Documents disponibles écrits par cet auteur

Experimental investigation of an ultrathin manifold microchannel heat sink for liquid-cooled chips / W. Escher in Journal of heat transfer, Vol. 132 N° 8 (Août 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 8 (Août 2010) . - pp. [081402-1/10] Titre : Experimental investigation of an ultrathin manifold microchannel heat sink for liquid-cooled chips Type de document : texte imprimé Auteurs : W. Escher, Auteur ; T. Brunschwiler, Auteur ; B. Michel, Auteur Article en page(s) : pp. [081402-1/10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Manifold  Microchannels  Impinging  jet  Heat  transfer  Electronics  cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : We report an experimental investigation of a novel, high performance ultrathin manifold microchannel heat sink. The heat sink consists of impinging liquid slot-jets on a structured surface fed with liquid coolant by an overlying two-dimensional manifold. We developed a fabrication and packaging procedure to manufacture prototypes by means of standard microprocessing. A closed fluid loop for precise hydrodynamic and thermal characterization of six different test vehicles was built. We studied the influence of the number of manifold systems, the width of the heat transfer microchannels, the volumetric flow rate, and the pumping power on the hydrodynamic and thermal performance of the heat sink. A design with 12.5 manifold systems and 25 µm wide microchannels as the heat transfer structure provided the optimum choice of design parameters. For a volumetric flow rate of 1.3 l/min we demonstrated a total thermal resistance between the maximum heater temperature and fluid inlet temperature of 0.09 cm2 K/W with a pressure drop of 0.22 bar on a 2×2 cm2 chip. This allows for cooling power densities of more than 700 W/cm2 for a maximum temperature difference between the chip and the fluid inlet of 65 K. The total height of the heat sink did not exceed 2 mm, and includes a 500 µm thick thermal test chip structured by 300 µm deep microchannels for heat transfer. Furthermore, we discuss the influence of elevated fluid inlet temperatures, allowing possible reuse of the thermal energy, and demonstrate an enhancement of the heat sink cooling efficiency of more than 40% for a temperature rise of 50 K. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Experimental investigation of an ultrathin manifold microchannel heat sink for liquid-cooled chips [texte imprimé] / W. Escher, Auteur ; T. Brunschwiler, Auteur ; B. Michel, Auteur . - pp. [081402-1/10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 8 (Août 2010) . - pp. [081402-1/10] Mots-clés : Manifold  Microchannels  Impinging  jet  Heat  transfer  Electronics  cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : We report an experimental investigation of a novel, high performance ultrathin manifold microchannel heat sink. The heat sink consists of impinging liquid slot-jets on a structured surface fed with liquid coolant by an overlying two-dimensional manifold. We developed a fabrication and packaging procedure to manufacture prototypes by means of standard microprocessing. A closed fluid loop for precise hydrodynamic and thermal characterization of six different test vehicles was built. We studied the influence of the number of manifold systems, the width of the heat transfer microchannels, the volumetric flow rate, and the pumping power on the hydrodynamic and thermal performance of the heat sink. A design with 12.5 manifold systems and 25 µm wide microchannels as the heat transfer structure provided the optimum choice of design parameters. For a volumetric flow rate of 1.3 l/min we demonstrated a total thermal resistance between the maximum heater temperature and fluid inlet temperature of 0.09 cm2 K/W with a pressure drop of 0.22 bar on a 2×2 cm2 chip. This allows for cooling power densities of more than 700 W/cm2 for a maximum temperature difference between the chip and the fluid inlet of 65 K. The total height of the heat sink did not exceed 2 mm, and includes a 500 µm thick thermal test chip structured by 300 µm deep microchannels for heat transfer. Furthermore, we discuss the influence of elevated fluid inlet temperatures, allowing possible reuse of the thermal energy, and demonstrate an enhancement of the heat sink cooling efficiency of more than 40% for a temperature rise of 50 K. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

On the cooling of electronics with nanofluids / W. Escher in Journal of heat transfer, Vol. 133 N° 5 (Mai 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 5 (Mai 2011) . - pp. [051401/1-11] Titre : On the cooling of electronics with nanofluids Type de document : texte imprimé Auteurs : W. Escher, Auteur ; T. Brunschwiler, Auteur ; N. Shalkevich, Auteur Année de publication : 2011 Article en page(s) : pp. [051401/1-11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nanofluid  Nanoparticle  Suspension  Thermal  conductivity  Convection  heat  transfer  Electronics  cooling  Experiment Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids have been proposed to improve the performance of microchannel heat sinks. In this paper, we present a systematic characterization of aqueous silica nanoparticle suspensions with concentrations up to 31 vol %. We determined the particle morphology by transmission electron microscope imaging and its dispersion status by dynamic light scattering measurements. The thermophysical properties of the fluids, namely, their specific heat, density, thermal conductivity, and dynamic viscosity were experimentally measured. We fabricated microchannel heat sinks with three different channel widths and characterized their thermal performance as a function of volumetric flow rate for silica nanofluids at concentrations by volume of 0%, 5%, 16%, and 31%. The Nusselt number was extracted from the experimental results and compared with the theoretical predictions considering the change of fluids bulk properties. We demonstrated a deviation of less than 10% between the experiments and the predictions. Hence, standard correlations can be used to estimate the convective heat transfer of nanofluids. In addition, we applied a one-dimensional model of the heat sink, validated by the experiments. We predicted the potential of nanofluids to increase the performance of microchannel heat sinks. To this end, we varied the individual thermophysical properties of the coolant and studied their impact on the heat sink performance. We demonstrated that the relative thermal conductivity enhancement must be larger than the relative viscosity increase in order to gain a sizeable performance benefit. Furthermore, we showed that it would be preferable to increase the volumetric heat capacity of the fluid instead of increasing its thermal conductivity. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] On the cooling of electronics with nanofluids [texte imprimé] / W. Escher, Auteur ; T. Brunschwiler, Auteur ; N. Shalkevich, Auteur . - 2011 . - pp. [051401/1-11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 5 (Mai 2011) . - pp. [051401/1-11] Mots-clés : Nanofluid  Nanoparticle  Suspension  Thermal  conductivity  Convection  heat  transfer  Electronics  cooling  Experiment Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids have been proposed to improve the performance of microchannel heat sinks. In this paper, we present a systematic characterization of aqueous silica nanoparticle suspensions with concentrations up to 31 vol %. We determined the particle morphology by transmission electron microscope imaging and its dispersion status by dynamic light scattering measurements. The thermophysical properties of the fluids, namely, their specific heat, density, thermal conductivity, and dynamic viscosity were experimentally measured. We fabricated microchannel heat sinks with three different channel widths and characterized their thermal performance as a function of volumetric flow rate for silica nanofluids at concentrations by volume of 0%, 5%, 16%, and 31%. The Nusselt number was extracted from the experimental results and compared with the theoretical predictions considering the change of fluids bulk properties. We demonstrated a deviation of less than 10% between the experiments and the predictions. Hence, standard correlations can be used to estimate the convective heat transfer of nanofluids. In addition, we applied a one-dimensional model of the heat sink, validated by the experiments. We predicted the potential of nanofluids to increase the performance of microchannel heat sinks. To this end, we varied the individual thermophysical properties of the coolant and studied their impact on the heat sink performance. We demonstrated that the relative thermal conductivity enhancement must be larger than the relative viscosity increase in order to gain a sizeable performance benefit. Furthermore, we showed that it would be preferable to increase the volumetric heat capacity of the fluid instead of increasing its thermal conductivity. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Self-contained, oscillating flow liquid cooling system for thin form factor high performance electronics / R. Wälchli in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051401-1/7] Titre : Self-contained, oscillating flow liquid cooling system for thin form factor high performance electronics Type de document : texte imprimé Auteurs : R. Wälchli, Auteur ; T. Brunschwiler, Auteur ; B. Michel, Auteur Article en page(s) : pp. [051401-1/7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microchannel  Liquid  cooling  Thermal  pachaging  Oscillating  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : A self-contained, small-volume liquid cooling system for thin form-factor electronic equipment (e.g., blade server modules) is demonstrated experimentally in this paper. A reciprocating water flow loop absorbs heat using mesh-type microchannel cold plates and spreads it periodically to a larger area. From there, the thermal energy is interchanged via large area, low pressure drop cold plates with a secondary heat transfer loop (air or liquid). Four phase-shifted piston pumps create either a linearly or radially oscillating fluid flow in the frequency range of 0.5–3 Hz. The tidal displacement of the pumps covers 42–120% of the fluid volume, and, therefore, an average flow rate range of 100–800 ml/min is tested. Three different absorber mesh designs are tested. Thermal and fluidic characteristics are presented in a time-resolved and a time-averaged manner. For a fluid pump power of 1 W, a waste heat flux of 180 W/cm2 (DeltaT=67 K) could be dissipated from a 3.5 cm2 chip. A linear oscillation flow pattern is advantageous over a radial one because of the more efficient heat removal from the chip and lower hydraulic losses. The optimum microchannel mesh density is determined as a combination of low pump losses and high heat transfer rates. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Self-contained, oscillating flow liquid cooling system for thin form factor high performance electronics [texte imprimé] / R. Wälchli, Auteur ; T. Brunschwiler, Auteur ; B. Michel, Auteur . - pp. [051401-1/7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051401-1/7] Mots-clés : Microchannel  Liquid  cooling  Thermal  pachaging  Oscillating  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : A self-contained, small-volume liquid cooling system for thin form-factor electronic equipment (e.g., blade server modules) is demonstrated experimentally in this paper. A reciprocating water flow loop absorbs heat using mesh-type microchannel cold plates and spreads it periodically to a larger area. From there, the thermal energy is interchanged via large area, low pressure drop cold plates with a secondary heat transfer loop (air or liquid). Four phase-shifted piston pumps create either a linearly or radially oscillating fluid flow in the frequency range of 0.5–3 Hz. The tidal displacement of the pumps covers 42–120% of the fluid volume, and, therefore, an average flow rate range of 100–800 ml/min is tested. Three different absorber mesh designs are tested. Thermal and fluidic characteristics are presented in a time-resolved and a time-averaged manner. For a fluid pump power of 1 W, a waste heat flux of 180 W/cm2 (DeltaT=67 K) could be dissipated from a 3.5 cm2 chip. A linear oscillation flow pattern is advantageous over a radial one because of the more efficient heat removal from the chip and lower hydraulic losses. The optimum microchannel mesh density is determined as a combination of low pump losses and high heat transfer rates. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]