Showing papers on "Electronics cooling published in 2000"

Assessment of high-heat-flux thermal management schemes

Abstract: This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, micro-channel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of individual applications, system considerations always play a paramount role in determining the most suitable cooling scheme. It is also shown that extensive fundamental electronic cooling knowledge has been amassed over the past two decades. Yet there is now a growing need for hardware innovations rather than perturbations to those fundamental studies. An example of these innovations is the cooling of military avionics, where research findings from the electronic cooling literature have made possible the development of a new generation of cooling hardware which promise order of magnitude increases in heat dissipation compared to today's cutting edge avionics cooling schemes.

Application of thermoelectric cooling to electronic equipment: a review and analysis

Abstract: This paper provides a review of thermoelectric cooling and its application to the cooling of electronic equipment. A background discussion of thermoelectric cooling is provided briefly citing early history, current developments, and the defining thermoelectric heat pumping equations. Several examples are provided of early IBM applications of thermoelectric cooling. An analysis to assess thermoelectric cooling enhancement in terms of increases in allowable power dissipation or chip temperature reduction is described along with results.

Fundamental investigation of roll bond heat pipe as heat spreader plate for notebook computers

Abstract: A roll bond heat pipe (RBHP) is very promising in the cooling of electronic equipment such as notebook computers. This study presents prediction data on maximum capillary limit obtained for the RBHP with 7.8 mm wide flow channel. Further, experimental study has been conducted to show the difference between the highest and lowest temperatures on the RBHP. These data determine the optimum working fluid charge volume and number of capillary loops for the RBHP.

Cabinet cooling with heat pipe

Abstract: An electronics cooling system in accordance with the principles of the present invention includes an electronics cabinet that is thermally connected with the ground in the vicinity of the cabinet. The cabinet may or may not sit directly on the earth, but the thermal connection is made with the earth below, and in the near vicinity of, the cabinet, thereby employing the earth as a heat sink. In an illustrative embodiment, an enclosed cabinet includes a heat pipe that makes thermal contact with the ground in the immediate vicinity of the electronics cabinet. An electronics cabinet in accordance with the principles of the present invention is particularly suited for use in uncontrolled environments, such as may be encountered by remote telecommunications switches and wireless telecommunications equipment, for example.

Heat-pipes for electronic devices and evaluation of their thermal performance

Abstract: This paper reports on the performance of miniature heat-pipes developed for cooling of electronic equipment, and on evaluating the notebook computer cooling systems in which they are used. Experiments for the miniature heat-pipe were conducted on their thermal properties and reliability. The results indicate the miniature heat-pipe can be applied to electronic equipment cooling. Evaluating tests of the cooling system using this miniature heat-pipe have clarified the effectiveness of the miniature heat-pipe.

Single chamber compact thermosyphons with micro-fabricated components

Abstract: This study presents the thermal performance evaluation of a compact single-chamber thermosyphon. The thermosyphon set-up has a central evaporator section with integrated fins for cooling along the edges. The evaporator employs a microfabricated three-dimensional copper structure for enhancing boiling heat transfer. The thermal performance of the system was characterized at various power levels and condenser cooling conditions. The size of the boiling enhancement structure and effects of liquid fill volumes on performance were also investigated. Incorporation of the enhancement structure resulted in an improvement in the thermosyphon performance by decreasing the wall temperature at the evaporator by 8/spl deg/C, for a power dissipation of 36 W/cm/sup 2/ at an air speed of 1 m/s. The maximum heat flux obtained based on a maximum evaporator temperature of 75/spl deg/C for an air speed of 1 m/s was 42.5 W/cm/sup 2/. Variation in the liquid fill volume showed negligible effect on the maximum temperature at the evaporator, as long as the enhanced structure was fully flooded. Increasing the footprint size of the enhancement structure showed marginal improvement in boiling heat transfer performance. This increased the number of pores in the enhancement structures and did not result in a corresponding increase in the performance.

Rapid design of heat sinks for electronic cooling using computational and experimental tools

Abstract: Design of electronic cooling systems for high volume manufacturing within the time frame of months for increasingly aggressive performance and cost requirements is difficult without the use of sophisticated computational and experimental tools. Described here are the tools and methods for evaluating designs of electronic cooling heat sinks. Examples using thermal finite element analysis (FEA) and computational fluid dynamics (CFD) are presented. Quantitative data from wind tunnel testing compare well with model results. Qualitative data from infrared (IR) spectroscopy provides insight on the interfacial effect. Issues associated with the interface resistance are discussed.

Use of zero thickness conducting plate object in electronics cooling applications of CFD

Abstract: Zero thickness conducting plates are CFD objects that may be used to model 3 dimensional conduction in thin objects used in electronic cooling applications The use of zero thickness conducting plates, when applicable can result in significant reduction in finite volume element count The validity of using these thin conducting plates for CFD modeling of certain objects frequently used in electronic systems was studied using ICEPAK, a CFD software for electronics cooling application

High efficiency active cooling system

Abstract: In this paper we present a new method of active cooling of microstructures. The method consists in controlling the active heat sink in relation to the dissipated power in the microstructure and a thermal model of the package. We intend to design an on-chip controller as an ASIC cell. The cell could be placed on the same silicon substrate together with a requiring cooling structure. A special silicon current sensor was designed to estimate the dissipated power in the structure. Simulation results of the active cooling with a new method are presented as well as a design of current sensor.

Heat exchanger for heater in vehicle provided with hybrid driving part

Abstract: PROBLEM TO BE SOLVED: To use waste heat from electronics for electric power for heating cooling water with the temperature kept below an allowable operating temperature of an electronic component such as a power semiconductor and to secure a basic heater function for the interior of a vehicle during a stop phase of an internal combustion engine in a vehicle provided with a hybrid driving unit constructed of the internal combustion engine and an electric driving unit connected to each other. SOLUTION: Cooling fluid in an electronics cooling circulation system 10 flows through an engine cooling circulation system 9 for the internal combustion engine for cooling the internal combustion engine 1. Inside the cooling circulation system 10 for the semiconductor 11 for electric power, an electrically driven cooling fluid pump 12 and a connecting member are arranged. The connecting member connects the cooling circulation system 10 of the power semiconductor 11 to the engine cooling circulation system 9 when a cooling fluid temperature is still low so that the cooling fluid temperature does not exceed an upper limit temperature for cooling the semiconductor 11 for electric power. COPYRIGHT: (C)2001,JPO

Heat exchange system for the heating of a vehicle with hybrid propulsion

Abstract: The presented invention relates to a heat exchange system for a vehicle having one of an internal combustion engine (1) and an electric motor with associated power semiconductors (11) existing hybrid motor, the engine cooling circuit (9) with a mechanical water pump (3) and the electronics cooling circuit (10) is provided an electric water pump (12). The two cooling circuits (9, 10) are openable by optionally by valves or closable connection lines (l The invention is a Grundheizfunktion for the passenger compartment during standstill phases of the internal combustion engine (1) is ensured (Figure 1).

An experimental and numerical investigation of pressure drop in a closed loop two phase thermosyphon system

Abstract: The increase of heat fluxes from electronic components requires new methods of cooling of electronics. One efficient method of cooling is to use a closed loop two-phase thermosyphon system. The advantage of these systems is that extremely high heat fluxes can be dissipated at a low temperature difference due to the high heat transfer coefficients in boiling and condensation. In this paper experimental results of the pressure drop in the evaporator, riser and condenser of an advanced closed loop thermosyphon and numerical calculations of the pressure drop in the thermosyphon system, based on correlations from the literature, are presented. The thermosyphon system consists of a downcomer, an evaporator, a riser and a condenser. Heat was supplied by a power resistor and tests were performed with the heat loads 30, 60 and 90 W dissipated through the system. Two different refrigerants were tested, R134a and R600a. Pressure drop was measured across each of the four basic components by a differential pressure transducer. Comparisons between the experimental and numerical results are presented.

Experimental study on performance of a miniature heat pipe with woven-wired wick

Abstract: The thermal density of electronic parts and systems has been increased continuously as high speed and high density are required for them. The heat generation of the CPU of a notebook PC of higher than the Pentium-II grade has been recently increased to be more than 10 W, and the available packaging space has been compacted. Therefore, it has become inevitable to perform cooling by using miniature heat pipes. In the present study, new woven-wired-type wick with a large capillary limit and a high productivity has been developed, and heat pipes with the diameter of 3 mm or 4 mm to cooling of small-sized electronic parts such as CPU of a notebook PC. Have been designed and manufactured. Further, in as much as the operational characteristics of miniature heat pipes (MHPs) with the diameter of 3 mm or 4 mm are different from those of general medium-sized heat pipes, a performance test has been performed in order to review heat-transfer characteristics and affects of various factors on the performance of MHPs. The operational factors include charging ratio of working fluid, the total length of heat pipes, lengths of an evaporator and a condenser, inclination of installation, number of wick strands, thermal load, etc. The limiting powers of 3 mm MHP and 4 mm MHP are shown to be 6.8 W and 19.5 W, respectively, with angle of inclination of -5/spl deg/. These show that there is a high possibility of application if one or two MHPs are installed for cooling of CPU more than 10 W.

Electronic cooling technology with use of turbulent impinging jets

Abstract: An investigation on cooling of the solid surface was performed by studying the behaviors of impinging jets onto a fixed flat plate. The flow and local heat transfer coefficient distributions on a plate with a constant heat source were numerically investigated with a normally impinging axisymmetric jet. Numerical predictions of the mean velocities across the jet were. Made with several different nozzle-to-plate stand-off distances were considered. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation turbulence model of the k-/spl epsi/ model version. The finite-volume differencing (FVD) scheme was used to solve the thermal and flow fields. The predicted velocities and heat transfer coefficients were compared with previously obtained experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients. Predictions by the present model show good agreement with the experimental data.

A PWM controller for extended temperature applications

Abstract: Conventional pulse width modulated (PWM) switching power supplies are not suitable for operation at extended temperatures beyond 125/spl deg/C. In virtually all power switching applications, mechanical apparatus is always attached to the power supply because the system mandates sufficient heat removal. The attachment is usually bulky and heavy compared with integrated circuit and electronics component. For commercial applications, power supply without a heat sink means a boost of power density. For aerospace applications, reduction or elimination of the weight and volume of the cooling system is extremely desirable. In recent years, there has been an increased demand for distributed engine and flight actuator electronics control. Commercial/military airplanes, supersonic and space vehicles benefit from the use of smart sensors and remote actuators. These ruggedized electronics must operate in harsh environments where active cooling is unavailable. Furthermore, ruggedized electronics have found other uses in the petroleum industry for geothermal instruments and data logging equipment. Such opportunities even extend to the automobile industry where electronic systems will be mandatory for improved fuel economy, smart braking, emission/exhaust monitoring and control. Perhaps the most challenging task for such ruggedized electronics is power supply design. This paper describes a new PWM power supply controller, a switch-mode ASIC (SMA) that has been developed to operate over the -55/spl deg/C to +225/spl deg/C temperature range.

On some electrical characteristics of AlN and Al/sub 2/O/sub 3/

Abstract: In power electronics, the development of new IGBT power modules allows them to switch kV and kA during us. However, such components need to be cooled and ceramic materials like AlN and Al/sub 2/O/sub 3/ are used as an interface between the electronic devices (the chips) and the cooling. Such materials have to present very well known electrical and thermal characteristics since the reliability of the inverters these components are used in is strongly dependant on them. In order to increase the knowledge of the physical mechanisms involved during aging of these materials, we present in this paper the very first results obtained in this field. Finally, all these results are discussed and analyzed in view of power electronics applications.

Sixteenth Annual IEEE Semiconductor Thermal Measurement and Management Symposium, March 21-23, 2000, DoubleTree Hotel, San Jose, CA, USA

Abstract: This text constitutes proceedings from the IEEE Annual Semi Conductor Thermal Measurement and Management Symposium (Semi-Therm), which took place in 2000. Topics covered include simulation in thermal management, materials in electronics cooling and package thermal performance.