Adnan Midilli

Mathematical modeling of thin layer drying of pistachio by using solar energy

This paper presents a mathematical modeling of thin layer forced and natural solar drying of shelled and unshelled pistachio samples. In order to estimate and select the suitable form of solar drying curves, eight different mathematical models, which are semi-theoretical and/or empirical, were applied to the experimental data and compared according to their coefficients of determination (r,χ2), which were predicted by non-linear regression analysis using the Statistica Computer Program. It was deduced that the logarithmic model could sufficiently describe thin layer forced solar drying of shelled and unshelled pistachio, while the two term model could define thin layer natural solar drying of these products in evaluation by considering the coefficients of determination, rsfsd=0.9983, χ2sfsd=2.697×10−5; rufsd=0.9990, χ2ufsd=1.639×10−5 for thin layer forced solar drying and rsnsd=0.9990, χ2snsd=3.212×10−6; runsd=0.9970, χ2unsd=4.590×10−5 for thin layer natural solar drying.

Gasification of sewage sludge using a throated downdraft gasifier and uncertainty analysis

The most important objectives to gasify sewage sludge are to produce a clean gas of acceptable composition for synthesis or combustion, and to convert this solid resource into combustible-clean gas at high efficiency. The experiments of the gasification were conducted using a 5 kWe-throated downdraft gasifier. It was concluded that sewage sludge can be gasified to produce low-quality combustible gas, and would be an acceptable alternative source to fossil fuels for the production of the clean energy. It is suggested that the downdraft gasifier should be operated at 3.69–3.71 kg/h±1.43% of the feed rate, at 2.28–2.34 N m3/kg±1.84% of the air fuel ratio, around 497.74–514 N m3/m2 h±1.50% of specific gasification rate and around 93.64–94.15%±1.92% of turndown ratio in order to achieve good quality gas and to avoid clinker formation at the throat of the gasifier because of high ash content of sludge. The thermal efficiency was calculated as between 39% and 40% at the optimum operation levels given above.

Hydrogen production from sewage sludge via a fixed bed gasifier product gas

Abstract The main objective pursued in this work is to investigate the hydrogen production potential from sewage sludge by applying downdraft gasification technique. An experimental study was conducted using a pilot scale ( 5 kWe ) throated downdraft gasifier. During the experiments, all data were recorded with an analog to digital (ATD) converter linked to a computer for every 15 s . The flow rates of the wet product gas, the mass flow rate and volumetric percentage of hydrogen were determined and illustrated. The effects of temperatures of oxidation zone on the production of hydrogen were discussed, and the conversion ratios of dried sewage sludge to hydrogen and ash were also designated. It was concluded that substantial amount of hydrogen gas could be produced utilizing a renewable biomass source such as dried and undigested sewage sludge pellets by applying air blown downdraft gasification technique. The product gas obtained mainly consists of H 2 , N 2 , CO , CO 2 and CH 4 with a maximum average gross calorific value of 4 MJ/m 3 . Around 10–11%( V / V ) of this product gas is hydrogen which could be utilized for fuel cells. Moreover, sewage sludge can be assumed as an alternative renewable energy source to the fossil fuels, and the environmental pollution originating from the disposal of sewage sludge can be partially reduced.

Hydrogen production from hazelnut shell by applying air-blown downdraft gasification technique

The main objective pursued in this work is to investigate the potential of hydrogen production from hazelnut shells by applying downdraft gasification technique. An experimental study was carried out using a pilot scale-5 kW-throated downdraft gasifier. During the experiments, the temperatures at zones of downdraft gasifier and pressure drops across the downdraft gasifier were recorded with an Analog to Digital (ATD) converter linked to computer at every 15 s. The flow rates of produced dry gas, combustible gas, hydrogen gas and the percentage of hydrogen gas in the produced gas were determined and illustrated. The effects of air fuel ratio and oxidation zone temperatures on the production of hydrogen gas were discussed. Additionally, the production of hydrogen gas from hazelnut shells was also estimated for a year. It was concluded that hazelnut shells could be easily converted to hydrogen gas by applying downdraft gasification technique.

Combustible gas production from sewage sludge with a downdraft gasifier

Abstract Recently, sewage sludge has particularly become an important problem all over the world because of its harmful impacts on the environment and living beings. It should be converted to combustible gas or useful energy in order to remove all its negative effects and to contribute to a significant portion of the power generation. In this study, combustible gas production from sewage sludge was experimentally investigated using a gasification technique by a downdraft gasifier. The amount of combustible gases, which are H 2 , CO, CH 4 , C 2 H 2 and C 2 H 6 , was found to be 19–23% of the total produced gases in the operating conditions. The average calorific value of the product gas was obtained between 2.55 and 3.2 MJ (N m 3 ) −1 . However, its average energy quantity was estimated between 12.19 and 28.97 MJ h −1 . Consequently, combustible gases were produced from sewage sludge by utilizing as a feedstock in a downdraft gasifier. Henceforth, sewage sludge can be considered a renewable energy source for gasifiers in order to produce thermal energy to help get rid of sewerage all over the world.

A Review on Thin-Layer Drying-Curve Equations

This paper presents a comprehensive review of thin-layer drying-curve models available in the literature and their comparisons for single-layer drying applications from 2003 to 2013. In this regard, a total of 67 models are selected and classified under 28 performance assessment criteria for comparison purposes. These models are then evaluated by considering the following parameters: (1) product type; (2) pretreatment type; (3) drying parameters, such as temperature, air velocity, layer thickness, microwave power levels, amount of solar radiation, vacum pressure, frequency of sound wave, excitation amplitude, relative humidity, bed depth, product shape, pH, salt content, absolute pressure, etc.; and (4) drying method employed. Furthermore, the best models obtained are employed for product drying applications and compared for different drying methods, drying parameters, and dried products.

Exergetic and exergo–economic analysis of a turboprop engine: a case study for CT7–9C

The turboprop engine has played an important role in short haul commuter and military transport aircraft where high speed is not critical. It may provide the aviation sector with one of the most significant means of achieving reduced operating costs through reductions in fuel consumption. This paper deals with exergo–economic analysis of a modern turboprop engine (CT7–9C) with a free power turbine used for a medium–range twin–engine transport plane that was jointly developed as a regional airliner and military transport. The investigated main components of the engine are the compressor, the combustor, the gas generator, the power turbine and the exhaust. Exergetic parameters, along with exergo–economic parameters, have been calculated for each engine component.

Experimental studies on mushroom and pollen drying

In this study, drying periods of mushrooms and pollens (for Anzer honey) were investigated. The experiments of mushrooms were carried out under both laboratory and shady- and sunny-atmospheric conditions and those of pollens were conducted in the drying cupboard heated by electric heater and under sunny atmospheric conditions. The temperature of the drying cupboard was regulated at 45°C during the drying experiment of pollen. The mass loss of pollens and the temperature of each shelf including pollens in the drying cupboard were measured. Drying curves of mushrooms and pollens for each experiment and the variation of the mass change ratio, the moisture ratio of pollens and the temperatures in the shelves with drying time were presented, respectively. Furthermore, their equations of drying curves and the average experimental uncertainty ratios were calculated based on the experimental results. It was concluded that mushrooms can be dried in the cupboards by using hot air at 50°C in a time period of 5–6 h, and the dried must be protected in vacuum, and the pollens also must be dried at temperatures between 40 and 45°C in a time period of 2·5–3 h without their losing the colour, flavour, smell and structure. The average experimental uncertainty ratio of mushrooms and pollens during the drying process were calculated to be 22 and 18%, respectively. Copyright

Component–based exergetic measures of an experimental turboprop/turboshaft engine for propeller aircrafts and helicopters

In this paper, component–based exergetic assessment is presented for an experimental turboprop/turboshaft engine, including comparisons and exergetic performance such as their efficiencies, improvement potentials, exergy destruction rates, relative exergy destructions, fuel depletion ratios, productivity lacks, and fuel and product exergy factors with different power settings and torques. The exergetic assessment of the engine components provided here should be helpful for designing shaft–power aero engines. Results from this study also evaluate effects of the operating parameters on the exergetic performance of the engine components commonly used in regional propeller aircrafts and helicopters.

Thermodynamic modelling of a proton exchange membrane fuel cell

This paper presents the thermodynamic modelling of a proton exchange membrane (PEM) fuel cell at various operating conditions through energy and exergy analyses. In addition, the correlations and equations available in literature were used to determine thermodynamic irreversibilities in the PEM fuel cell at different operating conditions such as cell temperature, pressures of anode and cathode, current density, and membrane thickness as a design parameter. In accordance with the practical conditions, it is considered that the anode and cathode pressures range from 3 to 5 atm; cell temperature from 50 to 80°C. Also, the membrane thickness is chosen as 0.016, 0.018 and 0.02 cm, respectively. Depending on these data, thermodynamic irreversibilities throughout PEM fuel cell operation are estimated and discussed in detail. Consequently, it is found that thermodynamic irreversibilities in fuel cell increased with a rise of membrane thickness and with a decrease of the cell temperature and pressure.