One simple way of increasing the heat transfer for a fin-and-tube heat exchanger is to increase the fin surface area. In this study, a series of tests were conducted on wide slit fin heat exchangers having an increased fin area (Pl/Pt = 0.87), and the results were compared with those of standard slit fin heat exchangers (Pl/Pt = 0.6). Thermal performances of wide silt-finned samples were superior to those of standard slit fin samples. For one row configuration, the j factor of the wide slit fin sample was 11% larger, and the f factor was 33 % smaller than those of the standard slit fin sample. The difference decreased as the number of tube row increased, although wide slit fin sample always yielded superior performance, The reason was attributed to the many narrower slits formed on the wide fin sample. Furthermore, the effect of fin pitch on j and f factor was not significant, and j factor decreased with the increase of the number of tube row.

An enthalpy exchange element (EEE) is frequently made of papers, and a concern exists on growth of fungus or bacteria. This concern may be eliminated if polymer membrane is used instead of paper. Furthermore, most existing enthalpy exchangers have cross-flow configuration, which yields lower performance than counter-flow one. In this study, a counter-flow enthalpy exchange element was made using PVDF and cellulose composite. Heat and moisture transfer tests were conducted changing the frontal air flow rate from 150 m 3 /h to 350 m 3 /h at both the heating and the cooling condition. Results showed that the temperature efficiencies were approximately the same independent of the weather condition. Humidity efficiencies at the heating condition, however, were higher than those at the cooling condition. Furthermore, the heat transfer coefficients approached the theoretical value as the flow rate increased. In addition, the vapor transmission rates at the heating condition were higher than those at the cooling condition, probably due to the higher humidity efficiency at the heating condition. Future research will be focused on moisture diffusion characteristics of the composite membrane, which requires further measurements of water holdup, equilibrium adsorption curve, etc.

Indirect evaporative coolers (IECs) are widely used for cooling of outdoor air in building air-conditioning and for cooling of indoor air in data center air-conditioning. However, for each case, the inlet air temperature and humidity condition to IEC are different, which may yield different cooling efficiency. In this study, tests were conducted at the two air conditions using two IEC samples having different channel pitch (3 mm × 5 mm, 5 mm × 5 mm). Results showed that the efficiencies of the 3 mm × 5 mm sample were 12~32% larger than those of the 5 mm × 5 mm sample due to 25% larger heat transfer area and the usage of smaller diameter channel. The efficiency was 10% larger at the data center condition than at the building condition. The reason may be attributed to a larger absolute humidity difference between the liquid film and the air at the data center condition. At the same air velocity, the pressure drops at the wet channel were 64~128% larger than those at the dry channel due to the presence of liquid film at the wet channel. Comparison of the data with predictions by the analytical model revealed that both the efficiency and the pressure drop were over-predicted. Possible reason may be the simplification of the channel geometry and the assumption of fully developed flow, which may be improved in the future.

Due to the concern on global warming, refrigerants having high GWP(Global Warming Potential) are being replaced to low GWP refrigerants. As for small slush maker, R-134a is being to replaced to R-290, whose GWP is 3. In this study, performance tests were conducted on the slush maker having dual evaporator, which was designed to operate using R-290. Results showed that the optimum refrigerant charge amount was 100g. At the charge amount, 61 minutes was needed to make a slush from a raw milk substance, which contained 10% sucrose. The power consumption was 0.89 kW, which yielded COP of 0.252. Tests were further conducted changing the outdoor air temperature. It was resulted that slush-making was possible at all outdoor temperatures except at an extreme temperature of 43°C. Even at the temperature, slush-making was possible if the machine operated with a single evaporator. The COP increased with the decrease of the outdoor temperature.

Improvement of living and life style led to increased sales of frozen milk products, such as ice creams or ice bars. These frozen milk products are commonly stored in a small refrigeration stocker. R-502, which has long been used as the refrigerant of a stocker, is being replaced with R-404A due to the ozone layer depletion issue. In this study, thermal analysis was conducted for the stocker, and the results are compared with experimental data. For the compressor analysis, performance curves were used. Evaporator or condenser was discretized into small volumes, and energy balance was applied. Capillary tube was also discretized into small volumes, and energy and momentum balance were applied. Comparison with the test data of the stocker having 500 liter internal volume revealed that the condensation or evaporation temperature was predicted well except for the initial start-up period. Slightly lower prediction (maximum 4oC) was obtained for the stoker room temperature at the initial operation period. The effect of radiation heat transfer for prediction of the stocker room temperature was assessed.

Nickel-based and iron-based alloys have been developed and commercialized for a wide range of high performance applications at severely corrosive and high temperature environment. This alloy foam has an outstanding performance which is predestinated for diesel particulate filters, heat exchangers, and catalyst support, noise absorbers, battery, fuel cell, and flame distributers in burners in chemical and automotive industry. Production of alloy foam starts from high-tech coating technology and heat treatment of transient liquid-phase sintering in the high temperature. These technology allow for preparation of a wide variety of foam compositions such as Ni, Cr, Al, Fe on various pore size of pure nickel foam or iron foam in order for tailoring material properties to a specific application.

노년시대를 대비하는 기능성 게임의 교과목을 개발하기 위하여 인문대학과 공과대학의 관련학과 학생들을 대상으로 연구진의 교과 항목들에 대해 중요성과 필요성에 대한 설문을 조사하였다. 양 대학의 학생들의 인지에 대한 공통점과 차이점을 분석하여 이를 토대로 융합 학제간 신 교과목을 개발하였다. 노인용 기능성 게임의 인식을 학생들에게 확산시키고자 본 교과목을 양대학의 교과과정에 포함시켜 시행하였다.

Currently, the application of TiO2 photocatalyst has been focused on purification and treatment of wastewater. However, the use of conventional TiO2 slurry photocatalyst results in disadvantage of stirring during the reaction and of separation after the reaction. And the usage of artificial UV lamp has made the cost of photocatalyst treatment system high. Consequently, we studied that solar light/TiO2 film system was designed and developed in order to examine disinfection characteristics of sewage wastewater treatment. The optimum conditions for disinfection such as solar light intensity, characteristic of sewage wastewater, amounts of TiO2 and comparison of solar ligth/TiO2 systems with UV light/TiO2 system was examined. The results are as follows: (1) photocatalytic disinfection process with solar light in the presence of TiO2 film more effectively killed total coliform (TC) than solar light or TiO2 film absorption only. (2) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with remain resistant material. (3) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with the increase of amounts of TiO2. (4) TC survival ratio decreased linearly with increasing UV light intensity. (5) The disinfection effect of solar light/TiO2 slurry system decreased more than UV light/TiO2 film systems. (6) The disinfection reaction followed first-order kinetics. We suggest that solar light instead of using artificial UV light was conducted to investigate the applicability of alternative energy source in the disinfection of TC and the degradation of organic material.

This study make a comparison between the phosphorus removal performance of FNR(Ferrous Nutrient Removal) process and A/O process by the laboratory experiments. For simultaneous removal of phosphorus, iron electrolysis was combined with oxic tank. Iron precipitation reactor on the electrochemical behaviors of phosphorus in the iron bed. The phosphorus removal in FNR process was more than A/O process. Iron salts produced by iron electrolysis might help to remove COD and nitrogen. And the demanded longer SRT is the more removes the removes COD, nitrogen, and phosphorus. Also, FNR process of sludge quantity more reduce than A/O process to input cohesive agents.