• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.147-154
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• 2003

A three-dimensional numerical analysis of the flow and heat transfer characteristic of wood-flour-filled polypropylene melt in an extrusion die was carried out. Used for this analysis were Finite Concept Method based on FVM, unstructured grid and non-Newtonian fluid viscosity model. Temperature and flow fields are closely coupled through temperature dependent viscosity and viscous dissipation. With large Peclet, Nahme, Brinkman numbers, viscous heating caused high temperature belt near die housing. Changing taper plate thickness and examining some predefined parameters at die exit investigated the effect of taper plate on velocity and temperature uniformities. In the presence of taper plate, uniformity at die exit could be improved and there existed an optimum thickness to maximize it.

• Journal of Mechanical Science and Technology
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• v.16 no.2
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• pp.246-254
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• 2002

Recent primary concern for the design of high performance heat exchanger and highly integrated electronic equipments is to develop an active and creative technologies which enhance the heat transfer without obstructing the coolant flows. In this study, we found through the LDV measurement that the gaseous cavitation induced by ultrasonic vibration applied to the CO$_2$saturated water in the square cross-sectioned straight duct flow enhances the turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation does. We also found that gaseous cavitation can enhance effectively the turbulent heat transfer between the heating surfaces and coolants by destructing the viscous sublayer.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.96-99
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• 2011

Fiber coatings are essential in optical fiber manufacturing, since they provide the protective layers from the surface damages and the adequate fiber strength. Flow and temperature fields of coating liquid in a fiber coating applicator are numerically investigated by using a commercial CFD software. The main focus of this computational study is on the thermal effects by viscous dissipation and the effects of coating supply temperature on the final fiber coating thickness. The numerical results reveal that the thermal effects play a major role in the high-speed optical fiber coating process and give substantial influences on the determination of coating thickness. Changing the supply temperature of coating liquid is found to relieve the radial variation of coating liquid viscosity in the coating die and it can be an effective way to control the fiber coating thickness.

• Journal of Adhesion and Interface
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• v.3 no.1
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• pp.20-23
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• 2002

The wetting properties of an uncured epoxy resin on both clean and oiled, galvanised steel have been studied. Since the polymer is very viscous at ambient temperature, and also with an aim to simulate industrial conditions, the spreading of drops of resin during a heating cycle (temperature increase at $10^{\circ}C/min$) was recorded and analysed. On clean steel, a contact angle, ${\theta}$, vs time, t, plot shows sigmoidal behaviour, whereas on the oiled substrate, spreading almost ceases in an intermediate stage. This strange behaviour is attributed to significant oil absorption by the polymer.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2194-2199
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• 2007

An experimental study is performed to investigate the thermal and flow characteristics of subcooled liquid nitrogen in a natural circulation loop. Experimental apparatus is designed and constructed such that a closed loop is cooled at the top by a cryocooler and heated nearly at the bottom by cartridge heaters. Steady state is obtained by controlling the heating power to the cartridge heaters and a thin-film heater to reduce the cooling power of the cryocooler. Temperature is measured at several locations of the loop and the mass flow rate through the loop is estimated from the energy balance in terms of the measured temperatures. Experiment is repeated for various values of the vertical height between the cooling and heating parts. The results show that the heat transfer capability of the loop has a maximum at a certain value of height. The optimal height to maximize the heat transfer is in a good agreement with analytical prediction to take into account the buoyancy and viscous forces in the loop.

• Journal of computational fluids engineering
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• v.8 no.4
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• pp.34-40
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• 2003

The effect of nose radius on aerodynamic heating is investigated by using the Navier-Stokes code extended to thermochemical nonequilibrium airflow, Spherical blunt bodies, whose nose radius varies from 0.O03048 m to 0.6096 m, flying at Mach 25 at an altitude of 53.34 km are considered. Comparison of heat flux at stagnation point with the solution of Viscous Shock Layer and Fay-Riddell are made. Results show that the flow for very small radius is in a nearly frozen state, and therefore the heat flux due to diffusion is smaller than that due to translational energy. As the radius becomes larger, the portion of heat flux by diffusion becomes greater than that of heat flux by translational temperature and approaches to a constant value.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1654-1659
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• 2017

The boundary layer of a two-dimensional forced convective flow along a persistent moving horizontal needle in an electrically conducting magnetohydrodynamic dissipative nanofluid was numerically investigated. The energy equation was constructed with Joule heating, viscous dissipation, uneven heat source/sink, and thermal radiation effects. We analyzed the boundary layer behavior of a continuously moving needle in Blasius (moving fluid) and Sakiadis (quiescent fluid) flows. We considered Cu nanoparticles embedded in methanol. The reduced system of governing Partial differential equations (PDEs) was solved by employing the Runge-Kutta-based shooting process. Computational outcomes of the rate of heat transfer and friction factors were tabulated and discussed. Velocity and temperature descriptions were examined with the assistance of graphical illustrations. Increasing the needle size did not have a significant influence on the Blasius flow. The heat transfer rate in the Sakiadis flow was high compared with that in the Blasius flow.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.70.3-70.3
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• 2020

Previous numerical simulations on planet-disk interactions revealed a lot of interesting phenomena including the planetary migration and the formation of many sub-structures inside the disks. However, these simulations were limited to an isothermal or adiabatic equation of state which does not account for various heating and cooling processes in the disks. Recent studies showed that the behavior of the planet-disk interaction can be significantly influenced by the disk thermodynamics. We develop a radiative diffusion module based on the two-temperature flux-limited diffusion approximation accounting for viscous heating and the accretion feedback. In this presentation, we describe our radiative diffusion solver, present some test results, and discuss potential applications of the module to planet-disk interactions,

• Journal of Energy Engineering
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• v.12 no.1
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• pp.29-34
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• 2003

Thermo-acoustic waves can be generated in a compressible fluid by rapid heating and cooling near the boundary walls. These phenomena are very important mechanism of heat transfer in the space environment in which natural convection does not exist. In this study, the generation and transmission characteristics of thermo-acoustic waves in an air filled enclosure with rapid wall heating are studied numerically. The governing equations were discretized using control volume method, and were solved using PISO algorithm and second-order upwind scheme. For the stable solution time step were considered as t=1$\times$$10^{-9}$ order, and grids are 50$\times$800. The induced thermo-acoustic wave propagates through the fluid until it decays due to viscous and heat dissipation. The wave showed sharp front shape and decreased with long tail.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.791-798
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• 1994

Ohmic heating is a food processing operation in which heat is internally generated within foods by the passage of alternating electric current. The process enables highly viscous paste foods such as Kochujang, and fermented soybean paste to be heated very fast. In order to develope the novel pasteurization process of paste foods, static Ohmic heating system was built, and heating characteristic during Ohmic heating under various conditions were studied. Electric conductivities of Kochujang and fermented soybean paste at room temperature were 1.865 S/m and 2.510 S/m, respectively and increased linearly with increasing temperature. Specific heating rate was highly dependent on the frequency. The highest heating rate was achieved at 5 KHz for Kochujang and 20 KHz for fermented soybean paste. Uniform heating throughout the sample was achieved during Ohmic heating with low frequency electrical currents, however above 5 KHz frequency, surface temperature was several degrees higher than the bulk.