• The KSFM Journal of Fluid Machinery
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• v.13 no.3
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• pp.30-36
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• 2010

The detailed heat transfer coefficients on a rotating dimpled channel were measured by the hue detection based the transient liquid crystal technique. The dimples were fabricated on the one side of the channel and the tested channel aspect ratio was 4, 6, and 12 with fixed channel width. Tested Reynolds number based on the channel hydraulic diameter was varied from 21,000 to 47,000. A stationary case and two different rotating conditions were tested so that the dimple fabricated surface became leading or trailing surface. For all rotating conditions, the minimum averaged heat transfer coefficient was measured for the channel aspect ratio of 6. Generally, the highest averaged heat transfer coefficient was observed for the highest aspect ratio cases due to increased dimple induced vortex strength.

• International Journal of Fluid Machinery and Systems
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• v.6 no.1
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• pp.1-10
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• 2013

Jet pump is one type of artificial lifts and is used when depth and deviation of producing wells increases and pressure depletion occurs. In the present study, numerical analysis has been carried out to analyze the flow behavior and find the performance of the jet pump. Reynolds-averaged Navier Stokes equations were solved and k-${\varepsilon}$ turbulence model was used for simulations. Water and light oil as primary fluids were used to pump water, light oil and heavy oil. The ratios of area and length to diameter of the mixing tube were considered as design parameters. The pump efficiency was considered to maximize for the downhole conditions. It was found that the increase in viscosity and density of the secondary fluid reduced efficiency of the system. Water as primary fluid produced better efficiency than the light oil. It was also found that the longer throat length increased efficiency upto 40% if light oil was used as primary fluid and secondary fluid viscosity was 350 cSt.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1035-1042
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• 2006

An experimental investigation was performed to study two-phase pressure drop of deionized water in a microchannel. Measurement and evaluation of two-phase frictional pressure gradient were carried out using a single horizontal rectangular microchanne1 having a hydraulic diameter of $100{\mu}m$. Tests were performed for mass fluxes of 90, 169, and 267 $kg/m^2$s and heat fluxes of 200-700 $kW/m^2$. Test results showed that the measured two-phase frictional pressure gradient increased with the mass flux and vapor quality. Most macro-channel correlations of two-phase frictional pressure gradient did not provide reliable predictions except under certain limited conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1043-1050
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• 2006

An experimental investigation was performed to study flow boiling heat transfer of deionized water in a microchannel. Measurement and evaluation of boiling heat transfer coefficients were carried out using a single horizontal rectangular microchannel having a hydraulic diameter of $100{\mu}m$. Tests were performed for mass fluxes of 90, 169 and 267 $kg/m^2$s and heat fluxes of 200-700 $kW/m^2$. Test results showed that the measured boiling heat transfer coefficients had no dependence on mass flux and vapor quality. Most macro-channel correlations of boiling heat transfer coefficient did not provide reliable predictions.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.3
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• pp.236-245
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• 1997

The flow characteristics of developing turbulent steady flow are investigated numerically and experimentally in the entrance region of a square duct ($40 mm{\times}40 mm$ and 4, 000 mm). The numerical anaysis are incorporated by finite- volume discretization with staggered grid system and SIMPLE algorithm. The numerical solution are compared with experimental results of mean velocity profiles, turbulence intensity and entrance length. For turbulent steady flow, the turbulent components in the velocity waveforms increase as the dimensionless transverse position approaches the wall. Thrbulence intensity increases as the dimensionless transverse position increases from the center to the wall of the duct for the developing turbulent steady flows. The entrance length of the turbulent steady flow is about 40 times as large as the hydraulic diameter under the present experimental condition.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.178-179
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• 2005

Numerical and experimental investigation of incompressible turbulent flow and heat transfer through square channels with varying number of ribbed walls were conducted to determined pressure drop and heat transfer. The CFX solver used for the computation. The rough walls have a $45^0$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results agreed well with experimental data that obtained for 7600$D_h$) of 0.0667. The results show that values of local heat transfer coefficient and friction factor increase with an increasing number of ribbed walls.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.287-290
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• 2002

'Backhole' is an extra empty volume where is located behind the tangential entries at the rear par of the vortex chamber in the swirl coaxial injector. With the backhole, there are three major hydraulic characteristics. First, mass flow rate is increased about $15{\%}$ compared with the case without the backhole. Second, with the backhole, the center region of the injected flow has more large volume than that of without the backhole. The last, some range of the cone angle can be controlled by the backhole Experiments are conducted by using a PDPA apparatus, a mechanical patternator, stroboscopic photography and etc. With the backhole, based on cold-flow tests, the model swirl injector has some Improvement in its performance.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.649-654
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• 2005

This paper presents fabrication and drive test of a peristaltic PDMS micropump actuated by the thermopneumatic force. The micropump consists of the three peristaltic-type actuator chambers with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port. The micropump is fabricated by the spin-coating process, the two-step curing process, the JSR (negative PR) molding process, and etc. The diameter and the thickness of the actuator diaphragm are 2.5 mm and $30{\mu}m$, respectively. The meniscus motion in the capillary tube is observed with a video camera and the flow rate of the micro pump is calculated through the frame analysis of the recorded video data. The maximum flow rate of the micropump is about $0.36\;{\mu}L/sec$ at 2 Hz for the zero hydraulic pressure difference when the 3-phase input voltage is 20 V.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.241-247
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• 2001

A comparison of fully developed heat transfer and friction factor characteristics has been made in rectangular ducts with ones roughened by five different shapes. The effects of rib shape geometries and Reynolds number are examined. The rib height-to-duct hydraulic diameter, pitch-to-height ratio, and aspect ratio of channel width to height are fixed at e/De=0.0476, P/e=8, and W/H=2.33, respectively. To understand the mechanisms of the heat transfer enhancements, the measurements of the friction factors are also conducted in the smooth and rough channels. The data indicates that the triangular type rib has a substantially higher heat transfer performance than any other ones in the range we studied.

• Journal of Power System Engineering
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• v.5 no.2
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• pp.30-35
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• 2001

A comparison of fully developed heat transfer and friction factor characteristics has been made in rectangular ducts with one wall roughened by five different shapes. The effects of rib shape geometries and Reynolds number are examined. The rib height-to-duct hydraulic diameter, pitch-to-height ratio, and aspect ratio of channel width to height are fixed at $e/D_e=0.0476$, P/e=8, and W/H=2.33, respectively. To understand the mechanisms of the heat transfer enhancements, the measurements of the friction factors are also conducted in the smooth and rough channels. The data indicate that the triangular type rib has a substantially higher efficiency index than any other ones in the range we studied.