred to the metal shield wall sequentially through the thermal pad, the heat sink member, and the heat pipe and then dissipated from the shield wall using fan-generated cooling air flowed along the shield wall.

Stacked low profile cooling system and method for making same

Abstract: A stacked array of low profile heat pipes each with a plurality of micro tubes extended therethrough. The stacked low profile heat pipes are placed into thermal connection with heat producing components. A heat transfer fluid is contained in the micro tubes of the low profile heat pipes and removes the heat from the heat producing components.

Heat pipe hinge structure for electronic device

Abstract: A heat pipe hinge structure for an electronic device comprises a heat pipe hinge member and a hinge portion. The heat pipe hinge member is made of a high heat-conductive material disposed at a coupling portion in which a pair of housing portions to be opened and closed are coupled. The heat pipe hinge member comprises a heat pipe hinge main body to receive a heat from a heat generating component disposed in one of the pair of housing portions, and a heat pipe holding portion provided in a vicinity of the heat pipe hinge main body to pivotably hold by an elastic member at least a part of a first heat pipe disposed in other of the pair of housing portions. The hinge portion is made of a low heat-conductive material to fox the heat pipe hinge member on at least one housing portion of the pair of housing portions.

Light weight rigid flat heat pipe utilizing copper foil container laminated to heat treated aluminum plates for structural stability

Abstract: A very thin flat plate shaped sintered copper powder wick with a waffle pattern on one surface is sealed between two sheets of thin copper foil The interior space within the sealed foil is evacuated and charged with sufficient water to saturate the wick through a copper tube which is then hermetically sealed, producing the working core of a flat plate heat pipe Heat treated aluminum plates are bonded with thin, thermally conductive adhesive layers to both the evaporator and condenser surfaces of the copper foil heat pipe container The resulting flat heat pipe is lighter in weight by about 40%, much more durable, and less expensive to fabricate than all-copper, machined container flat plate heat pipes, while high performance is maintained