1,721,045 research outputs found
EXPERIMENTAL SENSITIVITY ANALYSIS OF A TRICKLE BED REACTOR FOR LIPS PRODUCTION BY P. CHRYSOSPORIUM, PROCESS BIOCHEMISTRY
No full textUncertainty evaluation of thermodynamic properties estimated with online data tools: vapor pressure as case study
No full textOnline databanks are a convenient source of information whenever thermodynamic properties are required for calculations, in both scientific and engineering environment. The data listed in these repositories is usually reported along with a range of validity and their sources. The values of the thermodynamic properties can usually be retrieved from databases and handbooks, in the form of tables, curves or correlations with regression parameters. Most of the times, little to no information is given on the uncertainty of the reported estimates, let alone regression parameters uncertainty. Evaluating the sources of uncertainty in any model is fundamental to verify the significance of the results for a specific application. Knowing the uncertainty, makes the difference between trusted values and random values. Depending on the model where the property is required and its application (the use of results), the contribution to the total uncertainty of thermodynamic properties and constants can surpass the contributions of other experimental input quantities. In this work, the methods described in the 'Guide for the expression of uncertainty in measurement' are used to evaluate the uncertainty of a thermodynamic property of a pure substance, calculated based on the constants and references reported in two important online data banks (NIST and Dortmund Databank). The vapor pressure is considered as case study and several definitions with their relevant sources of uncertainty are presented. The aim of the work is to highlight the limitations of properties data commonly used in engineering estimations, as well as the importance of accounting for their uncertainty. Following established metrological guidelines, a full procedure has been developed, with specific considerations aimed to account for the 'quality' of the realization of the definition of the measurand as a source of uncertainty of the property
Uncertainty of thermodynamic properties available via online data banks: Vapor pressure as case study
Full text linkThe aim of the work is to highlight the limitations of properties data commonly used in engineering estimations, as well as the importance of accounting for their uncertainty. Following established metrological guidelines, a full procedure have been developed, with particular considerations aimed to account for the ‘quality’ of the realization of the definition of the measurand as a source of uncertainty of the property. The case study considered was the vapor pressure, a property commonly used in processes involving vapor-liquid equilibrium, common in the industry and climate related calculations
Uncertainty Evaluation of Human Risk Analysis (HRA)of Chemicals by Multiple Exposure Routes
No full textThe application of an ISO standard procedure (Guide to the Expression of Uncertainty in Measurement (GUM)) is here discussed to quantify uncertainty in human risk estimation under chronic exposure to hazardous chemical compounds. The procedure was previously applied to a simple model; in this article a much more complex model is used, i.e., multiple compound and multiple exposure pathways. Risk was evaluated using the usual methodologies: the deterministic reasonable maximum exposure (RME) and the statistical Monte Carlo method. In both cases, the procedures to evaluate uncertainty on risk values are detailed. Uncertainties were evaluated by different methodologies to account for the peculiarity of information about the single variable. The GUM procedure enables the ranking of variables by their contribution to uncertainty; it provides a criterion for choosing variables for deeper analysis. The obtained results show that the application of GUM procedure is easy and straightforward to quantify uncertainty and variability of risk estimation. Health risk estimation is based on literature data on a water table contaminated by three volatile organic compounds. Daily intake was considered by either ingestion of water or inhalation during showering. The results indicate one of the substances as the main contaminant, and give a criterion to identify the key component on which the treatment selection may be performed and the treatment process may be designed in order to reduce ris
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