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Wpływ składu paliw alternatywnych na ciepło spalania

100%

Sakleshpur Nagaraja S. , Czarnowska L. , Bogacka M.

Archiwum Gospodarki Odpadami i Ochrony Środowiska

2015

tom Vol. 17, nr 1

141--148

Ciepło spalania (Qw) jest ważnym parametrem charakteryzującym paliwa, a określane jest jako entalpia całkowitego spalania paliwa, z uwzględnieniem entalpii kondensacji skroplonej pary. Liczne korelacje empiryczne są dostępne w literaturze, na podstawie których można oszacować ciepło spalania Qw paliwa znając jego skład pierwiastkowy. W artykule, zestawiono 10 różnych wzorów empirycznych i na ich podstawie określono Qw dla wybranych paliw alternatywnych o różnym składzie. Dodatkowo obliczono średni błąd procentowy w odniesieniu do wyników eksperymentalnych. Stwierdzono, że użycie wzoru Dulonga w przypadku rozważanych paliw alternatywnych jest obarczone najmniejszym średnim błędem procentowym.

Heating value of a fuel is an important parameter in selection of fuel. Higher Heating value (HHV) is the enthalpy of complete combustion of a fuel, including the condensation enthalpy of formed water. Numerous empirical correlations are available in the open literature to obtain the HHV of the fuel from its elementary composition. In the present study, these correlations are used to obtain HHV of few alternative fuels and the value of HHV for each fuel is compared with experimental values and mean absolute error % is calculated. It was found that Dulong model had the least mean error percentage for alternative fuels considered in the present study.

Application of Predictive Relationships of Swelling Effects for Roadbeds

84%

Pruska J. , Sedivy M. , Pavelcova V.

Inżynieria Mineralna

2024

tom Vol. 1, no. 1

211--216

Impact of swelling can be observed in a wide range of civil and engineering structures. In the case of swelling in the subsoil of roadbeds, the destruction of the road pavement in cuts or collapse of slopes of cut is a frequent occurrence. Problems with deformation from swelling can also occur in the case of bridge abutments based on pile trestles. The unpleasant fact is that the impact of swelling can occur even after a long time. In the case of roads, high swelling pressures can lead to total destruction of the structure of the pavement even after years of operation. The susceptibility of soil to swelling can be described using swelling parameters. These parameters can be measured directly in the laboratory and in situ or indirectly estimated from empirical correlations. The paper describes the prediction of swelling processes using indirect measurements based on the methodology "Identification and solution of problems of soils prone to swelling" certified by the Ministry of Environment of the Czech Republic.

Analogy between thermal and mass diffusion effects of a free convective flow in rectangular enclosure

67%

Ambethkar V.

Journal of Applied Mathematics and Computational Mechanics

2020

tom Vol. 19, nr 4

5--20

In this investigation, the analogy between thermal and mass diffusive effects of a free convective flow in a rectangular enclosure is emphasized. The upwind finite volume method is used to discretize the governing equations of the continuity, momentum, energy and mass transfer. The novelty in this exploration is to appropriately modify the well-known Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm so that it suits to the present problem and thereby, the new flow variables such as the temperature and the concentration are computed. An empirical correlation for the average Sherwood number (Sh) that does not exist in literature is suggested in this work. The average Sherwood numbers for distinct fluids (gases and liquids) are calculated, and mass diffusion effects within the horizontal rectangle are analyzed. The average Nusselt numbers (Nu) are calculated for distinct fluids such as liquids (Pr ≫1), liquid metals (Pr≪1) and gases (Pr < 1) for different Rayleigh numbers in the range of 3x105 ≤ RaL ≤ 7x10 9 from relevant empirical correlations existing in the literature. Accordingly, the thermal diffusion effects within the horizontal rectangle are analyzed.