• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.147-147
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• 2007

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.3
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• pp.131-139
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• 2009

The simulation of refrigeration cycle is important since the experimental approach is costly and time-consuming. The present paper focuses on the simulation of a refrigeration cycle equipped with a capillary tube-suction line heat exchanger(SLHX), which is widely used in small vapor compression refrigeration systems. The present simulation is based on fundamental conservation equations of mass, momentum, and energy. These equations are solved through an iterative process. The non-adiabatic capillary tube model is based on homogeneous two-phase flow model. This model is used to understand the refrigerant flow behavior inside the non-adiabatic capillary tube. The simulation results show that both of the location and length of heat exchange section influence the coefficient of performance (COP).

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.10
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• pp.1011-1016
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• 2015

Gas piping systems in power plants and factories are always influenced by the mechanical vibrations of rotational machines such as pumps, blowers, and compressors. Unusual vibrations in a gas piping system influence possible leakages of liquids or gases, which can lead to large explosive accidents. Real-time measurements of unusual vibrations in piping systems in situ prohibit them from being possible leakages owing to the repeated fatigue of vibrations. In this paper, a non-contact 3-dimensional measurement system that can detect the vibrations of a solid body and monitor its vibrational modes is introduced. To detect the displacements of a body, a stereoscopic camera system is used, through which the major vibration types of solid bodies (such as X-axis-major, Y-axis-major, and Z-axis-major vibrations) can be monitored. In order to judge the vibration types, an artificial neural network is used. The measurement system consists of a host computer, stereoscopic camera system (two-camera system, high-speed high-resolution camera), and a measurement target. Through practical application on a flat plate, the measured data from the non-contact measurement system showed good agreement with those from the original vibration mode produced by an accelerator.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.216-222
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• 2005

An experimental investigation was executed to determine the capacity degradation due to fin conduction and non-uniform refrigerant distribution in a multi-path evaporator with cross-counter flow. The finned-tube evaporator, which had a three-path and three-depth-row, was tested by controlling inlet quality, exit pressure, and exit superheat for each refrigerant path. The capacity reduction due to superheat unbalance between each path was as much as $25\%$ for non-cutting evaporator, even when the overall evaporator superheat was kept at a target value of $5.6^{\circ}C$. It indicates that the internal heat transfer within the evaporator assembly causes the partial capacity drop. The capacity of cutting-evaporator with respect to non-cutting evaporator was enhanced according to the increment of air flow rate when superheat or superheat unbalance increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.388-393
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• 2008

This study has been conducted to select the suitable refrigeration oil for a $CO_2$ refrigeration system. Non-hygroscopic property of refrigeration oils is one of the most important properties for refrigeration oils. PAG and POE oils are considered as test oils in this study. Transient variation of water content of PAG and POE oils was measured for 3 different vessels in the environmental conditions, such as in the range of temperature $25^{\circ}C$ to $40^{\circ}C$ and relative humidity 40% to 85%. The results obtained that water content of both POE and PAG is increased with an increase in the contact area with ambient for 3 different vessels. It is also found that water content of both POE and PAG is increased as the ambient temperature and relative humidity is increased. Non-hygroscopic property of POE oil is found to be much superior than that of PAG oil.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.819-825
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• 2006

In a SOFC/GT (solid oxide fuel cell/gas turbine) hybrid power generation system, the recuperator is an indispensible component to enhance system performance. Since the expansion ratio to the recuperator core is very large, generally, the effective header design to distribute the flow uniformly before entering the core is crucial to guarantee the required performance. In the present study, we focus on the design of a diffuser type recuperator header with a 90 degree turn inlet port. To reduce the flow separation and recirculation flows, multiple horizontal vanes are used. The number of horizontal vanes is varied from 0 to 24. The air flow velocity is measured at 40 points just behind the core outlet by using a hot wire anemometer. Then, the flow non-uniformity is evaluated from the measured flow velocity. The experimental results showed that inlet air velocity did not effect on relative flow non-uniformity. According to increasing the number of horizontal vanes, flow non-uniformity reduced about $40{\sim}50%$ than without using horizontal vanes.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.3
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• pp.241-247
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• 2014

The voltage source PWM inverter generally used to drive the air conditioning (A/C) fans has been posing a large issue that the bearings in air conditioning fan motors are highly possible to be corroded electrically. Potential difference called shaft voltage is generated between inner and outer rings of the bearings due to inverter switching. The shaft voltage causes bearing lubricant breakdown dielectrically. As a result, bearing current is caused. This current causes the bearing corrosion. In previous work, we demonstrated that the shaft voltage can be reduced by using an insulator inserted between the outer and inner cores of the rotor in an air conditioning fan motor without grounding. This paper proposes the other countermeasure for reducing the shaft voltage in fan motors. The countermeasure which adds a capacitor between the brackets and the stator core is effective even for fan motors with non-insulated rotor. The effectiveness is confirmed by both simulated and experimental results.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.2
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• pp.94-101
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• 2001

Fin effectiveness and efficiency of a thermally asymmetric rectangular fin are represented as a function of non-dimensional fin length, width, fip tip surface Biot number and the ratio of fin bottom surface Biot number to top surface Biot number. For this analysis, three dimensional separation of variables method is used. One of the results shows that fin effectiveness can be increased or decreased depending on the fin length as the fin tip surface Biot number increases while fin efficiency decreases without depending on that as the fin tip surface Biot number increases.

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.62-62
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• 2007

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.6
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• pp.542-549
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• 1987

중요한 기본을 요약하고 엑서지를 에너지 변환에서 가장 중요한 기본 과정에 응용하는 열전달 문제를 제시한다. 열전달로 인한 엑서지 손실과 고온체, 저온체의 단열, 열교환기의 설계와 관련된 결과를 논의한다. 또한 비아제오트로픽(non-azeotropic) 혼합물을 응용한 열펌프 열교환기에서의 엑서지 절약에 대한 연구를 설명한다. 열전달과 압력강하로 인한 손실의 합인 총엑서지 손실이 최소로 되는 최적의 Reymolds 수가 존재함을 보여준다.