The Experts below are selected from a list of 13974 Experts worldwide ranked by ideXlab platform
Walter Leitner - One of the best experts on this subject based on the ideXlab platform.
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Supercritical carbon dioxide as a green reaction medium for catalysis.
Accounts of chemical research, 2002Co-Authors: Walter LeitnerAbstract:Carbon dioxide in its liquid or Supercritical State (scCO2) has a prodigious potential as an environmentally benign reaction medium for sustainable chemical synthesis. Since the mid-1990s, rapidly ...
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Supercritical carbon dioxide as a green reaction medium for catalysis
Accounts of Chemical Research, 2002Co-Authors: Walter LeitnerAbstract:Carbon dioxide in its liquid or Supercritical State (scCO2) has a prodigious potential as an environmentally benign reaction medium for sustainable chemical synthesis. Since the mid-1990s, rapidly increasing research efforts have shown that scCO2 can replace conventional and potentially hazardous solvents in a wide range of processes. There is also increasing evidence that the application of scCO2 can broaden the scope of catalytic synthetic methodologies. On the basis of the experience in our laboratories, this report analyzes the impact of scCO2 on green organometallic catalysis.
Hiroshi Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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an experimental study on evacuated tube solar collector using Supercritical co2
Applied Thermal Engineering, 2008Co-Authors: Xing Zhang, Hiroshi YamaguchiAbstract:A solar collector using Supercritical CO2 as working fluid is proposed in this paper. In order to investigate and estimate the CO2-based solar collector, an experimental set-up was constructed. Of particular interest of this paper are the basic collector characteristics, such as CO2 temperature and pressure in the collector, CO2 flow rate, and collector performances. The collector has been tested under various weather conditions. The results show that the CO2 temperature, CO2 pressure and mass flow rate increase with the solar radiation, which is different from those of traditional solar collector using liquid as working fluid. The solar radiation has influence on the CO2 States, being liquid, liquid-gas or Supercritical State in the test, furthermore, affects the CO2 mass flow rate. The annually-averaged collector efficiency is found to be above 60.0% in the case of Supercritical CO2 as working fluid, which is much higher than that of water-based solar collector. This study shows the potential of the Supercritical CO2-based solar collector in the field of solar thermal utilization.
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solar energy powered rankine cycle using Supercritical co2
Applied Thermal Engineering, 2006Co-Authors: Hiroshi Yamaguchi, Xinrong Zhang, Katsumi Fujima, Masatoshi Enomoto, N SawadaAbstract:Abstract A solar energy powered Rankine cycle using Supercritical CO2 for combined production of electricity and thermal energy is proposed. The proposed system consists of evacuated solar collectors, power generating turbine, high-temperature heat recovery system, low-temperature heat recovery system, and feed pump. The system utilizes evacuated solar collectors to convert CO2 into high-temperature Supercritical State, used to drive a turbine and thereby produce mechanical energy and hence electricity. The system also recovers heat (high-temperature heat and low-temperature heat), which could be used for refrigeration, air conditioning, hot water supply, etc. in domestic or commercial buildings. An experimental prototype has been designed and constructed. The prototype system has been tested under typical summer conditions in Kyoto, Japan; It was found that CO2 is efficiently converted into high-temperature Supercritical State, of while electricity and hot water can be generated. The experimental results show that the solar energy powered Rankine cycle using CO2 works stably in a trans-critical region. The estimated power generation efficiency is 0.25 and heat recovery efficiency is 0.65. This study shows the potential of the application of the solar-powered Rankine cycle using Supercritical CO2.
Weiqiang Song - One of the best experts on this subject based on the ideXlab platform.
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wellbore flow field of coiled tubing drilling with Supercritical carbon dioxide
Greenhouse Gases-Science and Technology, 2017Co-Authors: Weiqiang Song, Ruihe Wang, Mengyun ZhaoAbstract:To achieve better well control for Supercritical carbon dioxide drilling, a mathematical model was presented to investigate the pressure and temperature profile in both the tubing and the annulus. The closed model fully couples the hydraulics, heat transfer, and compressibility of carbon dioxide, and then the wellbore flow field is presented and analyzed based on field application. The results show that the pressure change of carbon dioxide is 36.7% smaller than that of water along the annulus in the study case. Carbon dioxide changes into Supercritical State when the depth equals 700 m ∼830 m in the tubing, and it could maintain in Supercritical State in the whole annulus. Both the pressure profile and the temperature profile are highly coupled with the physical properties of carbon dioxide. The density of carbon dioxide is large enough to drive downhole motors and its capacity is much larger than that of air in the wellbore. The pressure increases lightly with increasing mass flow rate in the annulus; however, it is significantly and positively impacted by the outlet pressure. The influence of outlet pressure on temperature profile is negligible in the tubing. The inlet temperature could not impact the pressure profile in the annulus, and its influence on temperature profile mainly lies in the shallow section of the tubing. It is newly validated that Supercritical carbon dioxide drilling is more suitable for the exploitation of unconventional reservoirs with narrow pressure windows. The results could lay a theoretical foundation for practical application. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.
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coupling model for carbon dioxide wellbore flow and heat transfer in coiled tubing drilling
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Hongjian Ni, Weiqiang Song, Ruihe Wang, Zhonghou ShenAbstract:Abstract In order to drill with carbon dioxide as the circulation fluid, a mathematical model was proposed to investigate the flow field in both tubing and annulus. Based on finite volume method, the closed model fully couples the hydraulics, heat transfer and physical properties of carbon dioxide. According to field application, the model is solved and discussed with a case study. The results show that, the pressure is in positive correlation with well depth in both tubing and annulus. The fluid temperature increases fast after liquid carbon dioxide is pumped into tubing and then the increasing rate slows down with increasing depth. Carbon dioxide changes into Supercritical State when the depth equals 780 m. The pressure drop of bit jet is 9.78 MPa and the temperature difference between carbon dioxide and formation rock is 12.11 K at bottom hole. In the annulus, the temperature decreases as carbon dioxide flows upward and it is higher than geothermal temperature when depth is less than 927 m. The changes in physical properties are mainly dominated by temperature change in the tubing and by pressure change in the annulus. The density, viscosity and thermal conductivity all witness a constant decrease along the flow route, and the changing trends develop faster at shallow well section in the tubing. At bottom hole, the density is large enough to drive down-hole motors. The heat capacity changes little in the tubing and then increases rapidly when flowing upward along the annulus. The capacity is much larger than that of air in wellbore. Carbon dioxide maintains in Supercritical State in the annulus and provides advantages for reservoir exploitation. This study aims to lay theoretical foundation for practical application.
Takeshi Morita - One of the best experts on this subject based on the ideXlab platform.
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density fluctuation of a van der waals fluid in Supercritical State
Journal of Chemical Physics, 2003Co-Authors: Keiko Nishikawa, Kouhei Kusano, Asako Ayusawa Arai, Takeshi MoritaAbstract:Density fluctuation is one of the fundamental parameters which determine the various physicochemical properties of Supercritical fluids. When the contour map of density fluctuation is drawn on the phase diagram, there exists a ridge which separates the Supercritical region in two. In order to obtain a phenomenological picture with physical clearness, we formulate the density fluctuation and its ridge for the van der Waals fluid. They are expressed by fairly simple equations with reduced temperature (Tr=T/Tc) and number density (nr=n/nc). It is analytically ensured that the law of corresponding States is applicable to the density fluctuation and its ridge and the ridge is different from the critical isochore. The ridge is the locus of the points where the third derivatives of the Gibbs free energy become zero, and that drawn on a density–temperature phase diagram directly connects with the locus of the inflection points of the van der Waals isotherms in the unstable region. From the viewpoint of the valance of volumes occupied by molecules and void, the physical meaning of the ridge is also discussed. The consistent agreements are confirmed in the characteristics of the density fluctuation and the ridge for the van der Waals fluid and several real Supercritical fluids.
Zhonghou Shen - One of the best experts on this subject based on the ideXlab platform.
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coupling model for carbon dioxide wellbore flow and heat transfer in coiled tubing drilling
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Hongjian Ni, Weiqiang Song, Ruihe Wang, Zhonghou ShenAbstract:Abstract In order to drill with carbon dioxide as the circulation fluid, a mathematical model was proposed to investigate the flow field in both tubing and annulus. Based on finite volume method, the closed model fully couples the hydraulics, heat transfer and physical properties of carbon dioxide. According to field application, the model is solved and discussed with a case study. The results show that, the pressure is in positive correlation with well depth in both tubing and annulus. The fluid temperature increases fast after liquid carbon dioxide is pumped into tubing and then the increasing rate slows down with increasing depth. Carbon dioxide changes into Supercritical State when the depth equals 780 m. The pressure drop of bit jet is 9.78 MPa and the temperature difference between carbon dioxide and formation rock is 12.11 K at bottom hole. In the annulus, the temperature decreases as carbon dioxide flows upward and it is higher than geothermal temperature when depth is less than 927 m. The changes in physical properties are mainly dominated by temperature change in the tubing and by pressure change in the annulus. The density, viscosity and thermal conductivity all witness a constant decrease along the flow route, and the changing trends develop faster at shallow well section in the tubing. At bottom hole, the density is large enough to drive down-hole motors. The heat capacity changes little in the tubing and then increases rapidly when flowing upward along the annulus. The capacity is much larger than that of air in wellbore. Carbon dioxide maintains in Supercritical State in the annulus and provides advantages for reservoir exploitation. This study aims to lay theoretical foundation for practical application.