Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining,which could promote further decomposition and expand mining areas of gas hydrate. St...Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining,which could promote further decomposition and expand mining areas of gas hydrate. Steam heat calculation would provide the basis for the design of heating device and the choice of the field test parameters. There were piping heat loss in the process of mining. The heat transfer of steam flowing in the pipe was steady,so the heat loss could be obtained easily by formula calculation. The power of stratum heating should be determined by numerical simulation for the process of heating was dynamic and the equations were usually nonlinear. The selected mining conditions were 500-millimeter mining radius,10 centigrade mining temperature and 180 centigrade steam temperature. Heat loss and best heating power,obtained by formula calculation and numerical simulation,were 21. 35 W/m and 20 kW.展开更多
The delivery of the inert gas through a vertical borehole using inert gas generator or IGG is investigated.Potential limitations and/or transient effects are highlighted.During the analysis,the borehole diameter,boreh...The delivery of the inert gas through a vertical borehole using inert gas generator or IGG is investigated.Potential limitations and/or transient effects are highlighted.During the analysis,the borehole diameter,borehole length,type of borehole and partial condensation prior to entering the borehole were varied.A choked flow will occur for a contraction exit or borehole of 0.3 m in diameter if no condensation prior to the contraction occurs.If partial condensation takes place,a borehole diameter of 0.3 m will be possible if almost 50%of the water vapour condensates.However,pressure losses along boreholes with a diameter of 0.3 or 0.4 m are significant and could pose a challenge if trying to mitigate the pressure losses.Adding a booster fan prior to the inlet of the 0.4 m lined borehole would still be a challenge.The corresponding case with a 0.5 m borehole presents much more favourable pressure losses.The 0.5 m diameter lined borehole should be regarded as the lower threshold.The rapid heating of the unlined borehole surface will increase the risk of thermal spallation and possibly imposing restrictions.Understanding the mechanisms during gas delivery will increase the likelihood of a successful inertisation.展开更多
Parabolic trough receiver is a key component to convert solar energy into thermal energy in the parabolic trough solar system.The heat loss of the receiver has an important influence on the thermal efficiency and the ...Parabolic trough receiver is a key component to convert solar energy into thermal energy in the parabolic trough solar system.The heat loss of the receiver has an important influence on the thermal efficiency and the operating cost of the power station.In this paper,conduction and radiation heat losses are analyzed respectively to identify the heat loss mechanism of the receiver.A 2-D heat transfer model is established by using the direct simulation Monte Carlo method for rarefied gas flow and heat transfer within the annulus of the receiver to predict the conduction heat loss caused by residual gases.The numerical results conform to the experimental results,and show the temperature of the glass envelope and heat loss for various conditions in detail.The effects of annulus pressure,gas species,temperature of heat transfer fluid,and annulus size on the conduction and radiation heat losses are systematically analyzed.Besides,the main factors that cause heat loss are analyzed,providing a theoretical basis for guiding the improvement of receiver,as well as the operation and maintenance strategy to reduce heat loss.展开更多
基金Supported by project of China Geological Surrey(No.GZHL20110326)
文摘Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining,which could promote further decomposition and expand mining areas of gas hydrate. Steam heat calculation would provide the basis for the design of heating device and the choice of the field test parameters. There were piping heat loss in the process of mining. The heat transfer of steam flowing in the pipe was steady,so the heat loss could be obtained easily by formula calculation. The power of stratum heating should be determined by numerical simulation for the process of heating was dynamic and the equations were usually nonlinear. The selected mining conditions were 500-millimeter mining radius,10 centigrade mining temperature and 180 centigrade steam temperature. Heat loss and best heating power,obtained by formula calculation and numerical simulation,were 21. 35 W/m and 20 kW.
文摘The delivery of the inert gas through a vertical borehole using inert gas generator or IGG is investigated.Potential limitations and/or transient effects are highlighted.During the analysis,the borehole diameter,borehole length,type of borehole and partial condensation prior to entering the borehole were varied.A choked flow will occur for a contraction exit or borehole of 0.3 m in diameter if no condensation prior to the contraction occurs.If partial condensation takes place,a borehole diameter of 0.3 m will be possible if almost 50%of the water vapour condensates.However,pressure losses along boreholes with a diameter of 0.3 or 0.4 m are significant and could pose a challenge if trying to mitigate the pressure losses.Adding a booster fan prior to the inlet of the 0.4 m lined borehole would still be a challenge.The corresponding case with a 0.5 m borehole presents much more favourable pressure losses.The 0.5 m diameter lined borehole should be regarded as the lower threshold.The rapid heating of the unlined borehole surface will increase the risk of thermal spallation and possibly imposing restrictions.Understanding the mechanisms during gas delivery will increase the likelihood of a successful inertisation.
基金funded by the National Key R&D Program of China(No.2019YFE0102000)the National Natural Science Foundation of China(Grant No.51476165).
文摘Parabolic trough receiver is a key component to convert solar energy into thermal energy in the parabolic trough solar system.The heat loss of the receiver has an important influence on the thermal efficiency and the operating cost of the power station.In this paper,conduction and radiation heat losses are analyzed respectively to identify the heat loss mechanism of the receiver.A 2-D heat transfer model is established by using the direct simulation Monte Carlo method for rarefied gas flow and heat transfer within the annulus of the receiver to predict the conduction heat loss caused by residual gases.The numerical results conform to the experimental results,and show the temperature of the glass envelope and heat loss for various conditions in detail.The effects of annulus pressure,gas species,temperature of heat transfer fluid,and annulus size on the conduction and radiation heat losses are systematically analyzed.Besides,the main factors that cause heat loss are analyzed,providing a theoretical basis for guiding the improvement of receiver,as well as the operation and maintenance strategy to reduce heat loss.
