• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.9
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• pp.695-703
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• 2008

Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in a compact heat exchanger with flat tubes and continuous plate fins according to the aspect ratio. RNG k-$\varepsilon$ model is applied for turbulence analysis. Simulation results such as air velocity and temperature distributions are presented, and heat transfer coefficients are compared with previous correlations for circular tubes. The numerical conditions are considered for the aspect ratios ranging from 3.06 to 5.44 and Reynolds number ranging from 1000 to 10,000. The results showed that heat transfer coefficients decreased with the increase of aspect ratio. From the calculated results a correlation of Colburn j factor for the considered aspect ratio in the compact heat exchanger system is suggested. The predicted results in this study can be applied to the optimal design of air conditioning system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.5
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• pp.318-325
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• 2009

Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in compact heat exchanger with flat tubes and continuous plate fins having a symmetric and non-symm etric staggered arrangements. Simulation results such as air velocity and temperature distributions are presented, and heat transfer coefficients are compared with previous experimental results. In order to investigate the flow and heat transfer features by periodic boundary conditions, the three blocks were used. Predicted heat transfer coefficients between the three blocks are similar while there are relatively differences, compared with the experimental data. From the calculated results a correlation for Colburn j factor in the compact heat exchanger system is suggested. The predicted results in this study can be applied to the optimal design of air conditioning system.

• Journal of Distribution Science
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• v.14 no.9
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• pp.121-132
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• 2016

Purpose - This study has the following objectives. First, it seeks to build an integrated model that can analyze the path through which headquarters, subsidiary competence, and knowledge transfer performance influence subsidiary performance. Second, it analyzes the influence of the specificity of technology as a moderating effect factor on knowledge transfer process. Third, it will conduct an empirical analysis on distributive manufacturing MNEs and suggests an implication for companies that actually need technological localization. The difference of this study are as follows. First, unlike the existing studies, this study can expand a theoretical discussion as it uses subsidiary performance as the dependent variable. Second, it sets the specificity of technology as a moderating effect factor, not an antecedent, and can draw a theoretical implication. Research design, data, and methodology - This study built a path analysis model to identify the influence of the disseminative capacity and absorptive capacity of distributive manufacturing MNEs on subsidiary performance. Based on the previous studies, it set 19 items as 5 latent variables, and established 6 hypotheses by including the moderating effect of the specificity of technology between them. The final 203 companies were selected as analysis samples through a survey questionnaire. For empirical analysis, the study used PLS (Partial Least Square) that is based on structural equation model. Results - The empirical analysis result demonstrated that both headquarters' disseminative capability and subsidiaries absorptive capacity had a positive influence on knowledge transfer performance. Knowledge transfer performance also had a positive influence on subsidiary performance. In the analysis of moderating effect, the specificity of technology acted as a significant moderating variable only between knowledge transfer performance and subsidiary performance; it did not show a statistically significant moderating effect among disseminative capability, absorptive capacity, and knowledge transfer performance. Conclusions - The empirical analysis results of this study demonstrate the importance of disseminative capability and absorptive capacity in knowledge transfer to subsidiaries from the distributive manufacturing MNEs in Korea. The analysis on the moderating effect indicates that the specificity of technology in Korean companies influences on the process of making achievement by using the transferred knowledge.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1159-1165
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• 2009

In the present study, the flow and heat transfer characteristics of a large plate heat exchanger are investigated numerically. The flow passages are very complicated due to the grooved corrugation patterns of the plate surface so that the detailed mesh and the large amount of the computation time have to be required in the numerical simulation for the conjugate heat transfer analysis. In order to accomplish the efficient and fast analysis of the heat transfer characteristics in the plate heat exchanger, a semimicroscopic method using the porous media model has been investigated numerically. The results showed that the characteristics of the heat transfer and pressure drop, which are respectively presented with Colburn j-factor and Fanning f-factor, are in a good agreement between the detailed mesh and the porous media model. The results of the present study could be applicable to the numerical analysis of entire flow passages in the large plate heat exchanger using porous media treatment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.1
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• pp.50-63
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• 2017

While transit is inconvenient, it is also inevitable for the efficient public transportation. Reducing the number of transfers as much as possible is most important in providing the convenience of public transportation and facilitating the public transportation. As for the public transportation card data, 61,986 items on weekdays and 69,100 items on weekends were collected. Pattern analysis and traffic influence factors were analyzed using traffic data card. Trip chain results revealed that people have more transit transfers for shopping and leasure than commuting purposes on weekends and that commuting distance and time increase by 10 km and 9.9 minutes, respectively. Besides, results of the structural equation model showed that factor 1(total travel time, total travel distance), factor 2(number of people getting on and off), factor 3(transit time), and factor 4(number of bus connections, number of operations) were found to have significant effects on the number of transfers.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.237-239
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• 2003

The present study investigates on design optimization of rib-roughened two-dimensional channel to enhance turbulent heat transfer. Response surface method with Reynolds-averaged Navier-Stokes analysis is used as an optimization technique. Standard $k-{\varepsilon}$model with wall functions is adopted as a turbulence closure. The objective function is defined as a linear combination of heat transfer and friction drag coefficients with weighting factor. Computational results for overall heat transfer rate show good agreements with experimental data. Four design variables are optimized for weighting factor of 0.02.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.17-22
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• 2001

This paper gave a review of form factor computations in the luminous flux transfer method and practical application of DiLaura's recently developed form factor computation. A systematic analysis of how the results of a contour integration solution differ from those of existing numeric solutions were undertaken with a developed computer simulation program. Various situations between sending and receiving surfaces were considered, including the facing, size, and distance between surfaces.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.871-879
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• 2002

The characteristics of flow and heat transfer in the heat exchanger of heat pipes with fins have been studied numerically for cooling enhancement of electronic components of KTX (Korea Train eXpress). Numerical analysis and methodology have been conformed by comparing the experimental results for inlined array of heat pipes. The staggered arrangement of heat pipes has been proposed in order to achieve heat transfer enhancement. As results, the geometry change to the staggered array is conformed to increase the heat transfer of the system accompanied by an increase of pressure drop. The current results of friction factor and Colburn j factor are presented in terms of Reynolds number and staggered distance, and are expected to use for design and manufacture of such a system.

• Journal of Korean Society of Transportation
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• v.33 no.6
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• pp.543-553
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• 2015

This study analyzed that the impact of the bus use environment on users' stress in each step of bus use, from accessing to leaving to transfer, in the city of Daejeon. For this, we collected the stress data from 300 users using personal interviews at the bus stops and on-board bus. Also, we used factor analysis and structural equation model method for analysis of the impact of external and internal bus environments on stress of users. The results of this study showed that the highest stress impact factor was an onboard factor(${\beta}=.416$) including 'density and crowding', 'no seat to seat' and 'low ride comfort and safe'. The next stress impact factor was transfer factor including 'insufficient transfer information', 'lack of connectivity of bus and subway' and 'uncomfort transfer route'. From the above, we recommend that bus policies need to focus on not the supplier but users and also, this user based policy need to be more specified considering the characteristics of various users such as females, the elderly, irregular users, and so on.

• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.173-185
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• 2003

This study mainly intends to determine the factors for which dental technicians are satisfied with their jobs and how much the resulting job transfer rate is and thus to identify the correlation between them. For these purpose, 200 subjects were sampled out of dental technicians in Seoul and Incheon, and the survey was performed from July 19, 2002 to August 15 (for 25 days) with self-administered questionnaire. Out of all collected questionnaires, 131 pieces(65.5%) were addressed for this study. As for the tools for this study, the structured questionnaire was used with its proven reliability and feasibility, and the contents of questionnaire consisted of 32 questions on the basis of related references. The contents of questionnaire were categorized into 3 sections: General attribute of subjects; Factors for which dental technicians are satisfied with their jobs; and their intention of job transfer. The questionnaire consisted of total 32 questions which included general attribute of subjects(10 questions), factors of their satisfaction with jobs(17 questions) and intention of job transfer(5 questions). The data analysis was processed by computerized system with SPSS(Statistical Package for Social Sciences). Statistical analysis techniques included frequency, percentage, T-test, F-test analysis and regression analysis. As a result of those analyses, the conclusion can be summarized as follows: 1. As a result of analyzing the factors for which the subjects were satisfied with their jobs, it was found that there were significant differences in career and job title out of question items(P<0.001). It was also shown that the factors of subjects' satisfaction averaged 3.43, which was considerably higher value than I expected. It was found that job and management factors were major job satisfaction factors. 2. As a result of analyzing the intention of subjects to decide their job transfer, it was found that there were significant differences in job title and marital status out of question items(P<0.001). It was shown that the total average of the intention of their job transfer amounted to 3.06. It was shown that dental technicians have relatively higher intention of job transfer from their current work place. 3. It was found that there was inverse correlation between the factors of subjects' satisfaction with their jobs and their intention of job transfer(r=-0.490, P<0.05). Likewise, it was also found that there was inverse correlation mostly between the evaluation value for each independent variable region in term of each factor of job satisfaction and the value for the intention of job transfer. In view of these correlations, it was concluded that higher job satisfaction likely led to lower job transfer. 4. As a result of regression analysis so as to determine the influences of job satisfaction factors on the intention of job transfer, it was found that the highest influential factor was management factor. And it was shown that the test values of model were statistically significant and its explanatory power amounted to 54.6%.