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The Chen (Ind. Eng. Chem. Process Des. Dev., 1966, 5(3): 322–329) correlation of saturated flow boiling heat transfer is one of the most influential flow boiling heat transfer correlations. It adopted the additive concept and incorporated the Reynolds number factor F and the suppression factor S. Chen presented F and S as the best-fit curves without any parametric equation. However, the parametric equations of F and S were widely used in citing the Chen work, among which some were not accurate, and some had typos in the original sources and then used by others. The objective of this paper is to point out the incorrect and inaccurate equations in the literature. For this purpose, the existing expressions of F and S in the available literature are presented and compared with the Chen best-fit curves. The work provides a reference for the correct use of the Chen correlation. 相似文献
3.
In this study, the effect of ultrasound irradiation temperature and ultrasound intensity on the freezing and nucleation in strawberry samples was studied. The application of ultrasound irradiation at different temperatures was able to induce nucleation at lower degree of supercooling compared to the control samples. The achieved degree of supercooling in the ultrasound irradiated strawberries was linearly correlated to the ultrasound irradiation temperature. At the ultrasound irradiation temperature of −1.6 °C, the characteristic freezing time (CFT) was significantly shorter than that in the control sample (p < 0.05). The application of ultrasound at higher intensities was found to effectively shorten the CFT. The degree of supercooling in ultrasound irradiated samples was not linearly correlated to ultrasound intensity. In conclusion, the combination of ultrasound irradiation temperature and intensity can be effective in controlling nucleation and freezing processes of perishable fruits such as strawberry. 相似文献
4.
A flow boiling heat transfer model for horizontal tubes is proposed for CO2 with entrained polyalkylene glycol (PAG) type lubricating oil in the pre-dryout region. A general power law-type model with a power number of 3 is used together with the average thermodynamic properties of the CO2–oil mixture. A convective enhancement factor (F) is recommended according to the relationship between the Lockhart–Martinelli parameter and the ratio αtp/αl, which was obtained based on previous experimental results for CO2 and oil. A new suppression factor (S) is introduced that comprises a suppression term for forced convection and oil concentration term for bubble generation. A comparison of six correlations showed that the proposed correlation can depict the influence of the mass and heat fluxes on both nucleate and convection boiling reasonably well. 相似文献
5.
A first-principles model for predicting the evolution of the porosity of a frost layer over time was advanced. The theoretical model was used together with experimental data obtained elsewhere to put forward a semi-empirical correlation for the frost density as a function of the time, and the modified Jakob number, which carries information about the thermodynamic conditions of the air stream and the chilled surface. When compared to experimental data, the proposed correlation showed errors within ±10% bounds. Comparisons with other frost density correlations available in the open literature are also reported. 相似文献
6.
Experimental results of local heat transfer coefficients for the boiling of working fluids (solutions of R600a with mineral naphthenic oil ISO VG 15) in a smooth tube with a small diameter (5.4 mm) are presented. The experiments have been performed in the following ranges: for the inlet pressure from 65.7 kPa to 82.2 kPa, for the heat flux from 2500 to 3300 W m−2, and for the mass velocity of the working fluid from 11.90 to 15.99 kg m−2 s−1). The quantitative estimation in reduction of the heat transfer coefficient of the wetted surface in the evaporator at a high oil concentration in the mixture is examined. The influence of heat flux and mass velocities on the values of the local heat transfer coefficients is analyzed. The equation for the modelling of the local heat transfer coefficient for boiling of an isobutane/compressor oil solution flow in the tube is suggested. 相似文献
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������ֵģ��ĸ��ӵز����ƻ������о� 总被引:19,自引:7,他引:12
分析和评述了从30年代以来国内外关于复杂地层套管破坏机理研究的发展过程和动态,提出目前尚未解决的问题就是“复杂空间力学系统地层”与套管破坏的各种耦合的数学、力学问题。因此提出首先要解决复杂地层数学模型、力学模型、以及地层与水泥环及套管之间的力学耦合问题,并且必须研究复杂地层遇水膨胀、地层滑动、地层蠕动、地表地层升降使套管破坏与地应力场状态关系,根据复杂地层套管破坏井段地质构造图、地震资料、测井资料及套管破坏特征,反演出整个研究地层区块现代地应力场。同时提出了用计算机数值模拟技术为主要研究手段及对现代地应力场的研究是今后复杂地层套管坏机理与预防措施研究的发展方向。该研究是一门综合性的、学科间大跨度交叉的边缘学科研究,将对地应力理论和推动地球科学、数理科学的发展具有重大的科学意义。 相似文献
10.
P.D Sanz L Otero C de Elvira J.A Carrasco 《International Journal of Refrigeration》1997,20(5):301-307
Experimental freezing of water in high-pressure domain is studied considering temperature reduction (TRF) as well as high-pressure-assisted freezing (HPAF). The most important advantage of HPAF is that the whole volume of the sample is subcooled when an expansion is made, so a rapid and uniform nucleation and growth of ice crystals are produced. In this work through mathematical modelling the amount of ice appearing instantaneously in the latter freezing, is predicted. 相似文献