Performance of a Compact Cooling Unit Utilizing Air-Water Mist Flow

1983 ◽  
Vol 105 (1) ◽  
pp. 18-24 ◽  
Author(s):  
T. Aihara ◽  
R. Saga
Keyword(s):  
Heat Transfer ◽  
Parallel Plate ◽  
Heat Transfer Performance ◽  
Thermal Conditions ◽  
Water Mist ◽  
Transfer Performance ◽  
Cooling Unit ◽  
Wide Range ◽  
Mist Flow ◽  
Plate Channel

Performance of a new compact cooling unit for semiconductors, being composed of an atomizer, a fan, and a heat-dissipating surface with no fin, has been measured over a wide range of the mass flow rate of spray water, m˙, and the wall heat flux. The heat transfer performance of the present compact, unit with m˙ = 0 to 1.05 g/s, attains 1.8 to 20 times that of the parallel-plate channel under the same thermal conditions.

Enhanced Condensation Heat-Transfer on Mini or Low Fin Tubes

2006 ◽  
Author(s):  
Adrian Briggs
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermophysical Properties ◽  
Heat Transfer Performance ◽  
Three Dimensional ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Shell Side ◽  
Wide Range ◽  
Fin Tubes

This paper presents an overview of the use of low or mini-fin tubes for improving heat-transfer performance in shell-side condensers. The paper concentrates on, but is not limited to, the experimental and theoretical program in progress at Queen Mary, University of London. This work has so far resulted in an extensive data base of experimental data for condensation on single tubes, covering a wide range of tube geometries and fluid thermophysical properties and in the development of a simple to use model which predicts the majority of this data to within 20%. Work is progressing on the effects of vapor shear and on three-dimensional fin profiles; the later having shown the potential for even higher heat-transfer enhancement.

Heat Transfer Enhancement in Ferrofluids Flow in Micro and Macro Parallel Plate Channels: A Comparative Numerical Study

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
Aditi Sengupta ◽  
P. S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Enhancement Factor ◽  
Parallel Plate ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Nanoparticle Concentration ◽  
Transfer Enhancement ◽  
Fully Developed Flow

This paper presents a comparative numerical study of heat transfer enhancement in steady, laminar, hydrodynamically fully developed flow of water-based ferrofluids under no magnetic field in micro and macro parallel plate channels subjected to constant equal heat fluxes on its top and bottom, considering Brownian diffusion and thermophoresis of ferroparticles in the base fluid. While the microchannel results match very well with the experimental data for water in an equivalent microtube (Kurtoglu et al., 2014, “Experimental Study on Convective Heat Transfer Performance of Iron Oxide Based Ferrofluids in Microtubes,” ASME J. Therm. Sci. Eng. Appl., 6(3), p. 034501.), the numerically predicted enhancement factor in ferrofluids is much below that for the same microtube. A detailed parametric study points to possible inaccuracies in the experimental results of Kurtoglu et al. (2014, “Experimental Study on Convective Heat Transfer Performance of Iron Oxide Based Ferrofluids in Microtubes,” ASME J. Therm. Sci. Eng. Appl., 6(3), p. 034501.) for ferrofluids. The nanoparticle concentration profiles in the microchannel flow reveal that (a) the nanoparticle concentration at the wall increases with axial distance, (b) the wall nanoparticle concentration decreases with increasing heat flux, and (c) the concentration profile of nanoparticles is parabolic at the exit. A comparison of thermally developing flow in microchannel and macrochannel of the same length (0.025 m) indicates that the enhancement factor at the microchannel exit is 1.089 which is only marginally higher than that at the macrochannel exit in the heat flux range of 20–80 kW/m2. On the other hand, for the thermally fully developed flow in both microchannel and macrochannel of the same length (0.54 m) the maximum enhancement factor for the macrochannel is 1.7, as compared to 1.1 for the microchannel, in the heat flux range of 1–4 kW/m2.

Heat Transfer Performance for Helium Gas Flowing in a Minichannel With Different Inner Diameters

2021 ◽  
Author(s):  
Feng Xu ◽  
Qiusheng Liu ◽  
Makoto Shibahara
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Heat Transfer Performance ◽  
Heat Transfer Process ◽  
Transfer Performance ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Helium Gas ◽  
Inner Diameter

Abstract The high heat load on the first wall of the helium cooled blanket is removed by tube flow of helium gas. Heat transfer augmentation is considered to be acquired by downsizing of channels. Therefore, this paper experimentally studied the influence of inner diameter on the heat transfer performance of helium gas flowing in a minichannel. The helium gas flowed in the small platinum tubes with the inner diameters of 0.8 mm and 1.8 mm, respectively. The heat generation rate of the tube was controlled by a heat input subsystem and raised with an exponential equation. The surface temperature and heat flux of the tubes were obtained under a wide range of e-folding time at different flow velocities. The heat transfer coefficients of different inner diameter tubes were compared at the same conditions. The heat transfer performance of the 0.8 mm-diameter tube was compared with a classical correlation. The experimental results showed that the heat transfer performance in the minichannel is better than a conventional large-diameter tube. The heat transfer coefficients of the 0.8 mm-diameter tube were higher than those of the 1.8 mm-diameter tube. The heat transfer process was enhanced with reducing the inner diameter of the minichannel. The heat transfer process was divided into two parts including transient and quasi-steady-state regions.

An Experimental Study on Heat Transfer Performance of Iron Oxide Based Ferrofluids

2012 ◽  
Author(s):  
Evrim Kurtoglu ◽  
Alihan Kaya ◽  
Havva Funda Yagci Acar ◽  
Ali Kosar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Solid Phase ◽  
Aqueous Media ◽  
Intermolecular Forces ◽  
Transfer Performance ◽  
Wide Range ◽  
Materials Used ◽  
Weak Intermolecular Forces ◽  
Transfer Properties

Nanofluids are colloidal compounds, where the solid phase material is composed of nano sized particles, and the liquid phase can potentially be any fluid but aqueous media are common. As a common nanofluid type, ferrofluids are formed by holding solid nanoparticles in suspension by weak intermolecular forces and may be produced from materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids is one of the crucial properties among many others that should be analyzed and considered for their wide range of applications. For this purpose, experiments were conducted in order to characterize heat transfer properties of ironoxide based ferrofluids flowing through a microchannel. Promising results were obtained from this study, which are suggesting the use of ferrofluids for heat transfer applications can be advantageous.

Experimental Study on Convective Heat Transfer Performance of Iron Oxide Based Ferrofluids in Microtubes

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Evrim Kurtoğlu ◽  
Alihan Kaya ◽  
Devrim Gözüaçık ◽  
Havva Funda Yağcı Acar ◽  
Ali Koşar
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Base Fluid ◽  
Heat Transfer Performance ◽  
Volume Fraction ◽  
Heat Fluxes ◽  
Outer Diameter ◽  
Transfer Performance ◽  
Wide Range

Ferrofluids are colloidal suspensions, in which the solid phase material is composed of magnetic nanoparticles, while the base fluid can potentially be any fluid. The solid particles are held in suspension by weak intermolecular forces and may be made of materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids should be carefully analyzed and considered for their potential of their use in wide range of applications. In this study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions varying from 0% to ∼5% and average particle diameter of 25 nm, in a hypodermic stainless steel microtube with an inner diameter of 514 μm, an outer diameter of 819 μm, and a heated length of 2.5 cm. Heat fluxes up to 184 W/cm2 were applied to the system at three different flow rates (1 ml/s, 0.62 ml/s, and 0.36 ml/s). A decrease of around 100% in the maximum surface temperature (measured at the exit of the microtube) with the ferrofluid compared to the pure base fluid at significant heat fluxes (>100 W/cm2) was observed. Moreover, the enhancement in heat transfer increased with nanoparticle concentration, and there was no clue for saturation in heat transfer coefficient profiles with increasing volume fraction over the volume fraction range in this study (0–5%). The promising results obtained from the experiments suggest that the use of ferrofluids for heat transfer, drug delivery, and biological applications can be advantageous and a viable alternative as new generation coolants and futuristic drug carriers.

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