• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1172-1176
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• 2009

In the present study, natural convection over a heat sink with a horizontal circular base and rectangular fins was numerically analyzed. To calculate natural convection heat transfer, the assumptions of ideal gas and laminar flow were made for air. Flow patterns around the heat sink were chimney-like. The resultant temperature distribution on the circular base appeared almost uniform. Parametric studies were performed to compare the effects of fin length, fin height, the ideal number of fins, and heat flux on the average temperature of a heat sink and the average heat transfer coefficient from the heat sink array. Correlation to predict the average Nusselt number was presented.

• KIEAE Journal
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• v.7 no.6
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• pp.9-15
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• 2007

Ventilation of buildings provide occupants with comfort and plays a very informant role in supplying indoor ventilation requirement. Also, natural ventilation is more comfortable than forced ventilation taking account of mental comfort. Especially factors, airflow velocity and direction etc., should be reflected in establishment of comfortable indoor environment because indoor airflow can directly affect comfort of occupants. However, a device which enables indoor air movement to be analyzed has not existed until now. Hence, it has mostly depended on simulation results of fluid analysis but the results often differ far from reality. PST(Particle-Streak-Tracking) System, an alternative to improve this problem, is currently applied to natural ventilation in building, air conditioning, and airflow analysis in the inside of a plane etc. This study closely examine the property and strength and weakness of PST that is first introduced into KICT and then evaluate applicable possibility.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.10
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• pp.705-710
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• 2012

This study aims to analyse changes of inner temperature of PVS(Passive ventilation skin) and heat recovery when it has ventilation of air through PVS using numerical simulation in the winter condition. Results are as follows. 1) In case of the air inflows through PVS, change of inner temperature of PVS is lower than in case of the air flows inner space to out space, by dynamic insulation. 2) It was identified that the temperature gradient of PVS were bigger by increases of ventilation amount. To reduce ventilation load, heat transfer efficiency at the inner side of PVS is important and what performance of insulation at the inner side of PVS secure helps to improve heat performance of all PVS.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.12
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• pp.502-508
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• 2016

An optimized PI controller design method is presented to promote the control performance of an oil cooler system for high precision machine tools. First, a transfer function model of the oil cooler system with a variable rotating speed compressor was obtained by the perturbation method as the first order system with a negligible dead time. Then, the closed-loop control system was described as the second order system with a zero. Its dynamic behaviors are mostly governed by characteristic parameters, the damping ratio, and the natural frequency which is incorporated in PI gains. Next, an optimum integral of the time-weighted absolute error (ITAE) criterion was applied to the second order system. The characteristic parameters can be determined by the given design specifications, percent overshoots and settling times and comparisons with the ITAE criterion. Hence, the PI gains were plainly identified in a deterministic way. Finally, the PI gains were fine-tuned to obtain desirable dynamics in real systems, considering the zero effect and parameter variations. The validity of the proposed method was proven by computer simulations and real experiments for selected cases.

• Journal of the FoodService Safety
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• v.2 no.2
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• pp.67-77
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• 2021

Concerns regarding work and food safety in foodservice operations are growing. The purpose of the study is to suggest guidelines for designing foodservice facilities, including school foodservices and Korean restaurants. A case of a franchise restaurant specializing in a Korean food item, Seolleongtang, was used to explain the facility design. The contents of the manual included ways to determine space allocation, calculate the application of utilities and the diameters of supply utility pipelines, and suggestions on how to decide on air conditioning equipment. The standards of the American Gas Association and the Japan Foodservice Equipment Association (JFEA) were applied to design the restaurant space. The JFEA standards and knowledge based on experience and statistics were applied to calculate the usage of utilities like fuel and water. The standards of JFEA and the Society of Heating, Air-Conditioning, and Sanitary Engineers of Japan were applied to calculate the diameters of the water supply and drainage pipelines. For the setting of the heating, ventilation, and air conditioning systems, three ways to carry out the calculation of effective ventilation were explained, as well as options to dicide the standard parameters of the duct and ventilation fans. This manual can contribute to the design of effective and efficient foodservice facilities and help secure the work safety of foodservice employees thereby ensuring food safety.

• Proceedings of the SAREK Conference
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• 2006.11a
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• pp.88-88
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• 2006

• Proceedings of the SAREK Conference
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• 2006.11a
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• pp.77-77
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• 2006

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.24-24
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• 2007

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.34-34
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• 2003

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.61-66
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• 2008

Recently a certain level is required in natural ventilation for improving on the 'quality' aspect in housing. It is simulated the external flow around building which affact natural ventilation using CFD. Natural ventilation is estimated on the specific household which considered topography and not considered.