Hayati Olgun

Autothermal reforming as a hydrocarbon fuel processing option for PEM fuel cell

Abstract In this paper, we discuss the results of a preliminary systematic simulation study: the effect of operating parameters on the product distribution and conversion efficiency of high and low molecular weight hydrocarbon mixtures in autothermal reforming (ATR). The HYSYS simulation software has been utilized for the simulations and calculations of the fuel processing reactions. It is desired to produce hydrogen-rich reformate gas with as low as possible CO formation, which requires different combinations of TATR, S/C and O/C ratios. Fuel properties only slightly effect the general trends.

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

Investigation of the performance of a cross‐flow turbine

An experimental investigation was conducted to study the effects of some geometric parameters of runners and nozzles (e.g., diameter ratio and throat width ratio) on the efficiency in the cross-flow turbines, by varying of ratio of inner-to-outer diameters of runners and gate openings of two different turbine nozzles under different heads. In this study, four different types of runners (170 mm outer diameter, 114 mm width) were designed and manufactured to investigate the effects of the ratio of inner-to-outer diameters of runners on the turbine efficiency. Each runner had 28 blades and the ratios of inner-to-outer diameters of runners were 0·75, 0·67, 0·58 and 0·54, respectively. The runners were denoted with the numbers 1, 2, 3 and 4, and nozzles A and B. The blade inlet and outlet angles were selected as 30° and 90°. Nozzles A and B were of rectangular cross-sectional channels. Nozzles outlet angles of two solid walls of 16° were measured from the circumferential direction. The performance parameters namely output power, efficiency, runaway speed, reduced speed and power for different nozzle/runner combinations were investigated by changing head range from 8 to 30 m, the nozzle A-runner combinations (A–1, 2, 3, 4) and from 4 to 17 m, the nozzle B-runner combination (B–2) at different gate openings. The results of the present study clearly indicated that there was a negligible difference (e.g., 3% in total between 0·54 and 0·75 diameter ratio) in the efficiency of turbine for different diameter ratios and heads, and that the highest efficiency was obtained as 72% for A–2.

Simulation of Biomass and/or Coal Gasification Systems Integrated With Fuel Cells

This paper presents the results of a system simulation study. The HYSYS 3.1 - ASPEN code has been used for simulation. The system consists of a fixed bed gasifier followed by reforming and clean-up units. The produced hydrogen gas is fed to a PEM fuel cell. The gasified hydrocarbons are hazelnut shells, bark, rice straw, animal waste, and two lignites. Hydrocarbon properties, gasification, and reforming process parameters all affect the system efficiency. The effect of the moisture content and oxygen to carbon ratio of the hydrocarbon fees on the fuel processing and overall system efficiencies are presented. The overall efficiency of the system increases with increasing hydrocarbon fees oxygen to carbon ratio; this tendency is more evident at higher moisture levels.

Simulation Study of a PEM Fuel Cell System with Steam Reforming

Abstract This article summarizes the results of a study for a 100 kWe DC electrical power PEM fuel cell system. The system consists of a pre-steam reformer, a steam reformer, high and low temperature shift reactors, a preferential oxidation reactor, a PEM fuel cell, a combustor, and an expander. Acceptable net electrical efficiency levels can be achieved via intensive heat integration within the PEM fuel cell system. The calculations take into account the auxiliary equipment such as pumps, com pressors, heaters, coolers, heat exchangers and pipes. The process simulation package “Aspen-HYSYS 3.1’’ has been used. The operation parameters of the reactors have been determined considering all the technical limitations involved. A gasoline type hydrocarbon fuel has been studied as hydrogen rich gas source. Thermal efficiencies have been calculated for all of the major system components for selected operation conditions. The fuel cell stack efficiency has been calculated as a function of cell numbers (500, 750, 1000, and 1250 cells). Efficiencies of all of the major system components along with auxiliary unit efficiencies determine the net electrical efficiency of the PEM fuel cell system. The obtained net electrical efficiency levels are between 34 (500 cells) to 41% (1250 cells). #Contributed by the Organizing Committee for the First International Exergy, Energy and Environment Symposium (IEEES-1). Paper presented at IEEES-1, Izmir, Turkey,13-17 July 2003. Manuscript received by IJGE on 2003-12-23; final revision received on 2004-02-10. Corresponding guest editors: I. Dincer and A. Hepbasli.

Effect of interior guide tubes in cross-flow turbine runner on turbine performance

The cross-flow turbine has attracted much attention as a source of hydropower generation for small and micro-systems, especially for low head establishments. Such turbines have a distinct advantage of lower initial and operating costs over other small scale turbines, but their efficiency is lower than others. Efficiency predictions of these turbines are generally based on the assumption that the entire flow crosses from the first stage to the second stage of the turbine runner. In this study, interior guide tubes were designed and used inside the runner of a cross-flow turbine to collect and guide the crossing flow towards the second stage of the runner. The interior guide tubes were designed on the basis of observed flow patterns inside the runner. Experimentally, three different types of tubes were tested. The laboratory tests were conducted to calculate the turbine efficiency with different gate openings of nozzle and different positions of interior guide tubes. Results of this work with and without interior tubes have been presented in this paper. When the experiments were done with and without interior guide tubes, it has been found that turbine efficiency with the interior guide tube decreased about 5 per cent. Copyright

Drying and conservation conditions of pollen

In this study, drying and conservation conditions of pollens (for Anzer Honey) were experimentally investigated, and the general drying curve equation was derived by applying the Least Squares Method. Drying experiments were conducted in solar- and electric-assisted dryers. Pollens were placed on the shelves as 50 each g in a single layer having a depth of 2.5 mm. During the drying experiments, the shelf temperatures of the drying cupboard were regulated between 40 °C and 45 °C. Weight losses, moisture contents and mass shrinkage of pollens and average temperatures in the shelves were determined and calculated based on drying time. Additionally, the experimental uncertainty values were calculated as approximately 18%, depending on the experimental results. It was concluded that pollens should be dried at temperatures between 40 °C and 45 °C for between 2.5 and 3 h so as not to change the colour, flavour, smell and structure, and conserved in brown bottles under vacuum in a shady medium. © 2000 Society of Chemical Industry

Solar drying of rainbow trout

The aim of this study is to dry rainbow trout (Oncorhynchus mykiss) by employing a solar energized system. For this purpose, an experimental apparatus was built in the Energy Research Laboratory of Mechanical Engineering Department, Karadeniz Technical University, Trabzon, Turkey. The pre-treated fish samples were dried at 33–36°C with about 1·8 m/s air velocity in 3 days. Results showed that the samples dried very quickly in the first 15 h of drying then a slow process occurred. The drying process was completed in about 75 h. It was concluded that fish drying is possible in the North East Black Sea region or other areas with a similar climate by a solar energy system if an additional heater is used. This technique was found to be safe for changeable weathers as well as simple. This system has economical advantages compared to other methods applied alone, and can also be used for other drying applications. Copyright

New drying systems for crops

Drying of agricultural products is an energy intensive operation. High prices and shortages in fossil fuels increase the emphasis on using solar energy as an alternative energy source, especially in developing countries. This paper deals with the construction of four different solar powered drying systems consisting of solar air heaters and drying chambers for small scale, natural convection, direct and indirect solar drying. Generally, solar drying systems which have two main parts, namely a solar air heater and a drying chamber, work during the day and they do not work at night and cloudy days. In this study, these drying systems were successfully tested for apple drying. The drying curves of those systems were compared with the traditional solar drying results. It is concluded that the using of the continuous drying system gave the best results with the reduction of drying time.

Preliminary studies of lignocellulosics and waste fuels for fixed bed gasification

This study was carried out to understand the decomposition behaviour of a range of biofuel and waste feedstock during gasification in a downdraft gasifier. A laboratory scale large sample thermogravimetric analyser (LSTA) is used which allows the data on burn-out characteristics of different fuel particles to be measured under agitated conditions. The conditions chosen simulate the combustion behaviour in a gasifier for a range of biofuels and wastes, namely hazelnut, pistachio, and peanut shells, wood chips and sewage sludge pellets. From this data the activation energy is calculated for a heating rate of 20°C/min. It was found that, as the weight loss increases, the activation energy decreases. In addition, the influence of a range of gasification air/N 2 levels on constituents of the gas released during hazelnut shell decomposition was observed. It was found that the composition of the product gases consisted of CH4, H2, CO, CO2, C2H 4, C2H6. This was analysed as function of time for hazelnut shells showing that the primary products are H2, CO, CH4 and CO2.