• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.4
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• pp.225-232
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• 2001

An experimental study is carried out to investigate the characteristics of heat transfer of outside helical tubes. The main heat exchanger consists of twelve curved columns with each 300mm diameter and the total length of 1.2m copper tube having an outer diameter of 19.05mm with 1.5mm thickness. Water flows down the outside of helical tube, where flow patterns are the vertical film falling flow, immerged flow, and mixed-flow which is the combination of film falling flow and immerged flow. Refrigerant 11 flow the inside of the tube countercurrently. The experimental range of inside flow rate is 1.7~3.2$\ell$/min and outside flow rate is 21-33$\ell$/min. The results are presented as Nusselt number with corresponding Reynolds number for variety of outside and inside flow rates. The heat transfer rates of the mixed flow are 8 to 56% higher than those of film falling flow or immerged flow only. Interpretation of the results is given on the basis of physical reasoning and the correlation equations.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.535-542
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• 2011

To utilizing CFX V12.0.l, internal flow characteristics of denture high-speed air turbine hand-piece unit was identified, in order to analyze the performance of the torque values were compared. In order to find out the difference of torque by mash values, under steady condition, performed grid convergence test. It compared theoretical torque with torque through flow analysis. To describe the motion of turbine blade was used to immerged solid method. Depending on the location of the turbine blade were calculated from five case. Maximum and minimum values of turbine blades was analyzed. To analyze the performance of the torque values were compared with speed of turbine blade.

• Journal of computational fluids engineering
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• v.9 no.2
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• pp.18-22
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• 2004

Numerical investigation has been conducted to figure out flow behavior and pressure drop characteristics of spirally corrugated steel pipe which is widely used in civil, industrial and agricultural field owing to many advantages such as good corrosion resistance and durability, strength, easy and quick installation. Also the poly-ethylene coating spirally corrugated steel pipe has the long life under condition of sea water immerged. In the present study, flow behavior in the spirally corrugated pipe and influence of P/d/sub h/(ratio of wave pitch to hydraulic diameter) to pressure drop are investigated by CFD with various Reynolds number. And also friction factor is estimated by pressure drop obtained by flow analysis. According to computation results, the flow runs spirally up and down along the spiral corrugation in the vicinity of wall, but the effect of spiral corrugation disappears in core region of pipe. As P/d/sub h/ becomes small, more pressure drop occurs in spirally corrugated Pipe. Besides, friction factor augmentation becomes much larger as Re increases. In case of p/d/sub h/=0.38, Pressure drop and friction factor of spirally corrugated pipe are about four times larger than smooth pipe at Re: 1.46×10/sup 6/.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.828-836
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• 1987

The inclusion of thermophoresis in particle deposition studies has often been treated separately from deposition due to flow characteristics. Also previously reported experimental results on thermophoresis have been studied in the regions of relatively small temperature gradients. In this study, using real-time laser light reflectivity method, we measured the angular dependence of the deposition rates of particles of the cylindrical collector surface, which immerged in laminar flow of a hot gas suspension of small particles. And we extended the previous narrowband results of thermophoretic deposition rates to the regions of large temperature gradients between the hot gas stream and the collector surface. Based on the obtained data, the cylinder's forward stagnation-point region is considerably enriched in particle 'phase' density owing to the compressibility effect, which leads to locally enhanced deposition while the downstream region from the stagnation point inertial force acts in the opposite direction, which tends to centrifuge particles away from the wall, thus the local deposition rates by thermophoresis are reduced.

• Archives of design research
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• v.12 no.4
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• pp.294-303
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• 1999

With the breakthrough development of computing environment, the design phases have been changed a lot nowadays. In the case of prior phases of transportation design such as cars and forklift-trucks design, designers have depended on surveys and 2D line drawings for fixing a product layout and extracting ergonomic data. In this method, designers don't meet only the problem of reliability of measuring data but also, the problems of unknown situation of operators' fatigue and comfort in work situation. In these methods, it has much less creditability to have a 2D human model to check the real world motion due to the limitation of the 3 Dimension. Even though with a 2D human model, perfect layout is determined, it is still difficult to measure about comfort and fatigue for a user because it measuring an analysing method is static. The development of computer hardware and software have not only changed the flow in the social-wide range but also immerged design into Virtual Environment. In conventional design method, visualization and data transferring have been the main issues but, in virtual environment, determining of design layout and analysing ergonomic data with sophisticated feeling about comfort and fatigue are possible by using 3D virtual human. In this study, the general characteristics of virtual environment was discussed and the possibility of digital process of design was treated. For these studies, layout design for forklift-trucks was tested. Eventually, the merits of each design phase applied virtual environment are discussed.