• Progress in Superconductivity and Cryogenics
• /
• v.21 no.1
• /
• pp.40-44
• /
• 2019

This study investigates mixtures of water and cryoprotectant agents (CPAs) to store high-grade cold energy. Although water is an ideal material for a cold thermal storage (CTS) due to its high specific heat, undesirable volume expansion may cause structural stresses during freezing. The volume expansion can be alleviated by adding the CPAs to water. However, the CPA aqueous solutions not only have different thermal properties but also transit to amorphous state different from pure water. Therefore, these characteristics should be considered when using them as material of the CTS. In experiments, glycerol and dimethyl sulfoxide (DMSO) are selected as the candidate CPA. The volume expansion of the solution is measured by an in-situ strain gauge in low temperature region. The specific heat capacity of the solution is also measured by differential scanning calorimetry (DSC). Both the amount of volume expansion and the specific heat capacity of the CPA aqueous solution decrease in the case of higher concentration of CPA. These characteristics should be contemplated to select optimal aqueous solution for CTS for liquid air energy storage system (LAES). The CPA solutions have advantages of having wide temperature range to utilize the latent heat of water and higher sensible heat of the CPA. The CPA solutions which can satisfy the allowable stress of the structure are determined. Consequently, among the CPA solutions investigated, DMSO 20% w/w solution is the most suitable for the CTS.

• Korean Journal of Environmental Biology
• /
• v.25 no.3
• /
• pp.205-214
• /
• 2007

Marine environmental characteristics on the dinoflagellate cysts distribution in surface sediment of the southwest sea of Korea were investigated from 21 stations in September 2003, and 36 stations in June, 2004. The water mass characteristics indicated that the southwest sea of Korea is characterized by various oceanographic conditions due to coastal waters of Korea and China. The Tsushima warm currents and the cold bottom water of the Yellow Sea. Mud contents and chlorophyll a concentrations were higher in central region such as, Namhaedo, Yeosu and Goheung coast than in western region such as, Wando, Haenam and Jindo coast in the South Sea of Korea. A total of 35 taxa of dinoflagellate cysts were identified representing 21 genera, 33 species, 2 unidentified species. Cyst abundance ranged from 13 to 527 cysts $g-dry^{-1}$, showing higher abundance in the coastal areas than in western region of the South Sea of Korea. From the result of the PCA analysis, the distribution of dinoflagellate cysts was not only related to the different water masses which appeared in the southwestern sea but also to physical and biological parameters such as water temperature, light, surface sediment faces and phytoplankton biomass.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.4
• /
• pp.404-412
• /
• 1994

Radium isotopes were measured together with oceanographical parameters in the southern coastal region of the Korean East Sea during the period of September $2{\sim}8$, 1991. In September, there were various water masses vertically distributed in this region due to formation of strongly seasonal thermoclines. These water masses were characterized by activity of radium isotopes as well as water temperature and dissolved oxygen. Among the water masses, Japan Sea Proper Water(JSPW) below $1^{\circ}C$ had the highest Ra-226 activities but the lowest Ra-228 concentrations. However, Tsushima Surface Water (TSW) above $20^{\circ}C$ in water temperature had the highest Ra-228 which decreased sharply with depth. In TSW, Ra-228 activities were in the range of $194{\sim}270$ dpm/kl, which were approximately 10 times higher than JSPW. Activity ratios(A.R's) of Ra-228/Ra-226 were $1.9{\sim}2.6$ for TSW, $0.7{\sim}1.1$ for Tsushima Middle Water(TMW) of $12{\sim}17^{\circ}C\;to\;0.4{\sim}0.7$ for North Korea Cold Water(NKCW) with $1{\sim}7^{\circ}C$ and below 0.2 for JSPW. The Ra-228/Ra-226 ranged from 0.6 to 0.9 in the cold waters of $2{\sim}6^{\circ}C$, which were observed at depth of $65{\sim}120\;m$ in this study area. Radium isotopes provided a useful means of identifying origins of the cold water which occurred annually at intermediate or bottom layers in the southern coastal zone of the Korean East Sea. By plotting radium isotopes against water temperature, it could be observed clearly that the cold waters between $2{\sim}6^{\circ}C$ did not originate from the mixed water of JSPW and TMW but from NKCW.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.4
• /
• pp.294-300
• /
• 2008

Abnormal cooling of the Korean East Sea Water(KESW) in the East Sea before and after the 1982-1983 and 1997-1998 ENSO events is examined using bimonthly routine observation data from the National Fisheries Research and Development Institute of Korea for the period 1965 to 2002. The KESW, which occupies roughly a region between the Korean Peninsula and west of approximately $131^{\circ}E$, showed extreme cold-state years(1981 and 1996) prior to the two strongest ENSO events of the last half-century. Inter-annual bimonthly mean anomalies at 100 m in the KESW region were $-3.10^{\circ}C\;and\;-3.41^{\circ}C(SD=1.4^{\circ}C)$ in 1981 and 1996, respectively. These results suggest that extreme cooling of the KESW may be a prelude to very strong ENSO events through large-scale teleconnections.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.19 no.2
• /
• pp.87-98
• /
• 2016

During the period between July 3 and 27 of 2009, water samples were collected from the Russian coast at a depth of 30m from 26 stations (including Ulleung and Japan basins) onboard the Russian survey vessel R/V Lavrentyev following 4 lines (D, R, E, and A). The samples were analyzed for nutrients and chlorophyll a contents. All parameters exhibited higher values in warm waters than in cold waters ($NH_4:1.8-fold$, $PO_4:1.8-fold$, $SiO_2:1.2-fold$, and chlorophyll-${\alpha}$:1.9-fold), except nitrates, which was 1.4-fold higher in cold waters than in warm waters. The horizontal distribution of ammonia, phosphate, and chlorophyll-${\alpha}$ was very similar to each other and showed the highest values in the waters near Russia, where a upwelling influence of cold current and bottom water prevails, while relatively low distribution was observed at the Ulleung Basin. On the other hand, nitrates showed the highest concentration at the Ulleung Basin, which is under the direct influence of the Tsushima warm water, and showed a gradual decrease northward. The N/P ratio showed the highest value in the Tsushima middle water, rather than in the North Korean Cold Water, the Tsushima Warm Water was the primary source of nitrate flow into the East Sea. However, the average concentration of phosphate in the warm waters was < $0.2{\mu}M$, thereby limiting phytoplankton growth, while a high concentration of phosphate in cold waters showed a direct correlation with chlorophyll-${\alpha}$. The results of principal component analysis for the identification of primary factors that influence the marine environment showed that principal component I was water temperature and principal component II was influenced chlorophyll-${\alpha}$ and nutrients. Therefore, Study area has greatest influenced by water temperature, and clearly distinct cold and warm water regions were observed in the East Sea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.2
• /
• pp.351-373
• /
• 2019

The cold eddies around the Ulleung Basin in the East Sea were identified from satellite altimeter sea level data using the Winding-Angle method from 1993 to 2015. Among the cold eddies, the Dokdo Cold Eddies (DCEs), which were formed at the first meandering trough of the East Korea Warm Current (EKWC) and were pinched off to the southwest from the eastward flow, were classified and their migration patterns were analyzed. The vertical structures of water temperature, salinity, and flow velocity near the DCE center were also examined using numerical simulation and observation data provided by the Hybrid Coordinate Ocean Model and the National Institute of Fisheries Science, respectively. A total of 112 DCEs were generated for 23 years. Of these, 39 DCEs migrated westward and arrived off the east coast of Korea. The average travel distance was 250.9 km, the average lifespan was 93 days, and the average travel speed was 3.5 cm/s. The other 73 DCEs had moved to the east or had hovered around the generated location until they disappeared. At 50-100 m depth under the DCE, water temperature and salinity (T < $5^{\circ}C$, S < 34.1) were lower than those of ambient water and isotherms made a dome shape. Current faster than 10 cm/s circulates counterclockwise from the surface to 300 m depth at 38 km away from the center of DCE. After the EKWC separates from the coast, it flows eastward and starts to meander near Ulleungdo. The first trough of the meander in the east of Ulleungdo is pushed deep into the southwest and forms a cold eddy (DCE), which is shed from the meander in the south of Ulleungdo. While a DCE moves westward, it circumvents the Ulleung Warm Eddy (UWE) clockwise and follows U shape path toward the east coast of Korea. When the DCE arrives near the coast, the EKWC separates from the coast at the south of DCE and circumvents the DCE. As the DCE near the coast weakens and extinguishes about 30 days later after the arrival, the EKWC flows northward along the coast recovering its original path. The DCE steadily transports heat and salt from the north to the south, which helps to form a cold water region in the southwest of the Ulleung Basin and brings positive vorticity to change the separation latitude and path of the EKWC. Some of the DCEs moving to the west were merged into a coastal cold eddy to form a wide cold water region in the west of Ulleung Basin and to create a elongated anticlockwise circulation, which separated the UWE in the north from the EKWC in the south.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.6
• /
• pp.862-875
• /
• 1996

The CTD data observed in the sea northwest of Cheju Island have been analyzed to figure out the seasonal circulation around Cheju Island. Warm and saline waters flow into the Yellow Sea through the middle region of the Yellow Sea in winter and along the west coast of Korean Peninsula in summer. On the other hand, cold and less saline waters flow out of the Yellow Sea through the middle region in summer and along the west coast of Korean Peninsula in winter. These flows make the seasonal circulation around Cheju Island. As dynamics, the monsoon wind and the variation of Kuroshio transport have been suggested. Comparing the observational result, the circulation driven by the variation of Kuroshio transport is strengthened by monsoon winds in the numerical model.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.8
• /
• pp.807-812
• /
• 2015

A microcapsule water slurry is a latent heat-storage material having a low melting point. In this study, the thermal properties of a microcapsule water slurry are measured. The physical properties of the test microcapsule water slurry, i.e., thermal conductivity, specific heat, latent heat, and density, are measured, and the results are discussed for the temperature region of solid and liquid phases of the dispersion material (paraffin). It is clarified that Eucken's equation can be applied to the estimation of the thermal conductivity of the microcapsule water slurry. Useful correlation equations of the thermal properties of the microcapsule water slurry are proposed in terms of the temperature and concentration ratio of the microcapsule water slurry constituents.

• Journal of Korean Society on Water Environment
• /
• v.40 no.2
• /
• pp.89-100
• /
• 2024

Climate change has a broad impact on the entire water environment, and this impact is growing. Climate adaptation in water supply systems often involves quantity and quality control, but there has been a lack of research examining the impacts of climatic factors on water supply productivity and operation conditions. Therefore, the present study focused on, first, building a database of climatic factors and water purification operating conditions, and then identifying the correlations between factors to reveal their impacts. News big data was analyzed with keywords of climatic factors and water supply systems in either nationwide or region-wide analyses. Metropolitan area exhibited more issues with cold waves whereas there were more issues with drought in the Southern Chungcheong area. A survey was conducted to seek experts' opinions on the climatic impacts leading to these effects. Pre-chlorination due to drought, high-turbidity of intake water due to rainfall, an increase of toxins in intake water due to heat waves, and low water temperature due to cold waves were expected. Pearson correlation analysis was conducted based on meteorological data and the operating data of a water purification plant. Heavy rain resulted in 13 days of high turbidity, and the subsequent low turbidity conditions required 3 days of high coagulant dosage. This insight is expected to help inform the design of operation manuals for waterworks in response to climate change.

• 한국해양학회지
• /
• v.20 no.3
• /
• pp.6-19
• /
• 1985

Hydrographic data and daily time series of longshore wind, sea level and sea surface temperature were used in order to explain why the upwelling effect in SST is especially prominent near Ulgi-Gampo although the sea level records along the whole southeast coast show a nearly uniform upwelling-downwelling response to wind. Regional difference in intensity of the wind-induced upwelling represented by the SST decrease is attributed to the combined influence of two factors; one is the baroclinic tilting of isotherms due to the East Korea Warm Current (EKWC) near the Ulgi-Gampo coast, the other is the topographic effects around the southeast coast. Baroclinic tilting effect of EKWC which is generally strongest near the coast of Ulgi to Gampo results in both of the shoaling of cold water and the westward trapping of the coldest bottom water over the shallower shelf rather than the deepest troough region off that coast regardless of the season. Therefore, becacse of the cold water ready for upwelling at the subsurface layer, SST responds very rapidly to the upwelling-favorable winds of summer only off the Ulgi-Gampo coast. Spreading isobaths from Pusan to Gempo can reinforce the upwelling of the cold bottom water and its westward trapping.