A relation for calculation of the effective overall heat transfer coefficient in a triple concentric-tube heat exchanger is proposed. The relation of the effective overall heat transfer coefficient is obtained based on total thermal resistance and it is applied within a case study for thermal analysis of two triple concentric-tube heat exchangers with different geometries, hot fluids and operating conditions. Through case study it is found that the values of effective overall heat transfer coefficient can be obtained with acceptable errors, up to 3 % for both heat exchangers.
In this paper there are presented laboratory studies on the influence of additives in diesel fuels on accidental pollution of the soil. The additive used in the experiments was cyclohexanone ketal glycerol. The presence of hydroxyl groups in the structure of ketals of glycerol decreases the solubility of hydrocarbons. To solve this disadvantage and for improving other features, in order to use as additives/ components for classic fuel, the hydroxyl group of glycerol ketal methyl ethyl ketone was block by transesterification with methyl esters of monocarboxylic acids. The results obtained were compared to the content of nutrients (N, P, K) in the soil polluted with diesel fuel additives and diesel oil without additives. It was performed the soils decontamination by applying the method of solvent extraction. For ecological reconstruction there were used unpolluted soil samples, samples contaminated with diesel oil with and without additives and the resulting samples after the extraction with the solvents.
Soil pollution by oil products is one of the most obvious environmental problems that Romania has been facing in recent years. Given the alert pace of use of petroleum products and for meeting energy needs, it is noted that both in Romania and abroad there are reported accidental oil spills to soil or water, which causes economic, social and environmental issues. In this paper we propose a review of the particularities of soil pollution with liquid petroleum products and opportunities for remediation. The analysis of remediation processes of soils contaminated with liquid petroleum products highlights the advantages and disadvantages of each method. The analyzed samples were subjected to thermal remediation methods: combustion and thermal desorption and one of the chemical processes, succesive extraction with solvents. The results of these experimental data allow us to conclude that the used method is efficient and can be applied at industrial level with high efficiency.
The paper compares the results obtained by applying three calculation methodologies for the height of the chimney of a hazardous waste installation. Thermal waste treatment processes are a feasible option after recovery (collection, sorting, recycling) and prior to controlled disposal. Monitoring data at a hazardous waste incineration plant made it possible to calculate three heights of the incinerator emission network. The incineration plant is thus operated in such a way that the emissions of the harmful substances of the chimney are in conformity with the VLE values transposed into the national legislation by Law no. 278/2013 regarding industrial emissions, Annex 6. Three methodologies are used to determine the height of the chimney: according to the Technical Instructions for Air Quality Control-"TA Luft", according to "Arrêté du 25/01/91 relatif aux incinération de résidus urbains" and according to "RS 814.318." 142.1 Ordonnance sur la l'air (Opair) ".
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