• Journal of Industrial and Engineering Chemistry
• /
• 제68권
• /
• pp.301-310
• /
• 2018

Various catalysts such as formic acid, acetic acid, sodium hydroxide, sodium bicarbonate, carbon dioxide and nitrogen gas were used for hydrolyzates production from deoiled mackerel muscle by subcritical water hydrolysis. Above 99% hydrolysis yield was obtained using sodium bicarbonate catalyst at $260^{\circ}C/70bar$. Histamine and heavy metals concentration were reduced in hydrolyzates. Highest amount of amino acid (400.36 mg/g) and reducing sugar (24.75 mg/g) were found in hydrolyzate obtained at $260^{\circ}C/70bar$ and $220^{\circ}C/30bar$, respectively with sodium bicarbonate catalyst. Antioxidant and ACE-inhibitory activities were significantly higher in hydrolyzates obtained using sodium bicarbonate than that of others.

• Nuclear Engineering and Technology
• /
• 제49권1호
• /
• pp.103-112
• /
• 2017

Application of the supercritical condition in reactor core cooling needs to be properly justified based on the extreme level of parameters involved. Therefore, a numerical study is presented to compare the thermalhydraulic performance of supercritical and single-phase natural circulation loops under low-to-intermediate power levels. Carbon dioxide and water are selected as respective working fluids, operating under an identical set of conditions. Accordingly, a three-dimensional computational model was developed, and solved with an appropriate turbulence model and equations of state. Large asymmetry in velocity and temperature profiles was observed in a single cross section due to local buoyancy effect, which is more prominent for supercritical fluids. Mass flow rate in a supercritical loop increases with power until a maximum is reached, which subsequently corresponds to a rapid deterioration in heat transfer coefficient. That can be identified as the limit of operation for such loops to avoid a high temperature, and therefore, the use of a supercritical loop is suggested only until the appearance of such maxima. Flow-induced heat transfer deterioration can be delayed by increasing system pressure or lowering sink temperature. Bulk temperature level throughout the loop with water as working fluid is higher than supercritical carbon dioxide. This is until the heat transfer deterioration, and hence the use of a single-phase loop is prescribed beyond that limit.

• 설비공학논문집
• /
• 제15권6호
• /
• pp.461-470
• /
• 2003

The purpose of this study is to investigate the performance of a transcritical cycle for hot water heating using $CO_2$ as a working fluid. Some of the main parameters that affect the practical performance of the $CO_2$ system are discussed; the performance on the variation of refrigerant charge, changes in flow conditions of secondary fluids, and that with or without internal heat exchanger, The experimental results show that the optimum charge is approximately the same for various mass flow rates of the secondary fluid at gas cooler. The experimental results on the effect of secondary fluids are in general agreement with the experimental results of transcritical cycle in the open literature and show similar trend for conventional subcritical vapor compression cycles. The heat exchanger effectiveness increases with an increase of the heat exchange area of the internal heat exchanger regardless of the mass flow rate at the gas cooler.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.1294-1299
• /
• 2009

Since the operating pressure of $CO_2$ gascooler is so high compared with that of previous subcritical condenser, the optimization of gascooler is needed for improve heat exchanger performance. In this study, the performance characteristics of five kinds of heat exchangers were analyzed and compared with operating conditions. As a result, the 4-20 HX-tube shows the maximum gascooler capacity because the heat transfer is effective and pressure drop is small. Beside, the high performance of 4-20 HX-tube could be keep for wide operating condition.

• Korean Chemical Engineering Research
• /
• 제48권6호
• /
• pp.741-746
• /
• 2010

오징어내장에서 초임계 이산화탄소를 이용한 추출잔류물에 에탄올을 이용하거나 초임계 처리를 하지 않은 오징어내장에서 다양한 유기용매를 이용하여 인지질을 추출하였다. 초임계이산화탄소 추출은 동결 건조된 오징어 내장 시료를 이용 $45^{\circ}C$ 20 MPa 조건에서 수행되었으며 무극성 지질의 추출에 사용되었다. 동결 건조된 오징어 내장은 클로로포름, 헥산, 메탄올, 에탄올을 이용해 인지질 추출을 시행하고 초임계 이산화탄소 추출을 거친 내장 시료는 에탄올 처리하여 인지질을 추출하였다. 각 인지질 추출과정에서 pH는 5.7로 고정하여 시행하였다. 각각의 인지질의 조성을 검출하기 위하여 evaporative light scattering detector(ELSD)를 이용하여 HPLC 분석을 행하였다. 포스파티딜 콜린(PC)과 포스파티딜 이노시톨(PI)은 초임계이산화탄소 잔류물을 에탄올 추출한 것에서 동결건조물을 에탄올만을 사용하여 추출한 것보다 많은 양이 검출되었다. 하지만 포스파티딜 에탄올아민(PE)과 포스파티딕 에시드(PA)의 경우 동결 건조된 오징어내장을 에탄올만을 사용하여 추출한 인지질에서 많은 양이 검출되었다. 초임계 이산화탄소 처리 후 회수된 추잔 물질에 에탄올을 사용하여 인지질 혼합물을 분리 후 분리된 인지질 혼합물에 대해 가스크로마토그래피를 이용하여 지방산을 분석한 결과 docosahexanoic acid(DHA)의 함량이 매우 높은 것을 확인하였다.

• 한국수소및신에너지학회논문집
• /
• 제19권6호
• /
• pp.537-544
• /
• 2008

In this paper, flow characteristics of an adiabatic capillary tube in a transcritical $CO_2$ have been investigated employing the homogeneous model. The model is based on fundamental equations of mass, energy and momentum which are solved simultaneously. Two friction factors(Churchill) and viscosity(McAdams) are comparatively used to investigate the flow characteristics. Supercritical and subcritical thermodynamic and transport properties of $CO_2$ are calculated employing EES property code. Flow characteristics analysis of $CO_2$ adiabatic capillary tube is presented to offer the basic design data for the operating parameters. The operating parameters considered in this study include inlet temperature and pressure of an adiabatic capillary tube, evaporating temperature and inner diameter tube. The main results were summarized as follows : inlet temperature and pressure of an adiabatic capillary tube, evaporating temperature, mass flowrate and inner diameter of $CO_2$ adiabatic capillary tube have an effect on length of an adiabatic capillary tube.

• 설비공학논문집
• /
• 제18권11호
• /
• pp.851-858
• /
• 2006

[ $CO_2$ ] and propane mixtures, which are environmentally benign, nontoxic, low in price, and compatible with materials and lubricants, were considered as promising alternative refrigerants. A fully instrumented air-conditioning system was developed for a precise performance evaluation of pure $CO_2$ and $CO_2/propane$ mixtures. In this paper, the effect of the charging amount and circulation concentration on the cooling performance of the system using $CO_2$ and propane mixtures was tested and discussed. Pure $CO_2$ and 85/15, 75/25 and 60/40 binary blends by the charged mass percentage of $CO_2/propane$ were selected as working fluids. An optimum charging amount was proposed as a parameter instead of the degree of subcooling, which can not be well defined in the transcritical cycle, to properly compare the performance between the transcritical and subcritical cycles.