Energy and Exergy Analysis of a Combined Cooling Heating and Power System with Regeneration
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Solar assisted trigeneration system has proved to be a potential method in generating power with net zero carbon emissions. The present work aims to address the potential ways to improve the efficiency of the solar energy-integrated carbon dioxide trigeneration system. A regeneration integrated combined cooling, heating, and power system is proposed. With a comprehensive thermodynamic model, the proposed system is simulated for various operating conditions. A component-level exergy analysis is also conducted to estimate the total irreversibility of the system. As the gas cooler exit temperature increases, the overall system irreversibility also increases. When the bleed mass is 20% of the total mass, the system has the lowest energy destruction rate. The potential component that contributes most to system irreversibility is the gas cooler, followed by the regenerator and expansion valve. The proposed system with regeneration yields 29% more COP than the conventional system when operating at lower compressor discharge pressure and a gas cooler exit temperature of 34 °C. It is inferred from the obtained results that to reduce the total irreversibility of the system, it is advised to operate the system at a lower compressor discharge pressure and gas cooler exit temperature.The generalized expressions of Exergy and its applications are discussed based on Thermodynamic Laws and exergy's definition. The heat exergy, pressure exergy, and chemical exergy are consequentially related with the variation of system entropy. It is indicated that the parlance of If there is no transferring or transforming of heat, there will be no increase of entropy in the process is incorrect.
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원자로 정지냉각계통은 원자로 정지 시 핵연료 잔열 제거를 위하여 냉각수가 충분히 공급하고 원자로기기들을 보호할 수 있는 냉각율을 유지할 수 있도록 설계되어야 한다. 경수로 정지냉각계통을 분석하기 위한 KDESCENT코드를 중수로 정지냉각계통에 적용하여 보았으며 기존의 중수로형 해석코드인 SOPHT, SDCS 코드 결과와 비교분석하였다. 정지냉각펌프 모드와 열수송펌프 모드에서 정상냉각 운전상태는 계통의 설계 요건을 만족시켰으며 정지냉각 열교환기를 열제거원으로 사용하였을 때 냉각률은 설계요건에서 규정하고 있는 제한치인 $2.8^{\circ}C/min$ 이하의 값을 얻었다. 전반적인 냉각능력 분석 결과 월성 2, 3, 4호기 정지냉각계통은 핵연료로부터 핵분열 생성물의 방출을 충분히 제한하고 핵연료채널의 건전성을 유지시키기 위한 충분한 냉각을 핵연료에 제공하였다. Following the reactor shutdown, the reactor shutdown cooling system must be designed to supply the coolant sufficiently not only to remove the decay heat but to maintain the adequate cooling rate to protect the reactor equipments. In this study, KDESCENT code for the light water reactor and SOPHT, SDCS codes for the heavy water reactor were compared and analyzed to investigate the cooling capability during the shutdown cooling process. The shutdown cooling system design requirements were satisfied during cooling process for both the SDCP and the HTP modes and the design cooling rate of $2.8^{\circ}C/min$ or below was maintained using the SDC heat exchangers. This study shows that the shutdown cooling system in the Wolsong 2, 3, 4 reactors provides sufficient cooling to maintain the nuclear fuel integrity by removing the decay heat of the nuclear fission product.
Shut down
Decay heat
Nuclear fission product
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Magnetic refrigeration
Cooling capacity
Cryogenics
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Abstract In order to explore the transfer law of exergy in the lines (pipes), based on the generalized expression equation of exergy and the generalized exergy transfers and conversion equation, the transfer law of exergy in the lines (pipes) is derived, and then the exergy loss of three typical energies are analyzed based on the exergy loss model, which are electric exergy loss, pressure exergy loss and heat exergy loss. This paper reveals the change mechanism of exergy transfer process, which can provide more comprehensive guidance for energy saving.
Exergy efficiency
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Exergy efficiency
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Exergy efficiency
Energy Analysis
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Exergy is the very useful tool to evaluate energy systems besides energy analysis based on the first law of the thermodynamics. In contrast to energy, exergy is not conserved and always decreases. There are many types of exergy analysis involving exergoeconomic, exergoenvironmental, advanced exergy-based analyses, extended exergy analysis etc. In this study, an application of the extended exergy analysis is performed. In extended exergy analysis, not only energy related system is considered but also all materials and energy flows’ exergy, non-energetic and immaterial fluxes (capital, labor and environmental impact) are turned into exergy equivalent values and utilized in the analysis, which are calculating for local econometric and social data. These methods can be applied to societies or energy based or non-energy-based system. In this study, dynamic exergy analysis and extended exergy application of electricity generation from photon enhanced thermionic emitter is conducted. According to results, some important values can be listed as; extended exergy destruction, conventional based exergy destruction, extended exergy efficiency, conventional exergy efficiency, extended sustainability ratio, conventional sustainability ratio, extended exergy-based depletion ratio and conventional exergy-based depletion ratio are 542106006 MJ, 542084601 MJ, 0.01094, 0.01094, 1.011, 1.011, 0.978 and 0.989 respectively.
Exergy efficiency
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We have investigated the characteristics of some layered structural regenerators (multilayer regenerators) with magnetic regenerator materials using a two-stage GM refrigerator. In this study, we newly used Er0·75Gd0·25Ni which is expected to be placed in the high-temperature part of the second regenerator. To confirm the effect of Er0·75Gd0·25Ni, the heat-exchange efficiency of the regenerator (regenerator efficiency) with Er0·75Gd0·25Ni, Er3Co and Er0·9Yb0·1Ni, which were in the volumetric ratio of x: (0.5-x): 0.5 (0≤x≤0.5) was calculated as a function of x by computer simulation. We found that the regenerator efficiency increased when x (i.e. the amount of Er0·75Gd0·25Ni) was increased and the optimum value of x was -0.25. We then made two kinds of second regenerators: a triplelayer regenerator with Er0·75Gd0·25Ni, Er3Co and Er0·9Yb0·1Ni, which were in the volumetric ratio of 0.25:0.25:0.5, and a doublelayer regenerator with Er3Co and Er0·9Yb0·1Ni, which were in the volumetric ratio of 0.5:0.5. We compared experimentally their refrigeration performances. With the triplelayer regenerator, the lowest temperature was 2.60K at the second stage and the maximum refrigeration capacity at 4.2K was 1.17W. These results were superior to those with the doublelayer regenerator.
Magnetic refrigeration
Cooling capacity
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Recenty, regenerative refrigerators such as the Gifford-McMahon (GM) refrigerator achieve liquid helium temperature level by using magnetic regenerator materials, which have larger heat capacity below 10K than a conventional regenerator material of Pb. The purpose of this study is to investigate the heat characteristic of the regenerator, which is operated with liquid helium temperature level. In the present paper, we describe the experimental results of the regenerator performance in a two-stage GM refrigerator. Temperatures and pressure in the regenerator were measured and the stored heat in the regenerator was calculated from these data. The stored heat was divided between that stored in regenerator material and that stored in helium gas. The stored heat is compared between ideal gas operation and non-ideal gas operation. The regenerator efficiency was calculated from the stored heat. For ideal gas operation, the stored heat was equal at each position; however, for non-ideal gas operation, it was slight from the middle of the regenerator to the cold end. The multi-layered regenerator constructed using several magnetic materials which have different peaks of the specific heat increases the stored heat in the part in which heat capacity was increased, and achieves higher regenerator efficiency. Regenerator efficiency is higher at lower flow rates, and at higher the hot end temperatures of the regenerator. Therefore, the best condition for cryocooler operation changes with the temperature range in which the regenerator is used.
Cooling capacity
Cryogenics
Dilution refrigerator
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