Electronics cooling

About: Electronics cooling is a research topic. Over the lifetime, 1135 publications have been published within this topic receiving 17608 citations.

Investigation of a Capillary Assisted Thermosyphon (CAT) for Shipboard Electronics Cooling

Abstract: As microprocessors shrink in size and increase in power dissipation levels, the current need for advanced electronics cooling techniques is paramount since power dissipation levels are rapidly exceeding the capabilities of forced air convection cooling. This paper reports an investigation of using a capillary assisted thermosyphon for the shipboard cooling of electronics components. The capillary assisted thermosyphon differs from the capillary pumped loop or loop heat pipe system in that the basic cooling loop is based on a thermosyphon. The capillary assist comes from the fact that there is a wicking structure in the flat evaporator plate, however, the wicking structure is there to spread the working fluid across the flat plate evaporator in the areas under the heat sources. This differs from a capillary pumped loop in that the wick structure does not produce a capillary pumping head from the liquid return to the vapor outlet side of the evaporator. In fact, the liquid return and vapor outlet are almost at the same pressure. The forced circulation in the thermosyphon is caused by a gravity head between the condenser cold plate and the flat plate evaporator. An experimental facility for conducting research on capillary assisted thermosyphon was developed. In order to simulate the shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility could be varied. A vertical flat plate, CAT evaporator was designed and tested under thermal sink temperatures of 4, 21 and 37°C. The condenser cold plate cooling water flow rate varied from 0.38 to 3 GPM. The heat input varied from 250 to 1500 W evenly spread over the area of the evaporator. The CAT flat plate evaporator performed very well under this range of heat inputs, sink temperatures, and cold plate flow rates. The main result obtained showed that as heat input increased the amount of subcooling between the evaporator vapor outlet line and liquid return line increased. This subcooling did not hinder thermal performance as measured by the internal operating temperature.Copyright © 2004 by ASME

Optimization of Phase Change Heat Transfer in Biporous Media

Abstract: As the heat transfer demands placed on small electronics devices increase, the demand for efficient evaporators for heat pipes and spreaders will increase in kind. Sintered copper porous media have found many uses in the electronics cooling industry as they effectively transfer energy while maintaining low heater side temperatures. Evaporator wicks of this type transfer heat through sensible and latent heat as the liquid evaporates. A biporous wick is particularly effective for this application as there are two distinct size distributions of pores; small pores to provide ample capillary pressure in order to drive flow through the wick and large pores to provide high permeability for escaping vapor. This dissertation is focused on the methods by which one can enhance and optimize the performance of biporous material. This includes changes to the geometry and a predictive model which can be used to predict dryout phenomenon in wicks. The experimental work consists of investigations carried out by the author on a variety of different wicks. These wicks' construction and purposes are detailed. Measurements of their peak effective heat transfer coefficients are presented and used as a basis for determining the most effective geometries in terms of heat transfer. Furthermore, the physics and motivations behind their geometries are also detailed.The modeling proposed in this work was inspired by the work by Kovalev [18], which used a pore size distribution in order to determine the most probable pore size at a given position. The model distinguishes phases by choosing a cutoff pore size, above which all pores were assumed to be filled with vapor and below which they are filled with liquid. For a given wick thickness and working fluid, this 1-D model predicts a temperature difference across the wick for a given input heat flux as well as other thermophysical properties. The modeling detailed in this work is compared to experimental data collected on biporous evaporators at UCLA for validation. The correlation of thermophysical properties such as phase permeabilities and a volumetric heat transfer coefficient to the pore size distribution are also explained. The experimental and simulation based methods discussed in this thesis are used as a basis to optimize sintered particle, biporous evaporators. Using the information gained in this thesis research effort, a methodology by which one could optimize a biporous wick for particular applications is explained as well as suggestions of future work needed to extend the foundations laid in this effort.

Experimental Characterization of an Open Loop Pulsating Heat Pipe Cooler

Abstract: Pulsating heat pipes (PHP) have emerged in the last years as suitable cooling devices for dissipating the high heat loads generated by electronic devices since they allow to extend the applicability of air cooling in area nowadays covered by water cooling. Two-phase cooling technologies based on the two phase pulsating heat pipe principle are promising solutions because, being entirely passive they can comply with long term operation without maintenance. The main advantage of a PHP compared to conventional thermosyphon technologies for electronics cooling is that a PHP is orientation independent. The authors has developed a novel, compact, and low cost PHP based on automotive technology. The present paper presents the experimental results of an air cooled open loop pulsating heat pipe with optimized manifold design to minimize fluid pressure drops in the fluid turns. The effect of several parameters including filling ratio and heat load are presented. Tests have been done with the refrigerant fluid R245fa in vertical and horizontal orientations. The measurements showed a maximum thermal resistance ranging between 40 and 48 K/kW in vertical and horizontal position respectively for a heat load of 2 kW and air temperature of 20 °C.Copyright © 2014 by ASME

Conjugate Numerical Investigation of a Miniature Flat Plate Evaporator of Capillary Pumped Loop

Abstract: The capillary pumped loop (CPL) is a two-phase thermal control device, which has become more active and interesting in the domain of electronics cooling. A two-dimensional conjugate numerical model for the miniature flat plate capillary evaporator is presented to describe liquid and vapor flow, heat transfer and phase change in the porous wick structure, liquid flow and heat transfer in the compensation cavity and heat transfer in the vapor grooves and metallic wall. The entire evaporator is solved with SIMPLE algorithm as a conjugate problem. The shape and location of vapor-liquid interface inside the wick are calculated, and side wall effect heat transfer limit is introduced to estimate the heat transport capability of capillary evaporator. The influences of different wall materials on the performance of miniature flat plate evaporator are discussed in detail, and the results show that evaporator with combined wall is capable of dissipating high heat flux and stabilizes the electronics devices temperature at a moderate temperature level.