• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.5
• /
• pp.666-672
• /
• 2001

Experiments have been carried out to investigate the evaporation heat transfer characteristics of various tubes on which hydrophilic surface treatment using plasma was employed. Spiral, corrugated and low-finned tubes were selected as test tubes. The evaporator tubes were bundled to form three rows of tubes connected in series, with each row being 400mm long. The results obtained indicate that hydrophilic treated tubes tested exhibit better evaporation heat transfer performance as compared with untreated tubes. It is found that the high wettability of the surface obtained through hydrophilic treatment induces film flow onto the tubes during the evaporation process, while sessile drops are formed on untreated tubes.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1367-1370
• /
• 1997

This paper presents a vision algorithm for finding the centers of steam generator tubes using the generalized symmetry transform, which is used for ECT(Eddy Current Test) of steam generator tubes in nuclear power plants. The geometrical properties of the image representing steam generator tubes shows that they have amost circular or somewhat elliptic appearances and each tube has strong symmetry about its center. So we apply the generalized symmetry transform to finding centers of steam geneator tubes. But applying the generalized symmetry transform itself without any modification gives difficulties in obtaining the exact centers of steam generator tubes. But applying the generalized symmetry transform itself without any modification gives difficulties in obtaining the exact centers of tubes due to the shadow effect generated by the local light installed inside steam generator. Therefore we make the generalized symmetry transform modified, which uses a modified phase weight function in getting the symmetry magnitude in order to overcome the misleading effect by the local light. The experimental results indicate that the proposed vision algorithm efficiently recongnizes centers of steam generator tubes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.5
• /
• pp.525-532
• /
• 2000

Evaporation heat transfer characteristics have been investigated experimentally when distilled water is sprayed on the outside wall of horizontal tubes in a evaporator. This problem is of particular interest in the design of evaporator of an absorption system. Hydrophilic surface treatment was employed to increase the wettability on copper tubes. The results indicate that evaporation heat transfer with hydrophilic tubes is shown to be 25-44% higher than that with bare tubes at evaporation pressure of 31.8 Torr(evaporation temperature$ 30^{\circ}C). Evaporation heat transfer rates of hydrophilic treatment tubes are improved substantially, comparing with those of conventional copper tubes in the wide range of operating parameters, such as water inlet temperatures, water mass flow rates and evaporation pressures.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.12 no.4
• /
• pp.198-205
• /
• 2004

An experimental study was carried on the characteristics of fluid flow and heat transfer in a fluidized bed shell-and-tube type heat exchanger with corrugated tubes. Seven different solid particles having same volume were circulated in the tubes. The effects of vari­ous parameters such as water flow rates, particle geometries and materials, and geometries of corrugated tubes on relative velocities and drag coefficients were investigated. The present work showed that the drag force coefficients of particles in the corrugated tubes were usually lower than those in the smooth tubes, meanwhile the relative velocities between particles and water in the corrugated tubes were little higher than those in the smooth tubes except the particles of glasses.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.522-524
• /
• 2005

The LED light source has many excellent advantages for the application of LCD backlight module. As we know, the operational temperature can significantly influence the characteristics of LEDs. Heat can damage the LED 's quality, and decrease its lifetime and output light intensity. In this paper, we perform computer software, Flomerics CFD (Computational Fluid Dynamics), to simulate heat distribution of the 20.1" LED backlight module we designing, and realize how the different heat sinks can solve the serious heat problem in practice.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.5
• /
• pp.406-412
• /
• 2003

An experimental study was carried on the characteristics of fluid flow and heat transfer in a fluidized bed shell-and-tube type heat exchanger with corrugated tubes. Seven different solid particles having same volume were circulated in the tubes. The effects of various parameters such as water flow rates, particle geometries and materials, and geometries of corrugated tubes on relative velocities and drag coefficients were investigated. The present work showed that the drag force coefficients of particles in the corrugated tubes were usually lower than those in the smooth tubes, meanwhile the relative velocities between particles and water in the corrugated tubes were little higher than those in the smooth tubes except the glass.

• Corrosion Science and Technology
• /
• v.13 no.1
• /
• pp.6-14
• /
• 2014

Copper metal is widely used in tubes installed in sprinkler water services because of its excellent corrosion resistance. Copper corrosion is considered to be insignificant in water system and the incident of copper pipeline failure is relatively low. However, pitting corrosion is a major problem with all copper tubes. In this study, leaked sprinkler copper tubes were collected from three different locations and examined on the causes of pitting corrosion of copper tubes in sprinkler water plumbing systems. Electrochemical tests such as potentiodynamic polarization, as well as surface and chemical analyses were performed. Results show that pitting corrosion of copper tubes were found as Type I pitting that the carbon film formed on the copper tubes have a harmful effects, causing the pinhole failure in the pipe and resulting in leakage of water. The contermeasures on Type I pitting corrosion of copper tubes were proposed.

• Korean Journal of Clinical Laboratory Science
• /
• v.39 no.3
• /
• pp.156-160
• /
• 2007

We evaluated the newly developed plastic sodium citrate tubes for routine coagulation test by direct comparison with glass citrate theophylline adenosine dipyridamole (CTAD) tubes. Blood was drawn from 100 patients into glass CTAD tubes and plastic sodium citrate tubes. After collection, samples were centrifuged at 1500 ${\times}$g for 15 min at $22^{\circ}C$. Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen were measured by using the Coagrex-800 (IRC, Japan). We used comparison plot by linear regression model and difference plot graphs to compare the results of the independent measurements of PT, aPTT, fibrinogen between glass CTAD tubes and plastic sodium citrate tubes. On the comparison study between glass CTAD tubes and plastic sodium citrate tubes, the correlation coefficients (R) were 0.99 for PT, 0.97 for aPTT and 0.97 for fibrinogen. This results implicated good correlation of each parameter between two tubes. Although the difference plot graph analysis showed statistically significant differences between glass and plastic tubes for PT, aPTT and fibrinogen, the range of difference was acceptable according to the CLSI/NCCLS guideline. The plastic sodium citrate tubes showed good correlation with the glass CTAD tubes, so it can substitute glass citrate tube for routine coagulation tests.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.110-113
• /
• 2004

Aluminum and CFRP tube is light-weight material representatively but collapse mechanism is different under axial loading. Aluminum tube absorbs energy by stable plastic deformation under axialloading. While CFRP(Carbon Fiber Reinforced Plastics)tube absorb synergy by unstable brittle failure but its specific strength and stiffness is higher than that of aluminum tube. In this study, for complement of detect and synergy effect by combination with the advantages of each member, the axialcollapsetests were performed for combined aluminum CFRP tubes which are composed of aluminum tubes wrapped with CFRP out side aluminum square tubes. Collapsecharacteristics were analyzed for combined square tubes which have different CFRP orientation angle and thickness. Test results were compared with that of aluminum tubes and CFRP tubes.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2000.05a
• /
• pp.134-139
• /
• 2000

Evaporating heat transfer characteristics of R-22 were measured inside smooth horizontal copper tubes with inner diameters of 3.36 mm and 5.35 mm respectively. The experiments were conducted in the closed loop which was driven by a magnetic gear pump. Experiments were performed for the following range of variables ; mass velocity of refrigerants (200 to 400 $kg/m^2$ .s) saturation temperature ($0^{\circ}C, \; 5^{\circC$}) and quality (0 to 1.0) The main results obtained are as follows : Evaporating heat transfer coefficients in the small diameter tubes (ID<7 mm) were observed to be strongly affected by a variety of diameters and to differ from those in the large diameter tubes. The heat transfer coefficients of the small diameter tubes are higher than those of the large diameter tubes. Comparing the heat transfer coefficients between experimental results and some well-known previous predictions (Shah's correlation Gungor-Winterton's and Kandlikar's correlation) it was very difficult to apply those to small diameter tubes.