Calculating Collection Efficiencies for Electrostatic Precipitators

The body of information presented In this paper is directed to those Individuals involved In research on, or the design of, electrostatic precipitators. A model for calculating collection efficiencies— one based solely on physical principles and, as a result, one requiring no prior Information from pilot plant or field testing—has been employed to generate performance curves for twelve Industries presently using electrostatic precipitators. These industries Include the electric power, cement, pulp and paper, steel, chemical, and petroleum industries. The performance curves describe the predicted collection efficiency as a function of preclpltator length, plate-to-plate spacing and average field strength, and are presented In graphical, tabular, and equation form. Wherever literature values for a particular Industry are available, comparisons are made between the collection efficiencies generated by the new model and those based on actual preclpltator performance. The two are generally found to be In reasonable agreement.

The use of the Deufsch-Anderson model for preclpltator design Is also discussed. Results from the new model demonstrate that collection efficiency Is sensitive to particle size distribution, a complication that cannot be easily treated In the Deutsch-Ander-son equation which, In Its unmodified form, requires the use of a single representative particle size. It is concluded that the new model Is potentially a more realistic and viable approach to the prediction of collection efficiencies and as such should prove to be a valuable aid in electrostatic preclpltator design.     

Agricultural landscapes as multi-scale public good and the role of the Common Agricultural Policy

During the last 50 years, the Common Agricultural Policy (CAP) has impacted the evolution of European agricultural landscapes by driving changes in land use and farming practices. We propose a typology characterising the scales relevant for agricultural landscapes management and argue that action is required on three scales: (1) a landscape oriented management at the farm level; (2) the coordination of land managers’ actions at the landscape level; and (3) the conservation of the diversity of agricultural landscapes in the EU. We provide evidence that until now the CAP has mainly focused on the first scale. We also illustrate how agricultural policy could encourage coordinated actions at the landscape- and EU-scales. In particular, we propose policy instruments to coordinate actions of individual land owners (e.g. collective bonus in agro-environmental contracts or support to environmental cooperatives (scale 2)). We also analyse how the recognition and transposition of the European Landscape Convention could promote trans-frontier landscape cooperation in order, not only to conserve high-quality rural landscapes, but also to ensure the conservation of the diversity of EU landscapes (scale 3). This paper provides a knowledge base to support an integrated CAP design in the direction of improved landscape management, as an important component of the EU project towards more sustainable agriculture.     

Driver hand-held cellular phone use: a four-year analysis

INTRODUCTION: The use of hand-held cellular (mobile) phones while driving has stirred more debate, passion, and research than perhaps any other traffic safety issue in the past several years. There is ample research showing that the use of either hand-held or hands-free cellular phones can lead to unsafe driving patterns. Whether or not these performance deficits increase the risk of crash is difficult to establish, but recent studies are beginning to suggest that cellular phone use elevates crash risk. METHODS: The purpose of this study was to assess changes in the rate of hand-held cellular phone use by motor-vehicle drivers on a statewide level in Michigan. This study presents the results of 13 statewide surveys of cellular phone use over a 4-year period. Hand-held cellular phone use data were collected through direct observation while vehicles were stopped at intersections and freeway exit ramps. Data were weighted to be representative of all drivers traveling during daylight hours in Michigan. RESULTS: The study found that driver hand-held cellular phone use has more than doubled between 2001 and 2005, from 2.7% to 5.8%. This change represents an average increase of 0.78 percentage points per year. The 5.8% use rate observed in 2005 means that at any given daylight hour, around 36,550 drivers were conversing on cellular phones while driving on Michigan roadways. The trend line fitted to these data predicts that by the year 2010, driver hand-held cellular phone use will be around 8.6%, or 55,000 drivers at any given daylight hour. CONCLUSIONS: These results make it clear that cellular phone use while driving will continue to be an important traffic safety issue, and highlight the importance of continued attempts to generate new ways of alleviating this potential hazard.     

Causal regulations vs. political will: why human zoonotic infections increase despite precautionary bans on animal antibiotics.

Using precautionary principles when facing incomplete facts and causal conjectures raises the possibility of a Faustian bargain. This paper applies systems dynamics based on previously unavailable data to show how well intended precautionary policies for promoting food safety may backfire unless they are informed by quantitative cause-and-effect models of how animal antibiotics affect animal and human health. We focus on European Union and United States formulations of regulatory precaution and then analyze zoonotic infections in terms of the consequences of relying on political will to justify precautionary bans. We do not attempt a political analysis of these issues; rather, we conduct a regulatory analysis of precautionary legal requirements and use Quantitative Risk Assessment (QRA) to assess a set of policy outcomes. Thirty-seven years ago, the Joint Committee on the Use of Antibiotics in Animal Husbandry and Veterinary Medicine (the Swann Report) warned that uncontrolled use of similar antibiotics in humans and food animals could promote the emergence of resistant strains of foodborne bacteria that could endanger human health. Since then, many countries have either banned or restricted antibiotics as feed additives for promoting animal growth. Others, including the United States, have relied on prudent use guidelines and programs that reduce total microbial loads, rather than focusing exclusively on antibiotic-resistant bacteria. In retrospect, the regulatory strategy of banning or restricting animal antibiotic uses has had limited success: it has been followed in many cases by deteriorating animal health and increases in human illnesses and resistance rates. Conversely, a combination of continued prudent use of antibiotics to prevent and control animal infections, together with HACCP and other improvements, has been followed by large improvements in the microbial safety of chickens and other food animals in the United States, leaving both animals and people better off now than they were decades ago. A quantitative risk assessment model of microbiological risks (Campylobacter because of data availability) suggests that these outcomes may be more than coincidental: prudent use of animal antibiotics may actually improve human health, while bans on animal antibiotics, intended to be precautionary, inadvertently may harm human health.     

Numerical parametric study of a new earth-air heat exchanger configuration designed for hot and arid climates

ABSTRACT

Thermal potential for cooling and heating can be achieved by new configuration of earth–air heat exchanger (EAHE). This paper presents a numerical investigation of thermal performance of a spiral-shaped configuration of EAHE intended for the summer cooling in hot and arid regions of Algeria. A commercial finite volume software (ANSYS FLUENT) has been used to carry out the transient three-dimensional simulations and the obtained results have been validated using the experimental and numerical data obtained from the literature. The agreement between our simulation results and those from literature is very satisfactory. A parametric analysis of the new geometry of (EAHE) has been performed to investigate the effect of pitch, depth, pipe length and of the flow velocity on the outlet air temperature and the EAHE’s mean efficiency as well as its coefficient of performance (COP). It has been shown that when the pitch space varies between 0.2 and 2 m the difference of outlet air temperature increases by 6 ^°C. When the air velocity increases from 2 to 5 m/s the mean efficiency decreases from 60 % to 33 % and the COP of the EAHE decreases from 2.84 to 0.46.