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Hydrophobic hollow fiber membrane-based solution mass exchanger
Sung Joo HONG,Eiji HIHARA,Chaobin DANG 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.6
This paper presents a hollow fiber membrane-based solution mass exchanger (HFM-SME) in vapor absorption refrigeration system. Due to a hydrophobic surface characteristic where water vapor passes through, but the liquid lithium bromide solution does not seep into it, the HFM-SHE is used for both heat and mass recovery to enhance the system efficiency whereas the conventional solution heat exchanger is only used for the recovery of heat. Mass recovery process is emphasized by understanding the simultaneous heat and mass transfer between two streams of the lithium bromide solutions. The characteristics of the mass recovery process are clarified regarding the flow direction of the solutions.
Hong Seok Kim,Eiji Hihara,Chaobin Dang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.1
In recent years, EVs have attracted considerable attention as eco-friendly vehicles. Owing to a significant decrease in fuel economy during the winter season, heat pump technology is currently being applied for EVs in lieu of the standard electric heater option. However, heat pumps need to defrost periodically due to the accumulation of frost on the heat exchanger’s outer surface, which compromises the security of the heat source as well as system efficiency. The proposed PCM module has a double-tube structure chargeable either from the heat pump through waste heat, or from the battery through the liquid line, during normal operation. As opposed to the electric heater, which reduces fuel economy during heat pump defrosting, the PCM module is proposed for cabin heating by air. The effectiveness of the unique inner fins located in the PCM is proven by CFD analysis, and the solidification thermal behavior is measured for a test section using C20H42 (Icosane). A one-dimensional thermal model with an accuracy of ± 1 °C is proposed to estimate the air outlet temperature and heat capacity over time during heat discharging, as a basis for future investigation of fuel economy improvement using the PCM module at vehicle level.
HFC 순수냉매 및 3성분 혼합냉매의 수평관내 응축열전달
오종택,비원 영치,Oh, Jong-Taek,Hihara, Eiji 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.2
An experimental study of condensation heat transfer was performed for pure refrigerants HFC32, HFCI25, and HFC134a, and a ternary refrigerant mixture of HFC32/125/134a (23/25/52wt%). The heat transfer coefficients were measured inside a horizontal smooth tube 5.8 mm I.D. and 8.0 m long. The refrigerant temperature at inlet was 40 $^{\circ}C$, and the mass flux was varied from 150 to 400 $kg/m^2s$. As for the pure refrigerants, the heat transfer coefficient of HFC32/125/l34a decreased as the quality decreased. In addition, the heat transfer coefficient of HFC32/l25/134a was about 20 % lower than HFC 134a at a low mass flux but showed no reduction at a high mass flux. The heat transfer coefficient of ternary refrigerant mixtures was 30% lower on the average than that of the pure refrigerant.