wall Superheat Excursions in the Boiling incipience of Dielectric Fluids
TL;DR: In this paper, a brief review of the mechanisms that may be responsible for delayed nucleation and examines the limited literature on incipience superheat excursions is presented. But the authors do not consider the effect of temperature variations on the nucleation of microelectronic components.
Abstract: Many of the candidate fluids for immersion cooling of microelectronic components possess both low surface tension and high gas solubility. As a consequence, ebullient heat transfer with such fluids is accompanied by nucleation anomalies and a frequently observed wall temperature overshoot. The difficulty in preventing this thermal excursion and in predicting its magnitude constrains the development of immersion cooling systems. This paper begins with a brief review of the mechanisms that may be responsible for delayed nucleation and examines the limited literature on incipience superheat excursions.
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21 Jul 2016
TL;DR: In this article, an experimental investigation of pool boiling on the heat spreader lid surface of a real central processing unit (CPU) was presented, where a highly wetting dielectric liquid, Novec 7100, was employed as coolant.
Abstract: An experimental investigation of pool boiling on the heat spreader lid surface of a real central processing unit (CPU) is presented in this paper. A highly wetting dielectric liquid, Novec 7100, was employed as coolant. The nucleate boiling process was observed and recorded through a high-speed camera. The boiling curves of saturated Novec 7100 liquid on the CPU heat spreader lid were obtained. The quantities used to characterize bubble dynamics, such as active nucleation site density, bubble departure diameter and bubble departure frequency, were measured through the high-speed video at different wall heat fluxes. The averaged values of all these quantities have increasing trends with increasing wall heat flux. The relationships between quantities and heat flux can be further embedded into nucleate boiling heat transfer models for validation.
4 citations
01 Jan 1989
TL;DR: In this article, a novel type of heat exchange process is described for use in semiconductor heat sinks, which involves the use of subcooled, nucleate boiling at concave curved surfaces where radial acceleration can be used to develop significant and beneficial buoyancy forces.
Abstract: A novel type of heat exchange process is described for use in semiconductor heat sinks. It involves the use of subcooled, nucleate boiling at concave curved surfaces where radial acceleration can be used to develop significant and beneficial buoyancy forces. This system provides a heat transfer surface with a uniform temperature, i.e. the boiling point of the fluid, and requires no vapor-liquid separation process since all vapor bubbles are immediately condensed in the subcooled liquid. The authors describe the use of concave curved surfaces to generate an extremely efficient heat transfer device, which provides a high packing density (3000 chips/ft/sup 3/) and is capable of a heat exchange rate of 300000 W/ft/sup 3/. Further benefits include a minimal thermal stress and a low thermal resistance on the order of 0.11 degrees C cm/sup 2//W. >
4 citations
TL;DR: In this article, the impact of pressure drop oscillations on the heat transfer coefficient and critical heat flux in microchannel heat sinks has been quantified through analysis of both time-averaged steady-state data as well as high-frequency pressure signals synchronized with high-speed visualization.
Abstract: Flow boiling in microchannel heat sinks is capable of providing the high-heat-flux dissipation required for thermal management of next-generation wide bandgap power electronics at low pumping power and uniform surface temperatures. One of the primary issues preventing implementation of these technologies is the presence of flow boiling instabilities, which may reduce the heat transfer performance. However, the effect of individual instabilities, such as the parallel channel instability or pressure drop oscillations, on the overall heat transfer coefficient and critical heat flux in microchannel heat sinks has not been fully quantified. The primary cause of these dynamic flow boiling instabilities is the interaction between the inertia of a two-phase mixture in a heated channel and sources of compressibility located upstream of the inlet. In order to isolate the effect of pressure drop oscillations on flow boiling heat transfer performance, experiments are performed in a single-square microchannel cut into a copper heat sink, with a controlled level of upstream compressibility. The impact of pressure drop oscillations on the heat transfer coefficient and critical heat flux is characterized through analysis of both time-averaged steady-state data as well as high-frequency pressure signals synchronized with high-speed visualization. The dielectric working fluid HFE-7100 is used in all experiments with a saturation temperature of 60 °C at the channel outlet pressure. The occurrence and effect of pressure drop oscillations in 20-mm-long microchannels of three different channel widths (0.5, 0.75, and 1 mm) are related to mass flux, the degree of two-phase flow confinement, and the severity of pressure drop oscillations.
4 citations
TL;DR: In this article, the authors provide a review and summary of the programs with emphasis on direct liquid cooling with respect to the following cooling modes: liquid free, mixed and forced convection, liquid jet impingement, flowing liquid film cooling, pool boiling, spray cooling, foreign gas jet impeding in liquid pool, and forcing convection air-cooling.
Abstract: During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cooling techniques for electronic and microelectronic devices. This paper provides a review and summary of the programs with emphasis on direct liquid cooling. Included in this review are the heat transfer investigations related to the following cooling modes: liquid free, mixed and forced convection, liquid jet impingement, flowing liquid film cooling, pool boiling, spray cooling, foreign gas jet impingement in liquid pool, and forced convection air-cooling.
3 citations
TL;DR: In this paper, the process dynamics of nucleate boiling is analyzed and its mechanism is discussed from the view point of self-organization, and the morphology and fractal analysis of fouling on low-energy surface and that with fouling inhibitors are studied and discussed.
Abstract: Boiling and fouling are taken as typical examples of new phase formation process to be analyzed and discussed in this paper. The process dynamics of nucleate boiling is analyzed and its mechanism is discussed from the view point of self-organization. Fouling, which is a more complicated phenomenon of new phase formation, involves series of underlying processes. The morphology and fractal analysis of fouling on low-energy surface and that with fouling inhibitors are studied and discussed. It is suggested that considering the process dynamics, fractal analysis and self-organization, a new avenue of research should be found.
3 citations
References
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Book•
01 Jan 1994
TL;DR: In this paper, the basic models of two-phase flow are discussed and empirical treatments of two phase flow are provided. But the authors focus on convective boiling and condensing.
Abstract: Introduction 1. The basic models 2. Empirical treatments of two-phase flow 3. Introduction to convective boiling 4. Subcooled boiling heat transfer 5. Void fraction and pressure drop in subcooled boiling 6. Saturated boiling heat transfer 7. Critical heat flux in forced convective flow - 1. Vertical uniformly heated tubes 8. Critical heat flux in forced convective flow - 2. More complex situations 9. Condensation 10. Conditions influencing the performance of boiling and condensing systems 11. Multi-component boiling and condensation Appendix Index
2,426 citations
TL;DR: In this article, a regression analysis was applied to the nearly 5000 existing experimental data points for natural convection boiling heat transfer, which can best be represented by subdividing the substances into four groups (water, hydrocarbons, cryogenic fluids and refrigerants) and employing a different set of dimensionless numbers for each group of substances.
710 citations
Book•
01 Jan 1983
TL;DR: In this article, thermal analysis and control of electronic equipment, thermal analysis of electronic devices and their control, thermal control and control in the field of software engineering, is discussed. ǫ
Abstract: Thermal analysis and control of electronic equipment , Thermal analysis and control of electronic equipment , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
339 citations
TL;DR: A survey of the evolution of surface geometries that promote high-performance nucleate boiling can be found in this paper, where the authors survey the development of a high area density of stable nucleation sites whose performance does not deteriorate with time.
Abstract: This paper surveys the evolution of special surface geometries that promote high-performance nucleate boiling. Early work by Jakob and Fritz in 1931 showed that emery paper roughening or machined grooves provided only temporary performance increase. However, this improvement dissipated after a few days to the flat surface value. There was little sustained interest in this unique, but apparently unuseful, phenomenon until the mid-1950s. During the period 1955-1965, supporting fundamental studies of the character and stability of nucleation sites provided a basis for renewed efforts to develop a high area density of stable, artificially formed nucleation sites whose performance does not deteriorate with time. Beginning in 1968 industrial research produced patented technology that achieved the long-sought goal. In 1980 at least six high-performance nucleate boiling surfaces were commercially available. The technology reported in this paper represents a dramatic advance in the field of heat transfer.
192 citations