Abstract. The aim of this paper is to develop a model for pollutant concentration prediction in a stream. The developed model that determines nitrogen and phosphorus concentrations in a river is based on a dimensional analysis. Application of dimensional analysis to water quality modelling is presented, pointing out possibilities of applying this methodology in water quality research. We investigate how dimensional analysis can be applied to water quality modelling and which benefits it can bring to researchers in this area. For modelling water quality in a water stream it is essential to know the parameters that influence water quality. The relevant parameters are flow of water in the river (discharge), its catchment area, velocity of water in the stream, temperature of water, temperature of air and measured concentrations of the pollutant -nitrogen and phosphorus. A sensitivity analysis shows that the concentration of pollutant in water stream is sensitive to changes in both water and air temperatures. The model performs well when average values are used; the prediction error increases when the single concentration values are considered. The model was developed, calibrated and evaluated using measured data from the river station Ižkovce, River Laborec in eastern Slovakia.
During the past decades, several models that predict the concentration profiles after a discharge of pollutants in a river have been developed. A model that predicts nitrogen concentrations in a river has been developed and is presented in this paper. The developed model that determines nitrogen concentrations in a water stream is based on a dimensional analysis. Fundamentals of the modelling of the pollutant predictions in a water stream consist of a derivation of function dependency from expressed non-dimension arguments. Non-dimension arguments are stated from variables, which influence the occurrence of pollutants. The model for the prediction of nitrogen concentrations in water streams has been developed for the Laborec River (eastern Slovakia). The differences between the nitrogen concentrations predicted from developed models and measured concentrations in the river are also discussed here. Study areaPrediction of nitrogen concentrations in the water stream was performed for the Laborec River -eastern Slovakia. Water quality is monitored in the Laborec River stations. For the purpose of this work, seven river staions were selected according Fig. 1. bs_bs_banner Water and Environment Journal. Print
The article presents the procedure for how to establish a mathematical model of nitrogen oxides formation based on the theory of dimensional analysis. The model is based on selected physical quantities (parameters) measurable during regular operation of a heat generation plant. The objective of using dimensional analysis to describe nitrogen oxides formation is to show that between operating parameters of the combustion equipment and the NO x formation there is a significant correlation. The obtained results, which are further described in this article, have proved this fact.The obtained formula expressing nitrogen oxides formation, based on dimensional analysis, applies universally to any boiler fuelled by coal, gas or biomass. However, it is necessary to find C, m, n constants for the formula by experiment, individually for each type of boiler and used fuel. The experiment is based on on-line measurements of selected operational parameters for a given boiler, combusting a certain type of fuel with its actual moisture content and calorific value. The methodology, described in this article, helps to find relationships between the operational parameters and the formation of NO x emissions for a particular furnace. The developed mathematical model has been validated with boilers fuelled by black coal and biomass. Both the results obtained from direct measurements of NO x in both types of boilers, and the results obtained by calculation using equation based on the dimensional analysis, are in a very good accord. When burning coal, the variation between NO x expression from the model and the on-line measurements ranges between -12.23 % and + 9.92 %, and for burning biomass between -0.54 % and 0.48 %.The intention of the authors is to inform the professional community about the suitability of the dimensional analysis to describe any phenomena for which there is currently no exact mathematical formulation based on differential equations or empirical formulas. Many other examples of dimensional analysis applications in practice may be found in the work of Čarnogurská and Příhoda (2011).
An original method for estimating fouled deposit thickness on the inside surfaces of natural gas cooler tubes is presented. This method does not require opening and inspecting a cooler as it is based on the measurement of gas cooling degree, i.e. the gas temperature difference between the cooler inlet and discharge. The deposit layer on the internal heat transfer surfaces is of semi-liquid consistency and its thermal conductivity coefficient has not been investigated until now. This paper describes the experimental determination of the deposit thermal conductivity coefficient. This parameter enables determination of a cooler's performance as a function of current deposit thickness. Practical application of the method is illustrated in the case of CH_R cooler working in the KS01 compressor station in Veľké Kapušany, Slovakia. For this type of cooler, a diagram for deposit thickness as a function of the gas cooling degree is presented.
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