• Journal of Energy Engineering
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• v.16 no.4
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• pp.181-186
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• 2007

In order to investigate the heat transfer coefficient and pressure drop during evaporation of $CO_2$, basic experiment on the evaporation heat transfer characteristics in a horizontal smooth tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes ($200{\sim}1200\;kg/m^2s$), heat fluxes ($10{\sim}80\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$). With the increase of quality, the evaporation heat transfer coefficient decreased. With the increase of heat flux, the evaporation heat transfer coefficient increased. Significantly change of the heat transfer coefficient was observed at any heat flux and mass flux. With the increase of saturation temperature, the heat transfer coefficient increased. Pressure drop increased with the increase of mass flux and the decrease of saturation temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.3
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• pp.297-305
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• 2005

The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter. a pre-heater and evaporator (test section). The test section consists of a smooth. horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$. saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greatly effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality. heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In making a comparison between test results and existing correlations. the present experimental data are the best fit for the correlation of Jung et al. But it was failed to predict the evaporation heat transfer coefficient of $CO_2$ using by the existing correlation. Therefore. it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.4
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• pp.167-174
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• 2005

The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500kg/m^2s$, saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$, and heat flux of 10 to $40kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greater effect on nucleate boiling than convective boiling. The evaporation heat transfer coefficient of $CO_2$ is highly dependent on the vapor quality, heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the correlation of Jung et al. But the existing correlations failed to predict the evaporation heat transfer coefficient of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.910-916
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• 2019

This paper describes the system implementation of the heating operation based on spatial distributing and zonal calorie measuring and analyzing of houses to calculate the fair amount of the heating meterage automatically. The heating space is distributed into 4 zones, which the flow rate and calories are checked by one meter respectively. The system is composed of a heating sources, adjuster of thermostat, valve controller, PC converter and total monitering. The returning temperature in the spatial zones is measured for the heating calorie to calculate the zonal calories according to the rooms temperature. The proposed system results in error by 1% or less in comparing with the dedicated experimental equipment, and reduces energy cost by 7% from conventional system. The fair checking system will be enhanced with building energy management system in the future.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.9
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• pp.143-150
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• 2019

The purpose of this study was to propose how to determine the setting time related to the determination of the surface finish working time of the concrete using a Durometer, which is used as a rubber hardness meter. Two different types of Durometer were used to measure the setting time of the concrete. High flowing concrete with 40% of water to binder ratio was fabricated maintaining $600{\pm}100mm$ of slump flow. The test results indicated that the application of the Durometer resulted in a high correlation with the penetration resistance tester in both mortar and concrete. When measuring the setting time of the concrete, with properly used with Durometer, evaluation of the setting time of the concrete can be available. Therefore, it is thought that the measurement of the final set of the durometer C type can be useful to decide the limit time of the finishing operation and the time of the rejuvenation of the curing process by measuring the finishing set at 40 HD in the case of the initial set and 10 HD in the case of D type.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.263-275
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• 2022

We conducted this study to provide essential data for implementing restoration measures on the physical properties of the geology, topography, and soil of the landcreep areas in Yangpyeong-gun, Gyeonggi-do. The strata of the survey area comprised topsoil, weathered soil, weathered rock, and soft rock layers. The landcreep area, caused by colluvial debris, was located in a convex topography shape distributed as bedrock with shales and incorporated with sandstone. According to the measurement of the displacement meter, the surveyed area has crept from 1.1 mm to 6.5 mm during the recurrent landcreep between 1 July and 27 August, 2020. The landcreep had progressed over two directions (S65° W, E45° S, and E70° S) which were similar to the groundwater flow direction (E82.5° S and S16.8° W). The average slope of the landcreep area occurred on a gentle slope (19.3°), lower than the average slope of the mountain area (25°) in Korea. The bulk density in the groundwater areas was lower than that in other surveyed areas.

• The Korea Journal of Herbology
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• v.28 no.5
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• pp.33-38
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• 2013

Objectives : The aim of this study was to examine anti-thrombotic effect of traditional herbal extracts in a rat model of ferric chloride ($FeCl_3$)-induced carotid arterial thrombosis. Methods : Thirty minutes prior to a 35% $FeCl_3$ application, Sprague Dawley(SD) rats were injected with the 10 types of traditional herbal extracts (100mg/kg, intraperitoneal injection), respectively. The effect of these herbal extracts was examined for time to occlusion(TTO) using the Laser doppler flow meter and measured for thrombus weight (TW) in $FeCl_3$-induced thrombosis model. Results : In the TTO, Salvia miltiorrhiza (Sm, $2.30{\pm}0.28$ min, p<0.001) and Santalum album (Sa, $2.19{\pm}0.19$ min, p<0.001) showed significantly delayed TTO more than twice compared with Saline-treated group. Cnidium officinale (Co), Psoralea corylifolia (Pc), Scutellatia baicalensis (Sba), Panax notoginseng (Pn), Angelica tenuissima (At), Scrophularia buergeriana (Sbu), Rhus verniciflua (Rv) and Picrasma quassioides (Pq), except for Rhus verniciflua (Rv) also meaningfully impeded TTO more than one fold. In addition, Salvia miltiorrhiza, Santalum album, Cnidium officinale, Psoralea corylifolia and Scutellatia baicalensis significantly reduced TW more than 10% compared with Saline-treated group. Especially, Salvia miltiorrhiza and Santalum album showed the most excellent anti-thrombotic effect among the 10 herbal extracts tested on the restoration of altered TTO and TW. Conclusions : These results suggest that Sm and Sa extracts have outstanding anti-thrombotic effect in $FeCl_3$-induced thrombosis model and is potentially useful as herbal medicines for the treatment and prevention of thrombosis.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.5
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• pp.9-16
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• 2022

Syngas, also known as synthesis gas, synthetic gas, or producer gas, is a combustible gas mixture generated when organic material (biomass) is heated in a gasifier with a limited airflow at a high temperature and elevated pressure. The present research was aimed at modifying the existing LPG engine generator for fully operated syngas. During this study, the designed gasifier-powered woodchip biomass was used for syngas production to generate power. A 6.0 kW LPG engine generator was modified and tested for operation on syngas. In the experiments, syngas and LPG fuels were tested as test fuels. For syngas production, 3 kg of dry woodchips were fed and burnt into the designed downdraft gasifier. The gasifier was connected to a blower coupled with a slider to help the air supply and control the ignition. The convection cooling system was connected to the syngas flow pipe for cooling the hot produce gas and filtering the impurities. For engine modification, a customized T-shaped flexible air/fuel mixture control device was designed for adjusting the correct stoichiometric air-fuel ratio ranging between 1:1.1 and 1.3 to match the combustion needs of the engine. The composition of produced syngas was analyzed using a gas analyzer and its composition was; 13~15 %, 10.2~13 %, 4.1~4.5 %, and 11.9~14.6 % for CO, H₂, CH₄, and CO₂ respectively with a heating value range of 4.12~5.01 MJ/Nm³. The maximum peak power output generated from syngas and LPG was recorded using a clamp-on power meter and found to be 3,689 watts and 5,001 watts, respectively. The results found from the experiment show that the LPG engine generator operated on syngas can be adopted with a de-ration rate of 73.78 % compared to its regular operating fuel.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.218-223
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• 2010

The zinc oxide thin film, which can be applied as the gas sensor of a semiconductor type, was grown on the silicon substrate by CFR(continuous flow reaction) method in this study. The growth property and the electrical property of the zinc oxide thin films synthesized by CFR method were also investigated. Zinc acetate solutions of 0.005~0.02 M were used as the precursor for the preparation of zinc oxide thin films. The size of ZnO particles consisted on the zinc oxide thin film increased not only with increasing concentration of precursor, but also the thickness of thin film increased. The growth rate of zinc oxide thin film by CFR method was proportionably depend on the concentration of precursor and the uniform ZnO thin film was prepared when zinc acetate of 0.01 M is used as the precursor. The charged currents on the zinc oxide thin films were obtained as its electrical property by I-V meter, and increased agree with increasing the thickness of zinc oxide thin film. Thus, it was concluded that the charged current on the zinc oxide thin film can be controlled with changing concentration of precursor solution in CFR method. The charged currents on the zinc oxide thin films also decreased when ZnO thin film is exposed under hydrogen sulfide of 500 ppmv at $300^{\circ}C$ for 5 min. From these results, it could be confirmed that the zinc oxide thin film prepared by CFR method can be used for the detection of sulfur compounds.

• Journal of Korea Port Economic Association
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• v.38 no.2
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• pp.11-30
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• 2022

Korean ports have some problems in the aspect of quality & quantity in the bunkering process. Quality of bunker is assessed as more higher than competing ports. However, quality of bunkering procedure is assessed as lower. Especially, supply chain from loading of bunker to the bunker barge at oil terminal, transport it, and supply it to the ship has not been secured. Furthermore, aspect of quantity of bunker is more serious rather than that of quality of bunkering process. Disputes on the quantity of bunker between seller and buyer occur frequently, and residue & theft of bunker is also popularized issue and serious problem. Low bunkering fee is recognized as major reason of that problem, however, though low fee can be solved, it can not be necessary secured that problem could be solved, Therefore, this paper investigates and suggests the scheme to solve the quality problems of bunker supplying procedure, and develop solution toward advanced bunkering ports through removal of the quantity disputes. Concretely, this paper suggests introduction of quality system of bunker supply chain in the aspect of bunker supply procedure, and diversion from conventional sounding method to innovative Mass Flow Metering System in the aspect of bunker measuring. These two innovative solutions contribute to the removal and improvement of current structural problems in bunkering procedure.