• Transactions of the KSME C: Technology and Education
• /
• v.1 no.1
• /
• pp.99-105
• /
• 2013

In this paper, we carried out the basic design of 36 MTD natural gas BOG re-liquefaction system to recover the generated natural gas during performance test of LNG pump and natural gas compressor. The re-liquefaction process of natural gas is designed to have 1500 kg/h of liquefaction rate with reverse Brayton refrigeration cycle. With the designed process, the variation of liquefaction rate is calculated for various inlet conditions of feed gas. From results, the liquefaction rate is more sensitive for inlet temperature than gas composition. The specifications of equipments such as gas blower, natural gas compressor, cryogenic heat exchanger and nitrogen compander are determined on the basis of the designed process. The requirement of power consumption and cooling water are also determined through the basic design.

• Journal of Korea Water Resources Association
• /
• v.38 no.4 s.153
• /
• pp.281-292
• /
• 2005

The water balance analysis for the long-term water resources plan is a simple calculation that compares water demands with possible water supplies. For a watershed being considered the reports on the performance of the water balance analysis, however, have shown inconsistent results and thus have not earned credibility due to the uncertainty of the data acquired and models used. In this research, uncertainties in the water scarcity estimate were assessed through probability representation based on the Monte Carlo simulation using Latin Hypercube Sampling (LHS). The natural flow, municipal demand, industrial demand, agricultural demand, and return flow rate were selected as representative input variables for the water balance analysis, and their distributions were set based on the linear regression and the entropy theory. The statistical properties of the output variable samples were analyzed in comparison with a deterministic estimate of the water scarcity of an existing study. Application of LHS to three sub-basins of the Geum river basin showed the deterministic estimate could be overestimated or underestimated. The sensitivity analysis as well as the uncertainty analysis found that the return flow rate of the agricultural water is the most uncertain but is rarely sensitive to the output of the water balance analysis.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.12
• /
• pp.863-870
• /
• 2012

The market trends of automatic meter reading associated with smart water meters were investigated. Also, recent developments and field applications of key technology for automatic meter reading associated with smart water meters were analyzed. Smart water meters have been manufactured mostly in United States and Europe and have been expanded their business to Asia. Integrated water management system combining with the additional functions such as real-time consumption metering, cost notification, water conservation, leak detection, water quality monitoring, and flow control have been operated in automatic meter reading. Both water quality and quantity data measured from smart water meters and sensors were transferred to data concentration units through neighborhood area network, and then were transferred to integrated server through wide area network. The data transfer methods were determined by comprehensively considering urban scale, density of smart water meters, power supply and network topologies. Common data collection methods such as fixed network to data concentation units, vehicles drive by, people walk by, and drone fly by have been applied. The automatic meter reading associated with smart water meters are spread throughout the world, and both water and energy savings result in saving the money and reducing the greenhouse gases emission.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.8
• /
• pp.411-419
• /
• 2016

The objective of this study was to evaluate the application possibility of tube type electrolysis module system using recirculation process through removal organic matters and nitrogen in the pigment wastewater. The tube type electrolysis module consisted of a inner rod anode and an outer tube cathode. Material used for anode was titanium electroplated with $RuO_2$. Stainless steel was used for cathode. It was observed that the pollutant removal efficiency was increased according to the decrease of flowrate and increase of current density. When the retention time in tube type electrolysis module system was 180 min, chlorate concentration was 382.4~519.6 mg/L. The chlorate production was one of the major factors in electrochemical oxidation of tube type electrolysis module system using recirculation process used in this research. The pollutant removal efficiencies from the bench scale tube type electrolysis module system using recirculation operated under the electric charge of $4,500C/dm^2$ showed the $COD_{Mn}$ 89.6%, $COD_{Cr}$ 67.8%, T-N 96.8%, and Color 74.2%, respectively and energy consumption was $5.18kWh/m^3$.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.1
• /
• pp.84-92
• /
• 2020

To supply a stable amount of standard material to detect paralytic shellfish toxin (PST), we examined possible increases in toxic content in Alexandrium catenella and A. pacificum using a light emitting diode (LED), which is one of the most eco-friendly and economical lighting method. When comparing the growth rates of organisms and wavelengths of light used, the half saturation constants (Ks) of red wavelength were higher than those of other wavelengths. In contrast, the Ks of blue wavelength were lower than those of other wavelengths. Moreover, when comparing the toxic contents and wavelengths of light used, red wavelength produced approximately 8 times more toxic content in A. catenella and approximately 3.2 times more toxic content in A. pacificum than other wavelengths. Thus, the toxic content present in the organism might be closely related to the Ks of light. The optimum light source to be used to ensure economically ef ective and productive growth in an Alexandrium culture system (photo-bioreactor) would likely consist of a two-phase culture, wherein a blue LED is used during the lag and exponential phases to increase growth rates, followed by the use of a red LED during late exponential and stationary phases to achieve increased PST yields.

• Particle and aerosol research
• /
• v.12 no.3
• /
• pp.95-102
• /
• 2016

Controlling exposures to occupational hazards is important for protecting workers. Certified facepiece respirators are recommended when engineering controls do not adequately prevent exposures to airborne nanomaterials. The objective of this study is to carry out the experimental performance test to investigate the fractional efficiencies of the filter media for two grades of facepiece respirators. Experimental performance evaluations were carried out for the test NaCl particles and silver nanoparticles. For media of respirator filter, the penetration of NaCl particles was less than 5% and the most penetrating particle size occurred at about 40 nm. For silver nanoparticles, the most penetrating particle size was about 20nm with higher efficiency than those of NaCl particles. Charge characteristics of airborne nanoparticles is important because the media of respirator filter is made by the electret filter media.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.2
• /
• pp.171-179
• /
• 2012

Cooling of hot sections, especially the turbine nozzle and rotor blades, has a significant impact on gas turbine performance. In this study, the influence of precooling of the cooling air on the performance of gas turbines and their combined cycle plants was investigated. A state-of-the-art F-class gas turbine was selected, and its design performance was deliberately simulated using detailed component models including turbine blade cooling. Off-design analysis was used to simulate changes in the operating conditions and performance of the gas turbines due to precooling of the cooling air. Thermodynamic and aerodynamic models were used to simulate the performance of the cooled nozzle and rotor blade. In the combined cycle plant, the heat rejected from the cooling air was recovered at the bottoming steam cycle to optimize the overall plant performance. With a 200K decrease of all cooling air stream, an almost 1.78% power upgrade due to increase in main gas flow and a 0.70 percent point efficiency decrease due to the fuel flow increase to maintain design turbine inlet temperature were predicted.

• Food Science and Preservation
• /
• v.12 no.2
• /
• pp.123-129
• /
• 2005

This study was conducted to investigate the quality characteristics of functional 'sunsik' as the nutritionally balanced diet for the moderns. The major nutrient of nutritionally balanced 'sunsik' was carbohydrate, while contained lower contents of protein and lipid than general 'sunsik'. Sucrose was the major free sugar of nutritionally balanced 'sunsik', and major organic acids were malic, tartaric, oxalic and citric acid. Free amino acids were predominantly serine, arginine, alanine and glutamic acid. Linolenic acid $(12.52\%)$ was contained in the nutritionally balanced 'sunsik'. Ca, Mg, K, Na and Fe were found as major minerals. Antioxidant activity was about $29\%$ compared to BHA and BHT(200 ppm), and about $40\%$ of $\alpha-tocopherol$(400 ppm). Sensory evaluation of nutritional balanced 'sunsik' gained higher sensory score in color, cooked aroma, flavor, chewiness and overall acceptance, compared to the general 'sunsik'.

• Economic and Environmental Geology
• /
• v.39 no.5 s.180
• /
• pp.607-613
• /
• 2006

For the reasonable use of low grade-shallow geothermal energy by Standing Column Well(SCW) system, the basic requirements are depth-wise increase of earth temperature like $2^{\circ}C$ per every 100m depth, sufficient amount of groundwater production being about 10 to 30% of the design flow rate of GSHP with good water quality and moderate temperature, and non-collapsing of borehole wall during reinjection of circulating water into the SCW. A closed loop type-vertical ground heat exchanger(GHEX) with $100{\sim}150m$ deep can supply geothermal energy of 2 to 3 RT but a SCW with $400{\sim}500m$ deep can provide $30{\sim}40RT$ being equivalent to 10 to 15 numbers of GHEX as well requires smaller space. Being considered as an alternative of vertical GHEX, many numbers of SCW have been widely constructed in whole country without any account for site specific hydrogeologic and geothermal characteristics. When those are designed and constructed under the base of insufficient knowledges of hydrgeothermal properties of the relevant specific site as our current situations, a bad reputation will be created and it will hamper a rational utilization of geothermal energy using SCW in the near future. This paper is prepared for providing a guideline of SCW design comportable to our hydrogeothermal system.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.6
• /
• pp.1023-1035
• /
• 2016

Suspended sediment concentration (SSC) is a crucial riverine parameter in terms that it can be utilized for analyzing sediment transport, stability assessment of river and structure and so on. However, in case of domestic, sediment discharge data are not enough because of using conventional sediment samplers. This study aimed at developing a practical technique for estimating suspended sediment concentration in high spatial and temporal resolution by building relationship between acoustic backscatter (or SNR) from H-ADCP with actually observed data using LISST-100X. In this regard, a dedicated correction algorithm was proposed particularly for the adapted H-ADCP (SonTek SL-3000). Then, a SNR-SSC relation was built based upon a real-scale field experiment, where both H-ADCP and LISST-100X were concurrently operated to observe SNR and SSC, respectively. The coefficient of determination for the developed regression equation of SNR-SSC relation was around 0.85~0.88, thereby the relation could be evaluated to be highly correlated. The result of this study might be potentially applied for real-time and simultaneous observation of SSC when H-ADCP could be applied.