• 한국정밀공학회지
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• 제24권12호
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• pp.95-103
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• 2007

This paper presents a liquid cooling concept for heat rejection of high power electronic devices existing in notebook computers etc. The design, fabrication, and performance of the planar ECF pump and farced-liquid cooling system are summarized. The electro-conjugate fluid (ECF) is a kind of dielectric and functional fluids, which generates jet flows (ECF-jets) by applying static electric field through a pair of rod-like electrodes. The ECF-jet directly acts on the working fluid, so the proposed planar ECF pump needs no moving part, produces no vibration and noise. The planar ECF pump, consists of a pump housing and electrode substrate, achieves maximum flow rate and output pressure of $5.5\;cm^3/s$ and 7.2 kPa, respectively, at an applied voltage of 2.0 kV. The farced-liquid cooling system, constructed with the planar ECF pump, liquid-cooled heat sink and thermal test chip, removes input power up to 80 W keeping the chip surface temperature below $70\;^{\circ}C$. The experimental results demonstrate that the feasibility of forced-liquid cooling system using ECF is confirmed as an advanced cooling solution on the next-generation high power electronic devices.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.197-202
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• 2007

In this study, the cooling characteristics of a liquid cooler using thermoelectric module was experimentally investigated. The experiment was conducted for various inner structures of liquid cooler (4 cases), hot fluid flow rates (0.15-0.25 L/min), number of T.E module (2, 4, 6 set), and the cooling water flow rates (200-600 cc/min) for both parallel and counter flow types. Among the results, better cooling performance geometry was selected. And experiment was also carried out to examine further enhancement of cooling performance by inserting coils (pitches: 0.2, 3, 6 mm) into the hot-fluid channel. Present results showed that the short serpentine type(case2) indicated the best cooling performance. In the case of coil pitch of 3 mm, the best cooling performance was shown, more than 10% increase of the inlet and outlet temperature difference, compared with the case of the cooler without coil. Consequently, the inserted coil pitch should be properly selected to improve cooling performance.

• 한국전산유체공학회지
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• 제16권4호
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• pp.92-99
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• 2011

In order to protect the turbine blade from working fluid of high temperature, many cooling techniques such as internal convection cooling, film cooling, impinging jet cooling and thermal barrier coating have been developed. With all other things, film-cooling has been widely used as the important alternative. In the present work, numerical analysis has been performed to investigate and to compare the film-cooling performance of various film-cooling hole schemes such as cylindrical, crescent, louver, and dumbbell holes. To analyze the turbulent flow and the film-cooling mechanism, three-dimensional Reynolds-averaged Navier-Stokes analysis has been performed with shear stress transport turbulence model. The validation of numerical results has been assessed in comparison with experimental data. The characteristics of fluid flow and the film-cooling performance for each shaped hole have been investigated and evaluated in terms of centerline, laterally averaged and spatially averaged film-cooling effectivenesses. Among the film cooling holes, the dumbbell shaped hole shows better film-cooling effectiveness than the other shaped holes. And the louver and cylindrical shaped hole show the worst film cooling performance, and concentrated flows on near the centerline only.

• 대한기계학회논문집B
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• 제28권7호
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• pp.780-788
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• 2004

This paper reports the fluid flow and heat transfer around a module cooled by forced air flow generated by a piezoelectric(PZT) cooling fan. The fluids are locally accelerated by a flexible PZT fan which deflects inside a fluid transport system of comparatively simple structure mounted on a PCB in a parallel-plate channel(450${\times}$80${\times}$700㎣). Input voltages of 20-100V and a resonance frequency of 23㎐ were used to vibrate the cooling fan. Input power to the module was 4W. The fluid flow around the module was visualized by using PIV system. The temperature distributions around a heated module were visualized by using liquid crystal film(LCF). The cooling effect using a PZT fan was independent of the vent area ratios at the channel inlet and was similar to the forced convection cooling. We found that the flow type was Y-shape and the cooling effect was increased by the wake generated by a piezoelectric cooling fan.

• 한국유체기계학회 논문집
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• 제14권3호
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• pp.33-38
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• 2011

Medicated water electrolysis apparatus, which electrolyzes water into acidic water and alkaline water, was in the spotlight as becoming known the effect of alkaline water. It is known as good for health as removing active oxygen in the human's body and promoting digestion. But, the customers could not get that desired water temperature because these apparatuses are directly connected with a water pipe. So, the cooling system was developed for controlling the temperature of the alkaline water. One of the typical way is to store water in water tank and control the temperature. But, in this way, storing water can be polluted impurities coming from outside. For protecting this pollution, the cooling system based on indirect heat exchange method through phase change between water and ice was developed. In this study, we have calculated efficiency of the cooling system with phase change by experiment and commercial CFD(Computational Fluid Dynamics) code, ANSYS CFX. To consider the effect of latent heat that is generated by melting ice, we have simulated two phase numerical analyses used enthalpy method and found the temperature, velocity, and ice mass distribution for calculating the efficiency of cooling. From the results of numerical analysis, we have obtained the relationship between the cooling efficiency and each design factor.

• 설비공학논문집
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• 제18권1호
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• pp.24-30
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• 2006

Three liquid cooling heat exchangers for cooling of telecommunication equipment were designed and their cooling performances were tested. The liquid cooling heat exchangers had twelve rectangular channels $(5\times3 mm)$ with different flow paths of 1, 4, and 12. Silicon rubber heaters were used to provide heat flux to the test section. Heat input was varied from 75 to 400 W, while flow rate and inlet temperature of working fluid were altered from 1.2 to 4.0 liter/fin and from 15 to 3$30^{\circ}C$, respectively. The 4-path heat exchanger showed lower and more uniform average inner temperatures between heaters and the surface of heat exchanger than those of the others. To obtain optimal distribution of working fluid to each channels of liquid cooling heat exchangers, 2-3-2 and 4-3 type tube distributors were designed, and their distribution performances of working fluid were numerically and experimentally investigated. The distributor of the 2-3-2 type showed superior distribution performance compared with those of the 4-3 type distributor.

• 센서학회지
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• 제20권1호
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• pp.19-24
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• 2011

Brain disorders such as epilepsy is a condition that affects an estimated 2.7 million Americans, 50,000,000 worldwide, approximately 200,000 new cases of epilepsy are diagnosed each year. Of the major chronic medical conditions, epilepsy is among the least understood. Scientists are conducting research to determine appropriate treatments, such as the use of drugs, vagus nerve stimulation, brain stimulation, and Peltier chip-based focal cooling. However, brain stimulation and Peltier chip-based stimulation processes cannot effectively stop seizures. This paper presents simulation of a novel heat enchanger network(HEN) technique designed to stop seizures by using a neural cooling probe to stop focal and spontaneous seizures by cooling the brain. The designed probe was composed of a U-shaped tube through which cold fluid flowed in order to reduce the temperature of the brain. The simulation results demonstrated that the neural probe could cool a 7 $mm^2$ area of the brain when the fluid was flowing atb a velocity of 0.55 m/s. It also showed that the neural cooling probe required 23 % less energy to produce cooling when compared to the Peltier chip-based cooling system.

• 설비공학논문집
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• 제12권4호
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• pp.381-387
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• 2000

An experimental study on the stratified fluids was carried out to investigate the flow characteristics, heat transfer through the interface of fluids, and the applications of thermal behaviors in the square cavity. The same volume of water and silicon oil was filled in it. The experiments were performed with the variations of initial temperatures and cooling surface temperatures. And the effect of vertical or horizontal cooling surface positions in the square cavity was investigated. When the cooling surface temperatures were $-4^{\circ}C$ , the supercooling phenomena were observed for both cases of cooling surface positions in the full region regardless of the initial temperature of fluid. In the square cavity with horizontal cooling surfaces, the lower the initial temperatures were, the longer the supercooling durations were, and with vertical cooling surface the lower the initial temperatures were, the shorter the supercooling durations were.

• 한국유체기계학회 논문집
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• 제12권4호
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• pp.44-53
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• 2009

Numerical design optimization of a fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial basis neural network method, a well known surrogate modeling technique for optimization. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. Twenty training points are obtained by Latin Hypercube sampling for three design variables. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate. The film-cooling effectiveness has been successfully improved by the optimization with increased value of all design variables as compared to the reference geometry.

• Coupled systems mechanics
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• 제11권1호
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• pp.43-54
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• 2022

In order to analyse the thermal performance of battery systems in electric vehicles complex simulation models with high computational cost are necessary. Using reduced order methods, real-time applicable model can be developed and used for on-board monitoring. In this work a data driven model of the cooling plate as part of the battery system is built and derived from a computational fluid dynamics (CFD) model. The aim of this paper is to create a meta model of the cooling plate that estimates the temperature at the boundary for different heat flow rates, mass flows and inlet temperatures of the cooling fluid. In order to do so, the cooling plate is simulated in a CFD software (ANSYS Fluent ®). A data driven model is built using the design of experiment (DOE) and various approximation methods in Optimus ®. The model can later be combined with a reduced model of the thermal battery system. The assumption and simplification introduced in this paper enable an accurate representation of the cooling plate with a real-time applicable model.