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Improvement of the T-history Method to Measure Heat of Fusion for Phase Change Materials
Hiki Hong,Chang Hyun Park,Ju Hwan Choi,Jong Hyeon Peck 대한설비공학회 2003 International Journal Of Air-Conditioning and Refr Vol.11 No.1
Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of inhomogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.
Measurement Methods of Latent Heat for PCM with Low Melting Temperature in Closed Tube
Hong Hiki,Kang Chaedong,Peck Jong Hyeon The Society of Air-Conditioning and Refrigerating 2004 International Journal Of Air-Conditioning and Refr Vol.12 No.4
Cycle test for developed phase change material (PCM) is necessary in order to assess the variation of latent heat, which decreases with time by deterioration. T-history method and measurement using heat-flux meter are appropriate for the cycle test in a tube filled with PCM because they do not need an extraction of sample in measuring heat of fusion. In the present study, these methods were applied to a PCM having a melting point below a room temperature, different to the past studies for PCMs melting above a room temperature. As a result of experiment using pure water as specimen, we can obtained rea-sonable values for heat of fusion.
Measurement Methods of Latent Heat for PCM with Low Melting Temperature in Closed Tube
Hiki Hong,Chaedong Kang,Jong Hyeon Peck 대한설비공학회 2004 International Journal of Air-Conditioning and Refr Vol.12 No.4
Cycle test for developed phase change material(PCM) is necessary in order to assess the variation of latent heat, which decreases with time by deterioration. T-history method and measurement using heat-flux meter are appropriate for the cycle test in a tube filled with PCM because they do not need an extraction of sample in measuring heat of fusion. In the present study, these methods were applied to a PCM having a melting point below a room temperature, different to the past studies for PCMs melting above a room temperature. As a result of experiment using pure water as specimen, we can obtained reasonable values for heat of fusion.
Melting of Ice on the Heating Plate with Split Fins
Hiki Hong,Moo Geun Kim 대한설비공학회 2001 International Journal Of Air-Conditioning and Refr Vol.9 No.2
One of the important applications of a contact melting process is a latent thermal energy storage system owing to its high heat flux and small temperature variation. In some previous works, the split fins have been employed in order to enhance the melting rate. In the present work, the direct contact melting was experimentally investigated using an ice as specimen for both split and non-split fins. It was shown that the contact melting by split fins increases the melting rate compared to that of non-split ones.
홍희기(Hiki Hong),김시환(Sihwan Kim) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.6
Ondol heating, a kind of radiant floor heating, is a main method used in housing units in Korea. Building energy simulation including ondol and relevant facilities has not been performed due to its complexity. For evaluating energy consumption and indoor temperature variation, a new method should be proposed. At the present work, a dynamic simulation on ondol heating was tried by combining TRNSYS and EES. Characteristic functions for a pump, hot water coils and a gas boiler were simutaneouly solved by EES, and calculated flow rates and supply temperature of hot water were provided as inputs of the active layer of TYPE 56 in TRNSYS. The results by the simulation on a typical housing unit in Korea shows a good trend in a viewpoint of actual behavior of ondol heating.
홍희기(Hiki Hong),최준영(Junyoung Choi),임신영(Shin Young Im) 대한설비공학회 2017 설비공학 논문집 Vol.29 No.10
Most European economies, Japan, and many governments have made it a major policy to expand the green business by disseminating heat pump technology, which has a large CO2 reduction effect. The heat pump of all heat sources has been recognized as renewable energy and the policy to encourage has been implemented. In the recently revised Renewable Energy Law, the hydrothermal source (surface sea water) heat pump was newly included in renewable energy. In addition, the scope of application of heat pumps has expanded in the mandatory installation of renewable energy for new buildings, remodeling buildings, and reconstructed buildings based on this law. However application to heat pumps using all natural energy as heat source has been put off. In this revision, the ratio of renewable energy to the total energy produced by the heat pump was fixed at 73%, which depends on coefficient of performance of heat pump. The ratio of renewable energy is 1-1.8/COPH, and should be calculated including the coefficient of performance of the heat pump. Using a high efficiency heat pump or a high-temperature heat source increases the coefficient of performance and also reduces CO₂ emissions. It is necessary to expand the application of heat pumps as renewable energy equipment and to improve the correct calculation of renewable energy production.
홍희기(Hiki Hong),김선국(Sunkuk Kim),유호선(Hoseon Yoo) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
This study was performed to determine the heating energy savings and CO₂ reduction resulting from turning off ondol heating in housing units in Korea. Lowering the room temperature and intermittent heating of a room are effective methods for reducing heating energy consumption. These techniques were proven by modeling simulations in our previous studies. To confirm the simulations, schedule controllers which automatically turned off the ondol heating in the living room and kitchen from 10 pm to 6 am were in stalled at the hot water distributor in five households. The heating gas used in each of the housing units was measured over a period of five years, with and without the schedule controllers. We found that approximately 30% of gas consumption, mainly used for heating, can be saved compared to turning on the appliance during the night.