Numerical Study on Natural Convection of Alumina-water Nanofluid in a Square Cavity with Two Localized Heat Sources on Adjacent Surfaces

In the present work, results of a numerical study carried out using finite volume method, to investigate the fluid flow and heat transfer characteristics of Alumina ( Al2O3 ) nanoparticles in the base fluid (water) in a square cavity under natural convection mode are presented. The Semi Implicit Method for Pressure Linked Equations (SIMPLE) algorithm was used to solve the discretized momentum and energy equations. Constant temperature heat sources of same strength are placed on bottom and left vertical surfaces whereas the right surface was kept cold, while the top surface was maintained as adiabatic. The impact of Rayleigh number (RaN) ( 1000 to 106 ) and nanoparticles volume fraction (Φ = 0 %, 5 %, 10 %, 15 % and 20 %) on fluid and heat flow characteristics were numerically investigated and presented in the form of streamlines, isothermal lines, mid line horizontal and vertical velocity components, local Nusselt number ( Nuloc ) and average Nusselt number ( Nuavg ). The obtained results indicate, for lower RaN ( i.e; 103 ), conduction dominates over convection near heated surfaces and results in lower fluid velocities and poor heat transfer. For higher values of RaN ( RaN = 105 and 106 ) and volume fraction of nanoparticles, there was a significant increase in mid horizontal and vertical velocity components, Nuloc and Nuavg due to increase in convective heat transfer and thermal conductivity of nanofluid

Biofuels and thermal barrier:a review on compression ignition engine performance, combustion and exhaust gas emission

The performance of an internal combustion engine is affected when renewable biofuels are used instead of fossil fuels in an unmodified engine. Various engine modifications were experimented by the researchers to optimise the biofuels operated engine performance. Thermal barrier coating is one of the techniques used to improve the biofuels operated engine performance and combustion characteristics by reducing the heat loss from the combustion chamber. In this study, engine tests results on performance, combustion and exhaust emission characteristics of the biofuels operated thermal barrier coated engines were collated and reviewed. The results found in the literature were reviewed in three scenarios: (i) uncoated versus coated engine for fossil diesel fuel application, (ii) uncoated versus coated engine for biofuels (and blends) application, and (iii) fossil diesel use on uncoated engine versus biofuel (and blends) use on coated engine. Effects of injection timing, injection pressure and fuel properties on thermal barrier coatings were also discussed. The material type, thickness and properties of the coating materials used by the research community were presented. The effectiveness and durability of the coating layer depends on two key properties: low thermal conductivity and high thermal expansion coefficient. The current study showed that thermal barrier coatings could potentially offset the performance drop due to use of biofuels in the compression ignition engines. Improvements of up to 4.6% in torque, 7.8% in power output, 13.4% in brake specific fuel consumption, 15.4% in brake specific energy consumption and 10.7% in brake thermal efficiency were reported when biofuels or biofuel blends were used in the thermal barrier coated engines as compared to the uncoated engines. In coated engines, peak cylinder pressure and exhaust gas temperature were increased by up to 16.3 bar and 14% respectively as compared to uncoated condition. However, changes in the heat release rates were reported to be between −27% and +13.8% as compared to uncoated standard engine. Reductions of CO, CO2, HC and smoke emissions were reported by up to 3.8%, 11.1%, 90.9% and 63% respectively as compared to uncoated engines. Significant decreases in the PM emissions were also reported due to use of thermal barrier coatings in the combustion chamber. In contrast, at high speed and at high load operation, increase in the CO and CO2 emissions were also reported in coated engines. Coated engines gave higher NOx emissions by about 4–62.9% as compared to uncoated engines. Combined effects of thermal barrier coatings and optimisation of fuel properties and injection parameters produced further performance and emissions advantages compared to only thermal barrier coated engines. Overall, current review study showed that application of thermal barrier coatings in compression ignition engines could be beneficial when biofuels or biofuel blends are used instead of standard fossil diesel. However, more research is needed combining coatings, types of biofuels and other engine modifications to establish a concrete conclusion on the effectiveness of the thermal barrier when biofuels are used in the compression ignition engine. Reduction of NOx emissions is another important R & D area

An Elective in College Mental Health for Training Adult Psychiatry Residents in Young Adult Psychiatry

In this report, we describe a college mental health elective for senior adult psychiatry residents

Trends in atrial fibrillation in patients hospitalized with an acute coronary syndrome

BACKGROUND: Atrial fibrillation is common among patients with cardiovascular disease and is a frequent complication of the acute coronary syndrome. Data are needed on recent trends in the magnitude, clinical features, treatment, and prognostic impact of preexisting and new-onset atrial fibrillation in patients hospitalized with an acute coronary syndrome. METHODS: The study population consisted of 59,032 patients hospitalized with an acute coronary syndrome at 113 sites in the Global Registry of Acute Coronary Events Study between 2000 and 2007. RESULTS: A total of 4494 participants (7.6%) with acute coronary syndrome reported a history of atrial fibrillation and 3112 participants (5.3%) developed new-onset atrial fibrillation during their hospitalization. Rates of new-onset atrial fibrillation (5.5%-4.5%) and preexisting atrial fibrillation (7.4%-6.7%) declined during the study. Preexisting atrial fibrillation was associated with older age and greater cardiovascular disease burden, whereas new-onset atrial fibrillation was closely related to the severity of the index acute coronary syndrome. Patients with atrial fibrillation were less likely than patients without atrial fibrillation to receive evidence-based therapies and more likely to develop in-hospital complications, including heart failure. Overall hospital death rates in patients with new-onset and preexisting atrial fibrillation were 14.5% and 8.9%, respectively, compared with 1.2% in those without atrial fibrillation. Short-term death rates in patients with atrial fibrillation declined over the study period. CONCLUSIONS: Despite a reduction in the rates of, and mortality from, atrial fibrillation, this arrhythmia exerts a significant adverse effect on survival among patients hospitalized with an acute coronary syndrome. Opportunities exist to improve the identification and treatment of patients with acute coronary syndrome with, or at risk for, atrial fibrillation to reduce the incidence and resultant complications of this dysrhythmia