• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.331-341
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• 2013

In a solar domestic hot water (SDHW) system, solar energy is collected using collector panels, transferred to a circulating heat transfer fluid (brine), and eventually stored in a thermal storage tank (TST) as hot water. In this study, a computational fluid dynamics (CFD) model was developed to predict the solar thermal energy storage in a hybrid-type TST equipped with a helical jacket heater (mantle heat exchanger) and an immersed spiral coil heater. The helical jacket heater, which is the brine flow path attached to the side wall of a TST, has advantages including simple system design, low brine flow rate, and enhanced thermal stratification. In addition, the spiral coil heater further enhances the thermal performance and thermal stratification of the TST. The developed model was validated by the good agreement between the CFD results and the experimental results performed with the hybrid-type TST in SDHW settings.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.825-829
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• 2011

We performed a dynamic characterization of passive flow-rate regulators, which compensate for inlet pressure variation and maintain a constant flow rate for precise liquid control in microfluidic systems. To measure the flow rate for a short time, much less than the period of the dynamic inlet pressure, we use the particle image velocimetry (PIV) method. DI water containing fluorescent beads with a $0.7-{\mu}m$ diameter was supplied to the flow-rate regulators, and two successive images of the particles were taken by a pulse laser and a fluorescent microscope to measure the flow velocity. For a dynamic inlet pressure of frequency 60 Hz, the flow velocity was constant with an average of 0.194 ${\pm}$ 0.014 m/s as the inlet pressure varied between 20 kPa to 50 kPa. The flow-rate regulators provided a constant flow rate of $5.82{\pm}0.29\;{\mu}l/s$ in the frequency range of the inlet pressure from 1 Hz to 60 Hz.

• Journal of the Korean Solar Energy Society
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• v.30 no.5
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• pp.17-24
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• 2010

태양열 제습냉방은 액체흡수제를 이용한 냉각효과로 기존의 전기에너지를 가능케 하는 해결책중 하나이다. 따라서 태양열을 거의 활용하지 않는 여름에 가열온수를 열원으로 활용하여 쾌적조건을 구현하는 본 연구의 대상인 태양열냉방시스템은 제습기와 재생기로 크게 이루어져 있다. 본 논문은 제습기의 유량 변화에 따른 열전달 및 물질전달의 변화를 실험과 이론적 해석으로 규명하고 있는데, 흐름의 양상은 병렬형과 대향류형을 대상으로 하고 있다. 실험결과와 이론해석이 비교적 잘 일치하였으며, 대향류형이 병렬형보다도 물질전달 면에서 유리하게 나타났으며, 입 출구의 엔탈피 차이에서도 크서 열전달에서도 우수한 것으로 나타났다. 또한 그 차이를 본 논문에서는 나타내었으며, 일정한 높이나 길이 이상에서는 항상 일정함을 알 수 있었다. 따라서 본 논문의 결과들은 제습기의 유동흐름을 통한 태양열냉방시스템 중 제습기의 설계 및 성능 향상에 도움을 줄 것이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.180-188
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• 1997

The theoretical analysis and experiment with simulator were performed to obtain the temperature distributions in radiant heating panel and heat supply from hot water to heating space for the purpose of the development of comfortable living space from a point of view of the improvement of air quality and the enhancement of system efficiency. The relations of various parameters, such as pipe pitch, room temperature as well as flow rate and temperature of hot water and so on, with the rate of heat supplied, mean temperature and maximum temperature difference at panel surface were discussed. The effects of these parameters were also verified on the thermal performance of heating panel using the relations which could be used for the optimal design and operation of the radiant heating panel.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2001.11a
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• pp.52-58
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• 2001

우리나라의 시설농업은 겨울철 난방에 소요되는 에너지원의 대부분을 수입에 의존하는 화석에너지를 이용하고 있다. 따라서 생산비중 난방비의 비중이 국제원유가의 상승에 비례하여 증가하므로서 농산물의 가격이 불안정하며, 결국에는 재배농민의 생산욕구를 저하시켜 농가소득의 감소를 초래하고 있는 실정이다. (중략)

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.11
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• pp.762-768
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• 2011

We use floor radiant heating system in the house of commons in winter Floor radiant heating system, which transfer heat by radiation, is one of the energy efficient and comfortable systems that. Floor radiant heating system is configured to be controlled by the room for energy-saving. Proper flow rate to a comfortable heating in the room is important. However, Using a constant speed circulation pump in separate rooms, heating system may cause an imbalance because of the difference of length of coil when operating in the rooms. In this study, our Research team examined heating imbalance due to the variation length through the coil length changes and flow control of the circulation pump.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.4
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• pp.276-285
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• 1991

The transient heat transfer characteristics in the radiant heating panel were predicted by numerical analysis. Thermal behaviors of panel, such as temperature distributions in panel and convective and radiative heat fluxes in panel surface with respect to time were obtained. Heating hours per day, rate of energy supplied and maximum temperature differences at panel surface were also compared for several important parameters. The performance and thermal comfort of heating panel were studied and compared for various operating and design conditions such as pipe pitch, pipe location, pipe diameter and flow rate of hot water for the purpose of producing useful data, which can be used for the test and decision of efficient operating condition of the conventional heating systems or the optimal design of the new panel heating systems.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.22-28
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• 2013

The heat transfer characteristics of LNG(Liquefied Natural Gas) vaporizer on the ship was performed by numerical simulation to get the optimum NG(Natural Gas) generating condition. The glycol-water was used for heating in LNG vaporizer, and the cooling water of main engine was used as heating souse for glycol-water. This cooling water temperature increases again after recirculating from the main engine, and then it can be used to heat the glycol-water. The numerical analysis results has good agreement with the experimental results by liquid nitrogen for validation. So CFD technique was used to simulate the heat transfer characteristics of LNG vaporizer on the ship. The numerical results show that the operation condition of LNG vaporizer shows NG temperature of $6^{\circ}C$ in the outlet of LNG vaporizer, and the mass flow rates of LNG and glycol-water were showed 0.111 kg/s and 1.805 kg/s, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.3
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• pp.269-274
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• 2007

A 3-way valve has been applied to a distributor in a hot-water heating system and the performance of the system was evaluated in view of the variations of pressure drop and flow rate. The 3-way valve has been designed to bypass overplus hot-water when a control valve is closed. Note that the flow goes through heating pipeline in normal operation. In the present study, the measured pressure drops in each part of the flow paths show that the contribution to the total pressure drop is in the order of the supply header with control valves, piping system of each room and return header of the distributor, even though the amount of it is different according to the flow paths. As a result of performance test by sequential closing of the control valves, the variations of pressure drop and flow rate in the distributor with 3-way valves is much lower than those with previous 2-way valves, which prevent noises induced by pressure fluctuations.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.335-341
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• 2019

In order to provide basic data for uniformization of temperature distribution in heating greenhouses, heating experiments were performed in two greenhouses with a hot water heating system. By analyzing heat transfer characteristics and improving pipes layout, measures to reduce the variation of pipe surface temperature and to improve the uniformity were derived. As a result of analyzing the temperature distributions of two different greenhouses and examining the maximum deviation and uniformity, it was found that the temperature deviation of greenhouses with a large amount of hot water flow and a short heating pipe was small and the uniformity was high. And it was confirmed that the temperature deviation was reduced and the uniformity was improved when the circulating fan was operated. The correlation between the surface temperature of the heating pipe and the indoor air temperature was a positive correlation and statistically significant(p<0.01) in both greenhouses. It was confirmed that the indoor temperature distribution in a hot water heating greenhouse was influenced by the surface temperature distribution of heating pipe, and the uniformity of indoor temperature distribution could be improved by arranging the heating pipe to minimize the temperature deviation. Analysis of the heat transfer characteristics of heating pipe showed that the temperature deviation increased as the pipe length became longer and the temperature deviation became smaller as the flow rate in pipe increased. Therefore, it was considered that the temperature distribution and the uniformity of environment in a greenhouse could be improved by arranging the heating pipe to shorten the length and controlling the flow velocity in pipe. In order to control the temperature deviation of one branch pipe within $3^{\circ}C$ in the tube rail type hot water heating system most used in domestic greenhouses, when the flow velocity in the pipe is 0.2, 0.4, 0.6, 0.8, $1.0m{\cdot}s^{-1}$, the length of a heating pipe should be limited to 40, 80, 120, 160, 200m, respectively.