• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.6
• /
• pp.440-447
• /
• 2001

This study investigate experimentally the effect of in height, thickness, and clearance on the boiling heat transfer. The heat surfaces having copper fin array is tested for pool boiling. The gas-liquid exchange interference is investigated based on fin array clearance. These test results can be applied to the design of tube bundle system. The fin height of 2 mm is found to be effective. Effects of heat transfer promotion reaches the highest level when the fin clearance is 0.5mm. Also, heat flux is increased when the fin thickness is smaller. But0.2 mm fin thickness is highly recommended.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.05a
• /
• pp.203-207
• /
• 2003

As the upending is one of the critical steps in the installation of offshore structure, datail procedure of upending operation is studied in the paper. For larger offshore structure installation, launching method is often applied. However after launching, the upending process is to be followed. To ensure successful upending operation, datail process is analysed considering various factors affecting on the operation including reserved buoyancy, free flotation position, seabed clearance, ballast and hook load. To investigate the influence of each factor on the procedure, twelve numerical jacket models with various dimensions are simulated and studied. From the study, it is revealed that the increase of buoyance and decrease of self weight generate a large seabed clearance. The law seabed clearance during flooding creates higher hook load and height. The paper also introduces a guideline for the related structure design and construction with the effects of contribution factors in the upending operation.

• Journal of Distribution Science
• /
• v.14 no.1
• /
• pp.17-28
• /
• 2016

Purpose - Given the increasing interest in the Eurasian Initiative, government-wide studies for the construction of the Silk Road Express are currently being conducted. However, the Korean Government has no experience in operating international freight railroads and has not encountered problems in train service plans, international conventions, and customs clearance, which will arise when TKR is connected to TSR, TCR, and TMGR. Research design, data and methodology - Given these conditions, the cases of direct services in international freight railroads between China and Europe are investigated to identify the possible problems in the connection between TKR and continental railroads. This study also identifies the plans for activating Eurasian railroad logistics. Results - For the service of international freight trains, Korea needs to join international conventions, such as OJSD, as a regular member. Furthermore, any relevant international conference after the conclusion of such an agreement is needed for the agreement on train service schedules, fees, and procedures for passing border stations. Conclusions - Customs clearance and relevant documents must be standardized to address the differences in clearance systems between nations.

• Journal of Power System Engineering
• /
• v.20 no.6
• /
• pp.34-39
• /
• 2016

This paper is the numerical study on the correlation of leakage by the variation of inlet pressure and clearance in hydrostatic bearing. The main goal of this study is to apply to the design of hydro system the results that the pocket pressure and the leakage rate according to the inlet pressure and the clearance between piston and cylinder tube. Because the hydrostatic bearing in hydraulic cylinder has the narrow rectangular channel between piston and cylinder tube, so to verify the numerical scheme, it has been compared with the experimental results of Brackbill and Kandlikar. The pressure data of numerical results inside narrow rectangular channel correlate was showed a good agreement with experimental results, thereby the numerical scheme was applied to the real model that is a hydraulic cylinder with the hydrostatic bearing. In conclusion, the pressure differences between inlet and pocket were shown within 3%. Leakage rates were showed rapidly increased pattern between about 4.5 and 6.7 times because the section area to calculate the leakage rates were proportioned to a square of diameter. The correlation equation was calculated among the inlet pressure, the clearance and the leakage rate by using the linear regression.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.10 no.1
• /
• pp.9-15
• /
• 2005

A bioartificial liver (BAL) is a medical device entrapping living hepatocytes or immortalized cells derived from hepatocytes. Many efforts have already been made to maintain the functions of the hepatocytes in a BAL device over a long term. However, there is still some uncertainty as to their efficacy. and their limitations are unclear. Therefore, it is important to quantitatively evaluate the metabolic functions of a BAL. In previous studies on in vitro BAL devices, two test methods, an initial bolus loading and constant-rate infusion plus initial bolus loading, were theoretically carried out to obtain physiologic data on drugs. However, in the current study, the same two methods were used as a perfusion model and derived the same clearance characterized by an interrelationship between the perfusate flow rate and intrinsic clearance. The interrelationship indicated that the CL increased with an increasing perfusate flow rate and approached its maximum value, i.e. intrinsic clearance. In addition, to set up an in vivo BAL system, the toxic plateau levels in the BAL system were calculated for both series and parallel circuit models. The series model had a lower plateau level than the parellel model. The difference in the toxic plateau levels between the parallel and series models increased with an increasing number of BAL cartridges.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.2
• /
• pp.351-358
• /
• 1994

A probabilistic model and analysis methods to determine the means and variances of the velocity and acceleration in stochastically-defined planar pin jointed kinematic chains are presented. The presented model considers the effect of tolerances on link length and radial clearance and uncertainty of pin location as a net effect on the link's effective length. The determination of the mean values and variances of the output variables requires the calculation of sensitivities of secondary variables with respect to the random variables. It is shown that this computation is straightforward and can be accomplished by a conventional kinematic analysis package with minor modification. Thus, the concepts of tolerance and clearance have been captured by the model and analysis. The only input data are the nominal linkage model and statistical information. The "effective link length" model is shown to be applicable to both analytical solution and Monte Carlo simulation. The results from both methods are compared. This paper Ksolves the higher-order kinematic problems for the probabilistic design analysis of stochastically-defined mechanisms.echanisms.

• International Journal of Highway Engineering
• /
• v.14 no.6
• /
• pp.159-165
• /
• 2012

PURPOSES : The lack of details of guidelines on how to install the Chicane for traffic calming leads the practical difference across the calming areas, so the benefits expected from these facilities are not hardly observed. In this context, this study analysed the relationship between the geometric design alternatives of Chicane with the dynamic behaviour of vehicles in terms of speed and trajectory. METHODS : The study analysed vehicle dynamic behaviour using dynamic analysis program Auto-Turn under various geometric conditions of Chicane. RESULTS : This study suggested the design alternatives of Chicane using terms such as "longitudinal displacement value", "lateral displacement value", etc. which are defined in the study. The suggested combination set is fulfilling the desired or target speed of vehicles and clearance between vehicle and roadside at the same time. CONCLUSIONS : The results from this study can be applied to install Chicane corresponding to the local condition where target speed is 30km/h. The study showed the design alternatives of chicane corresponding to the given road cross-sectional design and clearance to roadside for passenger cars and light truck respectively.

• International journal of steel structures
• /
• v.18 no.4
• /
• pp.1252-1264
• /
• 2018

Long span bridges such as steel cable stayed and suspension bridges are usually more flexible than short to medium span bridges and expected to have large deformations. Deflections due to live load for long span bridges are important since it controls the overall heights of the bridge for securing the clearance under the bridge and serviceability for securing the comfort of passengers or pedestrians. In case of sea-crossing bridges, the clearance of bridges is determined considering the height of the ship master from the surface of the water, the trim of the ship, the psychological free space, the tide height, and live load deflection. In the design of bridges, live load deflection is limited to a certain value to minimize the vibrations. However, there are not much studies that consider the live load deflection and its effects for long span bridges. The purpose of this study is to investigate the suitability of live load deflection limit and its actual effects on serviceability of bridges for steel cable-stayed and suspension bridges. Analytical study is performed to calculate the natural frequencies and deflections by design live load. Results are compared with various design limits and related studies by Barker et al. (2011) and Saadeghvaziri et al. (2012). Two long span bridges are selected for the case study, Yi Sun-Sin grand bridge (suspension bridge, main span length = 1545 m) and Young-Hung grand bridge (cable stayed bridge, main span length = 240 m). Long-term measured deflection data by GNSS system are collected from Yi Sun-Sin grand bridge and compared with the theoretical values. Probability of exceedance against various deflection limits are calculated from probability distribution of 10-min maximum deflection. The results of the study on the limitation of live load deflection are expected to be useful reference for the design, the proper planning and deflection review of the long span bridges around the world.

• Journal of KSNVE
• /
• v.7 no.4
• /
• pp.645-653
• /
• 1997

For high performance rotating machinery, unstable vibrations may occur caused by hydrodynamic forces such as oil film forces, clearance excitation forces generated by the working fluid, and etc. In order to improve the availability one has to take into account the vibrations very accurately. When designing a rotating machinery, the stability behavior and the resonance response can be obtained by calculation of the complex eigenvalues. A suitable modifications of seal and/or bearing design may effectively improve the stability and the response of a rotor system. This paper deals with the optimum length and clearance of seals and bearings to minimize the resonance response(Q factor) and to maximize the logarithmic decrement in the operating speed under the constraints of design variables. Also, for an avoidance of resonance region from the operating speed, an optimization technique has been used to yield the critical speeds as far from the operating speed as possible. The optimization method is used by the genetic algorithm, which is a search algorithm based on the mechanics of natural selection and natural genetics. The results show that the optimum design of seals and bearings can significantly improve the resonance and the stability of the pump rotor system.

• 유체기계공업학회:학술대회논문집
• /
• 1998.12a
• /
• pp.191-197
• /
• 1998

The recent results of the engine development performed in this you on Turbogreen 1200, the first industrial gas turbine engine developed in Korea, are presented. In order to improve the engine performance and structural stability from the first prototype engine, several variants of the engine and major components such as combustor and rotor assembly have been developed and tested. This paper shows these results especially focused on the engine test and performance analysis, in which test system, instrumentation and data processing are discussed as well. The engine performance and its trend give relatively good coincidence with the design ones. At design power of 1.2MW, the thermal efficiency of the engine is estimated over $25\%$ which is below the design target of $27.2\%$. This gap of efficiency is caused mainly by large tip clearance between turbine blades and casing. Considering high design efficiency superior to those of other competitive engines in this power class, Turbogreen 1200 would have a strong competition in its performance if the design efficiency is achieved by further developments such as tip clearance control, which are very possible and natural in final mass production of the developed gas turbine engine.