Predicting evaporation rates from pools

A number of simplified approaches, based on semi-empirical models and algebraic formulas, often derived from the correlation of experimental data, are available to predict the evaporation rate of chemicals from pools. In this work they are compared, based on their performances in estimating the evaporation rates determined in some sets of experiments reported in the literature, involving different chemicals, pool geometries, wind velocities, etc. Generally, the models predict correctly the data used in the fitting to determine their own parameters, but most of them fail when applied to other data sets. No model appear capable of predicting all the available sets of literature data with errors within  30%: nevertheless, some models application guidelines can be derived. In particular, the model of Heymes et al. (2013), provides reasonable estimates of the evaporation rates of a variety of compounds in rather different operating conditions, for wind speed exceeding 1 m/s, while the simple model of Mackay and Wesembeeck (2014) should be preferred in the absence of ventilation. Other models, such as those of Hummel et al. (1996), Stiver and Mackay (1996) and EPA (1999) can be applied within proper intervals of wind speed, molecular weight and vapour pressure of the chemical

Calculation of the flame size from burning liquid pools

The calculation of the consequences associated with a pool fire consists in a stepwise procedure where a number of parameters must be characterized, which depend on the geometrical size and shape of the flame. A number of calculation models exists in the literature, characterized by different levels of accuracy and complexity. In the present work we will focus on the characterization of the geometrical configuration of the flame generated from a pool fire: some of the most commonly adopted models will be shortly recalled, and compared against experimental data taken from the literature. It is expected that this would provide useful information about the range of applicability and the level of accuracy of these models. Also, it will help improve the quality of the results, and reduce the time required for carrying out important applications such as consequence assessment and risk analysis, where a large number of calculations must be run

Risk Assessment of Mildly Flammable Refrigerants with los GWP for Heat pump

Given the growing demand for cooling, and taking into account the impact of global warming associated with cooling technologies the global climate commitment to reduce the impact of fluorinated gases and the regulations controlling their use in the European Union has increased . This thesis investigates new refrigerants that have been recently proposed to meet the demands of the heat pumps in the refrigeration industry, which must satisfy the legislative requirements of the F-gas Regulation and facilitate meeting the goals of Montreal and Kyoto Agreement.The fluids R32, R1234ze, R1234yF, R452b and R454b have been theoretically analyzed in comparison with the commonly used fluorinated refrigerant in heat pump: R410A. To compare these refrigerants, an excel sheet has been used to calculate the COP for the different cases studied using the REFPROP computer program to know the thermodynamic data of each fluid. The cases studied are the three different heat pump applications : radiators, radiant floor and fan coil and it has been studied for an evaporator temperature range of -15 to 12 ºC, i.e. the COP has been calculated for eighteen different situations. For all of them, the same conclusion has been concluded: all these five proposed fluids have a higher COP than the fluid to be replaced, R410A. It based on this COP for all the cases studied, the best fluids are R454b and R1234Ze(E). Choosing the fluid R454b as the best alternative because its latent heat and vapour density are higher that R1234ze(E) and therefore the flow and size of the pump is smaller, which generally translates into economic savings.However, this refrigerant shows flammability characteristics. For this reason, this paper is checked the fluid risk by a risk assessment. For this assessment two scenarios are analyzed by numerical model, Plume Model: outside and inside of 20 m2 scenario using a 50 kW heat pump. Concluding on the one hand, that in outside conditions a leak would not enter ignition due to the concentration obtained is less than the minimum necessary. In addition from 200 meters of distance the concentration of this fluid would be zero.And that in the hypothetical case that a jet fire takes place is observed that from 10 meters of the leak there is no more radiation.On the other hand, for the room scenario the calculated concentration would be 550 g/m3. This concentration is higher than the acute toxicity exposure limit (435 g/m3) so it is not safe for a human being to work in the situations described.<br /

Comparison of the heat transfer efficiency of nanofluids

The continuously increasing power involved in many applications, coupled with the very small size of a number of component devices, is pushing the technical community to look for more efficient heat transfer systems, to remove the heat generated and keep the system under controlled operating conditions. In particular, significant interest has been devoted to the use of the so-called nanofluids, obtained by suspending nano-sized particles in conventional heat transfer liquids. According to some literature, these suspensions present enhanced heat transfer capabilities, without the inconveniencies of particles settlement and clogging of the channels encountered using larger particles. However, other results show that the actual improvement in the heat transfer efficiency may depend on the adopted working conditions and on the reference parameters (fluid velocity, Reynolds number, pressure drop, etc.) assumed to compare the performances of the nanoparticles suspensions with those of the clear thermal fluid. In the present work heat transfer experiments were carried out on a number of nanofluids systems, varying the type and the concentration of the nanoparticles, and the fluid dynamic regime. The investigated suspensions gave rise to heat transfer coefficients different from those of their respective clear thermal fluid, the thermal efficiency being higher or lower, depending on the fluid dynamic parameter used as a base for comparing the systems. Generally speaking, in most cases nanofluids may give an advantage from the heat transfer point of view only when the conditions are unfavorable for the traditional thermal fluid

Temperature Control of Lithium-ion Battery Packs under High-Current Abuse Conditions

Li-ion batteries are being widely used as power sources in a continuously increasing number of applications (from portable devices to electric vehicles and even more complex systems). Nonetheless these components are still characterized by serious concerns connected with their safety and stability, which often hinder their more widespread use. In particular, their operation is strictly dependent on their temperature which derives from the balance between the heat internally produced during operation and that dissipated towards the external environment. Beyond certain temperatures a thermal runaway can occur with possible dangerous events, such as fires and explosions. In the present paper, 3D simulations have been carried out to investigate the cooling efficiency of an air flow, under different operating conditions, on a cylindrical Li-ion cell located in a whole battery pack. Under the investigated configurations, it was found that, beyond a minimum value of the passing air velocity, it is possible to keep the cell within safe conditions, thus preventing a thermal runaway

Experimental evaluation of heat transfer coefficient for nanofluids

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The paper reports the results of heat transfer experimental tests on nanofluids. Measurements were performed in a two-loop test rig for immediate comparison of the thermal performances of the nanofluid with the base-fluid. The convective heat transfer was evaluated in a circular pipe heated with uniform heat flux and with flow regimes from laminar to turbulent. Tests have been performed to compare the heat transfer capability of nanofluids and water at the same velocity or Reynolds number , and they have been compared with values calculated from widely used correlations. In particular ten different nanofluids and three base fluids (in addition to the water) have been used. The analysis of the experimental data shows a different behavior depending on the parameter used in the comparison, and, as a consequence, the addition of nanoparticles to the heat transfer fluid can result advantageous or not, depending on the specific point of view. Furthermore some classical correlations have been used to estimate the heat transfer coefficients, and the analysis shows that they are able to provide good agreement with the experimental data both for the nanofluid and water

Transportation of hazardous materials via pipeline: a historical overview

The transportation of hazardous materials via pipelines is often considered a safer alternative to other transportation modalities such as railway, road and ship. However, pipelines often cross industrial and highly populated areas, so that their failure can pose a significant risk to the surrounding environment and the exposed population: the possible release of flammable and/or toxic materials in such areas can generate catastrophic events with very severe consequences. A number of accidents have actually occurred in the past years, and even when no deaths or injured are reported, significant damages to the surrounding environment often occur. This suggests that, given the extremely wide extension of the network worldwide, and the very high amounts of transported materials, a careful analysis is still required. In addition, the construction of pipelines also involves the contribution of expertise from a range of technical areas. As a consequence, the occurrence of accidents and the impact of their consequences, depend on the combination of a large number of parameters. In the present paper, an analysis of data relative to pipelines transporting hazardous materials has been carried out, and the influence of specific issues connected with their type and operation, has been assessed.Peer ReviewedPostprint (published version

Combined clean hydrogen production and bio-active compounds recovery from spent coffee grounds. A multi-perspective analysis

This study deals with the process simulation of an integrated system for energy production and valuable compounds recovery from spent coffee ground biomass and plasmix (non-recyclable plastic waste). The devised process consists of three maine units: a sub-critical water extraction column for the recovery of bio-compounds, an oxy-combustor of residual biomass and plasmix streams coupled with a production power energy unit, and a solid oxide electrolyzer (SOEC) for the production of pure H2 and O2. The process was exhaustively analyzed from an energy, exergy, environmental and economic point of view. The results of the analysis provided energy and exergy efficiencies higher than 60%, and the environmental analysis (CO2-cycle analysis) demonstrated a significant advantage of the process with respect to other hydrogen production methods. Finally, the feasibility of a plant with no net Greenhouse Gas emissions was shown to markedly depend on the costs associated to renewable energy sources

Osservatorio sulla componentistica automotive italiana 2017

La filiera automotive italiana vive un momento di crescita e sviluppo, che conferma il trend positivo avviato negli ultimi anni. Tuttavia, l’industria automotive globale è al centro di profondi cambiamenti che potrebbero portare all’affermarsi di scenari futuri dominati da veicoli a motorizzazioni alternative, auto a guida autonoma, o città riorganizzate sulla base di nuovi paradigmi di mobilità. Le imprese italiane della componentistica potrebbero rappresentare il futuro dell’industria della mobilità in Italia, ma le sfide da vincere sono numerose. Il volume Osservatorio sulla componentistica automotive italiana 2017 è stato realizzato con il duplice obiettivo di approfondire punti di forza e debolezza delle imprese italiane, e di collocarli nel quadro complessivo di opportunità e minacce che emergono dagli sviluppi dell’industria a livello internazionale

Conditional probabilities of post-release events for hazardous materials pipelines

Pipelines are commonly considered a safe alternative for the transportation of hazardous materials. However, in case of failure, pipelines still pose major risks to the environment and to the population potentially exposed. The aim of the present work is to provide occurrence probabilities of the intermediate and final events following the accidental release of hazardous materials from pipelines. A collection of incidents and accidents occurred worldwide in connection with the use of onshore long-distance pipeline networks, has been gathered to make up a specific database for the analysis of incidents in pipelines. A qualitative and quantitative analysis of the data has allowed to develop detailed event trees for the different classes of hazardous materials, and to calculate the probability of occurrence of the final outcomes. The investigation has also aimed at identifying, for each type of release, the relationship between the final events and the causes of the pipeline failure. The results obtained represent a useful and needed starting point in Quantitative Risk Analysis of hazardous materials transportation via pipelines.Peer ReviewedPostprint (author's final draft