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  • Author or Editor: Ferenc Lezsovits x
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Abstract

The department was commissioned to investigate the possibilities for animal-fat combustion in industrial steam generators operating originally on fuel–oil or natural gas. There are two main reasons for operating generators on animal fat as a fuel: On one hand, this material is considered as hazardous waste, thus an important goal is its environmentally benign elimination or disposal. On the other hand, fat is an excellent energy source and can be used as combustion fuel. This way fossil fuel usage can be saved while environmental regulations can also be met. The usage of animal fat as a fuel for furnaces required classification according to fuel classification rules, and comparison with the properties of fuel oil. In addition, its pollutant content was determined and the effects on the combustion process and emission were investigated. Finally the savings in fossil fuel energy consumption and related CO2 emission achieved were determined. The first stage involved the determination of the composition of animal fat. Subsequently other properties such as viscosity and flash point variation were investigated. These data were compared to the properties of fuel oil. The theoretical investigations of animal-fat classification were promising. Initially one steam generator, originally designed for fuel oil combustion, was modified and fitted with a parallel animal fat fuel supply system. The results of the test were encouraging, although there were some problems with power regulation and later with fuel supply. A rotary cup type burner was then fitted to the boiler. Using this system, all the requirements including environmental regulations were met.

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Abstract:

Development of thermal efficiency of the concentrated solar energy especially parabolic trough collector using various nanofluids types has a taken high interest in recent years. In this article enhancement thermal performance inside the heating collecting element of trough collector type LS-2 was simulated and improved using nanofluid consist of Tungsten Oxide WO3 inserting in Syltherm 800. Nanofluid effect was examined by solving the energy balance equation using MATLAB Software to cover wide range concentration volume 1-5% and inlet temperatures ranging from 350-650 K for the turbulent flow. The heat transfer performance and thermal efficiency were improved based on the results, and a notable increase was obtained when volume concentration had been increased compared with base fluid.

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In the present study, fully developed laminar flow with forced convection heat transfer of Al2O3/water and TiO2/water nanofluids inside a vertical tube subjected by constant heat flux from the wall was numerically analyzed using Ansys Fluent release 17.2. In this work, the single-phase model was proposed to simulate the water and nanofluids heat transfer characteristics; spherical nanoparticles with a constant diameter equal to 30 nm are used. The study has been carried out on a Reynolds number with ranges (400-2000) and nanoparticles volume concentration up to 1.5%. the results show that the average Nusselt number for nanofluid is higher than that the base fluid (water) especially for TiO2/water nanofluid, the Nusselt number increased with increasing Reynolds number and volume concentration in all cases. The enhancement ratio for nanofluids compared to water at different volume friction was studied; the higher improvement is about 3.51% for TiO2/water nanofluid with 1.5% volume fraction. Moreover, a study for pressure drop along vertical tube was discussed.

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This study aims to experimentally investigate the nucleate pool boiling heat transfer performance of magnesium oxide nanoparticles MgO based deionized water nanofluid at the atmospheric pressure condition. Dilute volumetric concentrations within a range of 0.001% to 0.01% Vol. were used to examine the pool boiling heat transfer performance represented by pool boiling curve, and pool boiling heat transfer coefficient. The heating element was a horizontal copper heated tube with a typical diameter 22 mm submerged inside the cubic boiling chamber. Efforts have been made to measure the surface temperatures along the heated tube to ensure the proper and accurate heat transfer coefficient calculations in this work. The results indicated that the pool boiling heat transfer coefficient enhancement ratio (PBHTC /PBHTC ) was intensified for volume fractions i.e. 0.001%, 0.004%, and 0.007% Vol. while it was degraded for volume concentrations i.e. 0.01%, and 0.04% Vol. compared to deionized water as baseline case.

Open access

Abstract

The thermal behaviours of a sewage sludge sample, woody (black locust, poplar and willow) and herbaceous (energy grass and wheat straw) biomass as well as mixed (sewage sludge and black locust in ratios 1:1 and 1:3) samples were compared under inert and oxidative atmosphere. The thermogravimetric experiments of each sample demonstrate that the beginning temperature of decomposition is similar in inert and oxidative atmospheres, i.e. the primary bond scissions are not affected by the atmosphere. Nevertheless, oxygen increases the decomposition rate and the volatile evolution of all samples at higher temperatures. Thermogravimetry/mass spectrometry (TG/MS) experiments have been performed to determine the mass loss of the samples and the formation of volatile products as a function of temperature in inert atmosphere. Wood and herbaceous biomass samples evolved various organic products (aldehydes, ketones, acids, furan derivatives, etc.) beside water and gaseous products. Sewage sludge released mainly water, carbon oxides, methane, hydrogen, hydrocarbons, ketones, acids as well as sulphur- and nitrogen-containing products. High heating value and low heating value of the samples have been determined by a bomb calorimeter. Principal component analysis (PCA) has been used to find statistical correlation between the data. The results unambiguously support the correlation between the thermogravimetric parameters (e.g. DTGmax) and the heating values of the samples.

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