전자급 고순도 이산화탄소 분리 공정의 전산 모사 및 공정 최적화에 관한 연구

박일수 공주대학교 대학원 2023 국내박사

현재까지 반도체 공정에 적용할 수 있는 99.99999%(7N) 이상의 고순도의 전자급 CO2를 분리해 내는 연구 결과가 발표된 바 없다. 본 연구 결과에 따르면 이러한 고순도 전자급의 CO2를 분리해 내기 위해서는 냉동사이클을 활용한 단순액화 공정으로는 불가능하다는 것이 연구 결과 밝혀졌다. 다만 순도 98% 이상의 공업용 CO2를 분리할 수 있다. 그러나 심냉 증류 공정을 통해서는 7N 이상의 고순도 전자급 CO2를 분리해 낼 수 있음이 전산모사를 통해 연구되었다. 특히 냉동사이클 대신에 LNG 냉열이나 LN2 냉열을 활용하면 7N 이상의 고순도 전자급 CO2를 98%까지 회수할 수 있으며 소요 동력도 68% 절감할 수 있다는 연구 결과가 도출되었다.

냉동 사이클의 동적 특성 모델링과 슬라이딩 관측기 기반 슬라이딩 모드제어

김낙훈 부산대학교 대학원 2017 국내박사

In this dissertation, a lumped parameter model of an air conditioning system for the control object is developed. Because thermal-uid systems have great complexity and dependency of environment, it is not easy to predict their physical behaviors and to design appropriate controllers. Several assumptions are made to simplify the governing partial dierential equations such as mass and energy conservation. Also, a time invariant mean void fraction and a moving boundary concept in the heat exchangers are employed to convert partial dierential equations to the set of ordinary dierential equations so as to extract state space representations. Simulations and experiments are conducted to show the validity of the proposed model. Based on this mathematical model, a robust controller and observer are designed by applying sliding mode theory. In the design of controller, a sliding observer is designed to estimate the unmeasurable state variables. Also, a new type discontinuous controller to reduce the eect of chattering and to improve the response time of the given system is introduced and computer simulation is conducted in order to demonstrate the eciency, chattering reduction, and robustness of the proposed control methodology for the given vapor compression cycle system.

다양한 냉매적용 캐스케이드 냉동사이클의 운전조건 변화에 따른 성능해석

유지호 조선대학교 2015 국내석사

The evaporating temperature which required for the low temperature freezing system is -50℃∼-30℃ range. Since it is difficult to keep the required capacity in a cabinet, it is advantageous to design the system by using cascade refrigeration system. Besides the research is needed to use carbon dioxide and ammonia because it is environment-friendly working fluid and has a high possibility for performance improvement. To investigate of performance characteristics of the R744-R717 cascade refrigeration system, the theoretical model was developed and performance analyzed according to cascade heat exchanger operating temperature. As a result, optimal cascade R744 condensing temperature was -5℃ and maximum COP was 1.13 when the temperature difference of cascade heat exchanger was 5℃. Besides the research is needed to use R744 and R1234yf because it is environment-friendly refrigerant and has a high possibility for performance improvement. Especially, the R1234yf may be used without changing the R134a system. As well, to investigate of performance characteristics of the R744-R1234yf and R744-R134a cascade refrigeration system, the theoretical model was developed and the performance analyzed according to cascade heat exchanger operating temperature. Maximum COP of R744-R1234yf system was 2.15 when the evaporation temperature of R1234yf was –10℃. The other system was 2.64 when the evaporation temperature of R134a was –15℃. In addition, the performance analysis of internal heat exchanger which is attached to the R744-R717 cascade refrigeration system operated with cascade condensing temperature. To compare the performance of cascade cycle with/without the internal heat exchanger, the operating condition was set to the optimal condition which has the maximum COP of the cascade cycle without internal heat exchanger. As a result, cooling capacity and COP increased by 2.16% and 1.85%, respectively, when the internal heat exchanger was attached into a low-temperature cycle. Besides, those increased by 2.62% and 1.69%, respectively when the internal heat exchanger attached both high- and low-temperature cycle.

부하모델을 이용한 전기자동차용 냉동탑차 냉동사이클 성능 특성에 대한 해석적 연구

김재범 고려대학교 대학원 2023 국내석사

베이퍼 인젝션이 저온 냉동 사이클에 미치는 영향 실험적 비교

이용주 부산대학교 대학원 2020 국내석사

최근 냉장냉동 업계에서도 에너지 효율에 대한 관심 및 규제로 고효율화에 대한 시장요구가 증대하고 있다. 이에 따라 저온 냉동 사이클의 효율성을 높이기 위해 Vapor Injection 기능을 냉동 사이클에 적용하여 시험하였다. 이 논문은 저온 사이클의 효율 향상을 위해 Vapor Injection을 활용하는 데 중점을 두고 연구를 진행하였다. 보다 구체적으로, COP에 대한 Vapor Injection의 효과를 비교하기 위해 압축기 수량 변호 및 Vapor Injection에 대한 실험을 진행하였다. 또한, 최근 추가로 요구되고 있는 외기 온도 상승에 따른 효율과 능력 의 상관 관계 또한 확인하였다.

냉동사이클 운전로직 변경에 따른 냉장실 정온도 개선연구

한탁원 부산대학교 대학원 2019 국내석사

식품을 보관하는 냉장고의 주요 본질 속성으로써 사용자들은 식품의 신선한 보관과 합리적인 에너지 소비를 중요한 요소라고 인식하고 있다. 냉장중에 일어나는 식품의 품질변화에 영향을 미치는 인자는 주로 저장시간과 온도인데 냉장온도가 높을 경우뿐만 아니라 온도변화가 심할 경우에도 품질변화가 일어난다. 따라서 식품의 최적 보관 온도를 맞추고, 온도의 편차를 줄여 정온화를 기한다면 품질 유지 기간을 연장할 수 있다. 본 연구에서는 냉장고의 냉동사이클 운전로직을 변경함에 따른 냉장실의 정온도 성능을 에너지는 기존의 운전로직 대비하여 동등 이하 수준을 유지하면서 개선할 수 있는 방법을 연구하였다. As a key attribute of refrigerators that store food, users recognize that fresh storage of food and rational energy consumption are important factors. The factors affecting the quality change of food during refrigeration are mainly storage time and temperature. The food quality changes occur not only when the refrigeration temperature is high but also when the temperature fluctuation is severe. Therefore, it is possible to extend the quality maintenance period by adjusting the optimum storage temperature of the food and decreasing the temperature fluctuation to maintain the constant temperature. In this study, the influence of the change of refrigeration cycle operation algorithm on the improvement of the constant temperature performance of fridge has been studied. The power consumption of the refrigerator was considered to be below the level of existing algorithm.

냉매유량 및 기기 제어에 의한 냉동장치의 성능특성에 관한 연구

순병기 동명대학교 2009 국내석사

산업시설이 고도화됨에 따라 냉동공조 시스템의 수요가 폭발적으로 증가 하고 소비자들의 기호 또한 다양해지고 있다. 따라서 장치에 대한 고성능 화가 요구되면서 정교한 제어가 필수적으로 요구되어 냉동사이클의 주된 점 3가지에 기초를 두고 있다. 첫째는 과냉각 시스템을 사용한 냉동사이클에서 과냉각도 및 증발온도 변화에 따른 냉각열량 및 성능의 향상을 가져올 수 있다. 둘째는 전자식 팽창밸브를 이용하여 팽창밸브의 개도를 변화시켜 냉매유량을 제어하며 증발기의 출구 과열도를 일정한 값으로 제어함으로써 냉동효과를 높이는 것이다. 과열도 제어는 정교한 제어가 불가능하며 이러한 문제점을 해결하기 위해 용량제어와 과열도 제어를 동시에 제어하는 방법이 제시되어야 한다. 셋째는 과열도 변화에 따른 냉동장치의 성능특성은 과열도 변화에 따라 성적계수 변화의 영향이 미비하였다. 그리고 R-22를 작동유체로 사용하는 냉동장치에서는 흡입증기의 과열도를 8℃이하로 억제하는 것이 효율상 좋으며, R-134a는 과열도 4℃와 R-717은 과열도 3℃정도를 유지하여 운전하는 것이 성능면에서 가장 적합하다는 것을 알 수 있다. According to the development of industrial technology, refrigeration system is widely used today. To obtain high efficiency, high intelligence, and energy saving for refrigeration system, the optimum control of the refrigeration system is inevitable. The conventional control schemes are mainly based on representative three control methods. First, the refrigerant mass flow rate and compressor shaft power were unchanged by the degrees of subcooling, that is, they were independent of degrees of subcooling. The cooling capacity of the new refrigeration system increase as the evaporating temperature and subcooling degrees increase and is higher by 25~30%, compared to the normal refrigeration system. The cop of the new refrigeration system increases as the degrees of subcooling and evaporating temperature increase and is higher by 28% than that of the normal refrigeration system. Second is capacity control for room temperature control and energy saving by compressor speed variation. The other is superheat control for enhancing coefficient of performance(cop) of the refrigeration system by varying opening angle of an electronic expansion valve. They have been controlled not be coupled but be separated. Moreover, the refrigeration system's elements are deeply connected with the pipe each other, so optimum control is not easy. Third, in this study, simulation studies on the effect of superheat degree occurring in the theoretical vapor compression cycle has been performed for the R-22, R-134a and R-717. Virtually all possible refrigerants are considered. The analysis has yielded no surprises in terms of cop, compression work, refrigeration effect and refrigerant selection. However, it was found that the most proffer superheat degree to improve cop for the R-22 is below 8℃, R-134a is around 4℃ and R-717 is around 3℃.

과도상태 냉동사이클 해석 프로그램 개발과 이를 이용한 냉장고의 동특성 해석

배정욱 부산대학교 2011 국내석사

가변속 냉동사이클 기반 배터리 열관리 시스템의 모델예측 제어기 설계

윤민기 국립부경대학교 대학원 2024 국내석사

The introduction and technological advancements of eco-friendly vehicles are increasingly recognized as effective alternatives to mitigate climate change. Electric vehicles (EVs), powered by electric motors, boast minimal or virtually zero exhaust emissions during operation. To drive the electric motors, batteries are essential for storing and supplying power. However, these batteries must be carefully managed to prevent overheating-related hazards such as explosions or fires. Additionally, battery performance is closely tied to operating temperatures, and deviation from the optimal temperature range can lead to reduced lifespan and decreased energy efficiency due to a decrease in charging capacity. To maintain the safety and performance of batteries, extensive research is currently being conducted on Battery Thermal Management Systems (BTMS) employing various cooling methods. Particularly, the variable-speed refrigeration cycle has proven effective in responding to a wide range of partial loads, offering high energy efficiency and rapid, precise temperature control during load fluctuations. This technology finds applications in diverse fields such as building HVAC systems, semiconductor processes, and commercial-industrial refrigeration. The variable-speed refrigeration cycle controls the temperature by regulating the compressor's rotation speed and the Electronic Expansion Valve (EEV), concurrently managing refrigerant superheat. In cases of indirect cooling, the cycle involves the circulation of secondary refrigerant, such as Brine, for cooling purposes. To facilitate this, a cooling water pump circulates coolant, absorbing heat from the coolant material, and maintains the temperature within an appropriate range. The Electric Water Pump (EWP) plays a vital role in this process, acting as a crucial control element alongside core components like the compressor, condenser, EEV, and evaporator. While existing research has investigated the control of coolant flow using rule-based approaches based on system characteristic analyses, which set the operating rotation speed of devices like EWP, these methods may face challenges in achieving energy optimization when multiple control variables coexist. Therefore, this study introduces the Model Predictive Control (MPC) technique to comprehensively regulate the coolant flow of EWP in conjunction with a variable-speed refrigeration cycle composed of a variable-speed compressor and EEV. MPC utilizes state feedback and system models to predict future states, concurrently configuring predicted control variables into the objective function to derive optimal control inputs. Consequently, MPC, designed as a multi-variable controller for Multi-Input Multi-Output (MIMO) systems, facilitates integrated control of various parameters. In this process, MPC assigns individual weights to each control variable, enabling swift and flexible adaptation to diverse performance requirements. Furthermore, MPC allows for the anticipation of control device constraints during the optimization process, ensuring control inputs stay within the permissible maximum output range of actuators and guaranteeing optimal control performance. This study applies MPC to design and assess its control performance for an Oil Cooler System (OCS) and BTMS configured with a variable-speed refrigeration cycle. Initially, the feasibility of MPC design for OCS is verified, followed by the application of MPC to BTMS with EWP control. The performance of MPC in regulating battery module temperature, coolant temperature, and refrigerant superheat is thoroughly examined. The models for OCS and BTMS, essential for MPC design, are derived from continuous-time state-space models converted from transfer functions obtained through dynamic experiments. Subsequently, the continuous-time BTMS model is discretized, leading to an augmented model expressed in discrete-time state-space form. Based on this augmented model, MPC is designed in the MATLAB/Simulink environment, and simulations are conducted to validate the proposed design. The impact of key MPC design parameters, namely prediction horizon and control horizon values, is extensively analyzed through simulations.

壓縮式 冷凍機에서 冷媒狀態가 冷凍 Cycle에 미치는 影響

계용길 仁川大學校 1990 국내석사