Showing papers on "Heat pipe published in 2003"

Electrosurgery with cooled electrodes

Abstract: A cooled electrosurgical system includes an electrosurgical device having at least one electrode for applying electrical energy to tissue. In one embodiment, the electrode includes an internal cavity in which a cooling medium such as water is contained. The internal cavity is closed at both ends of the device such that the cooling medium is contained within the electrode at the surgical site such that the cooling medium does not contact the tissue being treated. The electrosurgical device has an electrode and a heat pipe to conduct heat from the electrodes where substantially all heat conducted from the electrode through the heat pipe is dissipated along the length of the heat pipe. The heat pipe can have a thermal time constant less than 60 seconds and preferably less than 30 seconds.

Vapor escape microchannel heat exchanger

Abstract: A vapor escape membrane for use in a heat exchanging device, including a heat pipe or heat sink that runs liquid into a cooling region positioned adjacent to the heat producing device, the vapor escape membrane comprising: a porous surface for removing vapor produced from the liquid in the cooling region, the membrane configured to confine the liquid only within the cooling region. The vapor escape membrane transfers vapor to a vapor region within the heat exchanging device, wherein the membrane is configured to prevent liquid in the cooling region from entering the vapor region. The membrane is configured to include a hydrophobic surface between the membrane and the cooling region, wherein the liquid in the cooling region does not flow through the porous surface. The vapor escape membrane includes a plurality of apertures for allowing vapor to transfer therethrough, each of the apertures having a predetermined dimension.

Evaporation Heat Transfer in Sintered Porous Media

Abstract: A two-dimensional model is presented to predict the overall heat transfer capability for a sintered wick structure. The model considers the absence of bulk fluid at the top surface of the wick, heat conduction resistance through the wick, capillary limitation, and the onset of nucleate boiling. The numerical results show that thin film evaporation occurring only at the top surface of a wick plays an important role in the enhancement of evaporating heat transfer and depends on the thin film evaporation, the particle size, the porosity, and the wick structure thickness. By decreasing the average particle radius, the evaporation heat transfer coefficient can be enhanced. Additionally, there exists an optimum characteristic thickness for maximum heat removal. The maximum superheat allowable for thin film evaporation at the top surface of a wick is presented to be a function of the particle radius, wick porosity, wick structure thickness, and effective thermal conductivity. In order to verify the theoretical analysis, an experimental system was established, and a comparison with the theoretical prediction conducted. Results of the investigation will assist in optimizing the heat transfer performance of sintered porous media in heat pipes and better understanding of thin film evaporation.

Automotive lighting assembly cooling system

Abstract: An automotive lighting assembly cooling system includes a heat pipe with an evaporation area proximate to a heat generating component, such as a Light Emitting Diode (LED), and a condensing area located remote from the evaporation area. Evaporation of fluid within the heat pipe transfers heat away from the heat generating component. The efficiency of the cooling system in one embodiment is increased by including fins associated with the condensing area and placing the fins in an area where air flow external to a moving vehicle assists in cooling the fins.

Thermofluid dynamic study of flat-plate closed-loop pulsating heat pipes

Abstract: Meandering-tube pulsating heat pipes (PHPs) have already found some applications in cooling power/microelectronic components. Reliable experimental data for PHPs is very limited, especially in the wake of the ongoing miniaturization process and efforts to combine electronic components and heat spreaders on the chip level. In fact, the basic operation of PHPs is far from being fully understood, and there are no available design tools for given microelectronics cooling requirements. A logical next step for further applications of PHPs in microelectronics cooling is to design integral structures, i.e., PHPs as an integral part of thermal spreader/substrates, having typical dimensions as applicable for multichip modules or printed circuit boards (PCBs). In this article, experimental results for flat-plate, closed-loop PHP structures (rectangular and circular, Dhyd ≈ 2.0 mm) which are integrally machined into an aluminum substrate (115 × 36 × 3 mm3) and covered by a glass plate for visualization are presented....

Thermal management system and method for electronics system

Abstract: A thermal energy management system is provided having a heat spreading device that is operatively engaged with at least one semiconductor chip and a thermal bus operatively engaged with the heat spreading device so as to transport thermal energy from the heat spreading device to a heat sink. The heat spreading device includes a heat pipe and the thermal bus includes a loop thermosyphon. A second thermal bus may be operatively engaged with the first thermal bus so as to transport thermal energy from the first thermal bus to a heat sink. The second thermal bus may also include a loop thermosyphon. A method of managing thermal energy in an electronic system is also provided that includes spreading thermal energy generated by one or more devices over a surface that is relatively larger than the devices, thermally coupling an evaporator portion of a loop thermosyphon to the surface, and thermally coupling a condensing portion of the loop thermosyphon to a thermal energy sink, e.g., a second loop thermosyphon, convection fin, or cold plate.

Heat conversion system

Abstract: An energy conversion system is provided for converting heat energy from a variety of heat sources to electric power for operating electrical appliances. The system may be incorporated in a power on demand pilot system of a gas operated equipment to provide the sole electric power for operating the equipment. Thermoelectric modules provide the basic transducer for converting the heat energy to electric power and a heat pipe is employed for conducting the heat energy from a heat source to the conversion system.

Fabrication and experimental investigation of silicon micro heat pipes for cooling electronics

Abstract: An experimental investigation was conducted to determine the thermal behaviour of micro heat pipe (MHP) arrays micromachined in silicon wafers. Two types of MHP arrays were tested, one with triangular channels, 230 μm wide, 170 μm deep, and the other with triangular channels, 500 μm wide, 340 μm deep, coupled with arteries. Both types of arrays were fabricated using an anisotropic etching process. Once fabricated, a plain Si wafer was used to seal the pipe array hermetically. Two working fluids were tested, ethanol and methanol. A polysilicon heater was used to supply the heat input, and cooling water flowing through the condenser was used as a heat sink. Fill charges from 0% up to 66% were tested. The axial temperature variation along the length of the pipe was measured using T-type thermocouples connected to a data acquisition system. The effective thermal conductivity was evaluated using the experimental temperature profiles and 3D thermal modelling. The results show a maximum improvement of 300% in effective thermal conductivity at high heat flux, which demonstrates enhanced heat transfer in a prototype with liquid arteries.

Method and apparatus for high heat flux heat transfer

Abstract: The subject invention pertains to a method and apparatus for high heat flux heat transfer. The subject invention can be utilized to transfer heat from a heat source to a coolant such that the transferred heat can be effectively transported to another location. Examples of heat sources from which heat can be transferred from include, for example, fluids and surfaces. The coolant to which the heat is transferred can be sprayed onto a surface which is in thermal contact with the heat source, such that the coolant sprayed onto the surface in thermal contact with the heat absorbs heat from the surface and carries the absorbed heat away as the coolant leaves the surface. The surface can be, for example, the surface of an interface plate in thermal contact with the heat source or a surface integral with the heat source. The coolant sprayed onto the surface can initially be a liquid and remain a liquid after absorbing the heat, or can in part or in whole be converted to a gas or vapor after absorbing the heat. The coolant can be sprayed onto the surface, for example, as a stream of liquid after being atomized, or in other ways which allow the coolant to contact the surface and absorb heat. Once the heat is absorbed by the coolant, the coolant can be transported to another location so as to transport the absorbed heat as well.

Heat pipe having a wick structure containing phase change materials

Abstract: A wick for use in a heat pipe is provided incorporating particles of micro-encapsulated phase change material bonded together to form the wick. Use of a wick structure comprising micro-encapsulated PCM particles has the advantage of providing an additional heat absorber. This greatly enhances the ability of the heat pipe to absorb excess heat and may help to prevent damage to the heat pipe or heat generating component, such as an electronic device, especially at times of peak thermal loads.

Heat dissipation tower for circuit devices

Abstract: A heat transfer device such as a heat sink has one or more heat pipe tubes mounted in a base plate. The heat pipe tubes have a working fluid in a vessel with a wicking material between an evaporator and condenser. The heat pipe traverses a through opening in the base plate and extends along a receptacle in the base plate facing the heat source, this portion preferably defining the heat pipe evaporator. The heat pipe has legs extending perpendicularly from the base plate, and preferably hold spaced heat transfer fins, the legs forming the condenser part of a stacked tower of fins on the base plate. Preferably two or more heat pipes are provided in the form of U-shaped or L-shaped tubes that are flattened along the underside of the base plate to bear against the heat source.

Heat dissipation apparatus

Abstract: A heat dissipation apparatus is described The heat dissipation apparatus is used in an electrical product, and especially in a notebook computer The heat dissipation apparatus has two cooling fans, at least one heat pipe, and at least two heat dissipation fins The first fan sucks cooling air from outside of the electrical product The heat pipe coupling with a heat source transfers heat generated by the heat source to the heat dissipation fins The first heat dissipation fin and the first fan remove part of the heat out of the electrical product The second heat dissipation fin further connects with the heat source and the heat pipe to utilize the second fan to remove part of the heat exhausted by the first fan from the electrical product The heat dissipation apparatus further comprises a third heat dissipation fin and a second heat pipe The second heat pipe efficiently transfers the heat to each of the heat dissipation fins The third heat dissipation fin is positioned in an outlet of the second fan to exchange heat again and thus enhance the heat dissipation efficiency

Thin sheet type heat pipe

Abstract: The present invention has proposed a thin sheet type heat pipe comprising: a hermetically sealed container which is formed of foil sheets opposed and jointed at peripheral portions; at least one spacer which is movably housed in said container and has a fluid path to exert a capillary force; at least one spacer which is movably housed in said container and has no fluid path; and a working fluid enclosed in said container.

Electronic thermal management

Abstract: Piezoelectric fan assemblies are provided to provide a conduction path and forced convection for space-limited electronic devices in accordance with embodiments of the present invention. The fan blade of a piezoelectric fan is thermally coupled to the heat source, such as, but not limited to, the fins of a heat sink, the condenser of the heat pipe, and to the thermal mass of a heat spreader or block. The high amplitude resonant vibration of the fan blade causes formation of a high velocity unidirectional flow stream. Maximum airflow occurs on axes of the piezoelectric fan's centerline, relative to both width and height dimensions. Air intake is above and below the swept out plane of the fan blade. The air flow provides forced convection for the fan blade and, secondarily, for the heat source.

Energy efficient sorption processes and systems

Abstract: The present invention relates to novel energy efficient sorption processes and systems for cooling, dehumidifying and heating using multistage liquid desiccant regenerators, or hybrid cooling systems or adsorption cooling systems involving appropriate combinations of rotating contacting devises, adsorption modules with heat transfer passages in thermal contact with the adsorption module wall and switchable heat pipes. The sorption processes of this invention help in flexible designing of compact cooling, dehumidifing, heating systems easy operability. The adsorption module of this invention leads to lower cycle times as low as 5 minutes; makes it possible to achieve high system Coefficient of Performance (COP) up to 0.9 due to reduced thermal mass; offers high specific cooling power in the range of 50 to 750 W/kg of AC; is easy to manufacture and operates at low costs. The refrigeration cum heating system of this invention with heat pipe in thermal contact with the adsorption modules increase the heat transfer rates without increasing the thermal mass leading to increase of COP and the single or multistage pressure equalisation increases the internal regeneration of heat thereby increasing the COP, reducing the cycle time resulting in increased specific cooling power (SCP), reducing the required quantity of adsorbent/refrigerant making the module compact and cost effective.

Improvement on thermal performance of a disk-shaped miniature heat pipe with nanofluid

Abstract: The present study used nanofluid as the working medium for a disk-shaped miniature heat pipe (DMHP) The nanofluid is a suspension with gold nanoparticles of an average diameter of 17 nm in an aqueous solution An experimental system was set up to measure the thermal resistance of the disk-shaped miniature heat pipe (DMHP) with both nanofluid and DI-water A mounting base is designed and integrated with the DMHP as a heat spreader for a laser diode TO can package The present mounting base is made of aluminum (6061 T6) The measured results show that the thermal resistance of the DMHP varies with the charge volume and the type of working medium At the same charge volume, a significant reduction in the thermal resistance of the DMHP can be found if nanofluid is used instead of DI-water

Silicon heat pipes used as thermal spreaders

Abstract: An increase in power densities in electronic devices is a direct consequence of their miniaturization and performance improvements. We propose the use of flat miniature heat pipes with micro capillary grooves to spread heat flux across a heat sink. Models of the structure were developed to calculate heat transfer limitations and temperature drops. A brass/water prototype was fabricated to demonstrate the feasibility of heat spreading using this type of heat pipe. Simulation and experimental results obtained with the prototype are described. The dissipated power reached 110 W/cm/sup 2/ without heat transfer limitations. The results are then extended to the design of this type of heat pipe in silicon. Thermal performance was calculated. Simulation, experimental results and the fabrication process are presented.

Miniature Loop Heat Pipes for Electronic Cooling

Abstract: Thermal management of modern electronics has become a problem of significant interest due to the demand for power and reduction in packaging size. Requirements of next-generation microprocessors in terms of power dissipation and heat flux will certainly outgrow the capability of today’s thermal control technology. LHPs, like conventional heat pipes, are capillary pumped heat transport devices. They contain no mechanical moving part to wear out or require electrical power to operate. But unlike heat pipes, LHPs possess much higher heat transport capabilities enabling them to transport large amounts of heat over long distances in small flexible lines for heat rejection. In fact, a miniature ammonia LHP developed for a NASA space program is capable of transporting 60W over a distance of 1 meter in 1/16”O.D. stainless steel tubing. Therefore, miniature LHPs using water as the working fluid are excellent candidates to replace heat pipes as heat transports in electronic cooling systems. However, a number of operational issues regarding system performance, cost, and integration/packaging must be resolved before water LHPs can become a viable option for commercial electronics.Copyright © 2003 by ASME

Integrated heat dissipation apparatus

Abstract: An integrated heat dissipation apparatus, having a first heat dissipating element, a second heat dissipating element, a thermal conductive heat sink and at least one L-shape heat pipe. The thermal conductive heat sink has a connecting surface and a thermal conductive surface opposing the connecting surface. The first heat dissipating element is mounted on the thermal conductive surface. A plurality of thermal conductors with thermal conductivity larger than that of the thermal conductive heat sink are mounted to the connecting surface. The L-shape heat pipe has two ends, including one end serial connecting to the second heat dissipating element, and the other end extending to connect with the thermal conductors on the thermal conductive heat sink.

Cooling system for electronics with improved thermal interface

Abstract: A heat pipe system including a heat transfer block and a heat pipe coupled to the heat transfer block by a clip By utilizing a clip to couple the heat pipe to the heat transfer block, a higher degree of thermal coupling may be achieved, thereby allowing more heat to be transferred from the heat transfer block to the heat pipe The heat pipe system has particular application in transferring heat away from heat-producing electronic components, such as computer chips

Magnetocaloric refrigeration device

Abstract: A magnetocaloric refrigeration device, placed in a controllable magnetic field, includes a heat release/absorption module. The heat release/absorption module includes a magnetocaloric working unit and at least one heat pipe. The magnetocaloric working unit is made of a magnetocaloric material. The temperature of the unit changes as the magnetic field is applied or removed. The heat pipe includes evaporation and condensation portions respectively extending from top and bottom of the magnetocaloric working unit. When a magnetic field is applied to the magnetocaloric working unit to absorb heat, the lower condensation portion of the heat pipe transfers heat upward to the magnetocaloric working unit. When the magnetic field is removed from the magnetocaloric working unit to release heat, the heat from the magnetocaloric working unit is transferred to the outside through the upper heat release portion. The magnetocaloric refrigeration device has advantages of simple structure, low production cost, and small size.