• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.61-67
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• 2018

The effects of subsurface inhomogeneities on the detection of buried metal pipes in ground-penetrating radar(GPR) signals are investigated numerically. To model the electrical properties of the subsurface inhomogeneities, the continuous random media(CRM) generation technique is introduced. For the electromagnetic simulation of GPR signals, the finite-difference time-domain(FDTD) method is implemented. As a function of the standard deviation and the correlation length of the relative permittivity distribution for a randomly inhomogeneous ground, the GPR signals of the buried metal pipes are compared using numerical simulations. As the subsurface inhomogeneities increase, the GPR signals of the buried pipes are distorted because of the effect of the subsurface clutter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.1
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• pp.44-49
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• 2018

High-strength plastic water supply pipe evaluation method was evaluated in this study. Up to date, high strength water supply pipes that we install are mostly ductile cast iron pipes. Sometimes, a few PVC pipes are installed. Metal pipes have rust problem on the surface, causing serious damage to metal pipes and reducing the expected life span of water piping system. Nowadays, depending on technology development, some companies have improved properties of general PVC pipe performance with remarkable properties that exceed KS and ASTM standard. Here, we suggest a new method of performance evaluation for high-strength water plastic pipes.

• Transactions of Materials Processing
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• v.28 no.5
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• pp.266-274
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• 2019

Metal sealing is used to connecting the parts between valves and fuel pipes for a FCEV which utilizes hydrogen gas of 700 bar. Instead of general carbon steel, stainless steel is the primary material used to manufacture fuel pipes due to hydrogen embrittlement. The shape of deformation between metals is an important factor on the air-tightness of the metal to metal contact. Since the stainless steel pipe is hardened using the plastic forming during the tip shaping stage, this work hardening could have an effect on the deformed shape and characteristics of contact surfaces in fastening of pipes. In this paper, the deformation history of the pipe model was considered in order to analyze the hydrogen-tightness on the metal sealing part. The contact distance and the forward displacement for fastening were compared using experimental results and the simulation results. The simulation of the effect of material change on the fitting body demonstrated that the hardness or the strength of the formed tip of the pipe was designed to a proper valued level since the characteristics of the contact surface was exhibited better when the strength of the pipe was lower than that of the fitting body.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.11
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• pp.595-599
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• 2013

The pipes used in buildings are generally categorized into metallic or plastic materials. Metal pipes, such as copper and stainless steel pipes, are mainly used for water and hot water supply, and for the heating system. However, plastic pipes made of polyethylene and cross-linked polyethylene are used for floor heating, water drainage, and air vent systems. Usually, plastic pipes have thermal demerits, such as high linear expansion coefficients and bending phenomenon by hot water, although the pipes have several merits of light weight, low price, low thermal conductivity, and the comparatively high workability of metal pipes. Therefore, if those kind of demerits are overcome, plastic pipes can be easily accepted for hot water systems. This research is aimed to evaluate the applicability for vertical heating pipes of a plastic pipe system consisting of electric fusion fitting of a conductive carbon compound and propylene random glass fiber pipe, through measurement of the expansion rate and leakage in summer and winter seasons, in the apartment construction field.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.271-274
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• 2001

Experiments on the yield strength of pipe connectors made of metal wire, joint pins, pole pipes, multi span insertion joints, and T-clamp joints used in pipe houses were conducted. The strength of connections of a pipe connector made of metal wire was adequate but it had a big difference according to loading direction. The collapse load of pipes connected with a joint pin was lower than that of single pipes. Also experimental results showed that pole pipes for use in a part of frame buried under the ground were safe, and the strength of multi span insertion joints should be increased. The resistant moment of T-clamp was about 13.7% of a single pipe.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2346-2351
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• 2008

This study deals with heat pipes inserted into the metal hydride(MH) reactor to increase the effective thermal conductivity of the system and thus to enhance the thermal control characteristics. A numerical analysis was conducted to predict the effect of inserted heat pipes on the heat transfer characteristics of MH, which inherently has extremely low thermal conductivity. The numerical model was a cylindrical container of O.D. 76.3 mm and length 1 m, which is partially filled with about 60% of MH material. The heat pipe was made of copper-water combination, which is suitable for operation temperature range between $10^{\circ}C$ and $80^{\circ}C$. Both inner -and outer- heat pipes were considered in the model. Less than two hours of transient time is of concern when decreasing or increasing the temperature for absorption and discharge of hydrogen gas. FLUENT, a commercial software, was employed to predict the transient as well as steady-state temperature distribution of the MH reactor system. The numerical results were compared and analyzed from the view point of temperature uniformity and transient time up to the specified maximum or minimum temperatures.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.11a
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• pp.291-297
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• 2003

For the present study, three heat pipes with different thickness of sintered metal wick were manufactured, and their operational performances, such as capillary limit and thermal resistance were tested and compared with theoretical predictions. Experimental results showed good agreement with those by the theoretical model, and that seemed to present that the sintering process we had developed ;n the present study was valid.

• Corrosion Science and Technology
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• v.3 no.2
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• pp.67-71
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• 2004

Galvanized Steel pipes have been widely used in industries and apartments, Unexpected early leakage has been found in an apartment. Tunneling corrosion or penetration was found in the water supply pipes. The chemical compositions of the pipes and properties of coating layer were evaluated. The pipes met the specification of KS D 3507. The cause of early failure was analyzed through the examination of macrostructures and microstructures, It was found that the pipes were failed by grooving corrosion, which resulted from galvanic corrosion of weld bead and matrix.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.104-106
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• 2004

There are many under grounds facilities like oil pipes, gas pipes, water pipes, oil tanks, etc. and severe corrosion of these facilities made big problems. Fire, wide area water and soil pollution, massive and hazardous explosion, etc. can make big problems and cause big economical loss. So, various technologies were developed to keep these undergrouns facilities safely, and cathodic protection is one of it. For cathodic protection, one must detect potential of pipes, and there are so many test box to check pipes potentials. In this thesis, we describe on the development of small size corrosion monitoring system that measure pipes potentials easily and economically.

• Journal of environmental and Sanitary engineering
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• v.7 no.1
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• pp.1-16
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• 1992

Corrosion of pipes Is one of the most serious problems in the maintenance of water worlds. Corrosion is promoted not only by physical factors such as temperature, but also by electrochemical factors including concentration of soluble metal ions, chlorine ion, pH, DO and microorganisms. Corrosion products also affect corrosion rate. In this research, study results are summarized as follows ; 1) Corrosion test was performed for 4 weeks at $70^{\circ}C$, pH 7.0 with specimens of 4 types of metal materials used as service pipes. Corrosion rate and S.E.M were analyzed. The results were showed that corrosion 1.ate of carbon steel pipe was 4.10~5.22 $mg/\textrm{cm}^2$ . week, galvanized steel pipe 0.98~1.34$mg/\textrm{cm}^2$. week, Copper pipe 0.02~0.04$mg/\textrm{cm}^2$. week, stainless steel pipe 0.05~ 0.10$mg/\textrm{cm}^2$ . week. 2) When corrosion rate was tested for tile types of pipes at pH 7 and both $25^{\circ}C$ and $75^{\circ}C$, avaerage corrosion rate for 6 weeks at $25^{\circ}C$ Ivas 2.26$mg/\textrm{cm}^2$ . week in carbon steel pipe, 1.99$mg/\textrm{cm}^2$. week in galvanized steel pipe, 0.26 $mg/\textrm{cm}^2$. week in stainless steel pipe. At $87^{\circ}C$, average corrosion rate for 4 weeks u.3s 4.56 $mg/\textrm{cm}^2$. week in carbon steel pipe,