• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.135-139
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• 2008

Development of surface heating technology using hot jet impingement onto mold inner surface for improvement of pattern transcription. This study is focused on how to control the parameters related to hot jet impingement. The mass flow rate, the jet temperature and the duration of the impingement are major parameters. The nozzle design and other geometric configurations also affect the heat transfer to the surface. In terms of heat transfer analysis, the most important number is the heat transfer coefficient, which is influenced by the mass flow rate, nozzle design, distance between the nozzle tip and the surface. In summary, several parametric studies using the developed model are conducted to investigate the effects of mass flow rate, jet temperature and Heating Time in Surface heating technology using hot jet impingement onto mold.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.5
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• pp.249-256
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• 2010

Water jet impingement cooling has been widely used in a various engineering applications; especially in cooling of hot steel plate of steelmaking processes and heat treatment in hot metals as an effective method of removing high heat flux. The effects of cooling water temperature on water jet impingement cooling are primarily investigated for hot steel plate cooling applications in this study. The local heat flux measurements are introduced by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are used to measure the heat flux distribution during water jet impingement cooling. The experiments are performed at fixed flow rate and fixed nozzle-to-target spacing. The results show that effects of cooling water temperature on the characteristics of jet impingement heat transfer are presented for five different water temperatures ranged from 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided with respect to different boiling regimes.

• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.9-14
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• 2007

In this paper, a mold temperature control method for injection molding is proposed. The inner surface of mold is locally heated by jet impingement to improve pattern transcription. Heating by hot jet is completed while the mold is open. An experimental system that realizes the proposed idea has been built, which includes mold, nozzle assembly and heater. Actual injection molding process including the proposed heating procedure has been conducted to verify the validity of the method. The process has been done for several conditions with different jet temperatures and duration of heating. The results from different conditions are compared.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.429-435
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• 1998

Experiments were conducted to investigate the turbulent flow characteristics from on oblique impingement surface to an plane jet at the jet Reynolds number(Re based on the nozzle width) $3{\times}10^4$ The jet mean velocity and turbulent intensity profiles have been measured along the impingement surface by hot-wire anemometer. The nozzle-to-plate distance(H/B) ranged from 2 to 10 and the oblique angle (a) from 45 to 90 degree. Also the secondary peak of the turbulent intensity was observed at H/B=4 S/B 5 and a=90 degree. It has been found that the stagnation point shifted toward the minor flow region as the oblique angle decreased and the position of the stagnation point nearly coincided with that of the maximum turbulent intensity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.8-15
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• 2007

The jet impingement cooling characteristics are investigated experimentally. The study is motivated by the potential application of local hot spot cooling by means of the vortex tube. The purposes of this research are to examine the effect of the nozzle-block spacing and flow rate. The results of jet through vortex tube is compared with ones of circular Jet. Flow visualization by the smoke-wire technique is also performed to investigate the flow structure. As the nozzle-block spacing is increased and flow rate decreased, the cooling effect of the Jet through the vortex tube decreases mere remarkably than that of the circular jet. So the cooling effect for the jet through the vortex tube is higher than that for the circular jet at $H/D{\leq}3$, $Q{\geq}10m^3/h$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.17-27
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• 2009

Water jet impingement cooling is used to remove heat from high-temperature surfaces such as hot steel plates in the steel manufacturing process (thermo-mechanical cooling process; TMCP). In those processes, uniform cooling is the most critical factor to ensure high strength steel and good quality. In this study, experiments are performed to measure the heat transfer coefficient together with the inverse heat conduction problem (IHCP) analysis for a plate cooled by planar water jet. In the inverse heat transfer analysis, spatial and temporal variations of heat transfer coefficient, with no information regarding its functional form, are determined by employing the conjugate gradient method with an adjoint problem. To estimate the two dimensional distribution of heat transfer coefficient and heat flux for planar waterjet cooling, eight thermo-couple are installed inside the plate. The results show that heat transfer coefficient is approximately uniform in the span-wise direction in the early stage of cooling. In the later stage where the forced-convection effect is important, the heat transfer coefficient becomes larger in the edge region. The surface temperature vs. heat flux characteristics are also investigated for the entire boiling regimes. In addition, the heat transfer rate for the two different plate geometries are compared at the same Reynolds number.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.385-386
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• 2010

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.448-450
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• 2010

Free surface liquid jet impingement, which is applicable to cooling of hot plates in a steel-making process, is investigated numerically by solving the conservation equations of mass, momentum and energy in the liquid and gas phases. The free-surface of liquid-gas interface is tracked by an improved level-set method incorporating a sharp-interface technique for accurate imposition of stress and heat flux conditions on the liquid-gas interface. The level-set approach is combined with a non-equilibrium $k-{\omega}$ turbulence model. The computations are made for slit nozzle jets to investigate their flow and cooling characteristics. Also, the effects of jetting angle, velocity and moving velocity of plate on the interfacial motion and the associated flow and temperature fields are quantified.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2562-2567
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• 2008

Jet impingement on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The liquid-gas interface or free surface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The computations are made for multiple jets as well as a single jet to compare their flow characteristics. Also, the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.81-94
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• 1988

A series of experiments was performed in this study to investigate the boiling heat flux between an impinging water jet and a hot surface. Test variables were surface roughness, jet velocity, saturation temperature excess of surface, nozzle diameter and the gap distance between nozzle plate and the hot surface. In order to make the impinged cooling water a forced flow streaming a long the hot surface immediately after the initial impingement, the flat nozzle tip was extended to a circular flat plate having the same diameter as the hot surface. Utilizing the dimensionless parameter study on continuity, momentum and energy equations, 5 groups of variables involved in the nucleate boiling heat transfer were derived so that it is possible to estimate the increased heat flux by impinging water jet in a similar experimental work. For the case of saturated water being impinging onto a high temperature surface, an applicable correlation among dimensionless parameters describing the heat flux was found to be as follow.