• Journal of the Korean Solar Energy Society
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• v.27 no.1
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• pp.47-54
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• 2007

Interests on renewable energy are increased due to oil price and environmental problems aroused from the fossil energy usage. In this study, performances of a solar assisted hybrid heat pump system are analyzed by experimental method. The developed system could runs at two types of operating mode. When the storage temperature is higher than the set temperature, the stored hot water in storage tank is supplied to the load directly. On the other hand, when the storage temperature lower than the set temperature, the water inside of the storage tank is used as heat source of the heat pump. In this study, the system control temperature for the alternation of the operating mode is set to $40^{\circ}C$ of the storage tank outlet. As results, it is founded that the COP of the developed heat pump system shows between 3.0 and 3.5. It is resonable performance for the heating system with a renewable energy as secondary heat source. The solar collect used in this study could supplies heat to the storage tank at over 400 W/m2 solar intensity. If the irradiation is lower than the 400 W/m2, the circulation pump stored and it could not supply heat to the storage tank. It is found that the difference temperature between the outlet of the storage tank and collector is $3^{\circ}C$. Even though, the extended study should be conducted to get a optimum performance of the developed system with various operating condition and control strategies.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.180-191
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• 2016

Optimizing energy usage for maximum efficiency is an essential goal for manufacturing plants in every industrial manufacturing sector. The generation and distribution of purifying compressed air is a large expense incurred in practically all manufacturing processes. Not only is the generation and treatment expensive equipment of compressed air, but frequent maintenance and effective operation is also required. As a plant's compressed air system is often an integral part of the production process, it needs to be reliable, efficient, and easy to be maintain. In this paper, we study to find operating method to save energy from the adsorption dryer in the process of purifying compressed air, which is required for a clean room production site in "A" company. The compressed air passes through a pressure vessel with two "towers" filled with a material such as activated alumina, silica gel, molecular sieve or other desiccant material. This desiccant material attracts the water from the compressed air via adsorption. As the water clings to the desiccant, the desiccant particle becomes saturated. Therefore, Adsorption dryer is an extremely significant facility which removes the moisture in the air $70^{\circ}C$ below the dew point temperature while using a lot of energy. Also, the energy consumption of the adsorption dryer can be varied by various operating conditions (time, pressure, temperature, etc). Therefore, based on existing operating experiments, we have searched operating condition to maximize energy saving by changing operating conditions of the facility. However, due to a short experiment period (from September to October), further research will be focused on considering seasonality.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2033-2038
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• 2008

The CPLs(capillary pumped loops) are two phase heat transfer devices which enable active control of operating temperature of heat absorbing elements(or evaporators). Although the CPLs gain increasing interests as promising heat transfer devices for future missions such as spacecraft and commercial applications, their intrinsic complexity in operating principles makes the widespread use of these devices difficult. The key element and main cause of this complexity in operating principles is the two phase hydrodynamic accumulator or reservoir which controls the saturation state of the remaining loop and, particularly for the CPLs, it is separated from the evaporator. Thus, in this study, the operating characteristics of the CPL is investigated experimentally and theoretically. Mainly focusing on the role of reservoir the thermodynamic operating principle is examined first and the experimentally obtained steady state and transient state operating characteristics are discussed in detail.

• Advances in Energy Research
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• v.4 no.3
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• pp.239-253
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• 2016

Air quality in hospitals has always concerned hospitals' health officials due to its dangerous particles and gases. Because of the importance of air conditioning in the operating room, a system must be embedded in operating rooms to direct the contaminated air outside, and inject fresh filtered air from outside back into the room. In this study, laminar flow air conditioning system is implemented in the operating room by slot linear diffusers and with the help of air curtain. For this, stimulation Computational Fluid Dynamic (CFD) was used due to its efficiency. The aim of the present study was to find a proper solution to overcome the unfavorable factors, namely, contamination, humidity, and also temperature, velocity and pressure inside the room. These factors were implemented with different values and then stimulated through FLUENT software program. Results showed that the aforementioned factors can be overcome using air curtain and slot linear diffusers.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2006.11a
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• pp.301-305
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• 2006

An electrical bill is one of the various factors that influence on energy use of residents. This study focused on electrical bills and searched that whether electrical bills affect resident behavior of operating air conditioner and their controlled indoor climate. We surveyed two groups for field study ; the one is residents who live in a studio apartment in Seoul and they are charged for electric as energy consumption they used, and the other is residents who live in a university dormitory and they are not charged for their energy consumption. We measured how long they used the air conditioner for cooling, on/off temperature of air conditioner and room temperature for these two groups. Residents were interviewed about their cooling needs, decisions about when to turn on their air conditioner and so on. We found that dormitory group has much amount of time used the air conditioner than studio apartment group and there are differences of room temperature between two groups when they turn on or off air conditioner. The result shows that perception of money affects resident behavior of operating air conditioner and their acceptable thermal range.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.43-49
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• 2010

The piping failure probability of the reactor coolant system in Kori unit 1 was evaluated considering stress corrosion cracking. The P-PIE program (Probabilistic Piping Integrity Evaluation Program) developed in this study was used in the analysis. The effect of some variables such as oxygen concentration during start up and steady state operation, and operating temperature, which are related with stress corrosion cracking, on the piping failure probabilities was investigated. The effects of leak detection capability, the size of big leak, piping loops, and reactor types on the piping failure probability were also investigated. The results show that (1) LOCA (loss of coolant accident) probability of Kori unit 1 is extremely low, (2) leak probability is sensitive to oxygen concentration during steady state operation and operating temperature, while not sensitive to the oxygen concentration during start up, and (3) the piping thickness and operating temperature play important roles in the leak probabilities of the cold leg in 4 reactor types having same inner diameter.

• Journal of Power System Engineering
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• v.4 no.3
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• pp.19-24
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• 2000

This study concerns the performance of the heat transfer of the thermosyphon having 80 internal groove in which boiling and condensation occur. Distilled water has been used as a working fluid. The liquid filling as the ratio of working fluid volume to total volume of thermosyphon has been used as the experimental parameters. The heat flux and heat transfer coefficient at the condenser are estimated from the experimental results. The experimental results have been assessed and compared with the existing theories. As a result of the experimental investigation, the maximum heat flow rate in the thermosyphon is proved to be dependent upon the liquid fill quantity. relatively high rates of heat transfer have been achieved operating in the thermosyphon with the internal groove. Also, a thermosyphon with the internal groove can be used to achieve some inexpensive and compact heat exchangers in low temperature. In addition, overall heat transfer coefficients and the characteristics as an operating temperature are obtained for the practical applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.8
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• pp.636-644
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• 2008

The objective of this paper is to investigate characteristics of an autothermal reformer at various operating conditions. Numerical method has been used, and simulation model has been developed for the analysis. Pseudo-homogeneous model is incorporated because the reactor is filled with catalysts of a packed-bed type. Dominant chemical reactions are Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Velocity(GHSV). Temperature at the reactor center, fuel conversion, species at the reformer outlet, and reforming efficiency are shown as simulation results. SR reaction rate is improved by increased inlet temperature. Reforming efficiency and fuel conversion reached the maximum at 0.7 of OCR. SR reaction and WGS reaction are activated as SCR increases. When GHSV is increased, reforming efficiency increases but pressure drop from the increased GHSV may decrease the system efficiency.

• Journal of Applied Reliability
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• v.10 no.1
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• pp.25-38
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• 2010

In this paper, an accelerated degradation test procedure for an electronic appliance compressor is proposed. We investigate the amount of wear of the compressor and consider several factors as accelerating factors. Finally we select the operating pressure as a main accelerating factor. The test condition of accelerated degradation test is determined. The modified accelerating test reduces the test time in design phase by using the suggested accelerating factor.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.227-230
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• 2004

The regulator that was designed for space use must be operating on the severe circumstance. For example, operating temperature is below 90K and operating pressure is 20.7 MPa. The design of regulator for liquid propulsion system was accomplished and dynamic characteristic was analyzed successfully.