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COAR Access Rights: metadata only accessPublisher: Turkish Soc thermal Sciences Technology

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    Article
    Experimental Study and Theoretical Investigation of High Temperature Proton Exchange Membrane Fuel Cell Micro-Cogeneration Application
    (Turkish Soc thermal Sciences Technology, 2018) Devrim, Yilser; Ozgirgin Yapici, Ekin; Energy Systems Engineering
    In this study, a house hold micro-cogeneration system is designed using high temperature proton exchange membrane (HTPEM) fuel cell. HTPEM type fuel cells gain the highest interest lately, due to their advantages in terms of increasing efficiency and power quality, reducing harmful emissions and flexibility of operation with respect to the other fuels. The micro-cogeneration system involves producing both electrical energy and hot water and/or vapor together in an economical way, utilizing single fuel (HTPEM fuel cells) for household applications. During the operation of the fuel cell, for high efficiency and stable power production, the access heat of the stack should be removed constantly and the temperature of the stack should be held stable. Heat recovered from the designed innovative cooling system is used for acquiring energy for heating water. This way, thermal efficiency is almost doubled compared to simple cycle. In the scope of this study, 225 W HTPEM fuel cell stack is designed and tested at 160 degrees C operation temperature with hydrogen gas and air. During operation, for homogenous distribution of temperature among the cells, for a short start up period leading to a fast required steady state temperature and for constantly removing the access heat produced in the cell, the cell stack is cooled by using a cooling fluid (Heat Transfer Oil 32- Petrol Ofisi). Selection of insulation material type and thickness for the cell stack is done using natural convection and radiation loss calculations. For the most efficient operating conditions, micro-cogeneration system water inlet and exit temperatures, water and cooling fluid flow rates, convenient pipe diameter and pump power calculations are done to finalize the design. With the cogeneration system designed during the studies, by recovering the access heat of the insulated HTPEM cell stack, district water with initial temperature of 15-20 degrees C is heated around 50 degrees C. Data gathered during studies indicate that fuel cell micro-cogeneration application is highly viable.
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    Article
    Citation - WoS: 5
    Measurement of Solar Radiation in Ankara, Turkey
    (Turkish Soc thermal Sciences Technology, 2013) Caglar, Ahmet; Yamali, Cemil; Baker, Derek K.; Kaftanoglu, Bilgin
    The solar energy potential of Ankara, Turkey, (39.89 degrees N, 32.78 degrees E) has been investigated using the measurements of global and beam radiation over the period May 2008 to May 2009. Surface air temperature was also measured and variation in clearness index evaluated over this period. Global and beam radiations have been analyzed using hourly, daily and monthly averages obtained from 1-minute averages of recorded data. Results show that annual average daily global and beam radiations were 17.04 and 15.72 MJ/m(2)/day, respectively, for this period. The results are compared with the data available for several other cities in Turkey. The study shows that Ankara has a large solar potential. The consistency of these data with that from the State Meteorological Service (SMS) weather station in Ankara was analyzed. Significant differences between these 2 stations were found and are attributed to measurement error at the SMS station. New radiation-measurement stations should be established to create a better national radiation database for Turkey.
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    Article
    Citation - WoS: 1
    A NEW FORMULATION FOR THE BOUNDARY ELEMENT ANALYSIS OF HEAT CONDUCTION PROBLEMS WITH NONLINEAR BOUNDARY CONDITIONS
    (Turkish Soc thermal Sciences Technology, 2019) Baranoglu, Besim
    An effective numerical method based on the boundary element formulation is presented to solve heat conduction equations which are governed by the Fourier equation, with nonlinear boundary conditions on one or more sections of the prescribed boundary. The solution involves the manipulation of the system matrices of the boundary element method and obtaining a smaller ranked matrix equation in which the unknown is only the temperature difference over the nonlinear boundary condition region. This way, the iterations to deal with the nonlinear conditions are performed faster. After finding the solution over the nonlinear boundary condition region, the solution over the entire boundary is obtained as a post-process through a prescribed relation. An example with a proven exact solution is employed to assess the results.