• Title/Summary/Keyword: Pumping power

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The Study on Drag Reduction Rates and Degradation Effects in Synthetic Polymer Solution with Surfactant Additives (계면활성제를 이용한 합성고분자 수용액의 마찰저항감소 및 퇴화 특성 향상 연구)

  • 이동민;김남진;윤석만;김종보
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.3
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    • pp.194-199
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    • 2001
  • The turbulent flow resistance of water solution with polymer is reduced as compared with that of pure water. This effects is named th drag reduction and offers the significant reduction of the pumping power and the energy consumption. But the intense shear forces and the high temperature experienced by the polymer solution when passing through the pipes cause the degradation a loss of drag reduction effectiveness. Especially, the degradation behavior is found to be strongly dependent on temperature. This mechanical and thermal degradation can be avoided by adding materials such as surfactant to the polymer solution, which enhance the bonding force between molecules. In the present study, Copolymer and SDS were utilized and they were mixed in 10 different mixture ratios, while total concentration was fixed as 100wppm. Degradation of Copolymer-SDS mixture solutions was investigated experimentally in closed loop at the temperature of $10^{\circ}C\; and\; 80^{\circ}C$ with various flow average velocities of 1.5 m/sec, 3.0m/sec, and 4.5m/sec. Degradation characteristics of polymer solution without surfactant show a radical loss of drag reduction effectiveness at high temperature. Degradation alleviation ability of surfactant is especially effective at high temperature. Consequently, this results show that the addition of surfactant to the polymer solution can control unfavorable degradation phenomena for high temperature systems.

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Visible green upconversion luminescence of Li+/Er3+/Yb3+ co-doped CaWO4 phosphor and effects of Yb3+ concentration

  • Cho, Hyun;Lee, Jung-Il;Ryu, Jeong Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.23 no.3
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    • pp.142-145
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    • 2013
  • The upconversion (UC) luminescence of $Li^+/Er^{3+}/Yb^{3+}$ co-doped $CaWO_4$ phosphors and effects of $Yb^{3+}$ concentration are investigated in detail. Single crystallized $CaWO_4$ : $Li^+/Er^{3+}/Yb^{3+}$ phosphor can be obtained, co-doped up to 35.0/5.0/30.0 mol% ($Li^+/Er^{3+}/Yb^{3+}$) by solid-state reaction. Under 980 nm excitation, $CaWO_4$ : $Li^+/Er^{3+}/Yb^{3+}$ phosphor exhibited strong green UC emissions visible to the naked eye at 530 and 550 nm induced by the intra 4f transitions of $Er^{3+}$ ($^4H_{11/2}$, $^4S_{3/2}{\rightarrow}^4I_{15/2}$). The optimum doping concentrations of $Yb^{3+}$ that would result in the highest UC luminescence were determined, and a possible UC mechanism that depends on the pumping power is discussed in detail.

The Inprovement of the Heat Exchanger Performance by Shape Modification(I)-Experimental Analysis of the Heat Transfer Enhancement by Attached Wires in a Double Pipe Heat Exchanger- (형상변화 에 의한 열교환기 의 열전달 성능 향상 (I) -이중 동심원관내에 와이어 부착시의 열전달 촉진에 대한 실험적 해석-)

  • 노승탁;이택식;강신형;김진오
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.1
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    • pp.71-80
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    • 1985
  • The various sizes of wires are attached to the outside of the inner tube in a double pipe heat exchanger to enhance the thermal performance. The diameters of the wires range from 0.5mm to 1.6mm while the pitches are chosen between 5mm and 50mm. Experiments have been performed with the range of Reynolds numbers from 15000 to 30000 in annular space where air flows. The friction factors are increased by 1.5 to 4.5 times depending on the sizes and the pitches of the wires. However, the Nusselt numbers are increased by the factors of 1.8 to 2.8 within this experimental range. It is suggested that there should be an optimum configuration rendered when the weighting values of the heat transfer promotion and the pumping power are given.

NUMERICAL SIMULATION OF FLOW AND HEAT TRANSFER IN COOLING CHANNEL WITH A STAGGERED V-SHAPED RIB (엇갈린 V-형 리브가 부착된 냉각유로에서의 열유동 수치해석)

  • Myong, H.K.;Kim, K.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.125-130
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    • 2008
  • The present study numerically simulates the flow and heat transfer characteristics of rib-induced secondary flow in a cooling channel with staggered V-shaped ribs, extruded on both walls. The rib pitch-to-height ratio (p/h) varies from 2.8 to 10 with the rib-height-to-hydraulic diameter ration ($h/D_h$) of 0.07 and the Reynolds number of 50,000. Shear stress transport (SST) turbulence model is used as a turbulence model. Computational results show that complex secondary flow patterns are generated in the duct due to the snaking flow in the streamwise direction for all tested cases. In the range of p/h=5 to 10 the staggered V-shaped rib gives about 3 times higher heat transfer augmentation than the reference smooth channel with high heat transfer on both front side and the area around the leading edge of the ribs, while the former cases give about 2.5 times higher streamwise pressure drop than the latter ones. Consequently, for the thermal performances, based on the equal pumping power condition, the staggered ones give about 2 times higher values than the latter ones with more uniform heat transfer distribution.

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Optimum Design of Microchannel Heat Sinks (마이크로채널 방열블럭의 최적설계)

  • Jo, Yeong-Jin;Choe, Chung-Hyeon;Kim, Jae-Jung;Lee, Jae-Heon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.1
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    • pp.117-123
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    • 2001
  • In present study a methodology has been developed and applied for the optimum design and performance evaluation of microchannel heat sinks. The optimum design parameters include channel number and fin thickness. For a trial model of 127mm in length, 52.5mm in width, 16mm in height and 2.5mm in base thickness, the optimum channel number and the fin thinckness have been determined to be of 194 and 0.08359mm, respectively in laminar flow region. Performance of the optimally designed microchannel heat sinks has been compared with those having 50% and 150% of the number of channels. The results showed that the 50% and 150% designs increased the pumping power by 200% and 150%, respectively.

The Proposal of a New Drainage System without Incline of Piping and Experiment on Drainage Flow Characteristics (구배가 없는 신배수시스템의 제안 및 배수유동 특성에 관한 실험적 연구)

  • Cha Young-Ho;Yee Jurng-Jae
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.5
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    • pp.452-458
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    • 2005
  • In Korea, pumping pipe using gravity way by water is most popular method in drainage system. But, it is difficult to repair a drainpipe in this method because the drain pipe diameter is increased as using this method. In this research, we propose a new drainage system. The system aim for an adaptedness with buildings, freedom of plan, construction and renewal in water pipe equipments, etc. The new system is not need of incline of piping, and it uses drainage power that is changed potential energy by high velocity flow as making Siphonage at vertical pipe. Therefore, the diameter of piping can decreased than existing piping system established in the ceiling. Also because connecting position will be located at the lower part, it is changed the potential energy of drainage to the high velocity flow. In addition, drainage will be smooth because the fixture drain is linked by each drain pipes.

Single Longitudinal Mode Operation of a Pulsed Dye Laser Injection-seeded with a CW Ring Dye Laser (인젝션 록킹 방법에 의한 펄스 색소레이저의 단일 종모우드 발진)

  • 김재완;공홍진;한재원;박승남
    • Korean Journal of Optics and Photonics
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    • v.5 no.1
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    • pp.84-89
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    • 1994
  • A tunable pulsed dye laser was operated in a single longitudinal mode by injection locking with a cw ring dye laser. A doubled Nd:YAG laser was used as the pumping source. Phase sensitive detection technique was applied to maintain the required match between the master laser frequency and the slave resonator cavity length. The fluctuation of the center frequency of the pulsed laser was < 10 MHz, and the pulse duration (FWHM) was 6 ns. The linewidth measured by scanning confocal interferometer was 130 MHz. When pumped by 50 mJ of the doubled Nd:YAG laser, the output energy of the pulsed dye laser was 2 mJ and the peak power was 330 kW. 30 kW.

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On the Instantaneous and Average Piston Friction of Swash Plate Type Hydraulic Axial Piston Machines

  • Jeong, Heon-Sul;Kim, Hyoung-Eui
    • Journal of Mechanical Science and Technology
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    • v.18 no.10
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    • pp.1700-1711
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    • 2004
  • Piston friction is one of the important but complicated sources of energy loss of a hydraulic axial piston machine. In this paper, two formulas are derived for estimating instantaneous piston friction force and average piston friction moment loss. The derived formula can be applicable for piston guides with or without bushing as well as for axial piston machines of motoring and pumping operations. Through the formula derivation, a typical curve shape of friction force found from several experimental measurements during one revolution of a machine is clearly explained in this paper that it is mainly due to the equivalent friction coefficient dependent on its angular position. Stribeck curve effect can easily be incorporated into the formula by replacing outer and inner friction coefficients at both edges of a piston with the coefficient given by Manring (1999) considering mixed/boundary lubrication effects. Novel feature of the derived formula is that it is represented only by physical dimensions of a machine, hence it allows to estimate the piston friction force and loss moment of a machine without hardworking experimental test.

Effects of Corrugation Angle on Local Heat/mass Transfer in Wavy Duct. (열교환기 내부 유로 꺾임각 변화에 따른 국소 열/물질전달 특성 고찰)

  • Jang, In-Hyuk;Hwang, Sang-Dong;Cho, Hyun-Hee
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.97-102
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    • 2003
  • An experimental study is conducted to investigate the effects of duct corrugation angle on heat/mass transfer characteristics in wavy ducts by using a naphthalene sublimation technique. The corrugation angles of the wavy ducts are $145^{\circ}$ , $130^{\circ}$ and $115^{\circ}$ . and the Reynolds numbers based on the duct hydraulic diameter vary from 300 to 3,000. At the low $Re(Re{\leq}1000)$, high heat/mass transfer regions are formed by the secondary vortex flows called Taylor-Gortler vortices on both pressure-side and suction-side walls. At the high $Re(Re{\geq}1000)$, the effects of these secondary flows are vanished. As corrugation angle decreases, the local peak Sh induced by Taylor-Gertler vortices are increased and average Sh also enhanced. More pumping power (pressure loss) is required with the smaller corrugation angle due to the stronger secondary vortex flows.

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Astigmatically compensated cw Ti:Sapphire laser pumped by $Ar^+$ laser (비점수차가 보상된 $Ar^+$ 레이저로 펌핑하는 cw Ti:Sapphire 레이저)

  • Yoon, Tai-Hyun;Kim, Gyu-Ug;Jo, Jae-Heung;Won, Jong-Wook
    • Proceedings of the KIEE Conference
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    • 1990.07a
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    • pp.451-454
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    • 1990
  • Room temperature cw operations of a standing wave and a unidirectional Ti:Sapphire laser pumped by a $Ar^+$ laser have been demonstrated in the same pumping cavity configuration. Laser emission at 790 nm was excited with all-line $Ar^+$ laser pump for both cavities. The maximum output power was found to be 600 mW in the standing wave cavity and 210 mW in the ring cavity. Values of (83 ${\pm}$ 10) % for the internal quantum efficiency and (3.0 ${\pm}$ 0.5) % for the round-trip cavity loss for standing wave cavity are obtained from the thresholds and slope efficiencies measured with 2.4 and 11.2 % optput couplers. The measured cavity-loss value at 790 nm gives a meterial figure of merit (FOM) to be 146. Unidirectional operation of the ring Ti:Sapphire laser will be discussed.

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