• 대한토목학회논문집
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• 제44권4호
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• pp.433-441
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• 2024

본 연구는 기존 국내 건축물의 동결을 방지를 위해 열선을 매립한 토목 및 건축물의 열선으로 인한 외부 에너지 사용으로 탄소 배출 및 유지관리비용이 증가하는 것을 절감시킬 수 있는 에너지 효율을 증대한 에너지 저장 시멘트 복합체를 제안한다. 최근 탄소 저감을 위해 상변화 물질(PCM)을 일반 시멘트 복합체에 통합하여 잠열 성능을 부여하는 연구가 진행되어왔다. 그러나 상변화 물질을 혼입한 콘크리트의 경우 상변화 물질의 유출, 강도 저하 및 부족한 열적 성능 등에서 문제점을 보이는 경향이 있다. 본 연구에서는 이러한 문제를 극복하기 위해 마이크로캡슐을 이용하여 상변화 물질을 캡슐화시켜 시멘트 복합체에 혼입하고 다중벽탄소나노튜브와 실리카 퓸을 사용하여 시멘트 복합체의 강도 감소를 최소화시킨 고효율 열저장 시멘트 복합체를 제안한다. 열선을 매립한 환경에서 보통 시멘트 복합체를 대체하여 고효율 열저장 시멘트를 사용한 경우 약 42 %의 에너지를 저감하는 효과를 보여주었으며 PCM만 혼입한 시멘트 복합체에 비해 압축강도, 휨강도는 각각 18 %, 23 %을 개선하여 사용성을 입증하였다.

• KIEAE Journal
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• 제12권4호
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• pp.97-104
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• 2012

A phase-change material is a substance with a high heat of fusion which, melting and freezing at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid. Therefore, PCMs are classified as latent heat storage (LHS) units. The purpose of this study is to analyze PCM wallboard design parameters using dynamic energy simulation. Among the factors of PCM, melting temperature, latent heat, phase change range, thermal conductivity are very important element to maximize thermal energy storage. In order to analyze these factors, EnergyPlus which is building energy simulation provided by department of energy from the U.S is used. heat balance algorithm of energy simulation is conduction finite difference and enthalpy-temperature function is used for analyzing latent heat of PCM. The results show that in the case of melting temperature, the thermal energy storage could be improved when the melting temperature is equal to indoor surface temperature. It seems that when the phase change range is wide, PCM can store heat at a wide temperature, but the performance of heat storage is languished.

• 설비공학논문집
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• 제1권4호
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• pp.319-329
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• 1989

Heat transfer phenomena during inward melting and solidification process of the phase change material were studied expertimentally. The phase change medium was 99% pure n-docosane paraffin ($C_{22}H_{46}$). The solid-liquid interface motion during phase change was recorded photographically. Measurements were made on the temperature, the solid-liquid interface, the melted or frozen mass and the various energy components stored or extracted from the cylinder wall. For melting, the experimental results reaffirmed the dominant role played by the conduction at an early stage, by the natural convection at longer time. For solidification, natural convection effects in the superheated liquid were modest and were confined to short freezing time. Although the latent energy is the largest contributor to the total stored or extracted energy, the aggregate sensible energies can make a significant contribution, especially at large cylinder wall superheating or subcooling, large initial phase change material subcooling or superheating.

• 대한기계학회논문집
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• 제19권12호
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• pp.3317-3328
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• 1995

The objective of the present study is to predict the characteristics of heat and mass transfer around an evaporative condenser. Numerical calculations have been performed using multi-zone method to investigate heat transfer rate and evaporation rate with the variation of inlet condition(velocity, relative humidity and temperature) of the moist air, the flow rate of the cooling water and the shape of the condenser tube. From the results it is found that the profile of heat flux is the same as that of evaporation rate since heat transfer along the gas-liquid interface is dominated by the transport of latent heat in association with the vaporization(evaporation) of the liquid film. The evaporation rate and heat transfer rate is increased as mass flow rate increases or relative humidity and temperature decrease respectively. But the flow rate of the cooling water hardly affect the evaporation rate and heat flux along the gas-liquid interface. The elliptic tube which the ratio of semi-minor axis to semi-major axis is 0.8 is more effective than the circular tube because the pressure drop is decreased. But the evaporation rate and heat flux shown independency on the tube shape.

• 태양에너지
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• 제17권2호
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• pp.67-74
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• 1997

잠열 저장물질로서 비조화 축열재인 sodium acetate trihydrate를 사용하여 구형의 PCM 입자를 제조하였다. 비조화 축열재의 단점인 상분리 현상 및 과냉각 현상을 방지하기 위하여 점증제로서 gelatin, 조핵제로서 sodium pyrophosphate decahydrate를 사용하였다. 혼합조성의 용융 PCM을 이용하여 연속적으로 지름이 3-3.5 mm 인 구형 PCM 입자가 제조되었다. 용융 PCM 방출속도가 1.3-1.8 ml/min 인 범위 내에서는 PCM 입자크기가 방출속도에 영향을 받지 않았다. 제조된 PCM 입자의 물성을 측정하기 위하여 DSC, SEM과 XRD를 이용하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.470-474
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• 2012

This paper deals with the thermal performances of PCM/diatomite composites for energy saving. The PCM/diatomite composites were prepared by incorporating PCMs in the pores of diatomite to increase form stability of PCMs. In experiment, we used the hexadecane, octadecane and paraffin as PCM and they have each 254.7 J/g, 247.6 J/g and 144.6 J/g of latent heat capacity, and those melting points are $20.84^{\circ}C$, $30.40^{\circ}C$ and $57.09^{\circ}C$, respectively. Thermal properties of PCM/diatomite composites were determined by using DSC. And PCM/diatomite composites were characterized by SEM and FTIR analysis. The results showed that the PCMs are well infiltrated into the structure of diatomite andt he latent heat capacity of PCM/diatomite composites was obtained by 40% of pure PCMs.

• 한국자동차공학회논문집
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• 제23권4호
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• pp.428-435
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• 2015

This paper presents the experimental study of cabin thermal comfort using a cold storage heat exchanger in a vehicle air-conditioning system. Recent vehicle-applied ISG functions for fuel economy and emission, but when vehicles stop, compressors in the air-conditioning system stop, and the cabin temperature sharply increases, making passengers feel thermal discomfort. This study conducts thermal comfort evaluation in the vehicle, which is applied to a cold storage system for the climate control wind tunnel test and the vehicle fleet road test with various airflow volume rates and ambient temperatures blowing to the cold storage heat exchanger. The experimental results, in the cold storage system, air discharge temperature is $3.1-4.2^{\circ}C$ lower than current air-conditioning system when the compressor stops and provides cold air for at least 38 extra seconds. In addition, the blowing airflow volume to the cold storage heat exchanger with various ambient temperature was examined for the control logic of the cold storage system, and in the results, the airflow volume rate is dominant over the outside temperature. For this study, a cold storage system is economically useful to keep the cabin at a thermally comfortable level during the short period when the engine stops in ISG vehicles.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.324-329
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• 2008

The liquid cooling effect of a natural convection type radiator by using the PCM has been investigated experimentally. The radiator size is $423{\times}295{\times}83$ mm and PCM container size is $398{\times}270{\times}26$ mm. The objective is elapsed time higher than maximum time to reach for maximum operating temperature of a general liquid cooling radiator. This study, in order to study on the effects of the phase-change phenomenon, carried out the various mass flow rate, input electric power, ambient and melting point of three type PCM. For the above experimental parameter, the melting time was performed about 180/250/560 min at input power 150 W and ambient $30^{\circ}C$ from using the three type PCM(PCM_S1/S2/S3) respectively. Furthermore, the effects of the thermal dissipation was decreased higher input power than lower input power at heating block and melting time of PCM. However, the effects of mass flow rate did not nearly affect of the thermal performance especially.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1051-1060
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• 2003

The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm ; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate.

• 한국군사과학기술학회지
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• 제19권4호
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• pp.469-475
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• 2016

Thermal batteries are primary reserve power sources, which are activated upon the melting of eutectic electrolytes by the ignition of heat sources. Therefore, sufficient thermal insulation is absolutely needed for the stable operation of thermal batteries. Currently, excessive amount of heat sources is being used to compensate the heat loss in the cell stack along with the insertion of metal plates and thermal insulators to reserve heat at the both ends of cell stack. However, there is a possibility that the excessive heat flows into the cell stack, causing a thermal runaway at the early stage of discharge. At the same time, the internal temperature of thermal batteries cannot be maintained above the battery operating temperature at the later stage of discharge because of the insufficient insulation. Therefore, the effects of Phase Changing Material(PCM) plates were demonstrated in this study, which can replace the metal and insulating plates, to improve the thermal insulation performance and safety of thermal batteries.