• Journal of Power System Engineering
• /
• v.13 no.2
• /
• pp.49-55
• /
• 2009

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new tube-and-plate type condenser which will cost less and will be as efficient as the spiral type. As a standard condenser type, tube-and-plate type condenser is used in this study. A two-dimensional numerical model for the tube-and-plate type condenser is proposed, and the flow and heat transfer characteristics for several types of condensers are investigated.

• Journal of the Korean Wood Science and Technology
• /
• v.15 no.3
• /
• pp.1-13
• /
• 1987

This study was carried out to investigate the variations of dimension and exterior shape of vessel elements, morphology of spiral thickening and ray-vessel pit in korean diffuse-porous woods (56 species, 18 families), The tangential pore diameter and vessel element length was increased, whereas the pore number per unit area($1mm^2$) was decreased from pith outwards. The tangential pore diameter was decreased but the length of vessel element was not changed from earlywood to latewood within an annual ring. However, the dimensional variations of vessel element was not able to be recognized among relative positions in peripheral variation. The exterior shape of vessel element could be classified into four types; Type 1 is without tail, Type 2 with ligulate tail, Type 3 with broad taper tail and Type 4 with the very short length between perforations. The distribution frequency of Type 2 and 3 was relatively high in comparision with the others. According to the prominence, distribution position and branched shape, the spiral thickenings could be divided into five types. The spiral thickenings occurred 52% in the species observed. Thus it was doubtful to consider the simple presence of spiral thickening as diagnostic index in diffuse-porous woods. The morphology of ray-vessel pit could be grouped as reticulate, scalariform, oval, linear and coalescent type. Most of species examined showed oval and linear type.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.786-791
• /
• 2009

This study focus on verification of the thermal efficiency of volumetric air receiver with $5kW_{th}$ Dish-type solar thermal system for high temperature uses by using numerical analysis compare with experimental data including shape change of absorber, direction of inlet and outlet. Porous material for radiation-thermal conversion used in former researches are substituted with the stainless steel wall installed along the spiral shaped flow path. Temperature variation and the flow change at the inside of the absorber has been analyzed by Star-ccm+ Version 3.02. Using the numerical model, the heat transfer characteristics of spiral type receiver for dish-type solar thermal systems are known and the thermal performance of the receiver can be estimated.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2292-2297
• /
• 2008

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new type condenser which will cost less and will be as efficient as the spiral type. The new type condenser consists of a steel tube, steel plates and louver fins attached to the tube. The tube and the plate are bent into a single-passage serpentine shape.

• Proceedings of the KIEE Conference
• /
• 2008.04c
• /
• pp.245-246
• /
• 2008

In this paper we calculated and compared the arc driving force of two spiral-tyre vacuum interrupter electrode models which have 3petals and 4petals respectively by means of commercial finite element method software Maxwell 3D. As a result we can find that the more petals the electrode has, the stronger arc driving force was generated. This simulation method can contribute to optimization of spiral-type electrode designs in a view of arc driving force.

• Journal of Magnetics
• /
• v.21 no.4
• /
• pp.616-621
• /
• 2016

This paper presents a new multifunctional active guidewire system for medical applications that uses a magnetic microrobot. The study demonstrated that the proposed microrobot system could swim and be controlled under Low-Reynolds-number (Re) environments in blood vessel models. The prototype of the robotic guidewire, which is driven within a three-axis Helmholtz coil system, consists of a guide-wire, spiral blade, drilling tip, and permanent magnet. The spiral-type microrobot showed stable active locomotion between 3 kA/m and 9.1 kA/m under driving frequency up to 70 Hz in a silicone oil (of viscosity 1000 cst). The microrobot produced a maximum moving velocity of $8.08{\times}10^{-3}m/s$ at 70 Hz and 9.1 kA/m. In particular, the robotic guidewire produced 3D locomotion with drilling in the three-axis Helmholtz coil system. We verified active locomotion, towing of guidewire, steering, and drilling of the proposed robotic guidewire system through experimental analyses.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.427-432
• /
• 1998

중수속의 삼중수소 제거 공정인 액상 촉매 교환 반응에서 중수의 촉매 표면 응축에 의한 성능 저하가 큰 문제의 하나로서 성능 저하를 감소시키기 위한 여러 가지 형태의 촉매탑이 고안 되었다. 본 연구에서는 membrane을 사용하여 중수와 촉매를 분리시킴으로써 촉매 성능 저하를 감소시킬 수 있는 촉매탑의 설계를 시도하였다. 세 가지 촉매탑이 고안되었는데 sheet type의 membrane을 사용한 multilayered type 과 double spiral type, hollow fiber membrane을 사용한 hollow fiber cartridge type 등이다. multilayered type은 구조가 단순하여 scale-up이 용이하고 double spiral type은 다른 type보다 유로의 blocking 문제가 작고 hollow fiber cartridge type은 최대의 비표면적을 가질 수 있다.

• Journal of the Korean Solar Energy Society
• /
• v.29 no.4
• /
• pp.22-27
• /
• 2009

This study focus on verification of the thermal efficiency of volumetric receiver with 5k Wth Dish-type solar thermal system. Spiral flow path shaped on receiver and working fluid(steam) flow along with this flow path. Porous material for radiation-thermal conversion used in former researches are substituted with the stainless steel wall installed along the spiral flow path. Numerical analysis for the flow path and temperature distributions are carried out. Numerical results are compared with experimental data. Using the numerical model, the heat transfer characteristics of spiral type receiver for dish-type solar thermal systems are known and the thermal performance of the receiver can be estimated.

• Bulletin of the Korean Mathematical Society
• /
• v.52 no.4
• /
• pp.1113-1122
• /
• 2015

This paper is concerned with the pattern formation of a diffusive predator-prey model with two time delays. Based upon an analysis of Hopf bifurcation, we demonstrate that time delays can induce spatial patterns under some conditions. Moreover, by use of a series of numerical simulations, we show that the type of spatial patterns is the spiral wave. Finally, we demonstrate that the spiral wave is asymptotically stable.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.89-93
• /
• 2002

In the present paper we suggested a parallel-branch structure of aluminum spiral inductor for the use of RF integrated circuit at 1∼3 GHz. The inductor was implemented on P-type silicon wafer (5∼15 Ω-cm) under the standard CMOS process and it showed a improved quality(Q) factor by more than 10% with no degradation of inductance. The effect of the structure modification on the Q factor and the inductance was scrutinized comparing with those of the conventional spiral inductors.