• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.43-50
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• 2013

The stringent emission regulation and future shortage of fossil fuel motivate the research of alternative powertrain. In this study, a system of proton exchange membrane fuel cell has been modeled to analyze the performance of the fuel cell system for automotive application. The model is composed of the fuel cell stack, air compressor, humidifier, and intercooler, and hydrogen supply which are implemented by using the Matlab/Simulink(R). Fuel cell stack model is empirical model but the water transport model is included so that the system performance can be predicted over various humidity conditions. On the other hand, the model of air compressor is composed of motor, static air compressor, and some manifolds so that the motor dynamics and manifold dynamics can be investigated. Since the model is concentrated on the strategic operation of compressor to reduce the power consumption, other balance of components (BOP) are modeled to be static components. Since the air compressor model is empirical model which is based on curve fitting of experiments, the stack model is validated with the commercial software and the experiments. The dynamics of air compressor is investigated over unit change of system load. The results shows that the power consumption of air compressor is about 12% to 25% of stack gross power and dynamic response should be reduced to optimize the system operation.

• Journal of the Korean housing association
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• v.20 no.3
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• pp.105-112
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• 2009

The purpose of this study is to investigate a top floor, indoor, thermal environment by comparison between the indoor air temperature and the rooftop surface temperature, and between the indoor air temperature and the outdoor air temperature using an experimental model. The model experiment was conducted with 4 cases,: no-rainfall, 1 em-height, 10 em-height and 20em-height of rainfall on the rooftop. According to the results of the height of stored rainfall, the average air temperature difference between the indoor and outdoor air with 1, 10 and 20 em-height of rainfall on the rooftop was $4.0^{\circ}C$, rooftop $1.2^{\circ}C$ and rooftop $1.0^{\circ}C$, respectively. The upper 10 em-height of rainfall on the rooftop acted to decrease the indoor air temperature on the top floor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.5
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• pp.634-644
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• 2001

The test facility of a 1/60-scale model for train-tunnel systems has been recently developed to investigate the effects of tunnel portal shapes, hood shapes and air-shafts for reducing the micro-pressure waves radiating towards the surroundings from the tunnel exit. The present test rig has been advanced from a 1/70-scale facility at NLR in Netherlands. The NLR test rig has the two-wise guidance system that needs two ears attached on the external surface of a model train nose. Therefore, their train models have irregular nose shapes. The main characteristics of the present facility are that the train model is guided by only one wire from the compressed air launcher to the absorber parts of test facility and the wire guidance hole is located at the axial center of a train model. In the present test rig, after a train model is launched, the air jet from the launcher does not enter the tunnel model. Experimental results were compared with numerical predictions to prove the performance of the test facility.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.91-97
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• 2002

The present study concerns an experiment on the supply-air control in variable air volume (VAV) system with a Pl control logic. A thermal chamber with a Pl control logic is constructed to verify the previously suggested multi-zone model. The stratified thermal model is adopted in the control logic for a thermal chamber cooling test. The effects of taler- mal parameters and control parameters such as supply air temperature and Pl control factor are investigated by implementing the thermal chamber cooling test. The experimental results obtained show that the transient behavior of the air-conditioned space temperature are in good agreement with the simulation results of the stratified thermal model.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.852-858
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• 2005

Modeling techniques for air quality are useful tools in air quality management. Especially, the air quality in urban area is significantly influenced by local surroundings such as buildings and traffic. When considering the air quality in a street canyon, which is usually filmed by a series of consecutive buildings and a street, currently available air dispersion model have a number of limitations to predict the air quality properly. In this study, it is aimed to propose an empirical model for the air quality in urban street canyons. A series of wind tunnel tests, followed by statistical analysis, were conducted. In conclusion, it is found that a wide street canyon and a perpendicular external wind to the street canyon are beneficial to achieve an enhanced air quality in street canyon environment. The model prediction using the proposed model also shows reliable correlations to the wind tunnel test results.

• Journal of Biosystems Engineering
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• v.15 no.1
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• pp.44-51
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• 1990

Four models in current use for cereal grain drying, equilibrium model, Morey model, partial differential equation model and simplified partial differential equation model, were modified to be suitable for natural air drying of barley. The predicted by the four models and experimental results were compared. Three models except equilibrium model predicted moisture comtent and grain temperature very well. But equilibrium model overpredicted moisture content and grain temperature of bottom layer. The degree of prediction of the four models for relative humidities of exhaust air didn't differ much from one another and equally the four models predicted relative humidity statisfatorily. Morey model took much shorter computing time than any other models. Therefore, considering the degree of prediction and computing time Morey model was the most suitable for natural air drying of barley.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.3
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• pp.281-289
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• 1999

A new E-$\varepsilon$ turbulence numerical model is proposed for analysing the turbulent air flow field within are urban street canyon. In this model the equations of eddy viscosity and energy dissipation ae reformed by considering the Kolmogorov time scale and streamline curvature effect. Application results of the new E-$\varepsilon$ model have been compared with those of standard E-$\varepsilon$ model and Yang and Shih's one, which are commonly used ones in engineering fields, and with field experiment results of DePaul and Sheih. The new model appears to be generally superior to other both models in the prediction of an air flow field within street canyon.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.589-593
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• 2007

In the mechanical ventilation system, it is a fundamental condition to distribute the air equally to the each room. In this study, distribution performance of the air distributor which generally connected to a circular duct was investigated by simulation and experiment. In the first CFD analysis, maximum air flow rate deviation was an 63% in the air distributor model. After numbers of model modification and simulation, maximum flow rate deviation was reduced to 19% in the final simulation model. An air distributor which used in the experiment was produced by using data obtained from the final analysis. When experimental result was compared with analysis result, there was a deviation difference as much as 9%.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.1
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• pp.10-16
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• 2003

The present study performs an experimental measurement on transient thermal response of an air-conditioned space by a variable air volume (VAV) system with a PI(pro-portional-integral) control logic. A thermal chamber with a PI controlled VAV unit is constructed to verify the previously suggested stratified multi-zone model. The effects of thermal parameters and control parameters such as supply air temperature and PI control factor are investigated by implementing the thermal chamber test. The experimental results obtained show that transient behavior of the air-conditioned space-temperature is in good accordance with the simulation results of the stratified thermal model.

• Journal of Korean Society for Quality Management
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• v.44 no.3
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• pp.677-688
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• 2016

Purpose: In this study, we examine the effects of circulatory diseases mortality in South Korea 2005-2013 using the air pollution index, Methods: We cluster the region of high risk mortality by SaTScan$^{TM}$9.3.1 and compare this result with the regional distribution of air pollution. We use the Geographically Weighted Regression (GWR) to consider the spatial heterogeneity of data collected by administrative district in order to estimate the model. As GWR is spatial analysis techniques utilizing the spatial information, regression model estimated for each region on the assumption that regression coefficients are different by region. Results: As a result of estimating model of the collected air pollution index, circulatory diseases mortality data combined with the spatial information, GWR was found to solve the problem of spatial autocorrelation and increase the fit of the model than OLS regression model. Conclusion: GWR is used to select the air pollution affecting the disease each year, the K-means cluster analysis discover the characteristics of the distribution of air pollution by region.