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Organic Rankine Cycle (ORC) is promising in utilizing low-medium thermal energy, and solar energy is widely considered as the most attractive renewable energy for the future. Consequently, electricity production by coupling ORC and solar energy can reduce the fossil fuel consumption and lower the CO2 emissions over the world. However, the intensity of solar radiation keeps changing throughout the...
A great amount of researches on thermodynamic cycles have been active in recent years, such as ORC (organic Rankine cycle), Kalina cycle, et al. However, the ultimate aim of such researches, which could even be traced back to more than one century ago, has not changed with a tireless pursuing to Carnot cycle. In exiting researches, the working fluid, as a medium for energy conversion, is commonly...
Distributed energy system (DES) has received much attention in the world to solve the conflict between energy saving and emission reduction. The cutting-edge DES can provide multi-products for the diversity of user, such as cooling, heating, power and even desalination, through a cascade utilization of energy. Furthermore, a large-scale application of renewable energy has been considered in DES with...
Currently, the significant energy penalty and performance limitation of energy consumption are the main technical barriers to the large-scale applications of CO2 capture. Carbon pump, which realizes an enrichment of CO2 from carbon source to carbon sink, is applied in a modeling for energy-efficiency analysis of CO2 capture technologies. In this study, two adsorption technologies, including vacuum-pressure...
The vapor slope of temperature-entropy saturation boundary of working fluids has a significant effect on the efficiency and the safety of thermodynamic processes. Therefore, how to predict the vapor slope efficiently and quickly is worth studying. In this work, the vapor slope represented by the slope angle is firstly correlated with the reduced temperature, the molecular weight, 10 molecular groups...
Currently, significant energy consumption is one of the main technical barriers to the large-scale application of CO2 capture technology. A novel concept—carbon pump—is proposed in this paper to analyze the energy-efficiency of these technologies. The analysis model, which embodies the carbon pump concept, includes the minimum CO2 separation work and the second-law efficiency. Based on this model,...
The slope of temperature-entropy saturation boundary of working fluids has a significant effect on the thermodynamic performance of cycle processes. However, for the working fluids used in cycles, few studies have been conducted to analyze the saturated slope from the molecular structure and mixture composition. Thus, in this contribution, an analytical expression on the slope of saturated curve is...
Owing to the poor performance of the previous CO2 two-rolling piston expander prototype, improvements were made to increase its efficiency. The improvement measures included increasing the expansion ratio by minimizing the size of the intermediate channel and adopting some sealing methods to block the leakages, such as integrating the intermediate plate and filling O-rings in the seal grooves of the...
The application of zeotropic mixtures may lead to the occurrence of the EPTD (extreme point of temperature difference), i.e. the Pinch Point, between the working fluid and the HTF (heat transfer fluid) in heat exchangers. The positions of the EPTD are related to the system operating conditions. In this paper, the influence of the system parameters on the temperature profile of the fluid and the location...
A novel auto-cascade Rankine cycle (ARC) is proposed to reduce thermodynamics irreversibility and improve energy utilization. Like the Kalina cycle, the working fluid for the ARC is zeotropic mixture, which can improve the system efficiency due to the temperature slip that zeotropic mixtures exhibit during phase change. Unlike the Kalina cycle, two expanders are included in the ARC rather than a expander...
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