Showing papers on "Heat pipe published in 2007"

Led lamp with a heat sink assembly

Abstract: An LED lamp includes a heat absorbing member having a hollow, cylindrical configuration, a lamp base, a plurality of LED modules and a heat sink The heat absorbing member defines a through hole therein The heat sink is secured to a top portion of the heat absorbing member The lamp base is secured to a bottom portion of the heat absorbing member The LED modules are mounted on an outer sidewall of the heat absorbing member, and each of the LED modules includes a printed circuit board and a plurality of LEDs mounted on the printed circuit board Each of the heat pipes has an evaporating portion received in an inner sidewall of the heat absorbing member and a condensing portion connecting with the heat sink The condensing portions of the heat pipes are radially arranged on the heat sink, radiating outwardly from a central point of the heat sink

Liquid metal cooling in thermal management of computer chips

Abstract: With the rapid improvement of computer performance, tremendous heat generation in the chip becomes a major serious concern for thermal management. Meanwhile, CPU chips are becoming smaller and smaller with almost no room for the heat to escape. The total power-dissipation levels now reside on the order of 100 W with a peak power density of 400–500 W/cm2, and are still steadily climbing. As a result, it is extremely hard to attain higher performance and reliability. Because the conventional conduction and forcedair convection techniques are becoming incapable in providing adequate cooling for sophisticated electronic systems, new solutions such as liquid cooling, thermoelectric cooling, heat pipes, vapor chambers, etc. are being studied. Recently, it was realized that using a liquid metal or its alloys with a low melting point as coolant could significantly lower the chip temperature. This new generation heat transfer enhancement method raised many important fundamentals and practical issues to be solved. To accommodate to the coming endeavor in this area, this paper is dedicated to presenting an overall review on chip cooling using liquid metals or their alloys as coolant. Much more attention will be paid to the thermal properties of liquid metals with low melting points or their alloys and their potential applications in the chip cooling. Meanwhile, principles of several typical pumping methods such as mechanical, electromagnetic or peristaltic pumps will be illustrated. Some new advancement in making a liquid metal cooling device will be discussed. The liquid metal cooling is expected to open a new world for computer chip cooling because of its evident merits over traditional coolant.

High power LED lighting assembly incorporated with a heat dissipation module with heat pipe

Abstract: A high power light emitting diode (LED) lighting assembly incorporated with heat dissipation module is provided. The LED lighting assembly includes a heat exchange base, at least one LED array, at least one heat pipe and a heat dissipation module. The heat exchange base includes at least one LED configuration plan for mounting of the LED array and at least a hollow part for insertion of the heat pipe. The LED array is arranged at a predetermined projecting angle at the LED configuration plane. The heat pipe includes a heated section, a cooling section and a conducting section, and contains a working fluid therein. The heat exchange base is mounted to the heated section and the heat dissipation module is mounted to the cooling section. The thermal energy generated by the LEDs is conducted from the heat exchange base to the heated section of the heat pipe, whereby allowing the working fluid in the heat pipe to be heated and vaporized, and flows, from the conducting section to the cooling section for dissipation at the heat dissipation module.

Dynamic van der Waals theory.

Abstract: We present a dynamic van der Waals theory starting with entropy and energy functional with gradient contributions. The resultant hydrodynamic equations contain the stress arising from the density gradient. It provides a general scheme of two-phase hydrodynamics involving the gas-liquid transition in nonuniform temperature. Some complex hydrodynamic processes with evaporation and condensation are examined numerically. They are (i) adiabatically induced spinodal decomposition, (ii) piston effect with a bubble in liquid, (iii) temperature and velocity profiles around a droplet in heat flow, (iv) efficient latent heat transport at small liquid densities (the mechanism of heat pipes), (v) boiling in gravity with continuous bubble formation and rising, and (vi) spreading and evaporation of liquid on a heated boundary wall.

Integral ballast lamp thermal management method and apparatus

Abstract: A lamp having a lighting source, integral electronics, and a thermal distribution mechanism disposed in a housing. The thermal distribution mechanism may include a variety of insulative, radiative, conductive, and convective heat distribution techniques. For example, the lamp may include a thermal shield between the lighting source and the integral electronics. The lamp also may have a forced convection mechanism, such as an air-moving device, disposed adjacent the integral electronics. A heat pipe, a heat sink, or another conductive heat transfer member also may be disposed in thermal communication with one or more of the integral electronics. For example, the integral electronics may be mounted to a thermally conductive board. The housing itself also may be thermally conductive to conductively spread the heat and convect/radiate the heat away from the lamp.

LED lamp cooling apparatus with pulsating heat pipe

Abstract: An LED lamp cooling apparatus ( 10 ) includes a substrate ( 11 ), a plurality of LEDs ( 13 ) electrically connected with the substrate, a heat sink ( 19 ) for dissipation of heat generated by the LEDs and a pulsating heat pipe ( 15 ) thermally connected with the heat sink. The pulsating heat pipe includes a plurality of heat receiving portions ( 154 ) and a plurality of heat radiating portions ( 155 ), and contains a working fluid ( 153 ) therein. The substrate is attached to the heat receiving portions of the pulsating heat pipe and the heat sink is attached to the heat radiating portions of the pulsating heat pipe. The heat generated by the LEDs is transferred from the heat receiving portions to the heat radiating portions of the pulsating heat pipe through pulsation or oscillation of the working fluid in the pulsating heat pipe.

Miniature Loop Heat Pipe With Flat Evaporator for Cooling Computer CPU

Abstract: This paper presents an experimental investigation on a copper miniature loop heat pipe (mLHP) with a flat disk shaped evaporator, 30mm in diameter and 10-mm thick, designed for thermal control of computer microprocessors. Tests were conducted with water as the heat transfer fluid. The device was capable of transferring a heat load of 70W through a distance up to 150mm using 2-mm diameter transport lines. For a range of power applied to the evaporator, the system demonstrated very reliable startup and was able to achieve steady state without any symptoms of wick dry-out. Unlike cylindrical evaporators, flat evaporators are easy to attach to the heat source without need of any cylinder-to-plane reducer material at the interface and thus offer very low thermal resistance to the heat acquisition process. In the horizontal configuration, under air cooling, the minimum value for the mLHP thermal resistance is 0.17degC/W with the corresponding evaporator thermal resistance of 0.06degC/W. It is concluded from the outcomes of the current study that a mLHP with flat evaporator geometry can be effectively used for the thermal control of electronic equipment including notebooks with limited space and high heat flux chipsets. The results also confirm the superior heat transfer characteristics of the copper-water configuration in mLHPs

Heat transfer system and method for turbine engine using heat pipes

Abstract: A heat transfer system is provided for a turbine engine of the type including an annular casing (14) with an array of generally radially-extending strut members (20) disposed therein. The heat transfer system includes at least one primary heat pipe (36) disposed at least partially inside a selected one of the strut members (20); at least one secondary heat pipe (48) disposed outside the fan casing (14) and thermally coupled to at least one primary heat pipe (36) and to a heat source. Heat from the heat source can be transferred through the secondary heat pipe (48) to the primary heat pipe (36) and to the selected strut member (20).

Effect of nanoparticles in nanofluid on thermal performance in a miniature thermosyphon

Abstract: An experiment was performed to investigate the effect of nanoparticles in the nanofluid on the thermal performance in a miniature thermosyphon. The nanofluids consisted of de-ionized water and CuO nanoparticles having an average size of 30nm. The experimental results show that the water-CuO nanofluids can greatly enhance the boiling heat transfer performance of the evaporator in thermosyphon compared with that using water at subatmospheric pressure conditions. A much lower and more uniform wall temperature of the thermosyphon can be obtained by substituting the nanofluids for water. Boiling heat transfer coefficients and the critical heat flux (CHF) of the nanofluids in the evaporator of the thermosyphon have significant increase compared with those of de-ionized water. There was an optimal mass concentration which was estimated to be 1.0wt% to achieve the maximum heat transfer performance. Operating pressure has very remarkable influences on both the heat transfer coefficients and the CHF of nanofluids, ...

Heat dissipation device with a heat pipe

Abstract: A heat dissipation device includes a heat conducting base, a heat sink on the base and two heat pipes thermally contacting with the heat sink and the base. The heat sink is made of metal extrusion and includes a heat conducting cylinder at a periphery of the heat sink and a plurality of fins extending from and surrounded by the cylinder. The cylinder includes four interconnected sides. The fins of the same side are parallel to each other. The two heat pipes thermally surround the cylinder of the heat sink and wholly contact the heat sink.

Heat and Mass Transport in Heat Pipe Wick Structures

Abstract: temperature field,areobtainedfortheporouswicksundertheactionofadiscreteheatsource(evaporator)mounted on one end. The working fluid, supplied from a condenser pool, evaporates from the wick surface primarily in the evaporator region and is condensed and collected into a container separate from the pool, to yield mass flow rates. Thus the liquid-pumping capability of the wick, coupled with flow impedance, is measured as a function of applied heat flux.Repeatableresultswithlowuncertaintyareobtained.Acarefulanalysisofthetransportpathsforheatand masstransferin thewickstructure confirmsthatmasstransfer duetovaporization oftheworking fluidisthelargest contributor to heat dissipation from the wick. The expected and measured values of evaporation rate are in good agreement. Results are also presented in terms of overall effective conductance based on measured temperatures.

Three-dimensional numerical analysis of heat and mass transfer in heat pipes

Abstract: A three-dimensional finite-element numerical model is presented for simulation of the steady-state performance characteristics of heat pipes. The mass, momentum and energy conservation equations are solved for the liquid and vapor flow in the entire heat pipe domain. The calculated outer wall temperature profiles are in good agreement with the experimental data. The estimations of the liquid and vapor pressure distributions and velocity profiles are also presented and discussed. It is shown that the vapor flow field remains nearly symmetrical about the heat pipe centerline, even under a non-uniform heat load. The analytical method used to predict the heat pipe capillary limit is found to be conservative.

Experimental Investigation of Oscillating Motions in a Flat Plate Pulsating Heat Pipe

Abstract: An experimental study was conducted to evaluate the motion of vapor bubbles and liquid plugs within a flat plate pulsating heat pipe to determine the effects of working fluids (water, ethanol, Flutec PP2, and Flourinert), power input, filling ratio, and angle of orientation on the pulsating fluid flow. Experimental investigations quantify the position and velocity of the liquid-vapor interface for various conditions. Through the use of a Photron high speed camera, precise locations of the liquid-vapor interface were tracked and analyzed. Experimental data show that both the macromovement and oscillating motion of vapor bubbles and liquid plugs exist for a functional pulsating heat pipe. The amplitude of these oscillations was increased as more power was inputted into the pulsating heat pipe. The pulsating heat pipe investigated here would not function when charged with 50% high performance liquid chromatography grade water and positioned horizontally. On the other hand, the experimental results show that when the heat pipe was charged with ethanol, it created the largest amplitudes and velocities. The oscillating motion of vapor bubbles and liquid plugs including the macromovement is very sensitive to the tilted angle, and large increases in amplitude were observed when the angle was increased (bottom heating mode) from horizontal.

Thermal Applications of Cellular Lattice Structures

Abstract: Numerous methods have recently emerged for fabricating cellular lattice structures with unit cells that can be repeated to create 3D space filling systems with very high interconnected pore fractions. These lattice structures possess exceptional mechanical strength resulting in highly efficient load supporting systems when configured as the cores of sandwich panels. These same structures also provide interesting possibilities for cross flow heat exchange. In this scenario, heat is transported from a locally heated facesheet through the lattice structure by conduction and is dissipated by a cross flow that propagates through the low flow resistant pore passages. The combination of efficient thermal conduction along the lattice trusses and low flow resistance through the pore channels results in highly efficient cross flow heat exchange. Recent research is investigating the use of hollow truss structures that enable their simultaneous use as heat pipes which significantly increases the efficiency of heat transport through the lattice and their mechanical strength. The relationships between heat transfer, frictional flow losses and topology of the lattice structure are discussed and opportunities for future developments identified.

Battery cooling system for vehicle

Abstract: PROBLEM TO BE SOLVED: To provide a battery cooling system for a vehicle having excellent cooling efficiency while suppressing noise. SOLUTION: This battery cooling system comprises a battery 2 mounted on a vehicle and used for travelling, a heat pipe heat-absorbing part 3 installed closely to the side of a battery case 1b in which the battery 3 is contained and absorbing heat by a refrigerant flowing therein, a heat pipe heat-dissipating part 4 installed on the outside of a cabin and dissipating heat by the refrigerant flowing therein, and connection parts 6, 7 for connecting the heat pipe heat-absorbing part 3 to the heat pipe heat-dissipating part 4 so that the refrigerant can be circulated therein. A heat pipe in which the refrigerant is circulated due to the condensation and evaporation of the refrigerant is formed of the heat pipe heat-absorbing part 3, the heat pipe heat-dissipating part 4, and the connection parts 6, 7. COPYRIGHT: (C)2008,JPO&INPIT

Cooling Concepts for High Power Density Magnetic Devices

Abstract: In the area of power electronics there is a general trend to higher power densities. In order to increase the power density the systems must be designed optimally concerning topology, semiconductor selection, etc. and the volume of the components must be decreased. The decreasing volume comes along with a reduced surface for cooling. Consequently, new cooling methods are required. In the paper an indirect air cooling system for magnetic devices which combines the transformer with a heat sink and a heat transfer component is presented. Moreover, an analytic approach for calculating the temperature distribution is derived and validated by measurements. Based on these equations a transformer with an indirect air cooling system is designed for a 10 kW telecom power supply.

Exhaust heat recovery system

Abstract: An exhaust heat recovery system (18) includes first and second loop heat pipes (20 and 30). The first loop heat pipe (20) recovers exhaust heat downstream of a catalyst (5) in an exhaust passage (4) of an internal combustion engine (1) to exchange heat with the catalyst (5). The second loop heat pipe (30) recovers heat of the catalyst (5) to exchange heat with coolant that is once delivered from the internal combustion engine (1).

Investigation of dry machining with embedded heat pipe cooling by finite element analysis and experiments.

Abstract: This paper investigates the performance of a cutting tool embedded with a heat pipe on reducing cutting temperature and wear in machining. The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as the tool life in machining. A new embedded heat pipe technology has been developed to effectively remove the heat generated at the tool–chip interface in machining, thereby, reducing tool wear and prolonging tool life. In particular, the technique can effectively minimize pollution and contamination of the environment caused by cutting fluids, and the health problems of skin exposure and particulate inhalation in manufacturing. The ANSYS finite element analysis simulations show that the temperature near the cutting edge drops significantly with an embedded heat pipe during machining. Temperature measurements at several locations on the cutting tool insert agree with the simulation results both with and without the heat pipe. Experiments were carried out to characterize the temperature distributions when performing turning experiments using a cutting tool installed with an embedded heat pipe. The performance of the heat pipe on reducing the cutting tool temperature was further supported by the observations of cutting tool material color, chip color, and the chip radius of curvature.