• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1603-1612
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• 1996

The pressure loss coefficient of Newtonian and non-Newtonian fluids such as water, aqueous solutions of Carbopol-934 and Separan AP-273 and blood in the stenotic tubes are determined experimentally and numerically. The numerical analyses for flows of non-Newtonian fluids in the stenotic tubes are conducted by the finite element method. The effect of the contraction ratio and the ratio of length to diameter on the pressure drop are investigated by the experiments and numerical analysis. The pressure loss coefficients are significantly dependent upon the Reynolds number in the laminar flow regime. As Reynolds number increases, the pressure loss coefficients of both Newtonian and non-Newtonian fluids decrease in the laminar flow regime. As the ratio of length to diameter increases the maximum pressure loss coefficient increases in the laminar flow regime for both Newtonian and non-Newtonian fluids. Newtonian fuid shows the highest values of pressure loss coefficient and blood the next, followed by Carbopol solution and Separan solution in order. Experimental results are used to verify the numerical analyses for flows of Newtonian and non-Newtonian fluids. Numerical results for the maximum pressure loss coefficient in the stenotic tubes are in fairly good agreement with the experimental results. The relative differences between the numerical and experimental results of the pressure loss coefficients in the laminar flow regime range from 0.5% to 14.8%.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.129.2-129.2
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• 2005

• Ocean Systems Engineering
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• v.4 no.4
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• pp.309-325
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• 2014

Geotextile tubes are basically a huge sack filled with sand or dredged soil. Geotextile tubes are made of permeable woven or non-woven synthetic fibers (i.e., polyester or PET and polypropylene or PP). The geotextile tubes' performances in strength, dewatering, retaining solid particles and stacked stability have been studied extensively in the past. However, only little research has been done in the observation of the deformation behavior of geotextile tubes. In this paper, a large-scale apparatus for geotextile tube experiment is introduced. The apparatus is equipped with a slurry mixing station, pumping and delivery station, an observation station and a data station. For this study the large-scale apparatus was utilized in the studies regarding the stresses on the geotextile and the deformation behavior of the geotextile tube. Model tests were conducted using a custom-made woven geotextile tubes. Load cells placed at the inner belly of the geotextile tube to monitor the total soil pressure. Strain gauges were also placed on the outer skin of the tube to measure the geotextile strain. The pressure and strain sensors are attached to a data logger that sends the collected data to a desktop computer. The experiment results showed that the maximum geotextile strain occurs at the sides of the tube and the soil pressure distribution varies at each geotextile tube section.

• Journal of Power System Engineering
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• v.4 no.1
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• pp.26-32
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• 2000

Single-phase heat transfer performance and pressure drop for internally grooved tubes with angles were studied. Experiments were carried out in a counter flow heat exchanger with water as a working fluid. Two commercially available internally grooved tubes and smooth tube were tested. The internal diameter of the smooth tube was 16.5mm and the internal diameters of grooved tubes were 15.4mm, 14.9mm, 15.0mm, 16.7mm, respectively. Grooved angles in the tubes were $37^{\circ},\;43^{\circ},\;45^{\circ},\;50^{\circ}$, respectively. An experimental device to measure the friction factor and heat transfer coefficient was constructed. The experimental results were obtained for the fully developed turbulent flow of water in tube on the condition of uniform heat flux. As the increase of flow rate, Reynolds number, numbers of groove and grooved angle led to the increase of pressure drop. Also this paper showed that heat transfer rate increased with increasing numbers of groove and grooved angle. An empirical relation taken from this study represented most of the data within ${\pm}25%$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.200-211
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• 1998

Heat transfer performance improvement by fin and groovs is studied for condensation of R-11 on integral-fin tubes. Eight tubes with trapczodially shaped integral-fins having fin density from 748 to 1654fpm(fin per meter) and 10, 30 grooves are tested. A plain tube having the same diameter as the finned tubes is also used for comparison. R-11 condensates at saturation state of 32 $^{\circ}C$ on the outside tube surface coded by inside water flow. All of test data are taken at steady state. The heat transfer loop is used for testing singe long tubes and cooling is pumped from a storage tank through filters and folwmeters to the horizontal test section where it is heated by steam condensing on the outside of the tubes. The pressure drop across the test section is measured by menas pressure gauge and manometer. The results obtained in this study is as follows : 1. Based on inside diameter and nominal inside area, overall heat transfer coefficients of finned tube are enhanced up to 1.6 ~ 3.7 times that of a plain tube at a constant Reynolds number. 2. Friction factors are up to 1.6 ~ 2.1 times those of plain tubes. 3. The constant pumping power ratio for the low integral-fin tubes increase directly with the effective area to the nominal area ratio, and with the effective area diameter ratio. 4. A tube having a fin density of 1299fpm and 30 grooves has the best heat transfer performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.731-740
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• 1995

The objective of this paper is to develop defect assessment technology for integrity evaluation of CANDU pressure tubes. In fracture mechanics analysis, three-dimensional and two-dimensional (line-spring model) finite element analyses were performed to obtain the stress intensity factor for axial and circumferential surface cracks. In leak before break (LBB) analysis, heat transfer analyses for through-wall cracks were performed by considering the cooling effect and the LBB application time was computed. It was shown that the analytical results obtained in this study provide less-conservative but accurate solution for defect assessment of CANDU pressure tubes.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.33-37
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• 2008

The main objective of this study is to identify the pressure drop characteristics of coolant flow passages of 154kV/1GVA High Temperature Superconducting (HTS) power cable, experimentally. The passages were consisted of two parts, the one is the circular path with spiral ribs in the core to cool the cable conductor layer and the other is annular path with spirally corrugated outer wall to cool the shield layer. Thus the experiments to acquire the pressure drop data were performed with two types of circular spiral tubes and eight types of the concentric annuli in various range of Reynolds number. The pressure drops in the core tubes and the annuli were much higher than those in the tubes with smooth surface. Therefore, modified correlations to present the experimental results in each flow passage were suggested.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.3
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• pp.220-227
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• 2007

Heat transfer and momentum transfer under conditions of both oscillating flow and oscillating pressure within pulse tubes show very different behavior from those for steady state conditions. The analytic solutions of axial velocity and temperature of the gas within pulse tubes were obtained by assuming that the variations in pressure and temperature were purely sinusoidal and small. The shear stress and the heat flux at the tube wall obtained from the solutions are expressed in terms of the cross-sectional averaged velocity, the difference between mean temperature and instantaneous cross-sectional averaged temperature and the difference between mean pressure and instantaneous pressure. It is shown that the complex shear factor, which has been applied to momentum transfer of incompressible oscillating flow, and the complex Nusselt number, which has been applied to either heat transfer with oscillating pressure only or heat transfer of incompressible oscillating flow, could also be used for momentum transfer and heat transfer subjected to both oscillating flow and oscillating pressure, respectively.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.18 no.2
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• pp.37-42
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• 2022

An influence analysis on multiple steam generator tube rupture (mSGTR) followed by an unmitigated station blackout is performed to compare the plant responses according to the number of ruptured u-tubes under the assumption of a total of 10 ruptured u-tubes. In all calculation cases, the transient behaviour of major thermal-hydraulic parameters, such as the discharge flow rate through the ruptured u-tubes, reactor header pressure, and void fraction in the fuel channels is found to be overall similar to that of the base case having a single SG with 10 u-tubes ruptured. Additionally, as the conditions of low-flow coolant with high void fraction in the broken loop continued, causing the degradation of decay heat removal, the peak cladding temperature (PCT) would be expected to exceed the limit criteria for ensuring nuclear fuel integrity. However, despite the same total number of ruptured u-tubes, because of the different connection configuration between the SG and pressurizer, a difference is foud in time between the pressurizer low-level signal and reactor header low-pressure signal, affecting the time to trip the reactor and to reach the PCT limit. The present study is expected to provide the technical basis for the accident management strategy for mSGTR transient conditions of CANDU-6 plants.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.425-432
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• 2001

Single-phase heat transfer coefficients and pressure drops of R-22 were measured in smooth, horizontal copper tubes with inner diameters of 3.36 mm, 5.35 mm, 6.54 mm and 8.12 mm, respectively. The experiments were conducted in the closed loop, which was driven by a magnetic gear pump. Data are presented for the following range of variables: Reynolds from 1000 to 20000. Single-phase heat transfer coefficients increased by $10{\sim}30%$ as the inner diameter of tube was reduced and it was found that a well-known previous correlation, Gnielinski's correlation, was not suitable for the small diameter tubes. But the pressure drop in the small diameter tubes have been shown slightly deviations with Blauius' correlation. Based on an analogy between heat and mass transfer, the new heat transfer correlation is proposed to predict the experimental data successfully.