In this work, a numerical 3D simulation of a longitudinal ventilation system (LVS) is developed to analyze the fire behaviour inside a road tunnel. The numerical modelling reproduces the Memorial Tunnel, a two-lane, 853 m long road tunnel, used for experimental purposes. On this tunnel, 98 full-scale fire ventilation tests with different ventilation systems were conducted, constituting the first significant experimental approach to analyze fire incidents inside road tunnels. A total number of 24 reversible jets fans were installed in groups of three, nearly equally spaced over the length of the tunnel, and cantilevered from the ceiling of the tunnel. The validation of a numerical model is developed in the present paper. For that purpose, the behaviour of the smoke generated during a fire incident inside a road tunnel is predicted and compared with previous experimental data collected in the Memorial Tunnel Project. The smoke evolution and the performance of the LVS is simulated with a commercial code, FLUENT, which allows 3D unsteady simulations of the Navier-Stokes equations for multispecies mixtures of gases. A sufficient mesh density was introduced for the spatial discretization in order to obtain accurate results in a reasonable CPU time. Hence, typical ratios between total number of cells and the overall tunnel length were employed in the modelling. As a result, good agreement was achieved in all the tested cases, defining an accurate methodology to predict the performance of a LVS in case of fire inside a tunnel.
Selection of new autochthon strains is necessary, and for the moment the best strategy, to find microalgae well adapted to the local climatological conditions able to simultaneously produce several compounds of biotechnological interest and grow at high rates. We describe the isolation and characterization of a new microalgal strain isolated from the marshlands of the Odiel River in the Southwest of Spain. The new microalga belongs to the genus Picochlorum, as deduced from the analysis of its 18S rRNA encoding gene, is able to grow at a high growth rate and thrive with adverse conditions. It has an appreciable constitutive level of lutein (3.5 mg g(-1) DW) and zeaxanthin (0.4 mg g(-1) DW) which is increased to 1.8 mg g(-1) DW at high light intensities. This strain is also characterized by a very low level of linolenic acid (3.8% of total fatty acids) and no polyunsaturated fatty acids with four or more double bonds. Although the total lipid content is not particularly high, 23% of the dry weight, its fatty acid profile makes of Picochlorum sp HM1 a promising candidate for biodiesel production, and the high content in the carotenoids lutein and zeaxanthin indicates that the microalga could also be a good source for natural eye vitamin supplements, which could be obtained as co-products.
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