• 수산해양기술연구
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• 제24권1호
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• pp.30-35
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• 1988

An electrical power generation system driven by main engine shaft, briefly SG system for middle or small size fishing boat is studied experimently. In the SG system, power transmission is performed by a variable displacement hydraulic pump driven by the main engine and a constant displacement hydraulic motor. It was verified that the SG system enabled the generation of electrical power with constant frequency regardless main engine speed. In the SG system, setting reference frequency, sensing generator output frequency and setting controller parameters are performed by performed by programming in a microcomputer, so a countermeasure for physical situations of control object is very easy. Futhermore, the SG system has following features; low initial installation cost, wide freedom of installation in engine room, advantage of application in existing ships, especially fishing boat with hydraulic fishing equipments.

• 유공압시스템학회:학술대회논문집
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• 유공압시스템학회 2010년도 춘계학술대회
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• pp.18-24
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• 2010

Because of the increasing demand on the high precision and high response of a machinery, electronic control valves are widely adopted at various application fields. This paper studies on the static characteristic of a first-stage proportional pressure control valve. At first an experimental apparatus including hyd. pump variable speed inverter, pressure and data aquisition system was setted up with the experimental apparatus, various tests such as P-Q-W test, hyd, pump, dynamic, static, frequency response test of the proportional valve was carride out and the results are discussed.

• 로봇학회논문지
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• 제16권2호
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• pp.86-93
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• 2021

This paper proposes a controller to regulate the supply pressure of the hydraulic power unit (HPU) for driving a bipedal robot. We establish flow rate models for charging accumulator, actuating joints and leaking from actuators and spool valves. This determines the pump driving motor speed to satisfy the demanded flow rate for operating the bipedal robot without the energy loss caused by the bypass through a pressure regulating valve. We apply proposed controller to an onboard HPU mounted on top of bipedal robot platform with twelve degrees of freedom. We implement air-walking motion and squat motion which require variable flow rate to the bipedal robot. Through this experiment, the energy efficiency of proposed controller was verified by comparing the electric energy consumed when the controller was applied and when the pump operated at constant speed. We also shows the capability of the HPU's control performance to regulate supply pressure.

• 대한기계학회논문집B
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• 제28권3호
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• pp.289-295
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• 2004

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooler(test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of the outer diameter of 9.53mm and of the inner diameter of 7.75mm. The length of the test section is 6m. The refrigerant mass fluxes were 200∼300kg/(m2$.$s) and the inlet pressure of the gas cooler varied from 7.5㎫ to 8.5㎫. The main results were summarized as follows : Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube show a relatively good agreement with the correlation by Blasius. The heat transfer coefficient of CO2 in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.

• Journal of Advanced Marine Engineering and Technology
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• 제28권3호
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• pp.500-508
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• 2004

The heat transfer coefficients during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments are conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater, and a gas cooler(test section). The water loop consists of a variable-speed pump, an isothermal tank, and a flow meter. The gas cooler is a counterflow heat exchanger by cooled water flowing in the annulus. The $CO_2$ flows in the horizontal stainless steel tube. which is 9.53mm in O.D. and 7.75mm in I.D. The gas cooler is 6 [m] in length. which is divided into 12 subsections, respectively. The experimental conditions considered in the study are following range of variables : refrigerant temperature is between 20 and $100^{\circ}C$. mass fluxes ranged from 200 to 400kg/($m^2$.s), average pressure varied from 7.5 to 10.0MPa. The main results were summarized as follows : The friction factors of $CO_2$ in the gas cooler show a relatively good agreement with those predicted by Blasius' correlation. The local heat transfer coefficient in the gas cooler has compared with most of correlations, which are the famous ones for forced convection heat transfer of turbulent flow. The results show that the local heat transfer coefficient of gas cooler agrees well with the correlation by Bringer-Smith except that at the region near pseudo critical temperature. while that at the near pseudo critical temperature is higher than the correlation.

• Journal of Advanced Marine Engineering and Technology
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• 제28권1호
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• pp.65-74
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• 2004

The heat transfer coefficient and pressure drop of $CO_2$(R-744) during gas cooling Process of carbon dioxide in a horizontal tube were investigated experimentally and theoretically. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop consist of a receiver. a variable-speed pump. a mass flowmeter, an evaporator. and a gas cooler(test section). The main components of the water loop consist of a variable-speed Pump. an constant temperature bath. and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus The test section consists of smooth, horizontal stainless steel tube of 9.53 mm outer diameter and 7.75 mm inner diameter. The length of test section is 6 m. The refrigerant mass fluxes were 200 ~ 300 kg/($m^2{\cdot}s$) and the inlet pressure of the gas cooler varied from 7.5 MPa to 8.5 MPa. The main results were summarized as follows : The predicted correlation can evaluated the R-744 exit temperature from the gas cooler within ${\pm}10%$ for most of the experimental data, given only the inlet conditions. The predicted gas cooley capacity using log mean temperature difference showed relatively food agreement with gas cooler capacity within ${\pm}5%$. The pressure drop predicted by Blasius estimated the pressure drop on the $CO_2$ side within ${\pm}4.3%$. The predicted heat transfer coefficients using Gnielinski's correlation evaluated the heat transfer coefficients on the $CO_2$ side well within the range of experimental error. The predicted heat transfer coefficients using Gao and Honda's correlation estimated the heat transfer coefficients on the coolant side well within ${\pm}10\;%$. Therefore. The predicted equation's usefulness is demonstrated by analyzing data obtained in experiments.

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.526-532
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• 2005

The cooling heat transfer coefficient of $CO_2$(R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter. a pre-heater and gas cooler(test section). The test section consists of a smooth, horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $400\;kg/m^{2}s$ and the inlet cooling pressure of 7.5 MPa to 10.0 MPa. The variation of heat transfer coefficient tends to decrease as cooling pressure of $CO_2$ increases. The heat transfer coefficient with respect to mass flux increases as mass flux increases. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with that predicted by Blasius's correlation. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Bringer-Smith.

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.552-559
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• 2005

The evaporation pressure drop of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth. horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$, saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation pressure drop of $CO_2$ are highly dependent on the vapor qualify, heat flux and saturation temperature. The evaporation pressure drop of $CO_2$ is very lower than that of R-22. In comparison with test results and existing correlations. the best fit of the present experimental data is obtained with the correlation of Choi et al. But existing correlations failed to predict the evaporation pressure drop of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation pressure drop of $CO_2$ in a horizontal tube.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.97-99
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• 2007

This paper presents a fuzzy logical control method to implement an on-line optimum efficiency control for Permanent Magnet Synchronous Motor. This method real-timely adjusts the output voltage of the inverter system to achieve the optimum running efficiency of the whole system. At first, the input power is calculated during the steady state in the process of efficiency optimizing. To exactly estimate the steady state of the system, this section needs check up the speed setting on timely. The second section is to calculate input power of dc-bus. The exact measurement of the voltage and current is the vital point to acquire the input power. The third section is the fuzzy logic control unit, which is the key of the whole drive system. Based on the change of input power of dc-bus and output voltage, the variable of output voltage is gained by the fuzzy logical unit. With the on-line optimizing. the whole system call fulfill the minimum input power of dc-bus on the running state. The experimental result proves that the system applied the adjustable V/f control method and the efficiency-optimizing unit possesses optimum efficiency, and it is a better choice for simple variable speed applications such as fans and pump.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권1호
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• pp.1-13
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• 2015

실외 열교환기의 착상 및 제상조건 하에서 VRF 멀티형 히트펌프의 동적 거동의 해석을 위한 시뮬레이션 기법이 제안되었다. 이를 위해 열전달-물질전달 완벽 상사 가정에 기반한 간단한 착상모델과 제상 모델이 제안되었다. 제안된 착제상 모델은 용량가변 압축기 모델과, 미소면적에 대한 열 및 모멘텀 평형에 근거한 열교환기 모델을 채택한 동적 사이클 해석모델에 적용되었다. 따라서, 제안된 모델은 공간에 대해 비균질 착상을 자연스럽게 예측할 수 있다. 개발된 동적 사이클 해석 모델은 실험결과와 비교하여 능력 및 효율을 10% 이내에서 잘 예측함을 확인하였다. 최종적으로, 개발된 모델은 표준적인 건물의 난방시즌 운전 해석에 적용되었으며, 착상 및 제상으로 인하여 동절기의 계절 성능계수를 7% 가량 하락 시킴을 보일 수 있었다.