Masse du fluide frigorigène dans un évaporateur en fonctionnement permanent ou transitoire: Refrigerant mass inside an evaporator in a steady or non-steady state

The present study was undertaken to achieve an experimental determination of the refrigerant mass inside an evaporator of a refrigerating machine operating under steady or non-steady conditions. The mass was measured during the steady regime over a wide range of operating conditions and the mass variations were evaluated during steps of the expansion valve. From the results of the laboratory experiments, a correlation of the refrigerant mass variation is proposed, taking into account the compressor variable-speed and the vaporization temperature. An analysis of the results is presented and a theoretical method for predicting the refrigerant mass in the evaporator is proposed.     

Direct-Contact Heat Transfer during n-Pentane Vaporization in a Two-Dimensional Water Column

Direct-contact vaporization heat transfer is investigated by analyzing the heat transfer coefficient with the area of liquid-liquid direct-contact interface. The interface areas of liquid-liquid heat transfer are determined by stroboscopic images. At higher temperature, the heat transfer area per unit volume decreases. The water temperature has no significant influence on the heat transfer coefficient. The effects on droplet size distributions of operating variables including inlet water temperature, n-pentane flow rate, and test position with packing and without packing are compared.     

Vaporization and condensation in the Al4C3-SiC system

Al₄SiC₄ is a refractory ceramic with a reported band gap of about 2.5 eV, making it an interesting semiconductor material for various applications in the field of energy. However, the synthesis of Al₄SiC₄ single crystals has so far not been investigated. In this study, the sublimation growth method is explored as a potential route for getting high quality single crystals. Combining a thermodynamic analysis with an extensive experimental approach, the vaporization and condensation phenomena in the Al₄C₃ – SiC system are described. Experimental conditions, such as initial composition, baking temperature and temperature gradient, are investigated and demonstrated regarding the crystallization of Al₄SiC₄. From the results obtained, a condensed phase diagram at equilibrium is established for the molar fraction X_{Al4C3/(Al4C3+SiC)} < 0.5, which corresponds to the suitable condition for the Al₄SiC₄ condensation. Indeed, Al₄SiC₄ single phase could be experimentally condensed either by self-nucleation or as oriented film on SiC substrates.     

大型低温液体贮存站贮罐设计选型论证(续)

运用热力学第一定律对低温液体在贮存、运输转注过程中的热力学特性进行了分析,定量分析、计算了低温液体节流过程的节流汽化率值,提出了减少节流过程所形成的汽化率的有效途径;论证了在大型低温液体贮存站贮罐设计选型时,应根据不同的低温液体液源、液体品质和操作工况等条件进行设计选型;论证了除合理地选择正确的低温液体贮罐结构形式外,还应高度重视低温液体贮罐的安全泄放设计,以确保低温液体贮存站的安全性能、使用性能和技术经济性能均处于最佳状态。     

废钢中锌蒸发的研究

叙述了钢铁脱锌的基本原理及其方法,给风蒸发脱锌的试验装置,提供了分别在Ｎ２、ＣＯ、ＣＯ２和ＣＯ＋ＣＯ２气氛中不同温度条件下锌蒸发的试验结果。     

ON THE PREDICTION OF HEATS OF VAPORIZATION OF PURE COMPOUNDS

An expression to predict the values of the latent heat of vaporization of pure compounds at their normal boiling point has been developed. A knowledge of the critical temperature, critical pressure, normal boiling point and acentric factor of the compound coupled with the use of generalized correlations for second virial coefficient and liquid molar volume allows to obtain good estimates, particularly for alcohols and ketones. Results for 71 various substances are compared with experimental values and with the results of eight other equations available in the literature. The possibility of using the calculated heats of vaporization at the normal boiling point to estimate values at other temperatures is discussed.     

MICROWAVE VACUUM DRYING OF POROUS MEDIA: VERIFICATION OF A SEMI-EMPIRICAL FORMULATION OF THE TOTAL ABSORBED POWER

Vacuum drying experiments were performed on a laboratory scale dryer with two porous materials: a packing of initially saturated glass beads and of unsaturated pharmaceutical granules. Several incident powers and two vacuum pressure levels were tested in order to demonstrate different drying mechanisms. The drying kinetics, temperature of the product and the absorbed power are presented and the coupling between the drying rate and the absorbed power is shown. A semi-empirical formulation of the total absorbed power is proposed taking into account the water content, the temperature and the dielectric properties of each phase. This formulation is based on a quasi-static assumption which allows the local electric field inside the material to be expressed with an analytical equation.     

Thermodynamic study of the CsCl–CeCl3 system by Knudsen effusion mass spectrometry

The vaporization of samples of different chemical and phase compositions covering the complete concentration range of the CsCl–CeCl₃ system was investigated in the temperature range between 749 K and 1098 K by the use of Knudsen effusion mass spectrometry. The gaseous species CsCl, Cs₂Cl₂, CeCl₃, Ce₂Cl₆ and CsCeCl₄ were identified in the vapor and their partial pressures determined. The thermodynamic stability of CsCeCl₄(g) was evaluated by second law treatment of the equilibrium partial pressures. The thermodynamic activities of CsCl and CeCl₃ were obtained at 950 K in the two phase fields {liquid+Cs₃CeCl₆(s)} and {CsCe₂Cl₇(s)+CeCl₃(s)} from the partial pressures of the vapor components. The Gibbs free energies of formation from the constituent halides of the pseudobinary phases Cs₃CeCl₆(s) and CsCe₂Cl₇(s) were evaluated from the thermodynamic activities of the components. The results are discussed with other literature data for the studied system.     

Boil off gas (BOG) management in Spanish liquid natural gas (LNG) terminals

Spain is a country with six LNG terminals in operation and three more scheduled for 2011. At the same time an increasing number of LNG tanks are under construction to compensate the Spanish lack of underground storage. A method for evaluating the daily boil off generated is presented in this paper. This method is applied to evaluate the increase of BOG to be handle by LNG terminals in 2016, studying the best commercially available solution to be installed. Finally, as a solution to tackle with the BOG a cogeneration plant is suggested. This option will reduce terminal’s operational costs increasing its availability.     

三效顺流部分强制循环蒸发装置

介绍了辽河集团氯碱厂三效顺流部分强制循环蒸发装置原设计中的不足之处 ,以及通过技术改造和加强生产管理而使装置达到设计能力的过程。