• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2321-2326
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• 2007

To return LNG to a gaseous state, it is fed into a regasification plant. For inland area, where pipelines do not exist or difficult to construct, the LNG is delivered to the inland-receiving terminal available at that area, regasified and delivered to consumers. At inland-receiving terminal, air-heating vaporizer type is usually used. To contribute in developing an efficient air-heating vaporizer, experiment on finned type air-heating vaporizer using 8 fins, 50 mm fin length (8fin50le) and 4 fins, 75 mm fin length (4fin75le) were conducted. The experiments were conducted by varying the ambient condition and the length of the vaporizer. The ambient air was controlled so that it has the same condition with air condition in every season available. $LN_2$ is used to substitute LNG because of safety reason. The results show that characteristics of the finned type 4fin75le vaporizer are comparable to finned type 8fin50le vaporizer at all season.

• Tribology and Lubricants
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• v.23 no.6
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• pp.288-297
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• 2007

Adhesion and friction tests were carried out in order to investigate the effect of temperature on the tribological characteristics of poly (methylmethacrylate) (PMMA) film using AFM. The pull-off and friction forces on the PMMA film were measured under a high vacuum condition (below $1{\times}10^{-4}$ Pa) as the temperature of the PMMA film was increased from 300 K to 420 K (heating) and decreased to 300K (cooling). Friction tests were also conducted in both high vacuum and air conditions at room temperature. When the temperature was 420 K, which is 25 K higher than the glass transition temperature $(T_g)$ of PMMA, the PMMA film surface became deformable. Subsequently, the pull-off force was proportional to the maximum applied load during the pull-off force measurement. In contrast, when the temperature was under 395 K, the pull-off force showed no correlation to the maximum applied load. The friction force began to increase when the temperature rose above 370 K, which is 25 K lower than the $T_g$ of PMMA, and rapidly increased at 420 K. Decrease of the PMMA film stiffness and plastic deformation of the PMMA film were observed at 420 K in force-displacement curves. After the heating to 420 K, the fiction coefficient was measured under the air condition at room temperature and was found to be lower than that measured before the heating. Additionally, the RMS roughness increased as a result of the heating.

• The Korean Journal of Food And Nutrition
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• v.33 no.4
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• pp.440-446
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• 2020

The purpose of this study was to derive the conditions for manufacturing rice porridge with optimum properties after reheating. The characteristics of rice porridge according to the soaking time, water addition rate, heating temperature, heating time, and cooling conditions were compared using the 'Samkwang' cultivar. In Step I, as the heating temperature increased, the weight change decreased and the viscosity increased, and the temperature known as the main factor of the gelatinization also appeared to affect the viscosity increase. In Step II, the viscosity and the texture properties was not significantly different as the soaking time was reduced, and 10 minutes was suitable because of due to the shortening effect of the total process time. In Step III, the residual heat was lowered by cooling after the rice porridge production, so the viscosity could be greatly reduced. Also, it was confirmed that the water addition rate of 900% and the heating temperature of 15 minutes were optimal manufacturing conditions. The next study will investigate the porridge processability of rice cultivars using these results.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.688-692
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• 2005

Importance of substitute energy has been increasing due to environmental issues and lack of fossil fuels. In addition, heating cost that occupies from 30 to $40\%$ of the total production cost in Korean protected cultivation needs to be reduced for profitability and global competition. But, studying on substitute energy to solve these problems has not been activated for Korean protected cultivation. Therefore, this study was conducted to develop a geothermal heat pump system for cool ing and heat ing of greenhouses at a lower cost than conventional hot air heater and air conditioner. Fundamental test of heat transfer characteristics in soil was conducted by computer simulation and controlled tests for its verification. Based on the results of the theoretical and empirical investigations, an optimum heat pump system was developed and the performance was evaluated for practical use in a greenhouse at the Pusan Horticultural Experiment Station. The system was compared with a conventional hot air heating system through a cucumber growing test and economic feasibility analysis. Results of the application test of the geothermal heat pump showed that with an initial setting of $15^{\circ}C$ the inside temperature of the greenhouse could be maintained between 15 and $17^{\circ}C$. Results of the cucumber growing test showed that there were no significant differences in average height, leaf length, leaf width, number of nods, leaf area, dry weight and yield between the plots wi th the geothermal heat pump system and a conventional hot air heater. Economic feasibility analysis indicated that the variable cost of the hot air heater could be saved $81.2\%$ using the geothermal heat pump system. It was concluded that the geothermal heat pump system might be a pertinent heating and cooling system for greenhouses because of the low operating cost and the use of environment-friendly geothermal energy.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.91-96
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• 2011

In this paper, friction welded joints were constructed to investigate the mechanical properties of welded 15-mm diameter solid bars of Mg alloy (AZ31B). The main friction welding parameters were selected to endure reliable quality welds on the basis of visual examination, tensile tests, impact energy test, Vickers hardness surveys of the bonds in the area and heat affected zone (HAZ), and macrostructure investigations. The study reached the following conclusions. The tensile strength of the friction welded materials (271 MPa) was increased to about 100% of the AZ31B base metal (274 MPa) under the condition of a heating time of 1 s. The metal loss increased lineally with an increase in the heating time. The following optimal friction welding conditions were determined: rotating speed (n) = 2000 rpm, heating pressure (HP) = 35 MPa, upsetting pressure (UP) = 70 MPa, heating time (HT) = 1 s, and upsetting time (UT) = 5 s, for a metal loss (Mo) of 10.2 mm. The hardness distribution of the base metal (BM) showed HV55. All of the BM parts showed levels of hardness that were approximately similar to friction welded materials. The weld interface of the friction welded parts was strongly mixed, which showed a well-combined structure of macro-particles without particle growth or any defects. In addition, an acoustic emission (AE) technique was applied to derive the optimum condition for friction welding the Mg alloy nondestructively. The AE count and energy parameters were useful for evaluating the relationship between the tensile strength and AE parameters based on the friction welding conditions.

• Journal of Environmental Impact Assessment
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• v.12 no.4
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• pp.281-290
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• 2003

The influence of land-use type on surrounding temperature was studied the relationships between land-use types and the air condition analyzing AWS (Automatic Weather Station) data of Seoul from KMA (Korea Meteorological Administration). The distribution of air temperature by land-use type has been influenced by the different heating and cooling rates. The difference of heating rates depending on the land-use type was largest at 2~3hours after sunrise and the difference of cooling rates was largest from 2hours before sunset to 2hours after sunset with its maximum at sunset. The difference of cooling rates is greatest in a clear and calm weather situation and the large difference in cooling rates between the green areas and built-up area is up to $1.5^{\circ}C/h$. By season, the difference of cooling rates is largest in fall and in turn spring, winter and summer. In a cloudy or rainy day, the difference in heating and cooling rates on land-use type is not distinct but the tendency is similar to a clear day. In all seasons, the rate of difference occurrence of the daily range of temperature between the green areas and built-up area was large, especially fall. In a fall with a clear and calm day, the magnitude of the daily range of temperature between the green areas and built-up area was largest.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.66-71
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• 2009

To reduce the building energy consumption, the major advanced nations are conducting actively many researches on so called a "self-sufficient building(or other words zero energy building)" which can support its required energy by itself. Given this background, KIER(Korea Institute of Energy Research) built full size test-bed of the zero energy solar house in early 2002, and has studied on the self-sufficient heating load up to now. We analyse the sensitivity between the heating load and the solar radiation gain according to the change the effective transmittance of windows. The authors classified 9 cases by solar transmittance of glass. The results demonstrate the solar radiation amount is 0.466 MWh from the eastern zone of Fl.,1(the first floor), 0.332 MWh from Fl.,2(the second floor), 1.194 MWh form the southern zone of F1., and 0.822 MWh from the southern zone of Fl.,2 on the case 1(each cases are classified by window types). On the case 9, the solar radiation amount is 3.127 MWh, 2.662 MWh, 8.799 MWh and 6.078 MWh from the same condition. For the Fl.,1, the amount of Heat Load that is saved per year ranged 10.5 to 48 %, and the reduction was anywhere from 0.2 to 17.9% for Fl.,2

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.91-97
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• 2013

Self-heating effects during operation of high current AlGaN/GaN power transistors degrade the current-voltage characteristics. In particular, this problem becomes serious when a low thermal conductivity Si substrate is used. In this work, AlGaN/GaN-on-Si devices were fabricated with various channel widths and Si substrate thicknesses in which the structure dependent self-heating effects were investigated by temperature dependent measurements as well as thermal simulation. Accordingly, a device structure that can effectively dissipate the heat was proposed in order to achieve the maximum current in a multi-channel, large area device. Employing via-holes and common electrodes with a 100 ${\mu}m$ Si substrate thickness improved the current level by 75% reducing the channel temperature by 68%.

• Journal of the Korean Wood Science and Technology
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• v.38 no.3
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• pp.205-212
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• 2010

This study was carried out to investigate the characterization of aerogel made by holocellulose, the thermal properties of the aerogel, and its shapes and porous structures. The aerogel was made by holocellulose through the gelation in alkali hydroxide-urea solution and freeze drying processes. Holocellulose aerogel had porous structure such as net or sponge. The density of holocellulose aerogel was 0.04 g/$cm^3$, and the specific surface area 145.3 $m^2$/g. Although thermal degradation occurred in the range of $210{\sim}350^{\circ}C$, significant thermal degradation occurred at low temperature with low heating rate, Micropore volume was sharply increased with low heating rate. Holocellulose aerogel char obtained by carbonization with $900^{\circ}C$ and $0.5^{\circ}C$/min. heating rate had the highest surface area, 656.7 $m^2$/g. The deformed and irregular structures of holocellulose aerogel chars due to the thermal degradation were observed in SEM.

• Current Photovoltaic Research
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• v.4 no.4
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• pp.159-163
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• 2016

Piled snow upon PV module interferes with Photoelectric Effect process through photovoltaic directly. As a result of this phenomenon, its generation efficiencies keep decreasing or are stuck at zero power generating status. In addition, PV facilities have been installed on those places such as water surface, roof-top, and other isolated places, dealing with conditions of "Securing high REC weighted value", "Difficulty of securing land" and so forth. Through this study, we are able to actualize the function of heating over PV modules when it snows. We adopted laminating method through heating film and modules, guaranteeing warranty more than for 25 years. Also we are trying remote control systemically, not by hardware control, to run parallel with automatic driving and monitoring system which enable to control operation time, insolation, amount of snowfall automatically. We applied analysis of actual proof to both snow removal PV system and general PV power system, and these led to bear power consumption analysis while snow-removing, and its comparison after finishing the task as "One stone, two birds." In the long run, we could carry out economic analysis against snow removal system, and this helps to verify the most maximized control method for snow removal conditons on a basis of weather information. this study shall let prevent people from negligent accidents, and improve power generation problems as mentioned from the top. Ultimately, we expect to apply this system to heavy snowfall regions in winter season in spite of its limited system installaion in Korean territory, initially.