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낮은 시상수를 이용한 전기화학-열역학 사이클 효율 최적화
김재훈(Jaehoon Kim),설재훈(Jae Hun Seol) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The heat sources richly exist and are readily available in various industries such as thermal power plants, solar plants, and renewable energies. However, after the heat is used as the primary energy, it remains as waste heat in various temperature ranges. In particular, low-grade heat, which is less than 130 ℃ of waste heat, cannot be used at 100% energy due to energy loss. The thermoelectric device has been studied to this heat usefully, but this device has a problem of low efficiency in low-grade heat. Recently, when the temperature of an electrochemical cell, i.e., battery, increases, a voltage rise due to a thermal-galvanic effect is discovered and is theoretically more efficient than the thermoelectric device. A phenomenon similar to this effect also occurs in supercapacitor. However, generated voltage is reduced under the influence of the self-discharge of the supercapacitor, which affects the thermodynamic cycle efficiency. In this study, self-discharge was minimized by lowering the supercapacitor’s time constant by controlling the water’s flow rate. As a result, the value of the temperature coefficient, which means the voltage change with the temperature change, has been improved, which is predicted to increase thermodynamic efficiency.
100 °C 이하 저온 폐열 활용을 위한 유기 냉매 랭킨 사이클의 효율 향상에 대한 연구
김동규(Dong Kyu Kim),김민수(Min Soo Kim) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-
The experimental and numerical study on the organic Rankine cycle to recover low grade waste heat using rotary expander. We developed rotary expanders having a pentagonal rotor to recover low grade heat efficiently. First, we compared the performance of the two rotary expanders that having triangular and pentagonal rotor. The amount of power generated by the rotary expander having a pentagonal rotor was 90 W greater than that having a triangular rotor. Then we manufactured a rotary expander having a pentagonal rotor and integrated it into the organic Rankine cycle system. When the pressure ratio was 2.4, the maximum power generation was 140 W and the efficiency of the system was 1.7%. Through the results, we can convince the possibility of introduction of the rotary expander as a power generation device in the organic Rankine cycle system.