Numerical Investigation of the Effect of Different Conical Turbulators on the Performance of a Liquid Fuelled Boiler

The increment in the combustion of fossil fuels for heating and power generation in recent years has led researchers to design more efficient energy conversion systems by increasing the efficiency of the existing systems and by minimizing energy losses. In this study, increasing the efficiency of the liquid fuelled smoke tube boilers used for domestic heating was researched. In this context, turbulators with full conical and frusto-conical geometries placed to smoke tubes of boiler and their effects on flame structure, heat transfer and boiler efficiency were investigated numerically. Calculations were carried out at two dimensional axisymmetric conditions and Fluent was used as the computational fluid dynamics software. In all cases, the standard k-ε model was used for modelling the turbulent flow and the species transport model was used for modelling the combustion. The results obtained by using these turbulators were evaluated for each placement condition of the turbulators. Besides, the temperature and the stream function distribution and the pressure drop in the boiler were investigated according to the type of turbulators. Finally, it was discussed which type of turbulator would be most appropriate at boilers. Keywords: Spray Combustion; Combustion Modelling; Boilers; Conical Turbulator

Numerical Investigation of Turbulent Hydrogen-Methane-Nitrogen Non-Premixed Jet Flame

In this work, the numerical investigation of the two-dimensional axisymmetric turbulent diffusion flame of a composite fuel was performed by using a computational fluid dynamics code to predict flame structure. The composite fuel was an H2/CH4/N2 gas mixture. The amount of H2 and N2 in the fuel mixture varies under constant volumetric fuel flow rate. Fluent, which solves the governing and reaction equations using the finite volume method, was used as the computational fluid dynamics program. The non-premixed model was used for computation of the combustion. The standard k-ε model was used for modeling the turbulent flow. The interaction of the chemistry and turbulence was accounted for by the program with the probability density function model. This model was validated against the experimental data taken from literature. In general, the numerical results of the temperature, velocity, and CO2 concentration distributions were in satisfactory agreement with the experimental results. The numerical results showed that adding H2 to the fuel mixture decreases the flame length and generally increases the maximum temperature of the flame. On the other hand, adding N2 to the mixture decreases both the flame length and maximum flame temperature. The flame length corresponds to the axial position of the peak flame temperature. Keywords: Combustion Modeling; Composite Fuels; Diffusion Flame; H2/CH4/N2 Flame; Flame Length; Emission

Symptomatic Giant Cavernous Haemangioma of the Liver: Is Enucleation a Safe Method?

Twenty-three patients with symptomatic giant hemangioma of the liver were treated by surgery between 1979 and 1996 at the department of General Surgery, Faculty of Medicine, University of Çukurova. Twenty-three enucleations were performed in 21 patients, left lateral segmentectomy in one patient and enucleation plus left lobectomy in one patient. The tumors were enucleated along the interface between the hemangioma and normal liver tissue. The diameters of the tumors ranged from 5×5 to 25×15 cm. The mean blood loss for enucleations was 525 ml (range 500–1000 ml). There was no mortality and no postoperative bleeding. Three patients had postoperative complications. Enucleation is the best surgical technique for symptomatic giant hemangioma of the liver. It may be performed with no mortality, low morbidity and the preservation of all normal liver parenchyma

Interaction of the Psychiatric Risk Gene Cacna1c With Post-weaning Social Isolation or Environmental Enrichment Does Not Affect Brain Mitochondrial Bioenergetics in Rats

The pathophysiology of neuropsychiatric disorders involves complex interactions between genetic and environmental risk factors. Confirmed by several genome-wide association studies, Cacna1c represents one of the most robustly replicated psychiatric risk genes. Besides genetic predispositions, environmental stress such as childhood maltreatment also contributes to enhanced disease vulnerability. Both, Cacna1c gene variants and stressful life events are associated with morphological alterations in the prefrontal cortex and the hippocampus. Emerging evidence suggests impaired mitochondrial bioenergetics as a possible underlying mechanism of these regional brain abnormalities. In the present study, we simulated the interaction of psychiatric disease-relevant genetic and environmental factors in rodents to investigate their potential effect on brain mitochondrial function using a constitutive heterozygous Cacna1c rat model in combination with a four-week exposure to either post-weaning social isolation, standard housing, or social and physical environmental enrichment. Mitochondria were isolated from the prefrontal cortex and the hippocampus to evaluate their bioenergetics, membrane potential, reactive oxygen species production, and respiratory chain complex protein levels. None of these parameters were considerably affected in this particular gene-environment setting. These negative results were very robust in all tested conditions demonstrating that Cacna1c depletion did not significantly translate into altered bioenergetic characteristics. Thus, further investigations are required to determine the disease-related effects on brain mitochondria

Benign chondroid syringoma of the orbit: a rare cause of exophtalmos

Chondroid syringoma (CS) of the orbit is an extremely rare benign neoplasm. To the best of our knowledege, this is the second case reported in the english litérature