The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of h...The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of high pressure pneumatics is seldom investigated. In this paper, the real gas effects on air enthalpy and internal energy are estimated firstly to study the real gas effect on the energy conversion. Under ideal gas assumption, enthalpy and internal energy are solely related to air temperature. The estimation result indicates that the pressure enthalpy and pressure internal energy of real pneumatic air obviously decrease the values of enthalpy and internal energy for high pressure pneumatics, and the values of pressure enthalpy and pressure internal energy are close. Based on the relationship among pressure, enthalpy and internal energy, the real gas effects on charging and discharging processes of high pressure pneumatics are estimated, which indicates that the real gas effect accelerates the temperature and pressure decreasing rates during discharging process, and decelerates their increasing rates during charging process. According to the above analysis, and for the inconvenience in building the simulation model for real gas and the difficulty of measuring the detail thermal capacities of pneumatics, a method to compensate the real gas effect under ideal gas assumption is proposed by modulating the thermal capacity of the pneumatic container in simulation. The experiments of switching expansion reduction （SER） for high pressure pneumatics are used to verify this compensating method. SER includes the discharging process of supply tanks and the charging process of expansion tank. The simulated and experimental results of SER are highly consistent. The proposed compensation method provides a convenient way to obtain more realistic simulation results for high pressure pneumatics.展开更多
Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD mod...Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.展开更多
The gas/solid flow regime of dense-phase pneumatic conveying of pulverized coal under a pressure of 4.0 MPa in horizontal pipeline 10 mm in diameter, is monitored by electrical capacitance tomography （ECT） using 8 e...The gas/solid flow regime of dense-phase pneumatic conveying of pulverized coal under a pressure of 4.0 MPa in horizontal pipeline 10 mm in diameter, is monitored by electrical capacitance tomography （ECT） using 8 electrodes. To improve the accuracy of the capacitance measurement, an AC-based singlechannel capacitance measuring circuit was developed, and a modified iterative Landweber algorithm was used to reconstruct the image. A two-fluid model based on the kinetic theory of granular flow was used to study the three-dimensional steady-state flow behavior of dense-phase pneumatic conveying of pulverized coal.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50575202)
文摘The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of high pressure pneumatics is seldom investigated. In this paper, the real gas effects on air enthalpy and internal energy are estimated firstly to study the real gas effect on the energy conversion. Under ideal gas assumption, enthalpy and internal energy are solely related to air temperature. The estimation result indicates that the pressure enthalpy and pressure internal energy of real pneumatic air obviously decrease the values of enthalpy and internal energy for high pressure pneumatics, and the values of pressure enthalpy and pressure internal energy are close. Based on the relationship among pressure, enthalpy and internal energy, the real gas effects on charging and discharging processes of high pressure pneumatics are estimated, which indicates that the real gas effect accelerates the temperature and pressure decreasing rates during discharging process, and decelerates their increasing rates during charging process. According to the above analysis, and for the inconvenience in building the simulation model for real gas and the difficulty of measuring the detail thermal capacities of pneumatics, a method to compensate the real gas effect under ideal gas assumption is proposed by modulating the thermal capacity of the pneumatic container in simulation. The experiments of switching expansion reduction （SER） for high pressure pneumatics are used to verify this compensating method. SER includes the discharging process of supply tanks and the charging process of expansion tank. The simulated and experimental results of SER are highly consistent. The proposed compensation method provides a convenient way to obtain more realistic simulation results for high pressure pneumatics.
基金Supported by the National Basic Research Program of China(2014CB745100)the National Natural Science Foundation of China(21576197)+1 种基金Tianjin Research Program of Application Foundation and Advanced Technology(14JCQNJC06700)Tianjin Penglai 19-3 Oil Spill Accident Compensation Project(19-3 BC2014-03)
文摘Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.
基金supported by National Natural Science Foun-dation of China under grants 50836003, 50906012,50906013Major State Basic Research Projects (grant 2010CB227002)
文摘The gas/solid flow regime of dense-phase pneumatic conveying of pulverized coal under a pressure of 4.0 MPa in horizontal pipeline 10 mm in diameter, is monitored by electrical capacitance tomography （ECT） using 8 electrodes. To improve the accuracy of the capacitance measurement, an AC-based singlechannel capacitance measuring circuit was developed, and a modified iterative Landweber algorithm was used to reconstruct the image. A two-fluid model based on the kinetic theory of granular flow was used to study the three-dimensional steady-state flow behavior of dense-phase pneumatic conveying of pulverized coal.
