• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.3
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• pp.27-35
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• 2001

Heat transfer characteristics of a heat exchanged for low temperature waste heat recovery using oscillating capillary tube heat pipe (OCHP) were evaluated against the charging ratio variation of working fluid and various working fluids. R-l42b, R-22 and R-290 were used as working a 2.6mm in outside diameter, 1.44mm in inside diameter with 101m length and 140 turns. Charging ratio of working fluid was 40% and 50%. water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and 9~27 $4kg/m^2s$, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-142b and R-290 and it was proportional to Figure of Merit for thermosyphon. As a result, it was thought that R-22 was the most reasonable working fluid of waste heat recovery for low temperature waste heat recovery.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.825-832
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• 2008

The ice slurry maker which can produce the ice slurry well for the ice particle in-flowing condition was revised. We removed the stagnant region at the top of the ice slurry maker, and IPF 40% could be realized. The IPF controller with 6 mm diameter holes at the bottom was designed. But the IPF controller with only 6 mm diameter holes could not control IPF in a pipe. This is because the ice particles at ice slurry flow exist homogeneously not only at the upper part but also at the bottom part. We changed the hole size of IPF controller surface using fine meshes and then, IPF in a pipe was increased by 70% when the hole size was $80{\mu}m$ and less.

• Journal of Hydrogen and New Energy
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• v.35 no.4
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• pp.428-436
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• 2024

Liquid hydrogen, which operates in cryogenic environments has a density 800 times greater than gaseous hydrogen, making it advantageous for large-scale storage and transportation. However, continuous evaporation due to external heat intrusion and internal heat generation poses challenges. To mitigate heat conduction, various insulation materials are used. In pipe systems, viscous heating effects from turbulence and viscosity, especially in bends, cause heat generation. This study employs computational fluid dynamics (CFD) to analyze the impact of fluid velocity, pressure drop, inner diameter, and curvature radius of pipe bends on viscous heating. Using liquid nitrogen at 77 K as a working fluid, the CFD results showed that increased velocity and pressure drop along with smaller inner diameter and curvature radius enhanced viscous heating, raising fluid temperature.

• Journal of Korea Water Resources Association
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• v.42 no.6
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• pp.505-511
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• 2009

When replacing deteriorated pipes, it is important to select pipe diameters of new pipes for improving the long-term reliability of a water distribution system. However, as the use of larger diameter pipes brings cost increase, it is required to evaluate the improvement of the reliability by the use of larger diameter pipes. In this study, we propose a methodology to evaluate the improvement of the reliability by the use of different pipe diameters. For this purpose, we rely on the segment-based minimum cutset method with the success mode approach to evaluate the reliability of a water distribution system and determine which pipes and their diameters will be replaced to improve the reliability using GA, After the suggested method is applied to a real water distribution system, the optimized pipe diameters produces higher reliability of the system than the current ones with the same construction cost. However, compared to the increase rate of the construction cost, the improvement of the reliability is not significant. Thus, in addition to the use the different pipe diameters, the structural modification or adding new valves to the system is necessary to improve the reliability efficiently.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.56-63
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• 1997

This paper presents a hybrid network model(HY-PIPENET) implementing a minimum cost spanning tree(MCST) network algorithm to be able to determine optimum path and constrained derivative(CD) method to select optimum Pipe diameter. The HY-PIPENET has been validated with the published data of 6-node/7-pipe network. Networking system and also this system has been optimized with MCST-CD method. As a result, it was found that the gas can be sufficiently supplied at the lower pressure with the smaller diameters of pipe compared to the original system in 6-node/7-pipe network. Hence, the construction cost was reduced about $40\%$ in the optimized system. The hybrid networking model has been also applied to a complicated domestic gas pipeline network in metropolitan area, Korea. In this simulation, parametric study was peformed to understand the role of each individual parameter such as source pressure, flow rate, and pipe diameter on the optimized network. From the results of these simulations, we have proposed the optimized network as tree-type structure with optimum pipe diameter and source pressure in metropolitan area, Korea, however, this proposed system does not consider the environmental problems or safety concerns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2368-2373
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• 2012

In this research, finite element method was carried out to evaluate the defomation of pipe and surface displacement for backfill of underground ficility. Various conditions for analysis were employer, including two different pipes(PE and concrete pipe), two different excavation depth(60cm and 150cm) and width(1.5D and 2D), a regular sand backfill, and four different flowable backfills. The vertical deformation of 60 cm diameter for PE was measured three times more than that of 30 cm diameter. The measured deformations for regular backfill and four flowable backfills were 0.320mm, and 0.135mm to 0.155mm, respectively. It ratio was around 40%. In case of 30cm diameter of concrete pipe, the measured vertical defomation was around 0.004mm for all the backfill materials. In case of installation depth, the effect of flowable backfill for flexible pipe is better than for rigid pipe. There is little effect on the deformation of concrete pipe with regular sand backfill and flowable backfill.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.1
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• pp.1-6
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• 2017

In this paper, the flow characteristics of water in the water supply pipes of a WBC array were evaluated. We simulated the flow velocities and pressures for a standard pipe, an expansion pipe with a concentric reducer, and an expansion pipe with an eccentric reducer using computational fluid dynamics. In the case of the standard pipe, when the inlet flow velocities were 0.5 m/s and 2.0 m/s, the maximum flow velocities at the center of the WBC array were 0.54 m/s and 2.74 m/s, respectively, which were the greatest values among those of all the pipe models considered. In the case of the expansion pipe, the maximum flow velocities at the center of the WBC array were almost the same under the same conditions regardless of the type of reducer. The pressure losses in the pipe due to the concentric and eccentric reducers were found to be (165.09 ${\times}$ inlet $velocity^{1.6677}$) and (210.98 ${\times}$ inlet $velocity^{1.6478}$), respectively. The coefficient of determination at this time was greater than 0.99 and was the same for both the models. As a simulation result, it was found that in order to reduce the pressure loss when pipe with WBC array is connected with a conventional pipe, diameter of the pipe with WBC array at that section should be enlarged by one step, and then connected to the conventional pipe with a concentric reducer.

• Journal of the Korean GEO-environmental Society
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• v.24 no.12
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• pp.61-67
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• 2023

Heat pipes located underground in urban areas and operated under high temperature and pressure conditions can cause large-scale human and economic damage if damaged. In order to predict damage in advance, damage and construction information of heat pipe are analyzed to derive independent variables that have a correlation with frequency of damage, and a simple regression analysis modified model using each variable is applied to the field. However, as the correlation between independent variables applied to the model increases, the independence between variables is harmed and the reliability of the model decreases. In this study, the independence of the pipe diameter, burial depth, insulation level of monitoring system, and disconnection or short circuit of the detection line, which are judged to be interrelated, was tested to derive a method for combining variables and setting categories necessary to apply to the frequency of damage estimation model. For the test of independence, the continuous variables pipe diameter and burial depth were each converted into three categories, insulation level of monitoring system was converted into two categories, and the categorical variable disconnection or short circuit of the detection line status was kept as two categories. As a result of the test of independence, p-value between pipe diameter and burial depth, level of monitoring system and disconnection or short circuit of the detection line was lower than the significance level (α = 0.05), indicating a large correlation between them. Therefore, the pipe diameter and burial depth were combined into one variable, and the categories of the combined variable were set to 9 considering the previously set categories. The insulation level of monitoring system and the disconnection or short circuit of the detection line were also combined into one variable. Since the insulation level is unreliable when the detection line status is disconnection or short circuit, the categories of the combined variable were set to 3.

• Journal of Trauma and Injury
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• v.29 no.1
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• pp.33-36
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• 2016

Traffic accidents involving agricultural machinery have been decreasing, but mortality is still high due to a lack of safety devices such as seat belts. Furthermore, secondary damage, such as abdominal impalement injury caused by loaded materials, is more likely to occur, and this type of injury leads to a poor prognosis. Impalement with pipes is often more fatal than other penetrating injuries because the diameter of the pipe is usually larger in size than other loaded materials. We report a case of a 72-year-old man with secondary abdominal impalement injury caused by a scaffolding pipe following a traffic accident.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.165-172
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• 1993

On the basis of Nikuradse laboratory experiments conducted in circular pipe with uniform roughness, five flow regimes are defined with respect to the characteristics of boundary layer such as laminar, transition laminar, smooth turbulent, transition turbulent and rough turbulent flows. Two cases are found for the transition laminar flow: one for the transition between laminar flow and smooth turbulent flow and the other for the one between laminar flow and rough turbulent flow. They all can be clearly determined by the relative roughness or the ratio of pipe diameter to the roughness. Explicit functions are developed for the estimation of pipe friction factor for the various flow conditions including turbulent flow regimes, which have excellent agreement with the Nikuradse laboratory data.