• Journal of Soil and Groundwater Environment
• /
• v.8 no.2
• /
• pp.1-8
• /
• 2003

Two types of ground-water sampling techniques for CFCs (chlorofluorocarbons) analysis, the cold-welded copper tube method and flame-sealed borosilicate glass ampule method, were compared and evaluated. CFCs concentrations by the copper tube method showed a poor reproducibility among triplicates whereas those by the glass ampule method showed a good agreement and relative standard deviations of triplicates were less than 5%. The poor reproducibility of the copper tube method appears to be attributed to the incomplete sealing in connection between faucets of wellhead and the sampling apparatus. The copper tube method also showed higher CFCs concentrations than the glass ampule method, which is more pronounced for CFC-11 than for CFC-12. The plastic tubings and rubber gasket of faucets in case of the copper tube method possibly contaminated the samples with CFC-11 and CFC-12. The potential of CFCs contamination for the glass ampule method was eliminated by using stainless steel and Nylon only and by connecting the sampling equipment directly to the main discharge pipe of wellhead. The validity of the glass ampule method were also verified by detecting very low level of CFCs for the ground-water sample which is old enough to have negligible CFCs.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.3
• /
• pp.1-6
• /
• 2011

This study focused on the localization of swivel type tube couplers, which all depend on imports. In this study, a computer application analysis was performed using a finite element method as a preliminary study. In the major developments related to the objective of this study, the air brake system produced by car makers represents a different in the installation point of an air tank according to the type of cars or in the length and direction of its hoses and that leads to cause lots of problems. For solving such problems, the design of the major elements in a swivel type tube coupler was analyzed using a finite element method, and its validity was also verified. In the process that verifies the validity of this study, it was necessary to investigate how much external force affects the desorption of the tube support, which is the most important element in swivel type tube couplers. For achieving the investigation, a pressure test was implemented for the tube support according to the Federal Motor Vehicle Safety Standards(FMVSS). In the results of the pressure test, all samples satisfied the FMVSS. In addition, several tests were implemented by installing the sample of the developed swivel type tube coupler to an actual vehicle. In particular, rotation tests with various angles were applied by welding the swivel type coupler to an air tank through an argon welding process. In the results of the installing test for an actual vehicle, it was verified that the designed structure was determined as a structure that is able to endure the eccentric torque and deformation pressure applied to several directions that are the major problems in such fixed type tube couplers. Therefore, in the comparison of the performance of the developed product with the product of PARKER, it was possible to verify that the localized swivel type tube coupler developed in this study shows more excellent than that of the existing products by PARKER.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.605-606
• /
• 2007

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.5
• /
• pp.563-569
• /
• 2012

The superheater and reheater tubes of a heavy-load fossil power plant boiler can be damaged by overheating, and therefore, the degree of overheating is assessed by measuring the oxide scale thickness inside the tube during outages. The tube temperature prediction from the oxide scale thickness measurement is necessarily accompanied by destructive tube sampling, and the result of tube temperature prediction cannot be expected to be accurate unless the selection of the overheated point is precise and the initial-operation tube temperature has been obtained. In contrast, if the tube temperature is to be predicted analytically, considerable effort (to carry out the analysis of combustion, radiation, convection heat transfer, and turbulence fluid dynamics of the gas outside the tube) is required. In addition, in the case of analytical tube temperature prediction, load changes, variations in the fuel composition, and operation mode changes are hardly considered, thus impeding the continuous monitoring of the tube temperature. This paper proposes a method for the short-term prediction of tube temperature; the method involves the use of boiler operation information and flow-network-analysis-based tube heat flux. This method can help in high-temperaturedamage monitoring when it is integrated with a practical tube-damage-assessment method such as the Larson-Miller Parameter.

• International Journal of Railway
• /
• v.2 no.4
• /
• pp.170-174
• /
• 2009

Super speed tube train is introduced to increase the speed of ground transportation. The super speed tube train levitates magnetically and runs in a partial vacuum tube, which can reduce the air resistance significantly. However, the strong magnetic force enough to propel the massive train can affect to the tube infrastructure. In this paper, authors have analyzed the leakage flux patterns and induced eddy current on the tube by using 3-dimensional Finite Element Method. These effects are investigated, especially by varying the materials and diameters of the tube. From the simulation results, the aluminum tube with the diameter of 3[m] is needed to be concerned because the induced eddy current produces joule heat, raises the inside temperature of the tube, and might be able to lead to electro-chemical corrosion on the tube, consequently reduce the durability.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.2
• /
• pp.52-58
• /
• 2007

This study shows a numerical method to predict automobile type air conditioner tube connector in the forming process. The simulation approach with 3-D FEM program(ABAQUS) for forming process, forming process simulation is in good agrement with it in tendency. Finally, we compared the forming result with simulation. The result of research showed thai forming process technology is promising to produce automobile type air conditioner tube connector.

• Journal of KSNVE
• /
• v.5 no.3
• /
• pp.337-344
• /
• 1995

A BEM program is developed for the performance analysis of axisymmetric mufflers. In the program the sub-region method is used to deal with singularity or inner boundary. The program is applied to typical axisymmjetric mufflers such as simple expansion, extended tube, perforated tube and absorptive expansion sufflers. The transmission losses of the mufflers are calculated by the program and compared with experiments. It is found that the prediction is in a good agreement with measurement, except for the absorptive muffler with parallel lining.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.27 no.1
• /
• pp.8-13
• /
• 2015

The objective of this paper is to provide design data of fin-tube heat exchanger which have a large diameter oval tube for dryer application. In this study, the heat transfer and pressure drop performance characteristics of the fin-tube heat exchanger were compared with Dittus-Boelter and a new correlation equation using Wilson plot method. The simulation results based on section by section method were compared with experimental results. These results showed that a new correlation equation using Wilson plot method provided better prediction, about 3 to 12%, than the Dittus-Boelter equation, from the experiment comparison. Also, the pressure drop of simulation results showed much more deviation with the experimental results.

• Steel and Composite Structures
• /
• v.13 no.5
• /
• pp.451-471
• /
• 2012

Concrete filled steel tube (CFST) structures have been used widely in high-rise buildings and bridges due to the efficiency of structurally favourable interaction between the steel tube and the concrete core. In the current design codes only one loading condition in the column members is considered, i.e., the load is applied on the steel tube and concrete core at the same time. However, in engineering practice the tube structures may be subjected to various loading conditions such as loading on the concrete core only, preloading on the steel tube skeleton before filling of concrete core, and so on. In this research, a series of comparative experiments were carried out to study the structural performance of concrete filled circular steel tube columns subject to four concentric loading schemes. Then, a generalized prediction method is developed to evaluate the ultimate load capacity of CFST columns subject to various loading conditions. It is shown that the predictions by the proposed method agree well with test results.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1997.04a
• /
• pp.182-190
• /
• 1997

A new method to prevent reinforced concrete columns from brittle failure. The method is called transversely reinforcing method in which only the critical regions are confined in steel tube. The steel tubes can change the failure mode of the latter columns from the shear to the flexure. The steel tubes also increase the compressive strength, shear strength and deformation capacity of the infilled concrete. The following conclusions are reached on bases of the study on the seismic performance of the high-strength RC rectangualr short columns confined in steel tube with shear span tho depth ratio of 2.0 The brittle shear failure of high-strength reinforced concrete short columns with large amount of longitudinal bars, which cannot prevented by using the maximum amount of welded hoops, can be prevented by using the steel tube which confines all the maximum amount of welded hoops, can be prevented by using the steel tube which confines all the concrete inclusive of cover concrete. High-strength RC short columns confined in rectangular steel tube provided excellent enhancement of seismic performance but, found that plastic buckling of the steel tube in the hinge regions tended to occur when the columns were subjected to large cyclic lateral displacements. In order to prevent the plastic buckling when the columns lies on large on cyclic lateral displacements, the steel ribs were used for columns. Tests have established that the columns provide excellent enhancement of seismic performance of inadequately confined columns.