• Nuclear Engineering and Technology
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• 제55권1호
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• pp.353-363
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• 2023

The STELLA-2 is a large-scale sodium thermal-hydraulic integral effect test facility and supports the development of PGSFR. The facility adopted Pump Simulation Loop System (PSLS) concept for the mechanical sodium pump in the reference reactor to control and to measure the primary sodium flow. Since the component (mechanical pump) is replaced by the loop, it is very important to evaluate the similarity between the pump and the loop. In this paper, to simulate the characteristic of the mechanical sodium pump, the pressure loss along the various options of the loop was evaluated and the comprehensive validity of each design options was analyzed. Using the similarity criteria based on the Richardson number and Euler number conservation, the PSLS design was finalized and the result was within the acceptable error range. Finally, the result of this study was used for construction of the overall facility, STELLA-2.

• 한국정보통신학회논문지
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• 제16권11호
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• pp.2495-2502
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• 2012

이 논문은 전하펌프를 추가하여 루프필터에서 공정에 따라 값이 크게 변하는 저항을 없앤 새로운 구조의 위상고정루프를 보여준다. 두 번째 전하펌프가 기존의 루프 필터 저항 역할을 하도록 하였다. 두 개의 전하펌프 출력은 공정 변화에 같은 방향으로 움직이므로 위상고정루프의 동작이 공정 변화 영향을 적게 받게 된다. 공정 조건(SS/TT/FF)에 따른 시뮬레이션 결과는 제안된 구조가 공정 변화에 무관하게 동작함을 보여주고 있다. 제안된 구조는 1.8V $0.18{\mu}m$ CMOS 공정의 파라미터를 이용하여 HSPICE로 시뮬레이션을 수행하였고 회로의 동작을 검증하였다.

• 전자공학회논문지S
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• 제35S권1호
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• pp.14-22
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• 1998

The Mathematic model of bit synchronization charge-pump Phase Locked Loop (PLL) is presented which takes into account the aperiodic reference pulses and the leakage current of the loop filter. We derive theoreitcal static phase error, overload and stability of bit synchronization charge-pump PLL using presented model and compare it with one of the conventional charge-pump PLL model. We can analysis bit synchronization charge-pump PLL exactly because our model takes into account the leakage current of the loop filter and aperiodic input data which are the charateristics of bit synchronization charge-pump PLL. We also verify it using HSPICE simulation with a bity synchronizer circuit.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.15-18
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• 2008

본 연구에서는 터보펌프 조립체-가스발생기 연계시험 중 개회로 시험에 대한 시동 특성을 분석하였고 수치적으로 해석하였다. 시험에서 터빈의 시동 및 구동은 수소 기체로 수행하였고 그에 따른 가스발생기 점화 및 연소압의 발달을 살펴보았고 해석도 동일한 조건으로 수행하여 결과를 비교하였다. 회전수의 발달 특성은 시험과 잘 일치하는 것을 볼 수 있었고 가스발생기 연소압 발달 특성의 경우 정성적인 기울기가 일치하는 것을 볼 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.19-22
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• 2008

본 연구에서는 터보펌프 조립체-가스발생기 연계시험 중 폐회로 시험에 대한 시동 특성을 분석하였고 수치적으로 해석하였다. 시험에서 터빈의 시동은 수소 기체로 수행하였고 구동은 가스발생기에서 연소로 발생하는 연소 기체로 작동하였다. 그에 따른 가스발생기 점화 및 연소압의 발달을 살펴보았고 해석도 동일한 조건으로 수행하여 결과를 비교하였다. 회전수의 발달 특성은 시험과 잘 일치하는 것을 볼 수 있었고 가스발생기 연소압 발달 특성의 경우 정성적으로 일치하는 것을 볼 수 있었다.

• 한국통신학회논문지
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• 제21권12호
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• pp.3069-3085
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• 1996

This paper shows an accurate charge-pump PLL model which considers the wave-form distortion in high speed operation of charge-pump PLL, the leakage current in loop filter, and a physical limit in charge-pump. With proposed model of charge-pump PLL, overload and stability are derived theoretically and the results are compared to the conventional model. Unlike the ideal charge-pump PLL that simplifies calculations, it is possible to analyze the transient-state and the steady-state at the same time with proposed accurate model. Thus, charge-pump over load, in the transient-state and the stead-state of charge-pump, is accuragely analyzed and the results are confirmed with simulation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.36-39
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• 2006

To evaluate the effect of groundwater flow on the outlet temperature of a geothermal heat pump, 3 dimensional numerical simulations are performed considering both groundwater flow and pipe flow in the U-tube using TOUGHS, The present study involved the following 4 simulation cases (1) no groundwater flow, (2) slow groundwater flow (hydraulic conductivity: $1.0{\times}10^{-9}m/s)$, (3) fast groundwater flow (hydraulic conductivity, $1.0{\times}10^{-7}m/s$), and (4) groundwater flow varying with the depth (hydraulic conductivity: $1.0{\times}10^{-7}-1.0{\times}10^{-10}m/s$). The effect of groundwater flow on the outlet temperature is significant where hydraulic conductivity of aquifer is $1.0{\times}10^{-7}m/s$. Where hydraulic conductivity of aquifer is $1.0{\times}10^{-10}m/s$, however, that effect is negligible.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1429-1435
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• 2021

The temperature distribution of an electromagnetic pump was analyzed with a flow rate of 1380 L/min and a pressure of 4 bar designed for the sodium thermo-hydraulic test in the Sodium Test Loop for Safety Simulation and Assessment-Phase 1 (STELLA-1). The electromagnetic pump was used for the circulation of the liquid sodium coolant in the Intermediate Heat Transport System (IHTS) of the Prototype Gen-IV Sodium-cooled Fast Reactor (PGSFR) with an electric power of 150 MWe. The temperature distribution of the components of the electromagnetic pump was numerically analyzed to prevent functional degradation in the high temperature environment during pump operation. The heat transfer was numerically calculated using ANSYS Fluent for prediction of the temperature distribution in the excited coils, the electromagnet core, and the liquid sodium flow channel of the electromagnetic pump. The temperature distribution of operating electromagnetic pump was compared with cooling of natural and forced air circulation. The temperature in the coil, the core and the flow gap in the two conditions, natural circulation and forced circulation, were compared. The electromagnetic pump with cooling of forced circulation had better efficiency than natural circulation even considering consumption of the input power for the air blower. Accordingly, this study judged that forced cooling is good for both maintenance and efficiency of the electromagnetic pump.

• 설비공학논문집
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• 제29권3호
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• pp.119-126
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• 2017

Recently, ground source heat pump systems are being used in buildings for cooling and heating to reduce greenhouse gas and save energy. However, ground source heat pump systems mainly use the vertical closed-loop geothermal system design rather than the open-loop geothermal system design. This is due to a lack of knowledge and few research feasibility studies. In this research, a dynamic thermal analysis numerical simulation based on a standard house model was conducted for an open-loop geothermal system. Based on heating load analysis results, the life cycle costs of a standard house using an open two-well geothermal system were analyzed and compared with a vertical closed-loop geothermal system, and a diesel boiler. As a result, it was found that using an open two-well geothermal system shows economic return on investment after three years.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3142-3147
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• 2008

A simple transient simulation of ground source heat pump system was carried out to investigate the effects of ground thermal conductivity on its performance. The TRNSYS code with a simple water to water heat pump model was used to compare the COP variation of the system. A new ground heat exchanger called by semi-closed loop was proposed and constructed in the real site. The effective thermal conductivity was measured using the test equipment developed by according to the line source model. The simulation results showed that highly efficient thermal conductivity of the grout material could increase the performance of the heat pump system very well. And the new ground heat exchanger showed the increased effective thermal conductivity as the penetration water flow rate(PWFR) was increased. Therefore, the performance improvement of the heat pump system using the proposed ground heat exchanger can be expected.