1,720,969 research outputs found
Protection systems for tanks containing hazardous materials exposed to fire
Full text linkThe catastrophic failure of a tank containing a pressure liquefied gas often gives rise to a physical explosion with serious consequences for the possibly exposed people and structures. In fact, the liquid is at a temperature higher than its boiling temperature at atmospheric pressure, and, once released, it will instantaneously vaporize, with the generation of a shock wave. If the involved chemical is also hazardous (flammable or toxic), additional consequences are also expected (fires or toxic cloud dispersion), so that it is important to prevent the occurrence of this phenomenon as far as possible. Few studies are available in the literature to analyze the dynamics of this scenario, and, given the complexity of setting up experimental facilities, mainly theoretical approaches have been adopted, though some useful experimental results are also reported. The models proposed over the years allow to calculating the trend of the main parameters involved in the accident, but, in most cases, reference to a bare vessel has been made, while less attention has been devoted to assess the influence of protection systems, such as thermal insulation or pressure relief devices. In the present paper, a number of reference scenarios have been simulated involving both unprotected and protected systems, and the results have been analyzed and compared, to identify a proper strategy capable of significantly reducing the probability of failure of the tank
Thermal model of cylindrical lithium-ion batteries
Full text linkDue to their characteristic of providing high energy density and long cycle life, Li-ion batteries are being widely used as power sources for a range of applications, including electric vehicles. The temperature of a Li-ion cell is important for its performance, capacity, efficiency and safety, and it is strongly influenced by the charging and discharging process modalities. Especially during electric vehicle operation, considerable heat is generated in the battery pack that needs to be removed. In the present paper a simplified model for predicting the temperature trend within a battery module with cylindrical cells, is presented. This allows to estimate the requirements for a given cooling system under specific discharge conditions. Three cooling fluids have also been experimentally compared: air, a dielectric oil and a perfluorinated polyether. The best performance was shown by a commercial perfluorinated polyether, by which it was possible to work in safe conditions with a very low pumping power: at 0.02 W, a maximum temperature of 48°C is reached at the end of the discharge using Galden HT135, while 55°C is reached with the Midel ICE. The results also showed that, under the assumed conditions, an air-cooling system needs between 100 and 1700 times more energy than the other methods to keep the same average temperature
Development of a process for n-butanol recovery from ABE wastewater streams by membrane technology
Full text linkThe aceton-butyl-ethanolic fermentation process (ABE) is a biotechnological process that leads to the production of acetone, n-butanol and ethanol (ABE compounds) from glucose sources and amides by use of certain biomasses. The process was developed initially during the middle of the last century and suffers from decline due to the greater petrochemical production of products and the lowering of the costs of the sector. Nowadays, the ABE process is regaining great interest because the fraction with the highest concentration, i.e. n-butanol, is an excellent constituent for biofuels. The ABE process has been optimized over time to obtain maximum yields of n-butanol, but the problem of separating and concentrating the butanol in the outlet stream of the ABE process persists. To allow an adequate use, often distillation by use of more columns is required. Moreover, the contained biomasses and suspended solids, in high quantity, must be eliminated, leading to overall high treatment costs. This work will report the main idea and some preliminary experimental results for the development and application of a process based on membrane technologies, to separate and concentrate the butanol from ABE process streams to sensibly reduce the difficulty to perform a final distillation. The proposed treatment process is composed by ultrafiltration, pervaporation, nanofiltration and a final mixing/demixing operation. Attention was paid to the productivity, selectivity and longevity of the used membranes. The optimization of these three parameters is essential to achieve a level of reliability and feasibility of the proposed process, in particular the avoidance of membrane fouling
A simplified model for improving thermal stability of Lithium-ion batteries
Full text linkLithium ion batteries represent a well established technology in a range of applications (laptops, mobile phones, etc.) but they are becoming key factors in many other areas were reliability and safety are of paramount importance (e.g. the space and automobile industries). However, a number of drawbacks still raise concerns about their wider use and hamper a more structured introduction in these additional applications. In particular, the management of heat effects remains a challenge, as an excessive temperature rise can cause reduction of cycle life, battery failures and, above all, may lead to thermal runaway of individual cells or of an entire battery pack, with associated damages to the surrounding people or environment. In the present paper, a simplified model capable of predicting the thermal behaviour of a battery pack refrigerated with a cooling fluid, is presented. It allows to quickly estimating the efficiency of a given cooling system under specific working conditions, and thus identify the range of operation within which a given energy storage system can safely operate
Thermal management of lithium-ion batteries: An experimental investigation
No full textThis paper describes a set of experimental tests carried out to better understand the thermal behavior of Lithium-ion batteries under load and the capability of various cooling fluids in maintaining the working conditions within a safe range for the cells. Despite several theoretical models are available in the literature, very few experimental data are reported. Different types of cells have been analyzed. The generation of hot spots has sometimes been registered, their occurrence being independent of cell geometry and size; instead, the battery's history and age, appeared the main factors in determining the onset of hot spots on the surface of the cell. Two experimental rigs have been set up to test the capability of different cooling fluids in removing the surplus heat generated in a Li-ion battery module, where the cells of interest have been replaced with electrically heated elements with the same thermal characteristics of the cells. It was thus possible to safely investigate “extreme” operating conditions, where the occurrence of a thermal runaway is possible. Among the tested fluids, air was unable to adequately limit the surface temperature increase, while a perfluorinated polyether, allowed to work within the optimal temperature range, even under severe operating conditions
Analisi della sicurezza nel trasporto di merci pericolose via strada e ferrovia in Sicilia
No full textRisk management of road and rail transport of hazardous materials in Sicily
No full textA Transportation Risk Analysis (TRA) tool has been used to accurately assess the risk associated to a variety of road and rail transportation cases representative of hazardous materials transport by land in Sicily. Due to the high risk level, some risk mitigation options have been investigated: the possibility of changing route and/or transport modalities have been examined for each transportation activity, all the combinations of road, rail and intermodal (roadCrail) transport have been calculated and that minimising the risk has been identified with the aid of the TRA tool
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
