高炉冷却循环水系统由闭路改为开路

介绍了济钢５３、６３高炉软水冷却循环系统。因生产的需要，由闭路循环改为开路循环，并取得了可观的经济效益。     

Microchannel condensation : Correlations and theory

Attention is drawn, to the fact that, while four different correlations for condensation in microchannels are in fair agreement for the case of R134a (on which the empirical constants in the correlations are predominately based) they differ markedly when applied to other fluids such as ammonia. A wholly theoretical model is compared with the correlations for both R134a and ammonia.     

浅析我国海底电缆标准的修订方向

介绍了国内外海底电缆标准的基本情况,提出了未来我国海底电缆标准修订时可增加额定电压66 kV等级海底电缆技术要求、减小绝缘和护层尺寸、“干式”设计和“湿式”设计判定测试、湿式绝缘鉴定试验、腐蚀性能测试、工程特殊和特定测试等要求。     

Performance evaluation indexes for quick-freezers

The idea of evaluating refrigeration equipment and the practical performance evaluation indexes of quick-freezers, namely energy utilisation efficiency, efficiency of airflow organisation, and uniform coefficient of airflow organisation, were suggested to compare the performances and to diagnose the existing problems for freezers. Based on the measurement, the performance evaluation indexes were applied to the performance analysis and the improvement for LSJ1500 spiral quick-freezer, the problem with LSJ1500 spiral quick-freezer was detected and the improved spiral quick-freezer LSJ1500A with the higher performance was achieved. It was proved that the suggested evaluation indexes are the effective tools in the food refrigeration industry.     

Thermal design calculations for food freezing equipment--past, present and future

The literature on methods for thermal design of food freezing equipment is reviewed with emphasis on two questions: what do those who design, build and commission freezers most need from researchers in terms of improved design calculation methods, and what are the most limiting factors in determining whether a particular freezer design will satisfactorily freeze the product at the required throughput rate? Freezing time prediction methods have been significantly improved over the last two decades and are now infrequently the factor most limiting accurate design. There is a much greater need for more accurate thermophysical properties and better information on heat transfer coefficients for a variety of practical situations. The failure of many industrial freezers to deliver the design conditions to product in all parts of the freezer is also important. Future research should address the full range of factors limiting accurate freezer design, which may mean less emphasis on freezing time prediction.

Résumé

La littérature concernant la conception thermique des congélateurs industriels est passée en revue et l'accent est mis sur deux aspects: qu'est ce que les concepteurs, les fabricants et les installateurs attendent le plus des chercheurs en termes d'amélioration des méthodes de calculs de conception, et quels sont les facteurs dans la conception d'un congélateur qui exercent la plus grande influence sur la performance, c'est à dire qui déterminent si une conception donnée va permettre de congeler un produit à la vitesse voulue? Pendant les deux dernières décennies, on a amélioré de façon significative les méthodes qui prédisent le temps de congélation, et de nos jours, ces méthodes sont rarement le facteur qui limite le plus la conception précise. On a nettement plus besoin de précision sur les propriétés thermophysiques et les coefficients de transfert de chaleur pour différentes situations. Il est important de savoir que beaucoup de congélateurs industriels n'arrivent pas à reproduire les performances prévues lors de leur conception en tout point de l'appareil. Dans l'avenir, la recherche devrait être axée sur tous les facteurs limitant la conception précise des congélateurs, quitte à mettre moins l'accent sur la prédiction du temps de congélation.     

三次均匀B样条与α-B样条的扩展

Spline curve and surface play an important role in CAD and computer graphics.In this paper,we propose several extensions of cubic uniform B-spline.Then,we present the ex- tensions of interpolatingα-B-spline based on the new B-splines and the singular blending technique.The advantage of the ex- tensions is that they have global and local shape parameters. Furthermore,we also investigate their applications in data in- terpolation and polygonal shape deformation.     

Effects of shapes of electrodes on freezing of supercooled water in electric freeze control

In order to clarify the effects of electric charge on freezing of supercooled water, experiments were carried out. Two kinds of shapes were used for tips of electrodes. One was the sharp end surface. The other was the flat end surface. Aluminum was selected as the material. Water sample was kept in a test tube and cooled down at a constant cooling rate. When the water sample was maintained under a supercooling state, an electric charge was applied to the water sample with a small electric current. The degree of supercooling and the electric current were measured, continuously. Then the degree of supercooling at freezing was determined. It was found that the effects of electric charge were distinct according to the shapes of electrodes. The degree of supercooling at freezing was the lower in the case of flat end surface of the anode than that in the case of sharp end surface of the anode.     

The effect of salt concentration on the freezing point of meat simulants

Accurate data on the initial freezing point of cured meat is required to predict freezing rates or identify optimal slicing temperatures. However, little data was found in the literature. Experiments were therefore carried out using the ‘Karlsruhe test substance’ (‘Tylose’) with varying salt concentrations as a cured meat substitute. Initial freezing points were −1.4, −3.1, −4.1, −5.2 and −6.3 °C at salt contents of 0.5, 2, 3, 4 and 5 kg salt/100 kg sample, respectively. These values were within ±0.5 °C of published values for cured pork and within ±0.9 °C of theoretical predictions. Modifying the salt content of Tylose is therefore a simple way of determining the initial freezing point of cured lean meats, and Tylose modified in this way can be used to simulate the freezing of cured meat.     

Transfert de matière et chute de pression lors d'un écoulement tourbillonnaire annulaire non-entretenu induit par une entrée tangentielle

This work is devoted to an experimental study of overall mass transfer and pressure in decaying swirlng annular flow induced by means of a tangential inlet. Overall mass transfer coefficients, obtained using an electrochemcal method, are found to be greater on the outer cylinder that on the inner core of the annulus, and remains largely greater than that obtained in fully developed axial flow on both cylinders. This enhancement in mass transfer rate is coupled with an increase in pressure drop, mainly due to the tangential inlet of the fluid. Nevertheless, an energetic correlation of overall mass transfer on both cylinders of the annular cell shows that decaying swirling flow induced by a single tangential inlet allows an important increase in mass transfer coefficients for a given energy consumption, compared with a fully developed annular axial flow.