• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1325-1331
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• 2007

In order to investigate the cooling capacity of an air-conditioner applying a variable capacity compressor and the temperature characteristics on a condenser and an evaporator, the experiment on the operation characteristics of the air-conditioner was performed along a compressor operation ratio and an indoor/outdoor temperatures, under a cooling operation mode. The system characteristics were measured by the psychrometric calorimeter. The cooling capacity increased with decreasing the outdoor temperature and increasing the indoor temperature. Also, it increased with increasing the compressor operation ratio. The temperature of the condenser was more sensitive for the variation of the outdoor temperature and the temperature of the evaporator was more sensitive for the variation of the indoor temperature. The operation characteristics of the cycle used in this present were also analyzed by a pressure-enthalpy chart.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.835-841
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• 2006

A $CO_2$ system using the two-stage compression cycle was tested by varying $1^{st}-2^{nd}$ compressor frequencies in the cooling mode. To improve the cooling performance of the two-stage compression $CO_2$ cycle, the following cycle options were applied: a basic cycle, a cycle with an intercooler, a cycle with an IHX (internal heat exchanger), and a cycle with an intercooler and IHX. The cycle with the intercooler-IHX showed the highest cooling capacity improvement among the cycle options at all compressor frequencies. The cycle with the intercooler, the cycle with the IHX, and the cycle with the intercooler-IHX improved the cooling COP by 7, 12, and 15%, respectively, over the basic $CO_2$ cycle when the compressor frequencies for the first and second compressors were 50 Hz and 30 Hz, respectively. In addition, the applications of the selected cycle options enhanced system reliability.

• Journal of Yeungnam Medical Science
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• v.5 no.1
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• pp.77-84
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• 1988

The principal mode of the transmission of Legionnaires disease is a inthalation of the cooling tower water droplets in which Legionellae exist. As a central cooling system is popularized in many public buildings and large buildings nowadays, the number of cooling towers is rapidly increasing. Therefore the possibility of an outbreak of Legionnaires disease is likely increased. To determine the presence of Legionella in cooling tower water as the first step for the prevention of Legionnaires disease, 48 samples of cooling tower water were taken from 24 buildings in Taegu city in july and september 1987. Three samples out of 24 water samples In September yielded Legionella but it was not isolated in the samples of July. Isolated 3 Legionellas were identified as Legionella peumophila. It seems that Legionella from the cooling tower will be isolated more frequently in late summer than early because central cooling system is stopped operation during winter season which is cool. As based on our survey, Legionnaires disease can occur in Taegu city and if it happens it is most likely due to L. pneumophila.

• Smart Structures and Systems
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• v.14 no.4
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• pp.541-558
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• 2014

This paper proposes a new design of shape memory alloy (SMA) wire actuated gripper for open mode operation. SMA can generate smooth muscle movements during actuation which make them potentially good contenders in designing grippers. The principle of the shape memory alloy gripper is to convert the linear displacement of the SMA wire actuator into the angular displacement of the gripping jaw. Steady state analysis is performed to design the wire diameter of the bias spring for a known SMA wire. The gripper is designed to open about an angle of $22.5^{\circ}$ when actuated using pulsating electric current from a constant current source. The safe operating power range of the gripper is determined and verified theoretically. Experimental evaluation for the uncontrolled gripper showed a rotation of $19.97^{\circ}$. Forced cooling techniques were employed to speed up the cooling process. The gripper is simple and robust in design (single movable jaw), easy to fabricate, low cost, and exhibits wide handling capabilities like longer object handling time and handling wide sizes of objects with minimum utilization of power since power is required only to grasp and release operations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.509-513
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• 2013

There are so many types of construction equipment. Excavator is one of typical construction equipment which is working under the tough and severe environments. It's important for engineers to design CE components by the vibration durability point of view. Traditionally, two typical vibration durability methods to verify the durability of components. The first is experimental method which is using the vibration durability test bench. But experimental approach on vibration durability is needed a lot of cost and time. The second is analytical method which is using the vibration durability analysis such as Dirlik, Stainberg, Lalanne and others methodologies. The one of main advantages on vibration durability analysis can reduce the cost and time. We present a vibration durability analysis process and methodology on the guardrail system in excavator.

• Tribology and Lubricants
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• v.15 no.2
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• pp.199-205
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• 1999

Using a coupled thermal-mechanical analysis, the thermal distortion of the ventilated disk brakes has been investigated based on the air cooling effects during 15 braking operations. The FEM results show that the bendings and distortions of the disk toward the left side are decreased, but the sinusoidal distortion of the disk rubbing surface along the arc length of the vent hole is highly increased by increasing the convective air cooling effects, which is heavily related to the squeal, wear and micro-thermal crackings at the rubbing surfaces due to uneven dissipation rates of friction heatings.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.127-134
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• 2004

Three-dimensional numerical investigations are carried out to understand the combustion characteristics inside a DLN(dry low NOx) utility gas turbine combustor during the combustion mode change period by applying transient fuel flow rates in fuel supply system as numerical boundary conditions. The numerical solution domain comprises the complex combustor liner including cooling air holes, three types of fuel nozzles, a swirl vane, and a venturi. Detailed three-dimensional flow and temperature fields before and after combustion mode changeover have been analyzed. The results may be useful for further studies on the unfavorable phenomena, such as flashback or thermal damage of combustor parts when the combustion mode changes.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.645-654
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• 1988

The microstructure and electrical characteristics of ZnO-Bi2O3 ceramics containing 5mol% Bi2O3 have been studied in relation to sintering temperature and mode. The distribution and thickness of Bi2O3 intergranular layer was varied with sintering temperature and mode. Intergranular layer was more homogeneous with increasing sintering temperature, when sintering by direct heating and rapid cooling mode showed the best distribution of intergranular layer. These microstructural changes affected electrical characteristics directly, at 140$0^{\circ}C$ and C mode obtained high value of electrical resistivity and nonlinear exponent. Varistor voltage decreased with increasing sintering temperature, increased with decreasing holding time at high temperature. Barrier voltage obtained by calculation was about 1.5V.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.260-270
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• 2018

Purpose: The purpose of this study is to evaluate the life of the capsule, which is a core part of the heat storage cooling system. This paper will develop a life test mode that can reproduce environment conditions through the analysis of capsule shrinkage and expansion characteristics. Methods: In order to determine the life test mode of the capsule, this paper analyzed the case of field failures and analyzed the deformation characteristics according to the pressure fluctuation of the capsule. The method to find out whether the field failure and deformation analysis results are consistent is the testing with the construction of the repetition pressure test equipment and the thermal cycle test to reproduce the freezing and thawing characteristics. Results: In this study, failure mode analysis and analysis of freezing and thawing characteristics regarding to the capsule positions were completed. Based on this test & analysis results, this paper have been able to determine the main parameters for determining the life test mode, the freezing and thawing time. Conclusion: Determining the lifetime mode of the capsule can be used to improve the life and performance of the thermal storage system.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.544-549
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• 2009

The purpose of this study is to investigate the field Operation Characteristics of a sea water heat source cascade heat pump system and system applicable to Building. Cascade heat pump system is composed R410A compressor, R134a compressor, EEV, cascade heat exchanger, Plate heat exchanger etc. Building area is $890m^2$ and has five floors above ground. R410A is used for a low-stage working fluid while R134a is for a high-stage. The system could runs at dual mode. One is mode of general R410A refrigeration cycle in summer and the other is cascade cycle. In order to gain a high temperature supply water in winter season, the system is designed to perform a cascade cycle. The filed test results show that the sea water heat source heat pump system exhibits a COP of about 5.5 in cooling mode along with a heating COP of about 4.0 in 1-stage heating mode. Cascade 2-stage heat pump system is enough to supply $60^{\circ}C$ water and heating COP is about 3.0