Alkali Capacity and Physical Properties of Blast Furnace Type Slags

Alkali compounds, mainly those of Na and K, generally play a negative role in ironmaking blast furnaces. As easily circulating substances they consume energy, disturb furnace operation in the shaft and represent undesired impurities in the discharged slag and dust. An important task is to concentrate the alkalis in the slag as the best possible way. Control and optimisation of BF slag composition with respect to the alkalis requires reliable knowledge of basic data on the thermochemical and physical properties of the various slag compositions in the relevant iron‐slag system and in a wider range of temperatures according to the different reaction zones in the blast furnace. In the present paper, data are critically reviewed on free energies of reaction, the solubilities, bacicities and capacities of alkali oxides as well as on physical properties of alkali‐containing slags such as density, viscosity and surface tension. Furthermore alkali behaviour in primary and secondary BF slags and alkali circulation in the blast furnace are outlined. In a subsequent paper, new data on the chemical activities of alkali oxides in BF type slags and the kinetics and rates of alkali evaporation from these slags will be presented.     

An experimental comparison between LPG and engine exhaust gas as energy source for an absorption refrigeration system

This paper presents an experimental analysis of an absorption refrigeration system, comparing two different energy sources. The exhaust gas from an internal combustion engine was evaluated against the original energy source, liquefied petroleum gas (LPG). The experiments were performed in a domestic refrigerator, monitoring the air temperature and humidity inside the equipment. A production engine was tested with 25% and wide‐open throttle valve (WOT), mounted on a bench dynamometer. The energy demand, cooling capacity and coefficient of performance (COP) were determined for both energy sources. The results showed that engine exhaust gas is a potential source for absorption refrigeration systems. When the engine exhaust gas was used as energy source, the energy available for the refrigerator was higher with 25% throttle valve opening. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental Studies of the Alkali Behaviour in Blast Furnace Type Slags

In a preceding paper, existing data on the chemical behaviour of alkali compounds and their influence on physical properties of BF slags as well as on materials circulation in the BF operations were critically reviewed. In the present work, new investigations based on fundamental experiments and thermochemical modelling are introduced. They have been focused on the determination of both chemical activity of Na₂O and kinetics of Na₂O and K₂O evaporation from BF‐type slags. The results for the activities a_Na2O agree fairly well with data obtained from calculation based on the slag model of H. Gaye which seems generally suitable to predict chemical activities in molten slags. Kinetics of alkali evaporation from BF‐type slags follow a first‐order reaction. The rate constants for K₂O are remarkably higher than those for Na₂O. Alkali evaporation is enhanced with decreased %(CaO)/%(SiO₂) ratio and lower Al₂O₃ content and is increased with temperature. It is further favoured under reducing conditions in the absence of iron oxide in the slag.     

Thermal characterization of a cross-flow heat exchanger with a new flow arrangement

The objective of the present paper is to thermally characterize a cross-flow heat exchanger featuring a new cross-flow arrangement, which may find application in contemporary refrigeration and automobile industries. The new flow arrangement is peculiar in the sense that it possesses two fluid circuits extending in the form of two tube rows, each with two tube lines. To assess the heat exchanger performance, it is compared against that for the standard two-pass counter-cross-flow arrangement. The two-part comparison is based on the thermal effectiveness and the heat exchanger efficiency for several combinations of the heat capacity rate ratio, C¹, and the number of transfer units, NTU. In addition, a third comparison is made in terms of the so-called “heat exchanger reversibility norm” (HERN) through the influence of various parameters such as the inlet temperature ratio, τ, and the heat capacity rate ratio, C¹, for several fixed NTU values. The proposed new flow arrangement delivers higher thermal effectiveness and higher heat exchanger efficiency, resulting in lesser entropy generation over a wide range of C¹ and NTU values. These metrics are quantified with respect to the arrangement widely used in refrigeration industry due to its high effectiveness, namely, the standard two-pass counter-cross-flow heat exchanger. The new flow arrangement seems to be a promising avenue in situations where cross-flow heat exchangers for single-phase fluid have to be used in refrigeration units.     

Mastery, sense of coherence, and mortality: Evidence of independent associations from the epic-norfolk prospective cohort study.

This study investigated the association between 2 distinct personal coping resources (mastery and sense of coherence) and all-cause, cardiovascular, and cancer mortality. During follow-up (up to 6 years), 994 deaths were recorded among 20,323 participants, ages 41 to 80 years, in the European Prospective Investigation into Cancer Study in the United Kingdom. A strong sense of mastery was associated with lower rates of mortality from all causes, cardiovascular disease, and cancer, after adjusting for age, sex, and prevalent chronic physical disease. The association with all-cause mortality was observed for both men and women and remained following further adjustment for cigarette smoking, social class, hostility, neuroticism, and extroversion. Analysis of the joint association between mastery and sense of coherence revealed both personal coping dispositions to be independently associated with lower rates of all-cause mortality. In addition, these data suggested that the association for mastery was specific to cardiovascular mortality, whereas the association for sense of coherence was specific to cancer mortality. These results may aid future study of coping resources as determinants of persistent well-being. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using engine exhaust gas as energy source for an absorption refrigeration system

This work presents an experimental study of an ammonia–water absorption refrigeration system using the exhaust of an internal combustion engine as energy source. The exhaust gas energy availability and the impact of the absorption refrigeration system on engine performance, exhaust emissions, and power economy are evaluated. A production automotive engine was tested in a bench test dynamometer, with the absorption refrigeration system adapted to the exhaust pipe. The engine was tested for 25%, 50%, 75% and wide-open throttle valve. The refrigerator reached a steady state temperature between 4 and 13 °C about 3 h after system start up, depending on engine throttle valve opening. The calculated exhaust gas energy availability suggests the cooling capacity can be highly improved for a dedicated system. Exhaust hydrocarbon emissions were higher when the refrigeration system was installed in the engine exhaust, but carbon monoxide emissions were reduced, while carbon dioxide concentration remained practically unaltered.     

A new approach for thermal performance calculation of cross-flow heat exchangers

A new numerical methodology for thermal performance calculation in cross-flow heat exchangers is developed. Effectiveness-number of transfer units (ε-NTU) data for several standard and complex flow arrangements are obtained using this methodology. The results are validated through comparison with analytical solutions for one-pass cross-flow heat exchangers with one to four rows and with approximate series solution for an unmixed-unmixed heat exchanger, obtaining in all cases very small errors. New effectiveness data for some complex configurations are provided.     

Mastery is associated with cardiovascular disease mortality in men and women at apparently low risk.

Objective: We examine the prospective relationship between mastery, where limited mastery is defined as the inability to control negative emotions (and perceiving stressful experiences as beyond personal control), and cardiovascular disease (CVD) mortality particularly among individuals at apparently low CVD risk. Design: Prospective population-based study of 19,067 men and women, aged 41–80 years with no previous heart disease or stroke at baseline assessment. Main Outcome Measures: Primary outcome measure CVD mortality. Results: A total of 791 CVD deaths were recorded up to June 2009 during a median 11.3 person-years of follow-up. Limited perceived mastery over life circumstances was associated with an increased risk of CVD mortality, independently of biological, lifestyle, and socioeconomic risk factors (hazard ratio 1.11 per SD decrease in mastery score, 95% confidence interval 1.01–1.21). This association was more pronounced among those participants apparently at low CVD risk (p = .01 for test of interaction according to the number of CVD risk factors at baseline). Conclusions: Limited perceived control over life circumstances is associated with an increased risk of CVD mortality, independently of classical cardiovascular risk factors, and particularly among those at apparently low risk. Future attention should be given to this potentially modifiable personal characteristic, through the design of preliminary intervention studies, to reduce cardiovascular risk. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

电容式接近检测技术在汽车电子中的应用

汽车电子应用领域对接近检测传感器的需求一直在稳定攀升,这种传感器无需物理接触,就能够可靠地检测出靠近传感器表面的物体,可应用于:●汽车门禁控制:检测手靠近门把,进而启动开锁程序。●当手掌靠近屏幕表面时,就能照亮和唤醒触摸屏