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한화택(Hwataik Han),김제연(Je-Yeon Kim),이원구(Won-Gu Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.6
It is intended to develop an experimental apparatus which can visualize flow patterns around cylindrical objects with various cross sections. The test objects are immersed in a fluid and traversed on a traversing system while the fluid remains stationary in a tank. Since there is no piping system to circulate the fluid, the apparatus is simple and does not require pumping power. Aluminum powders on fluid surface help to obtain clear flow images. A smart phone camera mounted on the traversing system can capture images and movies with a relative reference frame, and send the real-time data to computers through wireless communication. Karman vortex streets can be observed by varying traversing speed for various cross-sectional objects, and Strouhal number is obtained as a function of Reynolds number. Through the capstone design course, students can learn about a traversing system, fluid visualization techniques, design procedure and fluid theories around an object.
한화택(Hwataik Han),정영균(Young Kyun Jeong),이성환(Sung Hwan Yi) 한국실내환경학회 2009 한국실내환경학회지 Vol.6 No.2
In this paper, it is intended to investigate the condensation characteristics of a supply vent cap, which is designed and developed for natural ventilation systems for ondol heating spaces. Numerical simulations are conducted using a CFD package to analyze airflow and thermal conditions around the vent cap. Temperature and humidity distributions are obtained to predict condensation on the surface, depending on the material properties. As the thermal conductivity decreases, decreased is the condensation surface area. The thermal conductivity of the vent cap is found to be less than 1 W/mK in order to prevent condensation under the winter design condition of Seoul. An experimental technique is introduced to visualize condensation on surfaces using water-absorbing mud film. Analytical results are in good agreement with experimental observations. Discussion are also included for the thermal comfort and flow characteristics around the vent cap observed by the flow visualization and temperature visualization studies.
다중 급기구를 갖는 실내공간에서의 공기연령 산정방법에 관한 연구
한화택(Hwataik Han),신철용(Cheolyong Shin),이인복(In-Bok Lee),권경석(Kyeong-Seok Kwon),권용일(Yong-Il Kwon) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
This paper considers the age of air in a ventilated space with multiple supply inlets. The local mean age of air at a point from one supply inlet is different from those from the other supply inlets. It is the purpose of the present paper to investigate theoretically the relations between the LMA's from each supply and overall combined LMA whether or not to trace the origins of supply air. Transient concentration distributions are calculated with a step-up injection of tracer gas at each supply inlet, and at both inlets simultaneously. The steady state concentration with a continuous tracer injection at a supply inlet works as a weighting factor for the corresponding LMA in calculating the average overall LMA from multiple inlets.
외기 온습도 조건 변화에 따른 폐열회수 환기유닛의 성능 비교 실험
한화택(Hwataik Han),추연복(Youn-bok Choo) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.11
The purpose of the present paper is to investigate the effect of outdoor weather conditions on the performance of a heat recovery ventilator. Experiments have been performed by varying outdoor temperature/humidity conditions with the indoor conditions fixed at the standard conditions by KARSE. Results indicate humidity efficiency shows larger uncertainties than temperature efficiency in general. With the heat generation by an internal fan removed, the modified temperature efficiency remains almost constant regardless of the indoor-outdoor temperature difference. The enthalpy efficiency can have very large values or negative values in case the outdoor conditions are in the vicinity of the indoor enthalpy line. The direction of heat flow, in such a case, can be opposite to that of moisture flow between two air streams. Discussions are included about various interesting features of the psychrometric processes in a heat recovery ventilator.
실내 온열환경에 따른 재실자의 창개폐 환기시점에 관한 연구
한화택(Hwataik Han),이준용(Junyong Lee),신철용(Cheolyong Shin),장경진(Kyung-Jin Jang),김중경(JungKyung Kim),임시형(Si-Hyung Lim) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
Building ventilation is required to provide fresh outdoor air for occupant health and comfort. The ventilation airflow is often controlled rigidly to maintain constant temperature and concentrations, which may cause unnecessary ventilation. It is the objective of the present study to investigate the window open/close behavior and needs of ventilation by occupants depending on thermal environment in naturally ventilated space. Preliminary experiments have been conducted to correlate physical environmental quantities such as temperature and CO₂ concentration with respect to window use and number of occupants. Simple models for window operation are proposed based on experimental data. Energy efficient integrated ventilation control technologies can be developed based on the occupant behavior model in addition to physical environmental conditions.
한화택(Hwataik Han),신철용(Cheolyong Shin),이인복(In-Bok Lee),권경석(Kyeong-Seok Kwon) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
This paper investigates the age of air in a ventilated space with multiple supply inlets. The local mean age of air at a point from one supply inlet is different from those from the other supply inlets. It is the purpose of the present paper to evaluate the contributions of each supply inlet to an internal point, using LMA values from each inlet and/or steady state concentrations by each inlet. Transient concentration distributions are calculated with a step-up injection of tracer gas at each supply inlet, and at both inlets simultaneously. The steady state concentration with a continuous tracer injection at a supply inlet works as a weighting factor for the corresponding LMA in calculating the average overall LMA from multiple inlets.
한화택(Hwataik Han),한창호(Changho Han) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.11
We investigated occupancy estimation in a room for the purpose of demand control ventilation in buildings. Indoor CO₂ concentrations, ventilation rate and number of occupants were measured continuously for eight days in a computer room and vicinity zones. Networks were trained for various cases and results were obtained to investigate the effect of variables; ventilation rate and concentrations of vicinity zones. The results were verified by the exact number of occupants counted by a video camera installed near the entrance door.
한화택(Hwataik Han),한창호(Chang-Ho Han) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7
We investigate turbulent ventilation in a room with two openings by considering the inertia of air mass. We derive the governing equations and a new dimensionless parameter related to air mass in addition to dimensionless fluctuation frequency and opening area ratio. The pressure responses and the air flow rates through the openings are obtained using a the fourth-oder Runge-Kutta method. The flow regions are categorized into a synchronized region, an opening region, and a transition region, depending on the dimensionless parameters. We examine the effect of new dimensionless parameter of mass, and derive the range of the dimensionless parameter which needs to be considered
단순화된 결로 해석을 적용한 축사용 폐열회수 환기장치의 수치해석적 연구
한화택(Hwataik Han),남상훈(Sang-Hoon Nam),한건수(Geon-Su Han) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7
In cold climates, mechanical ventilation systems experience problems with condensing water from humid indoor air. it is important to consider the effect of condensation heat resulting from condensation on heat exchanger surface. In this study, we take into account the effects of condensation and evaluate heat exchanger efficiency by using a simplified condensation method with artificial specific heat according to the amount of latent heat. The condensation areas are also evaluated and the values are compared with the case when the condensation heat is not taken into account. Results show that the efficiency taking into account the condensation heat is about 16% higher than those not considering condensation heat when indoor relative humidity is 90%