• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.190-197
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• 2024

A commercial PbO₂ mesh cylinder electrode was utilized as the anode for the electrochemical degradation of the textile effluent after the biological treatment with the titanium cylinder as the cathode in a self-made tube electrolyzer. The electrochemical performances of the PbO₂ electrode in tube electrolyzer under different initial pH, electrolyte flow rates, current densities and times of the electrochemical degradation were investigated. The experimental results illustrated that the PbO₂ electrode can reduce the chemical oxygen demand (COD) of the textile effluent from 94.0 mg L^-1 to 65.0 mg L^-1 with the current efficiency of 88.3%, the energy consumption of 27.7 kWh kg^-1 (per kilogram of degraded COD) and the carbon emissions of 18.0 kg CO₂ kg^-1 (per kilogram of degraded COD) under the optimal operating conditions. In addition, the COD of the textile effluent could be reduced from 94.0 mg L^-1 to 22.0 mg L^-1 after the fifth electrochemical degradation. Therefore, PbO₂ mesh cylinder electrode in the tube cylinder was promising for the electrochemical degradation of the textile effluent.

• Journal of computational fluids engineering
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• v.17 no.3
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• pp.39-44
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• 2012

In this study, a longitudinal pitch effect on in-line tube bank heat transfer has been analyzed numerically. To verify the accuracy of the solver model and boundary conditions, global Nusselt number(Nu) and pressure drop across the 2 row tube bank are compared with the existing experimental correlations under 500 ~ 2,000 Reynolds number(Re) range. By changing transverse pitch($S_T$) or longitudinal pitch($S_L$) separately in tube bank, we're trying to identify the each effect on heat transfer. We found that the effect of transverse pitch can be accounted for Reynolds number evaluated with maximum velocity($V_{max}$) at the smallest flow area similar to most existing correlations. Variation of the longitudinal pitch($S_L$) has a greater impact on the heat transfer compared to the transverse pitch($S_T$). Overall Nusselt number increases with larger longitudinal pitch($S_L$), however individual Nusselt number of the tube row has significant difference after the first row.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.517-524
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• 2011

A vortex tube is a device that can separate small particles from a compressed gas or separate a compressed gas into hot and cold flows. We experimentally analyzed the energy-separation characteristics of a vortex tube with a diameter of 10 mm. We measured the energy-separation characteristics of the vortex tube for different inlet air pressures, orifice diameters, and tube lengths. The orifice diameter and inlet pressure are important for the vortex tube design and operation. The tube length has a small effect on the energy-separation performance. Maximum energy separation occurs for a vortex tube with Dc = 0.7 D and L = 16 D.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1603-1612
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• 1990

An experimental study is conducted to investigate the fluid flow and heat transfer around tubes arranged in line. All measurements are performed at Reynolds number 1.58*10$^{4}$ with varing tube spacings from the small pitch ratio(L/D=1.25) to the large pitch ratio(L/D=3.0). Mean static pressures and mean temperatures of the surface of tubes and mean velocities and turbulent intensities in tube banks are measured. The flow patterns and the characteristics of heat transfer are strongly influenced by the tube spacings. Especially, in the case of very small spacings(L/D=1.25), the flow between neighboring tubes becomes very stagnant and the heat transfer decreases. In the case of each tube spacing, the characteristics of heat transfer around the 3rd, the 4th and the 5th tubes are nearly similar to one another, because the flow around tubes becomes stable at the 3rd tubes. The local heat transfer has the peak value near the reattachment point which has the peak value of pressure, but the local heat transfer for the 2nd tube of L/D=1.25 without reattaching has the peak value at .theta.=75.deg.. For each pitch ratio, the mean heat transfer increases gradually toward the downstream tubes, because the oncoming flow through neighboring tubes comes closer to the forward and rear surfaces of the tube and the turbulent intensity becomes larger in the downstream direction.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.739-747
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• 1997

This study was performed to clarify various conditions on the test of lipoxygenase-l and to establish the application of new test method for varietal improvement of soybeans in order to decrease beany flavors. Potassium borate and Tris were used as buffer and O.1M potassium borate solution showed the best result for the lipoxygenase-l test. In the range of pH 8.5~9.0 of the buffer, 2mM linoleic acid as substrate was effective. For color development, 100$\mu$l of two solutions(KI and starch) were added to the half soybean seed, successively. The substrate solution included linoleic acid was stored safely for 10 days at 4$^{\circ}C$ in refrigerator and for 4 days at room temperature. The best result was as follows; the 1ml of substrate solution[0.1M potassium borate(pH 9.0), 0.1％ Tween-20, 2mM linoleic acid] was added to the chipped half soybean seed in l.5ml plastic tube, waited for 15 minutes, and 100$\mu$l of color development solutions(5％ saturated KI in 15％ acetic acid, 1％ starch) were added to the tube, successively. After 4 hours, the purple color was observed in the upper phase of the plastic tube in the presence of lipoxygenase-1 and milky color in absence of lipoxygenase-1. The purple color was stable from 4 to 24 hours. There was no interfering effect by lipoxygenase-2 and -3. The plastic tube should be placed in the tube stand without shaking during the lipoxygenase-l test.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.1
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• pp.26-33
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• 1991

An experimental study has been performed on the heat transfer by the natural convection from a conducting tube with two axial fins to a surrounding cylinder. In case of vertical fins, the maximum local Nusselt number of conducting tube appears at ${\theta}{\fallingdotseq}145^{\circ}$ and that of outer cylinder appears at ${\theta}=0^{\circ}$, for $l_F=0.3$. In case of horizontal fins, the maximum local Nusselt number of conducting tube appears at ${\theta}=180^{\circ}$ and that of outer cylinder appears at ${\theta}=0^{\circ}$. The local Nusselt number of the upper fin and the downward fin shows negative values for $l_F=1.0$. The local Nusselt number of the lower fin and the downward fin shows higher values than that of the upper fin and the upward fin. The mean Nusselt number of conducting tube in case of vertical fins are increased in order of $l_F=0.6$, 0.3, 1.0 and 0.0, but in case of horizontal fins, in order of $l_F=1.0$, 0.6, 0.3, and 0.0. The mean Nusselt number of outer cylinder in case of vertical fins are increased in order of $l_F=1.0$, 0.0, 0.3 and 0.6, but in case of horizontal fins, in order of $l_F=0.6$, 1.0, 0.3, and 0.0.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1419-1426
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• 2002

An experimental study was made to elucidate critical heat flux(CHF) characteristics in a two-phase concentric-tube thermosyphon. The experiment was performed by using saturated water, over the experimental range of configuration: inner diameter of heated outer tube D=12mm, outer diameter of unheated inner tube do=3 to 10mm and heated tube length L=100 to 1000mm. The experiment shows that the CHF is enhanced with increase in the inner tube diameter, and that the CHF decreases beyond a certain diameter of the inner tube. There is an optimum diameter for inner tube that maximizes the CHF, for each tube length and test liquid. The CHF maximum is about two to eight times as large as that without an inner tube. For a large inner tube, the CHF characteristics is similar to that for natural convective boiling in a vertical annular tube.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.93-100
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• 2007

The flow velocity distribution at inlet and exit of Diesel Particulate Filter(DPF) by fabricating L-shape connector with the DPF was measured using a Pitot-tube and 2-D transverse machine. An adaptor designed for making the Pitot tube probe access to the inlet and exit of the DPF was connected with the inlet and exit flange of the DPF, respectively. The Pitot tube which was mounted in the 2-D positioning machine could access to the inlet and exit of the DPF through the rectangular window of the adaptor. The L-shape connector in the DPF inlet has a flow guide which is a perforated steel pipe. The flow velocity distribution at the inlet of the DPF showed a chaotic velocity distribution which is different from that with a diffuser type connector. The velocity distribution at the exit of the DPF showed a crown shape which is similar to that of the diffuser type connector. The velocity distribution at the exit of DPF showed different patterns according to the air flow rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.5
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• pp.291-296
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• 2009

Ice accumulating system patterned ice-an-coil is the way of refrigerating regenerative materials on the surface of copper-tube inserted into the inside of ice-storage. The study experimented to understand ice-an-coil type ice making characteristics according to changing shape of ice making tube. The experiment were carried out under various conditions, that used brine temperature($-l0^{\circ}C$, $-6^{\circ}C$) brine flow rate(l.0m/s, 1.8m/s) and inlet water temperature($6^{\circ}C$, $12^{\circ}C$) etc. Mass of ice per making area increased according to the decrease of the brine temperature and inlet water temperature, but that was increased according to the increase of the brine flow rate. And I set up two hypotheses and compared the capacity of ice-making of the two cases; each had the same thermal area and one had an round-shaped copper tube but the other had an oval-shaped copper tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.3
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• pp.244-251
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• 1989

A numerical study has been performed on the natural convection heat transfer from a conducting tube with two axial fins to a surrounding cylinder. As increasing dimensionless fin length ($L_F$), the center of flow moves to the bottom of annulus and the recirculating flow rate is decreased. The maximum local Nusselt number of conducting tube appears at ${\theta}=180^{\circ}$ for $L_F=0.0$, but at ${\theta}=130^{\circ}$ for $L_F{\geq}0.3$ and that of outer cylinder appears at ${\theta}=13^{\circ}$ for $L_F{\leq}0.6$ but at ${\theta}=33^{\circ}$ for $L_F=1.0$. The fin temperature is decreased by increasing radial distance and the temperature distribution of the downward fin is generally less than that of the upward fin. By increasing fin length, the local Nusselt number of the upward fin appears negative values for $L_F=1.0$, but appears positive values for $L_F<0.8$, and that of the downward fin appears positive values.