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Hwataik Han,S. Y. Seo,M. H. Kim,Youngil Kim 대한설비공학회 1999 International Journal Of Air-Conditioning and Refr Vol.7 No.-
This paper investigates ventilation characteristics of an environmental chamber simulating an under-floor air conditioning system for isothermal and cooling supply air conditions. The tracer gas sulfur-hexafluoride SF6 was injected into a supply duct using step-up and step-down methods. Local mean and room mean ages were calculated from the concentrations measured at internal points and at the exhaust duct. The air change efficiency of the chamber has been found to be greater in cooling conditions than in isothermal conditions. Also the room air change efficiency is not significantly affected but slightly improved by the presence of a supply diffuser.
Hwataik Han,Min-Kyu Kim 대한설비공학회 2005 International Journal Of Air-Conditioning and Refr Vol.13 No.2
This study investigates the air leakage and heat transfer characteristics of a commercially available rotary-type air-to-air heat exchanger with a fiber polyester matrix. Crossover leakage between the exhaust and supply air is measured using a tracer gas method for various ventilation rates and rotational speeds of the wheel. A correlation equation for the leakage is obtained by summing up pressure leakage and carryover leakage. The pressure leakage is observed to be a function of ventilation rate only, and the carryover leakage is found to be a linear function of wheel speed. The real efficiency of the heat exchanger can be obtained from its apparent efficiency by taking into account the leakage ratio. The heat recovery efficiency decreases, as the ventilation rate increases. As the wheel speed increases, however, the efficiency increases initially but reaches a constant value for the speeds over 10rpm.
Distributions of Local Supply and Exhaust Effectiveness according to Room Airflow Patterns
Hwataik Han,Sun-Ho Choi,Woo-Won Lee 대한설비공학회 2002 International Journal Of Air-Conditioning and Refr Vol.10 No.4
A pulsed tracer gas technique is applied to measure the distributions of local mean age and local mean residual-life-time of air in a half-scale experimental chamber. The airflow patterns in the chamber are visualized by a Helium bubble generator for three different exhaust locations. A supply slot is located at the top of a right wall, and an exhaust slot is at either bottom-left(Case 1), bottom-right(Case 2), or top-left(Case 3) location. Results show that the distributions of local mean age and local mean residual-life-time are different from each other, but both of them are closely related to the airflow pattern in the space. Included are discussions on explaining the variations of overall room ventilation effectiveness depending upon airflow rates for three different supply-exhaust configurations.
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%
외기 온습도 조건에 따른 폐열회수 환기장치의 열전달 특성 및 불확실성에 관한 연구
한화택(Hwataik Han),추연복(Youn-bok Choo) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.9
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 indooroutdoor temperature difference. The enthalpy efficiency can have very large 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 taking place 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.
실간환기량 측정을 위한 추적가스 실험방법론에 관한 연구
한화택(Hwataik Han),조석효(Seok Hyo Cho) 대한설비공학회 2009 설비공학 논문집 Vol.21 No.11
Interzonal air movements are important to characterize overall ventilation performance of complicated multi-zone buildings. Tracer gas techniques are widely used to measure ventilation rates, ventilation effectiveness, and interzonal air movements. Depending on the number of gases used, they are divided into single and multi tracer gas methods. This paper deals with the comparison of the tracer gas methods in measuring air exchange rate between rooms. Experiments have been conducted in a simple two-room model with known airflow rates. In multi-gas procedure, the concentration decays of two tracer gases, i.e SF6 and R134a are measured after simultaneous injections in each room. The single tracer gas method is also applied by injecting SF6 gas with a time lag between two rooms. The data reduction procedures are developed to obtain the interzonal airflow rate using the matrix inversion, and various data manipulation methods are tested, such as data shift, interpolation, and smoothing. Uncertainty for each airflow rate is investigated depending on the parameters based on the setting values.
한화택(Hwataik Han),한창호(Changho Han),백창인(Chang-In Baek) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.6
We investigated occupancy estimation in a room for the purpose of demand control ventilation in buildings. Occupancy was estimated by the carbon dioxide concentration data using dynamic neural network model with time delay. Indoor CO2 concentrations and occupancy were measured continuously for three days in a single library room. Networks were trained using the first-day data and results were obtained for the rest of the days for various system parameters. The results were verified by the exact number of people obtained by a video camera installed near the entrance door.