• 설비공학논문집
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• 제25권12호
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• pp.641-646
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• 2013

The purpose of this study is to improve the cooling performance of single and cascade refrigeration systems using thermoelectric modules. The system consists of a heat sink, fan, and thermoelectric module. The operating parameters considered in this study include power distribution between the first- and second-stage thermoelectric modules, air flow, and variable condensing unit. The cooling capacity increased with decreases in the temperature difference between hot and cold surfaces, but decreased with increases in the condensing temperature. The COP decreased with increasing electric power of the thermoelectric module because of the increased Joule heat. The cooling performance improvement using the thermoelectric module is represented by the freezer temperature.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.556-560
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• 2009

In this paper, two different types of natural gas liquefaction process are simulated and designed for secure a competitiveness in the industry of natural gas liquefaction plant. These processes are based on basic cascade process, and one of these is improved with two staged intercooler and the other is modified two staged intercooler. These processes are compared characteristics of performance with basic process. COP of cascade process with two staged intercooler and modified two staged intercooler showed about 13.74% and 21.64% higher than basic process, and yield efficiency of modified process improved comparing with the basic process by 25.93% lower specific power, respectively.

• 설비공학논문집
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• 제25권5호
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• pp.225-232
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• 2013

Heat pump systems have been widely adopted in buildings for cooling and heating, due to their higher energy efficiency. Recently, the demand for hot water supply from the heat pump system has been increasing. To increase the water supply temperature with higher system efficiency and reliability, a heat pump water heater adopting cascade cycle was investigated in this study. The cascade heat pump water heater consisted of a low-stage cycle using R410A, and a high-stage cycle using R134a. A simulation program for the cascade heat pump water heater was developed, and verified by comparison with experimental data. The performance of the cascade heat pump water heater was optimized, by varying the compressor rotating speeds of the low- and high-stage cycles. At low ambient temperatures, the performance of the cascade cycle was compared with that of the single-stage cycle. The system efficiency of the cascade cycle was higher than that of the single-stage cycle, showing a lower compression ratio and compressor discharge temperature.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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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

• 설비공학논문집
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• 제28권5호
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• pp.202-207
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• 2016

Experimental studies for an indirect R404A-$CO_2$ refrigeration system and a direct R404A refrigeration system were conducted. The configurations of the indirect R404A-$CO_2$ refrigeration system are a R404A refrigeration system as a top cycle and a circulating $CO_2$ system as a bottom cycle. The direct R404A system was modified from indirect R404A-$CO_2$ refrigeration system by removing circuit for $CO_2$ circulation. Various tests for both systems were conducted by changing load side brine temperature from 0 to 5 and $10^{\circ}C$ with cooling brine temperatures for R404A system at 15, 20, or $25^{\circ}C$. The indirect R404A-$CO_2$ refrigeration system showed the highest COP when load side brine temperature was at $10^{\circ}C$ in the evaporator and at cooling brine temperature of $15^{\circ}C$. The COP of 3.04 under that condition was the highest. This indirect R404A-$CO_2$ refrigeration system showed 9.02% higher COP than the direct R404A system that had increased pipeline length of 15 m, which simulated actual installation in a supermarket.

• 설비공학논문집
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• 제16권11호
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• pp.1035-1043
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• 2004

For a long road tunnel, a tunnel ventilation system may be used in order to reduce the pollution level below the required level. To control the tunnel pollution level, a closed loop control algorithm may be used. The feedforward prediction algorithm and the cascade control algorithm were developed to regulate the CO level in a tunnel. The feedforward prediction algorithm composed of the traffic estimation algorithm and the CO density prediction algorithm, and the cascade control algorithm composed of the jet fan control algorithm and the air velocity setpoint algorithm. The verification of control algorithms was carried out by dynamic models developed from the actual tunnel data. The simulation results showed that control algorithms developed for this study were effective for the control of the tunnel ventilation system.

• 동력기계공학회지
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• 제19권4호
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• pp.89-96
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• 2015

This paper investigates some strategies to overcome the chattering problem of the conventional sliding mode observer (SMO) and to improve the rotor position estimation performance for full range sensorless control of a PMSM. An adaptive observer gain based on the Lyapunov's stability criterion and a cascade low pass filter with advanced phase delay compensation were proposed to reduce the chattering problem and to strengthen the filtering capability of the SMO. Several cases studies through experiments were carried out to confirm conventional SMO's problems and effectiveness of the proposed strategies. The experimental results show that the proposed method gives precise estimation on speed and rotor position when the motor rotates on 2% of its rated speed.

• 설비공학논문집
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• 제17권2호
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• pp.147-155
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• 2005

For a long road tunnel, a tunnel ventilation system may be used in order to reduce the pollution level below the required level. To control the tunnel pollution level, a closed loop control algorithm may be used. The cascade control algorithm, which composed of a jet fan control algorithm and an air velocity setpoint algorithm, was developed to regulate the CO level in a tunnel. The verification of control algorithms was carried out by dynamic models developed from real tunnel data sets. The simulation results showed that control algorithms developed for this study were effective to control the tunnel ventilation system.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2012년도 전기공동학술대회 논문집
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• pp.237-237
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• 2012

• Journal of Advanced Marine Engineering and Technology
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• 제36권5호
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• pp.574-579
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• 2012

본 논문에서는 $CO_2-C_2H_6-N_2$와 $CO_2-N_2$를 각각 적용한 캐스케이드 액화사이클을 새롭게 제안하고, HYSYS를 이용하여 이에 대한 성능 및 엑서지를 분석한 후, 이 사이클이 LNG-FPSO선에 적용가능여부를 확인하였다. 그 분석 결과로부터, 효율적인 측면에서는 $CO_2-C_2H_6-N_2$ 액화사이클이 우수하였고, 엑서지 손실측면에서는 장치 수가 적은 $CO_2-N_2$ 액화사이클이 오히려 높게 나왔다. 그리고 $CO_2-N_2$ 냉매용액화사이클은 기존의 $C_3H_8-C_2H_4-C_1H_4$ 보다 낮은 효율과 높은 압축일량을 보였다. 하지만, $N_2$ 사이클의 효율이 더 개선된다면 액화사이클의 구조가 간단하기 때문에 LNG-FPSO용 액화사이클로서 적합할 것으로 생각된다.