Wet compression is an effective way to enhance the performance of gas turbines and it has attracted a good deal of attention in recent years. The one sidedness and inaccuracy of previous studies,which took concentrati...Wet compression is an effective way to enhance the performance of gas turbines and it has attracted a good deal of attention in recent years. The one sidedness and inaccuracy of previous studies,which took concentration gradient as mass transfer potential are discussed. The mass transfer process is analyzed from the viewpoint of non equilibrium thermodynamics,by taking generalized thermodynamic driving force as mass transfer potential,and the corresponding mass transfer coefficient is obtained using the heat and mass transfer equilibrium occurring between moist air and water droplets at wet bulb temperature for the sake of avoiding complex tests and providing more accurate formulas. A mathematical model of wet compression is therefore established,and the general laws of wet compression are investigated. The results show that the performance of atomizer is critical for wet compression and wet compression is more suitable for compressors with higher pressure ratio and longer compression time.展开更多
报告了自行研制的质子转移反应质谱(Proton Transfer Reaction Mass Spectrometry,PTR-MS)装置结合动态气体提取技术直接测量水中苯浓度的新方法。N2连续地将水溶液中的苯提取出来,用质子转移反应质谱测量其在液面顶空中的分压强P随时...报告了自行研制的质子转移反应质谱(Proton Transfer Reaction Mass Spectrometry,PTR-MS)装置结合动态气体提取技术直接测量水中苯浓度的新方法。N2连续地将水溶液中的苯提取出来,用质子转移反应质谱测量其在液面顶空中的分压强P随时间的变化关系,从而得到苯的亨利常数H利用亨利定律就可以给出苯在水溶液中的浓度。考察了苯在提取气体及水溶液中达到平衡需要的液面高度,测量了28℃时苯的亨利常数。以此为基础测试了水中苯的浓度,测量结果与配制的溶液浓度相一致。PTR-MS结合动态气体提取技术测量水中苯的浓度,检出限为1μg/L。方法可以拓展到水中其它挥发性有机物浓度的测量。展开更多
A class of one-way isothermal mass transfer processes with Fick’s diffusive mass transfer law[g ∝Δ(c)]is investigated in this paper.Based on the definition of the mass entransy,the entransy dissipation function whi...A class of one-way isothermal mass transfer processes with Fick’s diffusive mass transfer law[g ∝Δ(c)]is investigated in this paper.Based on the definition of the mass entransy,the entransy dissipation function which reflects the irreversibility of mass transfer ability loss is derived.The optimal concentration allocations of the key components corresponding to the highand low-concentration sides for the minimum entransy dissipation of the mass transfer process are obtained by applying opti- mal control theory and compared with the strategies of the minimum entropy generation,constant mass transfer flux(constant concentration difference),and constant concentration ratio(constant chemical potential difference).The results are as follows. For the optimal mass transfer strategy of the minimum entransy dissipation,the product of the square of the key component concentration difference between the high-and the low-concentration sides and the inert component concentration at the low-concentration side is a constant,while for that of the minimum entropy generation,the ratio of the square of the key com-ponent concentration difference between the high-and the low-concentration sides to the key component concentration at the low-concentration side is a constant;when the mass transfer process is not involved in energy conversion process,the optimi-zation principle should be the minimum entransy dissipation;the mass transfer strategy of constant concentration difference is superior to that of constant concentration ratio.The results obtained in this paper can provide some theoretical guidelines for optimal designs and operations of practical mass transfer processes.展开更多
文摘Wet compression is an effective way to enhance the performance of gas turbines and it has attracted a good deal of attention in recent years. The one sidedness and inaccuracy of previous studies,which took concentration gradient as mass transfer potential are discussed. The mass transfer process is analyzed from the viewpoint of non equilibrium thermodynamics,by taking generalized thermodynamic driving force as mass transfer potential,and the corresponding mass transfer coefficient is obtained using the heat and mass transfer equilibrium occurring between moist air and water droplets at wet bulb temperature for the sake of avoiding complex tests and providing more accurate formulas. A mathematical model of wet compression is therefore established,and the general laws of wet compression are investigated. The results show that the performance of atomizer is critical for wet compression and wet compression is more suitable for compressors with higher pressure ratio and longer compression time.
文摘报告了自行研制的质子转移反应质谱(Proton Transfer Reaction Mass Spectrometry,PTR-MS)装置结合动态气体提取技术直接测量水中苯浓度的新方法。N2连续地将水溶液中的苯提取出来,用质子转移反应质谱测量其在液面顶空中的分压强P随时间的变化关系,从而得到苯的亨利常数H利用亨利定律就可以给出苯在水溶液中的浓度。考察了苯在提取气体及水溶液中达到平衡需要的液面高度,测量了28℃时苯的亨利常数。以此为基础测试了水中苯的浓度,测量结果与配制的溶液浓度相一致。PTR-MS结合动态气体提取技术测量水中苯的浓度,检出限为1μg/L。方法可以拓展到水中其它挥发性有机物浓度的测量。
基金supported by the National Natural Science Foundation of China(Grant No.10905093)the Program for New Century Excellent Talents in University of China(Grant No.NCET-04-1006)the Foun-dation for the Author of National Excellent Doctoral Dissertation of China(Grant No.200136)
文摘A class of one-way isothermal mass transfer processes with Fick’s diffusive mass transfer law[g ∝Δ(c)]is investigated in this paper.Based on the definition of the mass entransy,the entransy dissipation function which reflects the irreversibility of mass transfer ability loss is derived.The optimal concentration allocations of the key components corresponding to the highand low-concentration sides for the minimum entransy dissipation of the mass transfer process are obtained by applying opti- mal control theory and compared with the strategies of the minimum entropy generation,constant mass transfer flux(constant concentration difference),and constant concentration ratio(constant chemical potential difference).The results are as follows. For the optimal mass transfer strategy of the minimum entransy dissipation,the product of the square of the key component concentration difference between the high-and the low-concentration sides and the inert component concentration at the low-concentration side is a constant,while for that of the minimum entropy generation,the ratio of the square of the key com-ponent concentration difference between the high-and the low-concentration sides to the key component concentration at the low-concentration side is a constant;when the mass transfer process is not involved in energy conversion process,the optimi-zation principle should be the minimum entransy dissipation;the mass transfer strategy of constant concentration difference is superior to that of constant concentration ratio.The results obtained in this paper can provide some theoretical guidelines for optimal designs and operations of practical mass transfer processes.
