Mass, heat and momentum transfer in natural draft wet cooling tower with flue gas discharge

The paper presents CFD simulation results of a natural draught wet-coolingtower (NDWCT) with flue gas discharge. The problem considered is mixing of the fluegases with the rising plume and possible corrosion of the tower shell due to acid condensate.A previously developed CFD model of a NDWCT has been used in the analysis. Nowind conditions have been assumed and the results have shown that under this conditionthe corrosion is unlikely to occu

Thermophoresis and its effect on particle impaction on a cylinder for low and moderate Reynolds numbers

The effect of thermophoresis on the impaction of particles on a cylinder is investigated for different particle sizes, particle conductivities, temperature gradients and for Reynolds numbers between 100 and 1600. Simulations are performed using the Pencil Code, a high-order finite difference code. An overset-grid method is used to precisely simulate the flow around the cylinder. The ratio of particles impacting the cylinder and the number of particles inserted upstream of the cylinder is used to calculate an impaction efficiency. It is found that both the particle conductivity and the temperature gradient have a close to linear influence on the particle impaction efficiency for small particles. Higher Reynolds numbers result in higher impaction efficiency for middle-sized particles, while the impaction efficiency is smaller for smaller particles. In general, it is found that thermophoresis only has an effect on the small particles, while for larger particles the impaction efficiency is controlled by inertial impaction. Finally, an algebraic model, developed based on fundamental principles, which describes the effect of thermophoresis is presented. The model is found to accurately predict the DNS results. As such, this model can be used to understand the mechanisms behind particle deposition due to the thermophoretic force, and, more importantly, to identify means by which the deposition rate can be reduced

Monitorowanie losów absolwentów. Zarys metodologii i metodyki badania w Uniwersytecie Ekonomicznym w Poznaniu

W artykule przedstawiono przegląd polskich i zagranicznych doświadczeń z badań losów absolwentów. Zaprezentowano również charakterystykę okresu przejściowego między edukacją a pracą, w którym znajdują się absolwenci wkraczający na rynek pracy. Zdaniem autorów, specyfika aktywności ekonomicznej w tym okresie powinna zostać uwzględniona przy projektowaniu systemów monitorowania losów absolwentów. Na tym tle zaprezentowano zarys metodyki i metodologii monitorowania losów absolwentów w Uniwersytecie Ekonomicznym w Poznaniu

Dynamic modelling and operational optimisation of natural draft cooling towers

YesNatural draft cooling towers are subjected to dynamic air temperature and humidity ratio of air throughout the day. Their performances based on steady state model is restricted to single air temperature and humidity ratio of air values and thus are not accurate. In this work, a dynamic model for a natural draft cooling tower is developed. Air temperature and relative humidity data for Johannesburg were acquired to develop dynamic correlations for these two parameters and are embedded in the process model together with the dynamic model of the collection basin of the tower. A simple algorithm is proposed to solve the resulting boundary value problem. Finally, the common perception that seawater/river water should be used instead of freshwater as cooling medium is tested via optimisation where the operating costs of the process for two cooling mediums is minimised. The freshwater has been found to be cost effective cooling medium