• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.628-632
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• 2001

In this paper, Firstly, it is shown that the bending mode vibration source of vertical pump system is comparatively large because resonance. Secondly in order to the bending mode vibration of vertical pump some practical dynamic absorber have been developed and its effectiveness is investigated as installing it at the vertical pump system practically.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.669-674
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• 2006

The optimal control of heat pump performance for heating mode operation was investigated. Fuzzy logic was applied to control the heating performance of heat pump system and superheat at compressor discharge was taken as a control variable. Regression model was adapted to determine the optimal points where COP is maximized. Optimization of fuzzy rule table was investigated to improve operation performance of heat pump system. Experiments were carried out using original fuzzy table and the modified fuzzy rule table for heating mode operation of heat pump system. The results show that control performance of heat pump system with the modified fuzzy rule table was better than that with the original rule table.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.4
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• pp.43-52
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• 2018

This paper presents the cooling performance analysis results of a ground-source heat pump (GSHP) system using hybrid ground heat exchanger (HGHE). In this paper, the HGHE refers to the ground heat exchanger (GHE) using both a vertical GHE and a surface water heat exchanger (SWHE). In order to evaluate the system performance, we installed monitoring sensors for measuring temperatures and power consumption, and then measured operation data with 4 different load burdened ratios of the hybrid GHE, Mode 1~Mode 4. The measurement results show that the system with HGHE mainly operates in Mode 1 and Mode 2 over the entire measurement period. The average cooling coefficient of performance (COP) for heat pump unit was 5.18, while the system was 2.79. In steady state, the heat pump COP was slightly decreased with an increase of entering source temperature. In addition, the parallel use of SWHE and VGHE was beneficial to the system performance; however, further research are needed to optimize the design data for various load ratios of the HGHE.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1773-1778
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• 2010

To evaluate the structural integrity of the main cooling-water pump of a nuclear power plant under different seismic conditions, the seismic analysis was performed in accordance with IEEE-STD-344 code. The finite element computer program, ANSYS, was used to perform both mode frequency analysis and response spectrum analysis for the pump assembly. The natural frequencies, the mode shapes, and the mode participation factors were obtained from the results of the mode frequency analysis. The stresses resulting from various loadings and their combinations were within the allowable limits specified in the above-mentioned IEEE code. The results of the seismic evaluation fully satisfied the structural acceptance criteria of the IEEE code. Thus, it was proved that the structural integrity of the pump assembly was satisfactory.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.319-324
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• 2012

This paper introduces a 2-dimensional touch screen panel driver based on an improved capacitive sensing circuit. The improved capacitive sensing circuit based on charge pump can eliminate the remaining charges of the intermediate nodes, which may cause output voltage drift. The touch screen panel driver with mixed-mode circuits was built and simulated using Cadence Spectre. Verilog-A models the digital circuits effectively and enables them to interface with analog circuits easily. From the simulation results, we can verify the reliable operations of the simple structured touch screen panel driver based on the improved capacitive sensing circuit offering no voltage drift.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.173-178
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• 2005

Recently. we interested in renewable energy due to cost increase of the crude oil, etc. In this study solar assisted hybrid heat pump system that uses the solar heat and air as heat source analyzed by experimentally.'rho system could runs at dual mode. One is thermal storage mode of solar energy at day time and the other is heat pump mode with low temperature air as heat source at night time. In case of setting temperature over the limited range. high temperature water heated at the solar energy collecting tubes supplied to the storage tank. As results. it is founded that the heat pump performance Is higher than general heat pump which using the only air as a heat source. The developed system could be used as main healing equipment for the panel heating for the residential house.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.779-781
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• 2005

In this paper, Firstly, it is shown that the bending mode vibration source of vertical pump system is comparatively large because resonance. Secondly in order to reduce the bending mode vibration of vertical pump, The improvement of some boundary condition have been developed and its effectiveness is investigated as appling it at the vertical pump system pratically.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.288-293
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• 2008

The cooling load in winter is significant in many commercial buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. The development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the performance of a multi-heat pump with 3-piping system was investigated as a function of refrigerant charge and its performance was analyzed in cooling mode, heating mode, and heat recovery mode. COP in the heating or cooling mode showed little dependence on refrigerant charge at overcharge conditions, while those were strongly dependent on refrigerant charge at undercharge conditions and outdoor inlet temperature. In the heat recovery mode, the performance of the system was very sensitive to charge amount at all conditions. Optimum charge amount in the heat recovery mode was 14% lower than that in the cooling mode at the standard condition because the refrigerant only passed the indoor units. It is required to store the excessive refrigerant charge in a storage tank to optimize the system performance at operating modes.

• International Journal of Fluid Machinery and Systems
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• v.7 no.2
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• pp.42-53
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• 2014

Phase resonance in Francis type hydraulic turbine is studied. The phase resonance is a phenomenon that the pressure fluctuation in the penstock of hydraulic turbine installation can become very large when the pressure waves from each guide vane caused by the interaction with the runner vane reach the penstock with the same phase. Experimental and numerical studies have been carried out using a centrifugal fan. In the present study, comparisons between the pump mode and the turbine mode operations are made. The experimental and numerical results show that the rotational direction of the rotor does not affect characteristics of the pressure fluctuation but the propagation direction of the rotorstator interaction mode plays an important role. Flow rate fluctuations through the stator are examined numerically. It has been found that the blade passing flow rate fluctuation component can be evaluated by the difference of the fluctuating pressure at the inlet and the outlet of the stator. The amplitude of the blade passage component of the pressure fluctuation is greater at the stator inlet than the one at the stator outlet. The rotor-stator interaction mode component is almost identical at the inlet and the outlet of the stator. It was demonstrated that the pressure fluctuation in the volute and connecting pipe normalized by the flow rate fluctuation becomes the same for pump and turbine mode operations, and depends on the rotational direction on the interaction mode.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.9
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• pp.527-535
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• 2009

The aim of this study is to investigate the daily heating performance of ground source multi-heat pump system with vertical single U-tube type GLHXs, which were installed in a school building located in Cheonan. Daily average COP of heat pump unit on Jan. 12th, 2009 at heating mode was lower than it on Nov. 10th, 2008 and Dec. 15th, 2008, because of lower EWT of the outdoor heat exchanger and relatively smaller size of condenser and evaporator. But, the system COP on the former was higher than it on the latter because ground loop circulating pump was operated in rated speed. It is suggested that the new algorithms to control the flow rate of secondary fluid for GLHX according to load change have to be developed in order to enhance the performance of the system COP.