• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.980-981
• /
• 2008

Mechanical spring and hydraulic pressure operated mechanisms are applied in most of today's High Voltage Gas Insulated Switchgear(GIS)s. This paper proposes a new type of operation mechanism for GIS circuit breakers rated at 245kV and 40kA. The Motor-Direct-Drive-Mechanism (MDDM) has many advantages compared to conventional operating mechanisms. It has a very simple structure with only one moving part, low mechanical stress and audible noise. It also allows monitoring, operation speed control and self-diagnosis functions.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.4
• /
• pp.100-107
• /
• 2008

Bellows is an important component in Joule-Thomson cryocooler, which minimize the excessive flow of the cryogenic gas. The bellows is made of Monel 400 and its geometry is an axial symmetric shell. During cool-down process, the pressure and volume within bellows must be satisfied with Benedict-Webb-Rubin state equation. Moreover, Poisson's ratio of Monel 400 is nearly constants, but its Young's modulus varies for a drop in temperature. Under these conditions, bellows contracts in the axial direction like a spring. To evaluate deformation of bellows at cryogenic temperature, the numerical calculation of the volume within bellows and finite element analysis are iteratively used in this research. the numerical results show that deformation of the bellows is approximately linear for change of temperature.

• Progress in Superconductivity and Cryogenics
• /
• v.4 no.2
• /
• pp.58-62
• /
• 2002

The purpose of this study is to analyze the charging gas effect on the resonance and performance characteristics of the linear compressor for small scale FPFD Stirling refrigerator. To ensure high performance of FPFD type Stirling refrigerator, the operating frequency of the refrigerator should be around the natural frequency of compressor. The gas spring effect which is induced from Pressure change in cylinder due to motion of pistons has significant effect on the natural frequency of the compressor. The numerical results show the linear compressor has high natural frequency when the charging pressure of working fluid is high and the stroke of compressor, current, input power and efficiency of compressor were shown with different operating conditions.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.98-103
• /
• 2004

This paper presents modeling and simulation of the bump foil bearings with consideration of the elastic behavior of the foil and gas compressibility. Heshmat had originally introduced the simple compliance model to estimate the EHL(elasto-hydrodynamic lubrication) performance. But this approach can not consider the deflection of top foil at the edge of bearing, so model is insufficient to analyze in case that the eccentricity ratio is greater than I. So the top foil is considered as a simple beam model supported by linear spring elements, and the bump foil deflection can be simple compliance model. The EHL calculations are performed for convention rigid type, classical foil type, variable pitch type and double bump type toil bearings. This paper presents that 2nd or 3rd generation bearings have excellent performance in every speeds.

• Proceedings of the KIPE Conference
• /
• 2007.07a
• /
• pp.114-116
• /
• 2007

Mechanical spring and hydraulic pressure operated mechanisms are applied in most of today's High Voltage Gas Insulated Switchgear(GIS)s. This paper proposes a new type of operation mechanism for GIS circuit breakers rated at 245kV and 40kA. The Motor-Direct-Drive-Mechanism (MDDM) has many advantages compared to conventional operating mechanisms. It has a very simple structure with only one moving part, low mechanical stress and audible noise. It also allows monitoring, operation speed control and self-diagnosis functions.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.4
• /
• pp.429-435
• /
• 2015

A bellows is an important temperature control component in a Joule-Thomson micro-cryocooler. It is designed using a very thin shell, and the inside of the bellows is filled with nitrogen gas. The bellows is made of a nickel-cobalt alloy that maintains its strength and elastic properties in a wide range of temperatures from cryogenic to $300^{\circ}C$. The pressure of the gas and the volume within the bellows vary according to the temperature of the gas. As a result, the bellows contracts or expands in the axial direction like a spring. To explore this phenomenon, the deformation of the bellows and its internal volume must be calculated iteratively under a modified pressure until the state equation of the gas is satisfied at a given temperature. In this paper, the modified Benedict-Webb-Rubin state equation is adopted to describe the temperature-volume-pressure relations of the gas. Experiments were performed to validate the proposed method. The results of a numerical analysis and the experiments showed good agreement.

• Journal of the Korean Institute of Gas
• /
• v.3 no.1
• /
• pp.58-63
• /
• 1999

Experimental works were carried out to evaluate how the lapse of time affects the performance characteristics and the service life of low pressure LPG regulators for domestic use. Experimental results showed that the operating pressure of safety devices deviated from the opening pressure value and the closing pressure value from just 1 year after service, and the operating pressure of regulators used for 7${\~}$8 years notably deviated from the reference value of the adjusting pressure and the closing pressure. And the material properties of springs and diaphragms deteriorated after 5${\~}$6 years of service. Thus, it is estimated that low pressure LPG regulators have approximately 6 years of service life. However, it is highly recommended that regulators exceeding 5 years of service should be replaced for the safety of consumer and accident prevention even if they are operating normally.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.6
• /
• pp.42-49
• /
• 2007

In this study, we analyzed flow characteristics of micro-nozzles for basic research to develop micro propulsion system. Cold gas propulsion system was used, and micro-nozzles having nozzle throat diameters of 1.0, 0.5, 0.25 mm were fabricated with EDM method. Thrust was measured through the use of plate-spring and strain gage based thrust measurement system, and flow characteristics of micro-nozzles were analyzed under ambient condition and vacuum condition. We used argon and nitrogen gases as propellant, and compared experimental results with CFD analysis. From the result, we verified the flow losses of viscosity and back-pressure caused by minimization of nozzle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.9
• /
• pp.633-638
• /
• 2011

Increasing demand for comfortable indoor environment and air-conditioning demand is also increasing. Building energy consumption in university which is made up of many different kinds factor was researched. Central control air-conditioning systems are being replaced with individually controlled air-conditioning system. The amount of growth of electricity consumption is due to the increasing demand of EHP. Conversely, the demand for absorption chiller-heater is shrinking. Winter and in summer a lot of electricity and gas usage. On the other hand, showed less energy in spring and autumn. Increase the amount of electricity than the degree of decline in gas consumption was higher. Can be considered as transitional phenomena. Because EHP and the absorption chiller-heater are used at the same time in some of the buildings. To use energy efficiently is needed additional research about environmental impact, economic evaluation.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.303-306
• /
• 2009

High temperature solid oxide fuel cells (SOFCs) offer a clean, pollution-free technology to electrochemically generate electricity at high efficiencies. Solid oxide fuel cells in several different designs have been investigated; these include planar and tubular geometries. The tubular type cell is widely researched due to it have advantages about thermal expansion and sealing issues. Unfortunately, lab scale tubular cell for testing has thermal expansion and sealing problems. The previous Jig for lab scale tubular cell testing has many sealing problems. When we feed fuel gas to jig inlet, ceramic glue sealant has amount of gas expansion pressure, because temperature of feeding gas changes ambient temperature to high temperature ($700{\sim}900^{\circ}C$). Furthermore, when we carry out long time test, something like degradation test, crack of ceramic glue sealant due to weakness of mechanical properties can make stop working the test. Additionally, we reduce setting process for assembling, because micanite is not required drying or debinding process.