• Title/Summary/Keyword: The secondary loop

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Performance Optimization of a Hybrid Ground Source Heat Pump According to Secondary Flow Distribution Ratio between the Ground and the Supplemental Loop (지중 및 보조루프의 2차 유체 유량 분배비를 통한 하이브리드 지열히트펌프의 성능 최적화 연구)

  • Lee, Joo-Seong;Park, Hong-Hee;Kim, Won-Uk;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.2
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    • pp.102-110
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    • 2012
  • The objective of this study is to improve the performance of a hybrid ground source heat pump (HGSHP) by optimizing the flow distribution ratio of secondary fluid flow rate between a ground loop and a supplemental loop. Initially, a conventional ground source heat pump (GSHP) was tested to determine an optimum flow rate of the secondary fluid. Based on the selected optimum value, the HGSHP was also tested by varying the flow distribution ratio of the secondary fluid flow rate between the ground loop and the supplemental loop, such as 9:1, 7:3, 5:5, and 3:7. The results showed that the optimum flow distribution ratio of the secondary fluid flow rate was 7:3. The COP of the HGSHP was improved by 19% over the GSHP at a flow distribution ratio of 7:3 and an entering water temperature of $40^{\circ}C$.

Operating Characteristics of Hybrid Type Superconducting Fault Current Limiter (하이브리드형 초전도 한류기의 동작 특성)

  • Cho, Yong-Sun;Nam, Gueng-Hyun;Lim, Sung-Hun;Choi, Hyo-Sang
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.55 no.6
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    • pp.255-258
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    • 2006
  • We investigated the operating characteristics of the hybrid-type superconducting fault current limiter (SFCL) according to the inductance of secondary windings. The hybrid type SFCL consists of a transformer that has a primary winding and a secondary winding with serially connected $YBa_2Cu_3O_7$ (YBCO) films. The resistive-type SFCL has difficulty when it comes to raising the capacity of the SFCL due to slight differences of critical current densities between units and structure of the SFCL. The hybrid-type SFCL with closed-loop is able to achieve capacity increase through the electrical isolation and reduction of the inductance of the secondary winding with a superconducting element of the same critical current. On the other hand, the current limiting characteristics were nearly identical in the hybrid-type SFCL with open-loop compared to closed-loop, but quench time was longer than the hybrid-type SFCL with closed-loop. We confirmed that the capacity of the SFCL was increased effectively by the reduced inductance of the secondary winding. In addition, the power burden of the system also could be lowered by reducing the inductance of secondary winding.

The pollutants removal and disinfection of secondary effluent from sewage treatment plant in loop reactor using silver nanoparticles coated on activated carbon (은나노 활성탄을 이용한 Loop Reactor에서 하수 2차 처리수 중의 오염물질 제거 및 소독 효과)

  • Seon, Yong-Ho
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.4
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    • pp.361-367
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    • 2016
  • Pollutants removal and disinfection effect of secondary effluent from final settling tank of sewage treatment plant of W city were investigated in Loop Reactor using ordinary granular activated carbon(GAC) and GAC coated with silver nanoparticles. The results showed that the removal efficiency of $COD_{Mn}$, T-N and T-P using GAC with silver nanoparticles were higher than using the ordinary GAC. The removal efficiency of T-P using GAC with silver nanoparticles is 45.4% and that of T-P using ordinary GAC is 30.9% in the same case of the input amount of 20 g/L of GAC. The total califorms is reduced according to increasing input amount of GAC with silver nanoparticles and ordinary GAC. The disinfection efficiency of total coliforms in case of GAC with silver nanoparticles is much higher than that in case of ordinary GAC. For all experiments using the silver nanoparticles, the total coliforms is under 26 cfu/mL and this shows very excellent disinfection effect.

The Effects of Secondary Fuel Injection on Combustion Oscillation

  • Shigeru Tachibana;Laurent Zimmer;Park, Gyung-Min;Takeshi Yamamoto;Ufosawa, Yoji-K;Seiji Yoshida;Kazuo Suzuki
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.376-379
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    • 2004
  • The purpose of this work is to develop an effective active control system for combustion instabilities of premixed combustors. For the first step, the natural modes of combustion oscillation were investigated for a methane-air premixed combustor and the controls by secondary fuel injection were examined. The main premixed flame is stabilized by a swirler with orifices for secondary injection installed on the central hub. For sensing purposes, a pressure transducer and a chemiluminescence sensor were placed on the appropriate positions. The acoustic characteristics and the source of the oscillation were analyzed by those signals. To test the controllability, two methods of actuations by secondary fuel injection were examined. One is the open loop control and the other is the closed loop control. The comparison of the reduction levels of p $_{rms}$ shows that the closed loop control with a phase-shift injection performs best in this condition.ition.n.

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Evaluation of the Annual Performance of the Direct Expansion Vertical Closed-Loop Ground Source Heat Pump (직접순환식 수직밀폐형 지열원 열펌프의 연간 운전성능 평가)

  • Kim, Min-Sung;Woo, Joung-Son;Baik, Young-Jin;Jang, Jea-Chul;Kim, Ji-Young;Ra, Ho-Sang
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.534-542
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    • 2012
  • Vertical closed-loop ground source heat pump systems(GSHP) have been installed widely in Korea since it can extract moderate temperature level of geothermal heat in a small area. As a ground heat exchanger, a vertical closed-loop type with brine circulation is mostly preferred since it is simple and less harmful to ground environment. However, it requires a secondary heat exchange loop between the refrigerant in a heat pump and the brine. By adding a geothermal heat exchanger in the secondary heat exchange loop, circulation pumps should be attached and the temperature difference between refrigerant and ground is increased, which are important parts of performance degradation. In this paper, annual and seasonal performances of direct expansion(DX) geothermal heat pump were estimated mathematically as an alternative of classical indirect geothermal heat pump based on the annual performance evaluation. As a result, DX geothermal heat pump showed 43% higher annual performance than the classical U-tube geothermal heat pump.

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Annual Performance Evaluation of Direct Expansion Vertical Closed-Loop Ground Source Heat Pump for Residential Application (주거용 직접순환식 수직밀폐형 지열원 열펌프의 연간 운전성능 평가)

  • Kim, Min-Sung;Baik, Young-Jin;Ra, Ho-Sang
    • Journal of the Korean Solar Energy Society
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    • v.32 no.3
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    • pp.114-122
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    • 2012
  • Vertical closed-loop ground source heat pump systems(GSHP) have been installed widely in Korea since it can extract moderate temperature level of geothermal heat in a small area. As a ground heat exchanger, a vertical closed -loop type with brine circulation is mostly preferred since it is simple and less harmful to ground environment. However, it requires a secondary heat exchange loop between the refrigerant in a heat pump and the brine. By adding a geothermal heat exchanger in the secondary heat exchange loop, circulation pumps should be attached and the temperature difference between refrigerant and ground is increased, which are important parts of performance degradation. In this paper, annual and seasonal performances of direct expansion(DX) geothermal heat pump were estimated mathematically as an alternative of classical indirect geothermal heat pump based on the annual performance evaluation. As results, DX geothermal heat pump showed 43% higher annual performance than the classical U-tube geothermal heat pump.

ROSA/LSTF test and RELAP5 code analyses on PWR steam generator tube rupture accident with recovery actions

  • Takeda, Takeshi
    • Nuclear Engineering and Technology
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    • v.50 no.6
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    • pp.981-988
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    • 2018
  • An experiment was performed for the OECD/NEA ROSA-2 Project with the large-scale test facility (LSTF), which simulated a steam generator tube rupture (SGTR) accident due to a double-ended guillotine break of one of steam generator (SG) U-tubes with operator recovery actions in a pressurized water reactor. The relief valve of broken SG opened three times after the start of intact SG secondary-side depressurization as the recovery action. Multi-dimensional phenomena specific to the SGTR accident appeared such as significant thermal stratification in a cold leg in broken loop especially during the operation of high-pressure injection (HPI) system. The RELAP5/MOD3.3 code overpredicted the broken SG secondary-side pressure after the start of the intact SG secondary-side depressurization, and failed to calculate the cold leg fluid temperature in broken loop. The combination of the number of the ruptured SG tubes and the HPI system operation difference was found to significantly affect the primary and SG secondary-side pressures through sensitivity analyses with the RELAP5 code.

Development of Anti-windup Techniques for Cascade Control System (다단제어용 안티 와인드업 기술 개발)

  • Bae, Jeong Eun;Kim, Kyeong Hoon;Chu, Syng Chul;Heo, Jaepil;Lim, Sanghun;Sung, Su Whan
    • Korean Chemical Engineering Research
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    • v.58 no.3
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    • pp.430-437
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    • 2020
  • In this research, the anti-windup techniques for the cascade control system are newly developed. Cascade control system has an additional internal feedback control loop to reject disturbances better than the conventional control system. Remarkable difference between the conventional single-loop control system and the cascade control system is the interaction that the controller output saturation of the secondary control loop strongly affects the integral action of the primary control loop. In industry, local back calculation anti-windup method has been mainly used for each controller without considering the interaction between the two controllers. But it cannot eliminate the integral-windup of the primary controller originated from the saturation of the secondary controller output. To solve the problem, the two anti-windup techniques of the cascade conditional integration and the cascade back calculation are proposed in this research by extending the local anti-windup techniques for the single-loop control system to the cascade control system. Simulation confirmed that the proposed methods can effectively remove the integral windup of the primary controller caused by the saturation of the secondary controller output and show good control performances for various types of processes and controllers. If the reliability of the proposed methods is proved through the applications to real processes in the future, they would highly contribute to improving the control performances of the cascade control system in industry.

Design and Assessments of a Closed-loop Hydraulic Energy-Regenerative System (폐루프 유압 에너지 회생 시스템에 관한 연구)

  • Hung, H.T.;Yoon, J.I.;Ahn, K.K.
    • 유공압시스템학회:학술대회논문집
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    • 2010.06a
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    • pp.116-125
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    • 2010
  • In this study, a novel hydraulic energy-regenerative system was presented from its proposal through its modeling to its control. The system was based on a closed-loop hydrostatic transmission and used a hydraulic accumulator as the energy storage system in a novel configuration to recover the kinetic energy without any reversion of the fluid flow. The displacement variation in the secondary unit was reduced, which widened the uses of several types of hydraulic pump/motors for the secondary unit. The proposed system was modeled based on its physical attributes. Simulation and experiments were performed to evaluate the validity of the employed mathematical model and the energy recovery potential of the system. The experimental results indicated that the round trip recovery efficiency varied from 22% to 59% for the test bench.

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A Multi-Module Three-Loop Controlled Boost Converter for Distributed Power Applications (삼중 루우프 제어방식을 채택한 분산형 전력시스템을 위한 멀티 모듈 승압형 컨버터)

  • Cho, Byung-Cho;Han, Dong-Hoon
    • Proceedings of the KIEE Conference
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    • 1998.11c
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    • pp.1041-1045
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    • 1998
  • This paper presents the control design of a three-module boost converter with a two-stage output filter. An advanced three-loop control scheme is employed to the control design in order to obtain good dynamic performance of the converter at the presence of the secondary filter stage. The paper presents the control design, dynamic analysis and performance improvement with the three-loop control.

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