Coolant

Abstract: The problem of achieving compact, high-performance forced liquid cooling of planar integrated circuits has been investigated. The convective heat-transfer coefficient h between the substrate and the coolant was found to be the primary impediment to achieving low thermal resistance. For laminar flow in confined channels, h scales inversely with channel width, making microscopic channels desirable. The coolant viscosity determines the minimum practical channel width. The use of high-aspect ratio channels to increase surface area will, to an extent, further reduce thermal resistance. Based on these considerations, a new, very compact, water-cooled integral heat sink for silicon integrated circuits has been designed and tested. At a power density of 790 W/cm2, a maximum substrate temperature rise of 71°C above the input water temperature was measured, in good agreement with theory. By allowing such high power densities, the heat sink may greatly enhance the feasibility of ultrahigh-speed VLSI circuits.

Abstract: Fundamentals Need for Turbine Blade Cooling Turbine-Cooling Technology Turbine Heat Transfer and Cooling Issues Structure of the Book Review Articles and Book Chapters on Turbine Cooling and Heat Transfer New Information from 2000 to 2010 References Turbine Heat Transfer Introduction Turbine-Stage Heat Transfer Cascade Vane Heat-Transfer Experiments Cascade Blade Heat Transfer Airfoil Endwall Heat Transfer Turbine Rotor Blade Tip Heat Transfer Leading-Edge Region Heat Transfer Flat-Surface Heat Transfer New Information from 2000 to 2010 2.10 Closure References Turbine Film Cooling Introduction Film Cooling on Rotating Turbine Blades Film Cooling on Cascade Vane Simulations Film Cooling on Cascade Blade Simulations Film Cooling on Airfoil Endwalls Turbine Blade Tip Film Cooling Leading-Edge Region Film Cooling Flat-Surface Film Cooling Discharge Coefficients of Turbine Cooling Holes 3.10 Film-Cooling Effects on Aerodynamic Losses 3.11 New Information from 2000 to 2010 3.12 Closure References Turbine Internal Cooling Jet Impingement Cooling Rib-Turbulated Cooling Pin-Fin Cooling Compound and New Cooling Techniques New Information from 2000 to 2010 References Turbine Internal Cooling with Rotation Rotational Effects on Cooling Smooth-Wall Coolant Passage Heat Transfer in a Rib-Turbulated Rotating CoolantPassage Effect of Channel Orientation with Respect to the RotationDirection on Both Smooth and Ribbed Channels Effect of Channel Cross Section on Rotating Heat Transfer Different Proposed Correlation to Relate the Heat Transferwith Rotational Effects Heat-Mass-Transfer Analogy and Detail Measurements Rotation Effects on Smooth-Wall Impingement Cooling Rotational Effects on Rib-Turbulated Wall ImpingementCooling New Information from 2000 to 2010 References Experimental Methods Introduction Heat-Transfer Measurement Techniques Mass-Transfer Analogy Techniques Liquid Crystal Thermography Flow and Thermal Field Measurement Techniques New Information from 2000 to 2010 Closure References Numerical Modeling Governing Equations and Turbulence Models Numerical Prediction of Turbine Heat Transfer Numerical Prediction of Turbine Film Cooling Numerical Prediction of Turbine Internal Cooling New Information from 2000 to 2010 References Final Remarks Turbine Heat Transfer and Film Cooling Turbine Internal Cooling with Rotation Turbine Edge Heat Transfer and Cooling New Information from 2000 to 2010 Closure Index

Abstract: Open-cell metal foams with an average cell diameter of 2.3 mm were manufactured from 6101-T6 aluminum alloy and were compressed and fashioned into compact heat exchangers measuring 40.0 mm · 40.0 mm · 2.0 mm high, possessing a surface area to volume ratio on the order of 10,000 m 2 /m 3 . They were placed into a forced convection arrangement using water as the coolant. Heat fluxes measured from the heater-foam interface ranged up to 688 kW m � 2 , which corresponded to Nusselt numbers up to 134 when calculated based on the heater-foam interface area of 1600 mm 2 and a Darcian coolant flow velocity of approximately 1.4 m/s. These experiments performed with water were scaled to estimate the heat exchangers performance when used with a 50% water–ethylene glycol solution, and were then compared to the performance of commercially available heat exchangers which were designed for the same heat transfer application. The heat exchangers were compared on the basis of required pumping power versus thermal resistance. The compressed open-cell aluminum foam heat exchangers generated thermal resistances that were two to three times lower than the best commercially available heat exchanger tested, while requiring the same pumping power.

Abstract: Film cooling downstream of secondary gas injection through discrete holes has been studied experimentally. The influences of hole geometry, secondary fluid density, and mainstream boundary layer thickness are described. Significant improvements in the film cooling effectiveness are observed by having the coolant passages widened before the exit of the secondary fluid. The use of a relatively dense secondary fluid, as might be encountered in many applications, requires a significantly higher blowing rate to cause jet separation from the surface than when the densities of the freestream and secondary stream are the same. This results in considerably better film cooling over an important range of density ratios.

Abstract: During reactor operation the plasma-facing materials have to fulfil very complex and sometimes contradicting requirements. At present, tungsten shows the highest promise as plasma-facing material. Experiments in the ASDEX Upgrade tokamak indicate that plasma operation is feasible with walls and divertor surfaces mostly covered with tungsten. Thick tungsten coatings have been deposited by plasma spraying on EUROFER first wall mock-ups and show good adhesion and stability. The performance of tungsten surfaces under intense transient thermal loads is another critical issue, since the formation of a melt layer may favour the generation of highly activated dust particles. Work on `nanocrystalline' tungsten shall improve the mechanical properties under neutron irradiation which is especially important for designs, where tungsten has also to fulfil structural functions. Alternative divertor heat sink materials with very high thermal conductivity like SiC-fibre reinforced copper composites are presently being developed and should allow operation at reactor relevant coolant temperatures.