• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.63-68
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• 2005

In the present paper, the study on the optimal horizontal air jet velocity of a range hood system has been studied by three dimensional numerical simulation. It has been shown that the air jet of a range flood system generates coanda effect confining the contaminated (high temperature) air in a certain region while the jet pushes out more contaminated air into a room as the jet velocity increases. Therefore, the optimal jet velocity has been determined by the combination of the two mechanism.

• 설비공학논문집
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• 제17권4호
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• pp.333-340
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• 2005

Horizontal air-jet effect has been utilized in some air conditioning systems in order to control the contaminated air indoor. In the present study, the flow and heat transfer of the contaminated air from a range hood system has been investigated with or without horizontal air-jet effect when the hood fan is on or off. For the present numerical experiment, PAT Flow code has been used. From the present numerical simulations, it has been shown that the air jet of a range hood generates coanda effect confining the contaminated air in a certain region. Furthermore, the qualitative relation between the flow rate of the capture air jet and the distribution pattern of the contamination has been discussed.

• 한국분무공학회지
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• 제27권3호
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• pp.126-133
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• 2022

The objective of this is to experimentally investigate the effect of mixed jet on the oxygen transfer characteristics with the primary nozzle area ratio of an annular nozzle ejector for the application of a microbial fuel cell. A direct visualization method with a high speed camera system was used to capture the horizontal mixed jet images, and a binarization technique was used to analyze the images. The clean water unsteady state technique was used for the oxygen transfer measurement. The air-water mixed jet discharging into a water tank behaved similar to a buoyancy or horizontal jet with the primary nozzle area ratio. It was found that an optimum primary nozzle area ratio was observed where the oxygen transfer performance reached its maximum value due to the decrease of air volume fraction and the increase of jet length and air bubble dispersion.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1503-1506
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• 2009

Bubble jet loop heat pipe is a newly devised variation of heat pipe in which heat is effectively transported by the latent heat of evaporation and condensation as well as the heat capacity of circulating working fluid. The circulatory and oscillating motion of the working fluid becomes possible by the motion of bubble jet which is generated at a narrow circular gap. These bubbles are condensed at the condensing section. Bubble jet loop heat pipe makes it possible to carry heat long distances upward and horizontal directions. Because Its structure is a very simple and a low cost, it is available for the floor heating, vinyl house heating, the defrosting of heat pump system and home refrigerator.

• 대한기계학회논문집B
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• 제41권1호
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• pp.29-36
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• 2017

본 논문은 환형노즐 이젝터를 이용하여 세정수 공급과 기포생성을 동시에 할 수 있는 세정기술 개발을 위한 기초연구를 목적으로 한다. 환형노즐 이젝터의 피치변화에 따른 구동 및 부유체의 정량적 유동특성과 세정수조에 분출되는 분류의 정성적 가시화 이미지를 분석하였으며, 세정물의 농약 잔류물 성분의 농도를 검증하였다. 피치가 증가하면 구동유량은 증가하는 반면에, 유량비는 감소하였다. 피치가 증가하면 분류는 부력분류나 평형분류 거동을 나타내며, 잔류농약의 농도는 감소 후 증가하였다.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.1-8
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• 2005

Transition of momentum-controlling hydrogen jet to buoyant jet is experimentally investigated in order to develop a prediction model for the moving trajectory of hydrogen leaked from hydrogen devices. In the experiments, room-temperature helium, that has a similar density to the hydrogen leaked from high pressure tank, is horizontally injected through a 4mm tube and its moving trajectory is visualized by the shadowgraph method. The moving trajectories are found to be parabolic, thereby exhibiting increasing influence of the buoyancy. In analyzing the experimental results, the vertical movement is assumed to be controlled by the buoyancy while the horizontal movement is controlled by the air entrainment caused by the initial momentum. The resealing based on this assumption yields a single curve fitting to the all experimental results.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2011-2017
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• 2023

Gas submerged jet is an outstanding thermohydraulic phenomenon in pool scrubbing of fission products during a severe nuclear accident. Experiments were performed on the hydraulic characteristics in the ranges of air mass flux 0.1-1400 kg/m²s and nozzle diameter 10-80 mm. The results showed that the dependence of inlet pressure on the mass flux follows a power law in subsonic jets and a linear law in sonic jets. The effect of nozzle submerged depth was negligible. The isolated bubbling regime, continuous bubbling regime, transition regime, and jetting regime were observed in turn, as the mass flux increased. In the bubbling regime and jetting regime, the air volume fraction distribution was approximately symmetric in space. Themelis model could capture the jet trajectory well. In the transition regime, the air volume fraction distribution loses symmetry due to the bifurcated secondary plume. The Li correlation and Themelis model showed sufficient accuracy for the prediction of jet penetration length.

• Ocean Systems Engineering
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• 제11권1호
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• 설비공학논문집
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• 제27권12호
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• pp.652-658
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• 2015

The Bubble Jet Loop Heat Pipe (BJLHP) is designed to operate in the horizontal orientation. The motion of the bubble generated by boiling working fluid on a heater surface in the evaporating section of the BJLHP helps the working fluid transfer heat to the condensing portion. In this study, we changed the position of the heater in the evaporating section from concentric to eccentric. The concentric heater is located at the center of the tube in the evaporating part, and the eccentric heater is located at the bottom of the inner surface of the same tube. We used R-134a as the working fluid, and the charging ratio was 50%vol. We measured the temperatures of the evaporating and condensing sections by changing the input electric power from 50 W to 200 W, measuring every 50 W. The results of the experiment show that the effective thermal conductivity of BJLHP using an eccentric heater is four times higher than the BJLHP obtained using a concentric heater. Additionally, we conducted a visualization experiment on the evaporating portion of BJLHP to determine why the effective thermal conductivity was higher. The working fluid was water, and we took pictures of the flow visualization for BJLHP. Nucleate boiling with the eccentric heater was more intense and generated more bubbles. Therefore, the eccentric heater was more saturated by the liquefied working fluid.

• 에너지공학
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• 제2권3호
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• pp.285-292
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• 1993

A cylindrical-shape, horizontal furnace was used to investigate the effect of particle size on the pulverized coal combustion behavior. Three differently-sized fractions (5, 30, and 44 microns in average diameter) of high-volatile bituminous coal, were burned in the test furnace. Ignition characteristics of pulverized coal flame were determined through the amount of methane in the carrier gas for the self-sustaining flame. Easiest ignition occurred with the immediately-sized coal particles. Ignition of coal jet flame appeared to occur through a gas-phase homogeneous process for particles larger than 30 microns. Below this limiting size, heterogeneous process probably dominated ignition of coal flame. Oxygen concentration of combustion air was varied up to 50%, to determine the oxygen-enrichment effect on the coal ignition behavior. Oxygen enrichment of primary air assisted ignition behavior of pulverized coal flame. However, enrichment of secondary air didn't produce any effect on the ignition behavior.