• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.2
• /
• pp.47-56
• /
• 2008

The objective of this research is to evaluate the optimum recycling methods for the sewage sludge cakes at different microwave power-settings and for different periods of time. The dehydrated sewage sludge cakes used in this study was obtained from N wastewater treatment plan in the P City. The beginning drying processes were carried out in a microwave oven with 2,450 MHz frequency and power ranges of 1kW to 4 kW. The continuous conveyer drying system was also operated with 2,450 MHz frequency and power setting, ranging from of 1 kW to 6 kW. Initial moisture content of the sewage cake is 78~80%, and the moisture content decreased rapidly up to 0.2~2(wt%) within short periods due to breaking the cell walls. This study is also conducted to evaluate the characteristics of sewage sludge cakes with respect to important physical parameters effect on the thermal kinetics for evaporation water in the sludge which are operation times, moisture contents, drying rates, input amounts, flow rates and calorific values. It takes 60 minutes and 120 minutes to reach the critical moisture contents with power setting of 4 kW for 3kg/min and 6kg/min of the flow rates respectively. It takes 120 minutes and 110 minutes to reach the critical moisture contents with flow rates of 2.5 cm/min and sludge input of 6kg/min for the power settings of 4 kW and 6 kW respectively. The most effective value of the power for drying the sludge is 4 kW. Operation with 6kg/min and 4kW on 2cm of the sludge thickness can be effectively and inexpensively to reach the critical moisture contents, when you compare 2cm of the sludge thickness with 1cm and 3cm of the sludge thickness.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.12
• /
• pp.1734-1743
• /
• 2003

Aerosol generator using an electrically heated tube furnace is a stable apparatus to supply nanometer sized aerosols by using the evaporation and condensation processes. Using this method, we can generate highly concentrated polydisperse aerosols with relatively narrow size distribution. In this work, characteristics of particle size distribution, generated from a tube furnace, were experimentally investigated. We evaluated effects of several operation parameters on particle generation: temperature in the tube furnace, air flow rates through the tube, size of boat containing solid sodium chloride(NaCl). As the temperature increased, the geometric mean diameter increased and the total number concentration also increased. Dilution with air affected the size distribution of the particles due to coagulation. A smaller sized boat, which has small surface area to contact with air, brings smaller particles of narrow size distribution in comparison of that of a larger boat. Finally, we changed the electrical mobility diameter of aggregate sodium chloride particles by varying relative humidity of dilution air, and obtained non-aggregate sodium chloride particles, which are easy to generate exact monodisperse particles.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.100-106
• /
• 2001

The size distributions of electrospray droplets from the Taylor cone in cone-jet mode are directly measured by using a freezing method and a transmission electron microscope (TEM) image processing technique. These results are compared with the data obtained by an aerodynamic size spectrometer (TSI Aerosizer DSP). The use of glycerol seeded with NaI and a freezing method make it possible to sample droplets with their original sizes preserved. Since pictures of droplets are taken with TEM with very low vapor pressure of the solution, evaporation is suppressed by freezing. For liquid flow rates below 1 nl/sec, the measured droplet diameters by the TEM image processing technique and the aerosizer are in the range of 0.25 to $0.32{\mu}m$ and 0.30 to $0.40{\mu}m$, respectively. Comparing the TEM data with the aerosizer measurements, it has been revealed that the TEM image processing technique can afford more accurate values of droplet size distributions in the submicron range of 0.1 to $0.4{\mu}m$.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1686-1691
• /
• 2004

The effect of recirculated exhaust gas on performance and exhaust emissions with FGR rate are investigated by using a natural circulation, pressurized draft and water tube boiler with FGR system operating at several boiler loads and over fire air(OFA) damper openings. The purpose of this study is to apply the FGR system to a power plant boiler for reducing $NO_{x}$ emissions. To activate the combustion, the suction damper of two stage combustion system installed in the upper side of wind box is opened by handling the lever between $0^{\circ}$ and $90^{\circ}$ , and the OFA with 0 to 20% into the flame is supplied, as the combustion air supplied to burner is reduced. It is found that the fuel consumption rate divided by evaporation rate does not show an obvious tendency to increase or decrease with rising the FOR rate, and $NO_{x}$ emissions are decreased, at the same OF A damper opening, as FOR rates are elevated and boiler loads are dropped.

• Journal of Powder Materials
• /
• v.16 no.1
• /
• pp.28-32
• /
• 2009

The activation temperatures and hydrogen sorption rates of $Ti_{80-X}Zr_{20}V_X$ alloys were evaluated at room temperature. The alloy powders were prepared by arc melting and then hydride-dehydride(HDH) process. The alloy powders were apt to activate by increase of vanadium in Ti-Zr-V alloys. The easy activation was explained in terms of surface oxygen content which decreased with increase of vanadium on Ti-Zr-V alloys.

• Journal of the Korean Ceramic Society
• /
• v.44 no.12
• /
• pp.720-726
• /
• 2007

Current collectors of SOFC play a significant role on the performance of power generation. In this study a single cell stacked SOFC was assembled using Ag-mesh as a cathode current collector, and evaluated its performance. No gas leakages of the single cell stack occurred in the tests of gas detection and OCV measurement. The OCV and initial power of the stack were 1.09V and $0.45W/cm^2$, respectively, under the flow rates of air at 2,500 cc/min and $H_2$ at 1,000 cc/min at the test temperature of $750^{\circ}C$. A degradation rate of 44.0% was measured during the prolonged time of 307 h. The relatively low durability of the tested single cell stack was found to be the evaporation of Ag-mesh at the current corrector.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.920-923
• /
• 2003

We fabricated composite materials as a pellet structure with the various kinds of inorganic material powder. The composite materials were deposited onto the plastic film by the electron beam evaporation and water vapor transmission rates (WVTRs) were measured by the MOCON facility. As a result of WVTRs, the composite materials had lower WVTR value than any other inorganic materials. So, these films were proposed to protect the organic light emitting device (OLED) from moisture and oxygen. We can consider that the composite thin-film is one of the more suitable candidates for the thin-film passivation layer in the OLED. And, we are processing the XRD, XPS and EPMA to analyze the property of the composite material. We will also analyze properties of the current-voltage and luminescence for lifetime both the composite thin-film passivated OLED and non-passivated OLED.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.4
• /
• pp.833-846
• /
• 1988

Two-phase flow heat transfer phenomena with flash evaporation inside a vertical tube were studied experimentally. Void fractions were measured using electrical probes, and the flow patterns were identified from the output voltage signal itself. The flow pattern as well as the beat transfer rates were changing along the axial distance from the tube inlet with the system pressure. As the pressure inside the tube decreases with fixed inlet temperature, the overall heat transfer coefficient through the tube wall and the boiling heat transfer coefficient inside the tube increase whereas the condensation heat transfer coefficient outside the tube decreases. The boiling heat transfer coefficient inside the tube measured by the experiments appeared to be somewhat larger than the value obtained from the Chen's correlation. Also, the flow patterns identified from present experiments are at the larger quality region of the low pattern map based on the transition criteria of Mishima and Ishii. This may be due to the non-equilibrium flashing phenomenon occurred at the nozzle exit and the tube inlet ; this also implies that the flow pattern of the two-phase flow depends strongly on the inlet conditions.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.3
• /
• pp.363-372
• /
• 2000

An experiment was carried out to evaluate the heat transfer enhancement and the pressure drop characteristics for liquid nitrogen using wire-coil-insert technique under horizontal two-phase conditions. The tube inner diameters were 8 mm and 15 mm, respectively and the tube length was 4.7 m. The helix angle of the wire coil insert was $50^{\circ}$ and its length was 4.7 m. Heat transfer coefficients for both the plain and the enhanced test tubes were calculated from the measurements of temperatures, flow rates and pressure drops. A correlation in a power-law relationship of the Nusselt number, Reynolds number and Prandtl number for the heat transfer was proposed which can be available for design of cryogenic heat exchangers. The correlation showed that heat transfer coefficients for the wire-coil inserts were much higher than those for plain tubes, increased by more than $1.8{\sim}2.0$ times depending upon the range of the equivalent Reynolds number. The correlation was compared with other various correlations in the turbulent flow conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11b
• /
• pp.13-14
• /
• 2004

Using Se as a photoconductive element and ZnS as a luminescent element, a Se/ZnS thin film device for light amplifier applications was fabricated and its characteristics were investigated At various conditions of substrate temperatures, heat treatment times, and heat treatment temperatures, Se thin films and ZnS thin films were separately deposited by an EBE(Electron Beam Evaporation) method of an high accuracy in deposition rates and the optimum fabrication conditions for the Se thin film and the ZnS thin film with a hexagonal structure were obtained The Se/ZnS thin film light amplifier was fabricated by evaporating the ZnS thin film on an ITO(Indium Tin Oxide) glass and the Se thin film on the ZnS thin film in sequence.