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손권,강채동,이용주,홍희기 경희대학교 산학협력기술연구원 2001 산학협력기술연구논문집 Vol.7 No.-
Ice adhesion on cooling wall is troublesome in ice formation. The purpose of the present study is to investigate the possibilities of a two-component aqueous solution as a thermal storage material for continuous ice formation. By cooling and freezing under stirring the solution in a stainless steel (SUS304) container which was immersed in a controlled temperature bath, the behavior of ice formation and adhesion was observed by measuring temperature and load variation.
Evaluation of heat storage and release in a double shell and tube heat exchanger with a PCM layer
Donggyu Lee,CHAEDONG KANG 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8
In this study, a thermal storage type heat exchanger that combines heat storage and heat exchange functions has proposed and the heat transfer characteristics of the new type of heat exchanger were analyzed through experiments. The proposed thermal storage type heat exchanger has a shell and tube structure and allows mutual heat transfer between three or more mediums, including a phase change material (PCM). This thermal storage type heat exchanger contains 52.2 kg of a PCM with a phase change temperature of 68.8 °C to provide heat storage function. The heat transfer experiment of the heat exchanger confirmed the effect of the temperature change of the heating medium under the same flow conditions. Furthermore, due to the structural characteristics of the thermal storage type double shell and tube heat exchanger (TSDHE), the phenomenon of three-medium heat exchange (hot watercold water, hot water-PCM, additional water-PCM) was verified during the experimental process. In particular, due to the PCM filled inside the heat exchanger, the cold water received a heat transfer of 3 kW or higher from the PCM for at least 5 min (maximum 33 min), even when the hot water supply (heat source) was stopped. The results of this study will be used as basic data for applying a thermal storage type evaporator to a high temperature heat pump that generates steam using industrial waste heat.
Hwang, Minsik,Kang, Jeongmin,Seong, Kwang-dong,Kim, Dae Kyom,Jin, Xuanzhen,Antink, Wytse Hooch,Lee, Chaedong,Piao, Yuanzhe Elsevier 2018 ELECTROCHIMICA ACTA Vol.270 No.-
<P><B>Abstract</B></P> <P>Ni-Co hydroxide nanoneedles embedded in graphene hydrogel are fabricated using an efficient two-step method and further explored as a binder-free electrode for high-performance asymmetric supercapacitors. First, freestanding graphene hydrogel is prepared via reduction in a mild condition. Second, Ni-Co hydroxide nanoneedles embedded in graphene hydrogel are obtained using a simple hydrothermal method. The existence of many hydrophilic functional groups in graphene hydrogel results in the generation of well-dispersed Ni-Co hydroxide nanoneedles throughout the graphene nanosheet. Moreover, the freestanding property of graphene hydrogel allows it to be used as a binder-free electrode, which can improve the energy density of the asymmetric supercapacitor without inhibiting its high power capabilities. The composite shows an excellent capacity of 544 C g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP> in a three-electrode system. Moreover, the binder-free asymmetric supercapacitor achieves excellent performance with an energy density of 32.74 Wh kg<SUP>−1</SUP> at a power density of 320 W kg<SUP>−1</SUP> and good cycling stability with 85% capacitance retention at a current density of 10 mA cm<SUP>−2</SUP> after 5000 cycles. Therefore, the Ni-Co hydroxide nanoneedles embedded in graphene hydrogel have immense potential as electrochemically active materials for the development of high-performance supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni-Co hydroxide nanoneedles embedded in 3D graphene hydrogel were prepared by an efficient two-step method. </LI> <LI> The nanocomposite of Ni-Co hydroxide/graphene hydrogel was used as a binder-free supercapacitor electrode. </LI> <LI> The nanocomposite shows a high capacity of 544 C g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP> in a three-electrode system. </LI> <LI> The asymmetric supercapacitor prepared by using the nanocomposite shows excellent power/energy density and cycling stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The paper reported the Ni-Co hydroxide nanoneedles embedded in graphene hydrogel using facile two-step method. The asymmetric supercapacitor prepared by using the nanocomposite shows excellent energy density and cycling stability.</P> <P>[DISPLAY OMISSION]</P>