Two-phase fluid properties such as entropy, internal energy, and heat capacity are given by thermodynamically defined fit functions. Each fit function is expressed as a temperature function in terms of a power series ...Two-phase fluid properties such as entropy, internal energy, and heat capacity are given by thermodynamically defined fit functions. Each fit function is expressed as a temperature function in terms of a power series expansion about the critical point. The leading term with the critical exponent dominates the temperature variation between the critical and triple points. With β being introduced as the critical exponent for the difference between liquid and vapor densities, it is shown that the critical exponent of each fit function depends (if at all) on β. In particular, the critical exponent of the reciprocal heat capacity c﹣1 is α=1-2β and those of the entropy s and internal energy u are?2β, while that of the reciprocal isothermal compressibility?κ﹣1T is γ=1. It is thus found that in the case of the two-phase fluid the Rushbrooke equation conjectured α +?2β + γ=2 combines the scaling laws resulting from the two relations c=du/dT and?κT=dlnρ/dp. In the context with c, the second temperature derivatives of the chemical potential μ and vapor pressure p are investigated. As the critical point is approached, ﹣d2μ/dT2 diverges as c, while?d2p/dT2 converges to a finite limit. This is explicitly pointed out for the two-phase fluid, water (with β=0.3155). The positive and almost vanishing internal energy of the one-phase fluid at temperatures above and close to the critical point causes conditions for large long-wavelength density fluctuations, which are observed as critical opalescence. For negative values of the internal energy, i.e. the two-phase fluid below the critical point, there are only microscopic density fluctuations. Similar critical phenomena occur when cooling a dilute gas to its Bose-Einstein condensate.展开更多
pVT data for R22 and propylene around critical region were obtained through a AntonPaar DMT-512 oscillator densimeter.Vapor pressures in the corresponding region as well as criticalpressures and densities were also de...pVT data for R22 and propylene around critical region were obtained through a AntonPaar DMT-512 oscillator densimeter.Vapor pressures in the corresponding region as well as criticalpressures and densities were also determined based on the pVT data measured.展开更多
Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between...Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between the change of Ga content and melting time was determined. The results demonstrated that saturated vapor pressure of Ga was higher than that of Fe under the same conditions. The difference value of critical evaporation temperature of Ga with and without Ar was nearly 800 K. The critical evaporation temperature of Fe was higher than that of Ga under vacuum, indicating that Ga was more volatile than Fe. At 1800 K, the evaporation rate of Ga was 84 times higher than that of Fe in the melt of Fe81Ga19 alloy. Under this condition, the change of Ga content and smelting time kept a linear relationship. The higher the temperature was, the faster the Ga content decreased, which was consistent with theoretical calculations.展开更多
热物理学一直是物理学的非常重要的分支。随着1869年临界点的发现,显示出了理想气体模型的局限。为解释这一重要物理现象,理论物理学家van der Waals于1873年提出了vander Waals模型,这标志了平均场理论的首次引入。然而,随着实验技术...热物理学一直是物理学的非常重要的分支。随着1869年临界点的发现,显示出了理想气体模型的局限。为解释这一重要物理现象,理论物理学家van der Waals于1873年提出了vander Waals模型,这标志了平均场理论的首次引入。然而,随着实验技术的提高,发现了平均场理论给出的临界指数与实验结果相矛盾。随后引入了与实验一致的普适性与标度假定这两个突破了平均场理论框架的物理概念。这导致了理论物理学家Wilson于1972年提出了临界重整化群理论。目前,基于临界重整化群理论用简单普适的物理数学方法跨接描述流体的经典热力规律与奇异性物理规律,已为国际热物理界所关注。作者在读博士学位期间。展开更多
文摘Two-phase fluid properties such as entropy, internal energy, and heat capacity are given by thermodynamically defined fit functions. Each fit function is expressed as a temperature function in terms of a power series expansion about the critical point. The leading term with the critical exponent dominates the temperature variation between the critical and triple points. With β being introduced as the critical exponent for the difference between liquid and vapor densities, it is shown that the critical exponent of each fit function depends (if at all) on β. In particular, the critical exponent of the reciprocal heat capacity c﹣1 is α=1-2β and those of the entropy s and internal energy u are?2β, while that of the reciprocal isothermal compressibility?κ﹣1T is γ=1. It is thus found that in the case of the two-phase fluid the Rushbrooke equation conjectured α +?2β + γ=2 combines the scaling laws resulting from the two relations c=du/dT and?κT=dlnρ/dp. In the context with c, the second temperature derivatives of the chemical potential μ and vapor pressure p are investigated. As the critical point is approached, ﹣d2μ/dT2 diverges as c, while?d2p/dT2 converges to a finite limit. This is explicitly pointed out for the two-phase fluid, water (with β=0.3155). The positive and almost vanishing internal energy of the one-phase fluid at temperatures above and close to the critical point causes conditions for large long-wavelength density fluctuations, which are observed as critical opalescence. For negative values of the internal energy, i.e. the two-phase fluid below the critical point, there are only microscopic density fluctuations. Similar critical phenomena occur when cooling a dilute gas to its Bose-Einstein condensate.
文摘pVT data for R22 and propylene around critical region were obtained through a AntonPaar DMT-512 oscillator densimeter.Vapor pressures in the corresponding region as well as criticalpressures and densities were also determined based on the pVT data measured.
基金Item Sponsored by National Natural Science Foundation of China(51161019)Project of Department of Science and Technology of Jiangxi Province of China(20133BBE50011)Project of Department of Science & Technology of Jiangxi Province of China(20141BDH80025)
文摘Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between the change of Ga content and melting time was determined. The results demonstrated that saturated vapor pressure of Ga was higher than that of Fe under the same conditions. The difference value of critical evaporation temperature of Ga with and without Ar was nearly 800 K. The critical evaporation temperature of Fe was higher than that of Ga under vacuum, indicating that Ga was more volatile than Fe. At 1800 K, the evaporation rate of Ga was 84 times higher than that of Fe in the melt of Fe81Ga19 alloy. Under this condition, the change of Ga content and smelting time kept a linear relationship. The higher the temperature was, the faster the Ga content decreased, which was consistent with theoretical calculations.
文摘热物理学一直是物理学的非常重要的分支。随着1869年临界点的发现,显示出了理想气体模型的局限。为解释这一重要物理现象,理论物理学家van der Waals于1873年提出了vander Waals模型,这标志了平均场理论的首次引入。然而,随着实验技术的提高,发现了平均场理论给出的临界指数与实验结果相矛盾。随后引入了与实验一致的普适性与标度假定这两个突破了平均场理论框架的物理概念。这导致了理论物理学家Wilson于1972年提出了临界重整化群理论。目前,基于临界重整化群理论用简单普适的物理数学方法跨接描述流体的经典热力规律与奇异性物理规律,已为国际热物理界所关注。作者在读博士学位期间。
