• 대한환경공학회지
• /
• 제28권5호
• /
• pp.549-557
• /
• 2006

화력발전소에서 발생하는 폐 음이온교환수지를 분해하기 위해 초임계수 산화 특성 연구를 진행하였다. 폐수지는 음이온교환수지와 양이온교환수지가 혼합된 상태로 배출되었으며, 혼합된 폐수지에서 고-액 유동층을 이용하여 음이온수지를 분리하였다. 분리된 음이온 수지는 원소분석과 열분석을 통해 양이온 수지가 혼합되지 않았음을 확인하였다. 음이온수지를 고압 펌프를 이용하여 초임계수 산화 반응 장치에 연속적으로 주입하기 위해 습식 ball mill을 이용하여 분쇄, 슬러리로 제조하였다. 압력 25.0 MP콘 체류시간 2분, 반응 온도 $500^{\circ}C$에서 처리수의 COD는 99.9%이상 분해됨을 확인하였지만, 총 질소 분해율은 41% 정도로 나타났으며, 슬러리에 질산을 혼합하면 처리수의 총 질소가 감소하였다. 처리수의 COD와 총 질소(T-N) 함량을 목적변수로 설정하여 음이온 수지 슬러리를 분해하는 최적 조건을 도출하기 위해 통계적 실험계획법인 중심합성계획법을 적용하였다. 처리수의 COD는 반응 온도 $500{\sim}540^{\circ}C$, 압력 25.0 MPa, 반응기 체류시간 2분 조건에서 $99.9{\sim}100%$까지 충분히 분해되었으며, 온도 변화와 질산 주입량 변화에 영향을 받지 않았다. 그러나 처리수의 총 질소는 질산 주입량의 변화에 대한 영향이 큰 것으로 확인되었다. 처리수의 총 질소는 회귀분석을 통해 질산 주입량의 함수로 나타낼 수 있었으며, 결정계수($r^2$)는 95.8%로 계산되었다.

• 설비공학논문집
• /
• 제16권12호
• /
• pp.1234-1268
• /
• 2004

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2002 and 2003 has been carried out. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment/design. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation in diverse facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat transfer, humidity was also interesting to promote comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing research topics. Well developed CFD technologies were widely applied for analysis and design of various facilities and their systems. (2) Heat transfer characteristics of enhanced finned tube heat exchangers and heat sinks were extensively investigated. Experimental studies on the boiling heat transfer, vortex generators, fluidized bed heat exchangers, and frosting and defrosting characteristics were also conducted. In addition, the numerical simulations on various heat exchangers were performed and reported to show heat transfer characteristics and performance of the heat exchanger. (3) A review of the recent studies shows that the performance analysis of heat pump have been made by various simulations and experiments. Progresses have been made specifically on the multi-type heat pump systems and other heat pump systems in which exhaust energy is utilized. The performance characteristics of heat pipe have been studied numerically and experimentally, which proves the validity of the developed simulation programs. The effect of various factors on the heat pipe performance has also been examined. Studies of the ice storage system have been focused on the operational characteristics of the system and on the basics of thermal storage materials. Researches into the phase change have been carried out steadily. Several papers deal with the cycle analysis of a few thermodynamic systems which are very useful in the field of air-conditioning and refrigeration. (4) Recent studies on refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement when new alternative refrigerants are applied. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and new alternative refrigerants including natural refrigerants. Efficiency of various compressors and performance of new expansion devices are also dealt with for better design of refrigeration/air conditioning system. In addition to the studies related with thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out. It should be noted that the researches on two-phase flow are constantly carried out. (5) A review of the recent studies on absorption refrigeration system indicates that heat and mass transfer enhancement is the key factor in improving the system performance. Various experiments have been carried out and diverse simulation models have been presented. Study on the small scale absorption refrigeration system draws a new attention. Cooling tower was also the research object in the respect of enhancement its efficiency, and performance analysis and optimization was carried out. (6) Based on a review of recent studies on indoor thermal environment and building service systems, it is noticed that research issues have mainly focused on several innovative systems such as personal environmental modules, air-barrier type perimeterless system with UFAC, radiant floor cooling system, etc. New approaches are highlighted for improving indoor environmental conditions and minimizing energy consumption, various activities of building energy management and cost-benefit analysis for economic evaluation.

• 한국폐기물자원순환학회지
• /
• 제34권2호
• /
• pp.205-213
• /
• 2017

The current study was performed to investigate the effect of recycling coir substrates on the growth, fruit yield, and quality of strawberry plants. Analysis of physical properties revealed that the pH of a fresh coir substrate was 5.04 while those of substrates reused for one and two years were 5.20 and 5.33, respectively. The electrical conductivity (EC) of a new substrate was as high as $4.58dS{\cdot}m^{-1}$. This can cause salt stress after transplanting. The EC tended to decrease as the substrate was recycled, and the EC of a two-year recycled substrate was $1.48dS{\cdot}m^{-1}$. The fresh substrate had lower nitrogen and calcium concentrations, but higher phosphate, potassium, and sodium concentrations than the recycled coir substrate. The coir substrates recycled for one or two years maintained better chemical properties for plant growth than the fresh substrate. Strawberry growth varied depending on the number of years that the coir substrate was recycled. In general, strawberries grown in substrates that had been reused for two years did better than those grown in substrates that had been reused once or were fresh. Ninety days after transplanting, a plant grown in a substrate that had been reused for two years contained 25 leaves, which was 3.6 more than with a fresh substrate. In addition, the plants grown in a substrate that had been reused for two years exhibited larger leaf areas than those grown in other substrates. Coir substrates that had been reused for one year increased the number and area of leaves, but not as much as the substrate that had been reused for two years. One- and two-year reused coir substrates increased the weight of strawberries produced relative to the unused substrate, but the difference was not statistically significant. The plants grown in two-year reused substrates were longer and wider, as well. Also, the number of fruits per plant was higher when substrates were reused. Specifically, the number of fruits per plant was 28.7 with a two-year reused substrate, but only 22.2 with a fresh substrate. The fruit color indices (as represented by their Hunter L, a, b values) were not considerably affected by recycling of the coir substrate. The Hunter L value, which indicates the brightness of the fruit, did not change significantly when the substrate was recycled. Neither Hunter a (red) nor b (yellow) values were changed by recycling. In addition, there were no significant changes in the hardnesses, acidities, or soluble solid-acid ratios of fruits grown in recycled substrates. Thus, it is thought that recycling the coir substrate does not affect measures of fruit quality such as color, hardness, and sugar content. Overall, reuse of coir substrates from hydroponic culture as high-bed strawberry growth substrates would solve the problems of new substrate costs and the disposal of substrates that had been used once.