• Journal of Power System Engineering
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• v.9 no.2
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• pp.88-92
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• 2005

The experiment of thermal performance about closed-wet cooling tower was conducted in this study. A closed cooling tower is a device similar to a general cooling tower, but with cooling tower replaced by a heat exchanger. The test section for this experiment has the process that the cooling water flows from the top of the heat exchanger to the bottom side in the inner part of the tube, and spray water flows in the gravitational direction in the outer side. Air comes in direct contact with the spray water at the outer side of the tube while passing from the lower the upper part having a counterflow to the spray water. The heat transfer pipe used in this experiment is a bare-type tube having an outer diameter of 15.88mm. The heat exchanger is consisted of seven rows and fifteen columns. In this experiment, thermal performance of the cooling tower is derived from overall heat transfer coefficients between the process fluid and sprayed water and volumetric overall mass transfer coefficient between sprayed water and air.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.115-121
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• 1995

As the metal transfer in the GMAW process affects the weld quality and productivity, the mechanism of molten formation and detachment has been investigated at various welding conditions. The force balance and pinch instability models have been widely used to analyze the metal transfer in the globular and spray modes, respectively A new approach is proposed in this work by minimizing the energy of molten drop system. Effects of the surface tension, gravity, electromagnetic and drag forces are considered with no presumed molten drop geometry. Effects of various welding conditions on the metal transfer are explained. The results show that the proposed mode can be applied to the globular and spray transfer modes. When compared with other models, results of the proposed model show better agreements with the available experimental data, which demonstrates the validity of the present model.

• Journal of Mechanical Science and Technology
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• v.16 no.3
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• pp.376-385
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• 2002

Spray impingement and fuel film formation models with cavitation have been developed and incorporated into the computational fluid dynamics code, STAR-CD. The spray/wall interaction process was modeled by considering the effects of surface temperature conditions and fuel film formation. The behavior of fuel droplets after impingement was divided into rebound, spread and splash using the Weber number and parameter K(equation omitted). The spray impingement model accounts for mass conservation, energy conservation, and heat transfer to the impinging droplets. The fuel film formation model was developed by integrating the continuity, momentum, and energy equations along the direction of fuel film thickness. Zero dimensional cavitation model was adopted in order to consider the cavitation phenomena and to give reasonable initial conditions for spray injection. Numerical simulations of spray tip penetration, spray impingement patterns, and the mass of film-state fuel matched well with the experimental data. The spray impingement and fuel film formation models have been applied to study spray/wall impingement in high-speed direct injection diesel engines.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1321-1326
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• 2008

A study on the heat and mass transfer for the drying time in spray freezing drying process was experimentally presented in this paper. A spray freezing dryer for the production of an inhalable powder medicine is developed and an albumin solution as protein specimen is adopted. The freeze-drying for the albumin solution is tested in three different height of the particles piled up in a tray such as 2 mm, 5 mm, 7 mm, and the drying time is estimated as 10 h, 15 h, 22 h. From this results, the correlation is suggested and the drying time with various height of the particles piled up in a tray can be estimated. The assessment on the drying time is conducted thought a microbalance and the rate of water content is measured. The results based on temperature and weight are compared. The difference of the results happens due to the heat transfer from the lateral side of the vial. It is thought that the better estimation in drying time can be predicted by considering the heat transfer effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.503-511
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• 2011

Water spray cooling is a significant technology for cooling of materials from high-temperature up to $900^{\circ}C$. The effects of cooling water temperature on spray cooling are mainly provided for hot steel plate cooling applications in this study. The heat flux measurements are introduced by a novel experimental technique that has a function of heat flux gauge in which test block assemblies are used to measure the heat flux distribution on the surface. The spray is produced by a fullcone nozzle and experiments are performed at fixed water impact density of G and fixed nozzle-totarget spacing. The results show that effects of water temperature on forced boiling heat transfer characteristics are presented for five different water temperatures between 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided to a benchmark data for the actual spray cooling of hot steel plate cooling applications.

• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.7-14
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• 2004

A new electrostatic rotary atomizing painting equipment using air turbine was developed for high transfer efficiency. Based on the overall design requirements of painting equipment, basic design specifications of the equipment parts such as air turbine and atomizing disk ate defined from the present conceptual design model. Air turbine is designed with the section profile of NACA airfoil, and its internal flow field is analyzed by commercial CFD code. Atomizing disk is designed to achieve the ligament type spray of paint with the use of visualization technique. Various experiments and tests are conducted to investigate the spray and the transfer characteristics of newly-designed painting equipment, and the measurement results are compared with the those of conventional painting equipments. The comparison results show the present painting equipment is superior to the conventional ones in the aspects of transfer efficiency and coating surface characteristics.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.919-924
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• 2000

Spray impingement model and fuel film formation model were developed and incorporated into the computational fluid dynamics code, STAR-CD. The spray/wall interaction process were modelled by considering the change of behaviour with surface temperature condition and fuel film formation. We divided behaviour of fuel droplets after impingement into stick, rebound and splash using Weber number and parameter K. Spray impingement model accounts for mass conservation, energy conservation and heat transfer to the impinging droplets. A fuel film formation model was developed by Integrating the continuity, the Navier-Stokes and the energy equations along the direction of fuel film thickness. The validation of the model was conducted using diesel spray experimental data and gasoline spray impingement experiment. In all cases, the prediction compared reasonably well with experimental results. Spray impingement model and fuel film formation model have been applied to a direct injection diesel engine combustion chamber.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.36-43
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• 1999

The effect of Si content in welding wires on spattering characteristics and droplet transfer phenomena was studied. In MAG welding using 80% Ar-20% $CO_2$ shielding gas, spattering characteristics and droplet transfer phenomena were varied with Si content of wire. With increasing Si content, the spattering ratio and the ratio of large size spatter $(d\geq1.0mm)$ were increased. The increase of Si content in molten metal made surface tension increase due to reduction of oxygen content, which resulted from deoxidizing action of silicon. The increase of surface tension resulted in unstable transfer phenomena and arc instability in both short circuit and spray region. With changing Si content of wire, spattering characteristics and droplet transfer phenomena was directly influenced by the variation of surface tension, compared with the effect of arc stability.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1101-1117
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• 2006

In the present article, recent progress of spray-wall interaction research has been reviewed. Studies on the spray-wall interaction phenomena can be categorized mainly into three groups: experiments on single drop impact and spray (multiple-drop) impingement, and development of comprehensive models. The criteria of wall-impingement regimes (i.e., stick, rebound, spread, splash, boiling induced breakup, breakup, and rebound with breakup) and the post-impingement characteristics (mostly for splash and rebound) are the main subjects of the single-drop impingement studies. Experimental studies on spray-wall impingement phenomena cover examination of the outline shape and internal structure of a spray after the wall impact. Various prediction models for the spray-wall impingement phenomena have been developed based on the experiments on the single drop impact and the spray impingement. In the present article, details on the wall-impingement criteria and post-impingement characteristics of single drops, external and internal structures of the spray after the wall impact, and their prediction models are reviewed.

• Solar Energy
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• v.15 no.2
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• pp.91-99
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• 1995

The influence of deposition parameters on the deposition of $SnO_2$ thin films by spray pyrolysis has been studied. In the case of spray solution with tile concentration of 0.01M, at low deposition temperature the deposition was controlled by surface reaction and portion controlled by mass transfer is increased with increasing deposition temperature to $400^{\circ}C$. Above $400^{\circ}C$, the deposition is controlled by mass transfer at low spray pressure, and by surface reaction at high spray pressure. As the concentration of spray solution increased the deposition rate increased, and in this experiment the deposition depends on the Rideal-Eley mechanism. The deposition rate increased with increasing substrate temperature up to $400^{\circ}C$ and then decreased due to homogeneous nucleation. The thickness of the deposit increased with increasing spray duration, and the adhesion between substrate and deposit was formed physically.