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    Determination of mushroom drying conditions
    (BEGELL HOUSE, INC, 1999) Midilli, A; Olgun, H; Rzayev, P; Ayhan, T; Nasirova, T; Dincer, I; Ayhan, T
    In this study, drying behavior of mushrooms was investigated. The experiments were carried out under bath laboratory and shady-and sunny-atmospheric conditions. Drying curves were presented for each experiment. It was concluded that mushrooms can be dried in the cupboards by using air at 50 degrees C of temperature in a time period of 5 to 6 hours, and the mushrooms dried must be protected in a medium without air (in vacuum). The uncertainty error rate of drying is about 22 %.
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    Energy and exergy of potato drying process via cyclone type dryer
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Akpinar, EK; Midilli, A; Bicer, Y
    This paper is concerned with the energy and exergy analyses of the single layer drying process of potato slices via a cyclone type dryer. Using the first law of thermodynamics, an energy analysis was performed to estimate the ratios of energy utilization. An exergy analysis was accomplished to determine the location, type and magnitude of the exergy losses during the drying process by applying the second law of thermodynamics. It was concluded that the exergy losses took place mostly in the 1st tray where the available energy was less utilized during the single layer drying process of potato slices. It is emphasized that the potato slices are sufficiently dried in the ranges between 60 and 80 degrees C and 20-10% relative humidity at 1 and 1.5 ms(-1) of drying air velocity during 10-12 h despite the exergy losses of 0-1.796 kJ s(-1). (c) 2005 Elsevier Ltd. All rights reserved.
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    Exergetic performance analysis of a PEM fuel cell
    (WILEY, 2006) Ay, M; Midilli, A; Dincer, I
    In this paper we investigate the effects of thermodynamic irreversibilities on the exergetic performance of proton exchange membrane (PEM) fuel cells as a function of cell operating temperature, pressures of anode and cathode, current density, and membrane thickness. The practical operating conditions are selected to be 3-5 atm for anode and cathode pressures, and 323-353 K for the cell temperatures, respectively. In addition, the membrane thicknesses are chosen as 0.016, 0.018 and 0.02cm, respectively. Moreover, the current density range of the PEM fuel cell is selected to be 0.01-2.0 A cm(-2). It is concluded that exergy efficiency of PEM fuel cell decreases with a rise in membrane thickness and current density, and increases with a rise of cell operating pressure and with a decrease of current density for the same membrane thickness. Thus, it can be said that, in order to increase the exergetic performance of PEM fuel cell, the lower membrane thickness, the lower current density and the higher cell operating pressure should be selected in case PEM fuel cell is operated at constant cell temperature. Copyright (c) 2005 John Wiley & Sons, Ltd.
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    Gasification of leather residues - Part I. Experimental study via a pilot scale air blown downdraft gasifier
    (TAYLOR & FRANCIS INC, 2004) Dogru, M; Midilli, A; Akay, G; Howarth, CR
    This article presents an experimental study on the gasification of leather residues from a tannery by using a throated 10 kW(e) downdraft gasifier. The gasification process is conducted over a range of feed rates in the gasifier for the operating temperatures of 1,000degreesC and 1,100degreesC, slightly below atmospheric pressure. In this study, the experimental setup and procedure are also explained in detail. Moreover, the fuel characteristics, components in the produced gas, and side products from the gasification system were measured during the experiments and discussed. It was concluded that the briquetted leather residues were successfully gasified in a downdraft gasifier. However, the large briquette sizes of the leather residues occasionally formed bridging in the throat zone of the gasifier. Therefore the downdraft gasifier should be operated using smaller size briquettes to prevent the bridging in the throat zone in order to productively convert the leather residues into combustible gases.
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    Gasification of leather residues - Part II. Conversion into combustible gases and the effects of some operational parameters
    (TAYLOR & FRANCIS INC, 2004) Midilli, A; Dogru, M; Akay, G; Howarth, CR
    The main aim of this article is to investigate the conversion of leather residues into combustible gases by using a downdraft gasification technique. Second, the effects of leather residues on the operation of the throated-downdraft gasifier are explored. It was deduced that the percentage of the combustible gases, including around 11% of H-2, 20% of CO, and 2% of CxHx, varied between approximately 29% and 33% of the total produced wet gas. Moreover, the great amount of hydrocarbons was produced at almost 0.20 kgH(2)/kgC of the ratio of H-o/C-o. The most productive region for the gasification would be selected between 486.39 and 584.36 Nm(3)/m(2)h of the specific gasification rate (SGR). The optimum efficiency of cold gas was calculated as 46.50%, around 486.39 Nm(3)/m(2)h of the SGR. The overall results give a positive indication of the suitability of leather waste for both heat production and power generation using a downdraft type of gasification system.
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    Modeling and experimental study on drying of apple slices in a convective cyclone dryer
    (WILEY-BLACKWELL, 2003) Akpinar, EK; Bicer, Y; Midilli, A
    The main objective pursued in this paper is to experimentally investigate the single layer drying behavior of apple slices in a convective type cyclone dryer and also to perform the mathematical modeling by using single layer drying models in literature. The experiments were conducted at drying air temperatures of 60, 70 and 80C in drying air velocities of 1 and 1.5 m/s. It was concluded that apple slices with the thickness of 12.5 mm would perfectly dry in the ranges of 280-540 min while those with the thickness of 8 mm would dry in the ranges of 180-320 min in these drying conditions by using convective type cyclone dryer. Additionally, the mathematical model describing the single layer drying curves was determined by nonlinear regression analysis, and the logarithmic model was selected as the most suitable model to obtain the drying curve equation of apple slices. Considering the parameters such as drying time, drying rate, moisture transfer, velocity and drying air temperature it is suggested that the apple slices be dried at the above optimum processing conditions.
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    On hydrogen and hydrogen energy strategies I: current status and needs
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Midilli, A; Ay, M; Dincer, I; Rosen, MA
    This article deals with hydrogen energy as a clean energy carrier, discusses the key role of hydrogen energy technologies and systems, and compares hydrogen with other energy forms. Energy strategies that incorporate hydrogen are considered, and the importance of hydrogen energy in achieving a sustainable energy system is discussed. Exergetic, environmental, sustainability and other perspectives are considered. (C) 2004 Elsevier Ltd. All rights reserved.
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    On hydrogen and hydrogen energy strategies II: Future projections affecting global stability and unrest
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Midilli, A; Ay, M; Dincer, I; Rosen, MA
    This article focuses on hydrogen energy strategies and discusses the key role of hydrogen as an energy carrier in this century and beyond. Two important empirical relations that describe the effects of fossil fuels on world peace and global unrest are developed. These relations incorporate predicted utilization ratios for hydrogen energy from non-fossil fuels, and are used to investigate whether hydrogen utilization can reduce the negative global effects related to fossil fuel use, eliminate or reduce the possibilities of global energy conflicts, and contribute to achieving world peace and stability. Consequently, the highest levels of global peace and global unrest can be estimated. If hydrogen use from non-fossil fuels increases, for a fixed usage of petroleum, coal and natural gas, the level of global unrest decreases. However, if the utilization ratio of hydrogen energy from non-fossil fuels is lower than 100%, the level of global peace decreases as the symptoms of global unrest increase. Thus, to reduce the causes of global unrest and increase the likelihood of global peace in the future, it is suggested that hydrogen energy be widely and efficiently used as part of sustainable technologies and systems. It is expected that the results of this study will be of use to decision makers and scholars who want to develop and promote the use of hydrogen-based technologies and solve future energy and environment related problems globally. (C) 2004 Elsevier Ltd. All rights reserved.
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    The first and second law analyses of thermodynamic of pumpkin drying process
    (ELSEVIER SCI LTD, 2006) Akpinar, EK; Midilli, A; Bicer, Y
    This paper is concerned with the thermodynamic analyses of single layer drying process of pumpkin slices via cyclone type dryer. Using the first law of thermodynamics, energy analysis was performed to estimate the ratios of energy utilization. However, exergy analysis was accomplished to determine the location, type, and magnitude of exergy losses during drying process by applying the second law of thermodynamics. It was concluded that the exergy losses went up with the increase of the energy utilization in both trays and drying chamber. The most exergy losses took place during the drying of pumpkin slices on the first tray. It is emphasized that pumpkin slices are sufficiently dried in the ranges between 60 and 80 degrees C and 20% and 10% of relative humidity at 1 and 1.5 in s(-1) of drying air velocity during 5.66-12 h despite the exergy losses of 0-1.165 kJ s(-1). (c) 2005 Elsevier Ltd. All rights reserved.
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    Thermodynamic analysis of the apple drying process
    (PROFESSIONAL ENGINEERING PUBLISHING LTD, 2005) Akpinar, EK; Midilli, A; Bicer, Y
    This paper is concerned with thermodynamic analysis of the process of single-layer drying of apple slices by means of a cyclone-type dryer. Using the first law of thermodynamics, energy analysis was performed to estimate the ratios of energy utilization throughout the drying process. Exergy analysis was carried out to determine exergy losses during the drying process by applying the second law of thermodynamics. It was concluded that the exergy losses increased with increasing energy utilization in both trays and the drying chamber. Values of the energy utilization ratio (EUR) of the drying chamber varied in the range 0-41.64 per cent depending on the drying conditions. The most exergy losses took place on the first tray (EUR = 0-21.06 per cent) during the drying of apple slices. It is emphasized that apple slices are sufficiently dried in the range 60-80 degrees C with 20-10 per cent relative humidity and a drying air velocity of 1.5 m/s over a 3.33-5.33 h period in spite of exergy losses of 0-1.243 kj/s (EUR = 0-34.72 per cent).