Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Conference Object Citation - WoS: 7Modeling of Low Temperature Geothermal District Heating Systems(Taylor and Francis Ltd., 2004) Yıldırım, Nurdan; Gökçen, GüldenIn this work, low temperature geothermal district heating systems with heat pumps have been studied and compared with fuel-oil boiler heating systems for intermittent and continuous regimes according to the optimum indoor air temperature and operational cost. Izmir Institute of Technology (IZTECH) Campus is taken as a case study. Various heat pump and boiler configurations are studied to meet required duty. Operational cost analysis for each alternative is conducted. According to the results, for IZTECH Campus the best alternative, which gives the optimum indoor air temperature and the lowest operational cost, is heat pump continuous regime.Article Citation - WoS: 27Citation - Scopus: 28Effects of Wall-Located Heat Barrier on Conjugate Conduction/Natural- Convection Heat Transfer and Fluid Flow in Enclosures(Taylor and Francis Ltd., 2008) Hakyemez, Erinç; Mobedi, Moghtada; Öztop, Hakan FehmiThe effects of a heat barrier, located in the ceiling wall of an enclosure, on conjugate conduction/natural convection are investigated numerically. The vertical walls of the enclosure are differentially heated and the horizontal walls are adiabatic. Heatline technique is used to visualize heat transport. The variations of average Nusselt number, dimensionless heat transfer rate through the ceiling wall, and dimensionless overall heat transfer rate are studied. Calculations are performed for different Rayleigh numbers (10 3≤ Ra ≤ 10 6), thermal conductivity ratios (1 ≤ K ≤ 100), dimensionless locations of the heat barrier (0 < X h < 1),and two dimensionless ceiling wall thicknesses (D = 0.05 and D = 0.20). For high thermal conductivity ratio (K = 100), the heat barrier considerably reduces the dimensionless overall heat transfer rate. The effect of the heat barrier on dimensionless heat transfer rate through the enclosure increases as the Rayleigh number decreases. For low Rayleigh number (i.e., Ra = 10 3), a location exists in the ceiling wall for which the dimensionless overall heat transfer rate is minimum.Article Citation - WoS: 15Citation - Scopus: 16Geothermal Fields Suitable for Power Generation(Taylor and Francis Ltd., 2004) Gökçen Akkurt, Gülden; Öztürk, Harun Kemal; Hepbaşlı, ArifTurkey is located on the Mediterranean sector of Alpine-Himalayan Tectonic Belt with many grabens, acidic volcanism, hydrothermal alteration zones, numerous hot springs and fumaroles. The data gathered since 1962 indicate that Turkey has a high geothermal energy potential. By comparison, it is among the first seven countries in abundance of geothermal resources around the world, while the share of its potential used is only about 2%. This means that considerable studies on geothermal energy could be conducted in order to increase energy supply and to reduce atmospheric pollution in Turkey. The main objective of the present study is threefold, namely: (1) to overview Turkey's geothermal fields suitable for power generation together with their possible utilization opportunities, (2) to present problems encountered and research projects developed in the Denizli-Kizildere geothermal field with an estimated capacity of 200 MWe and (3) to assess the current status of geothermal energy use for electric energy production in Turkey. The Denizli-Kizildere geothermal power plant with an installed capacity of 20.4 MWe which is, at present, the only operating geothermal power plant of Turkey, was put into operation in 1984, while electricity from geothermal energy has been produced commercially since 1913. This plant produced on average an electrical energy of 84,920 MWh in the period between 1998-2001, representing an average electric power of 10.45 MWe in the same period. Parallel to the development of the geothermal energy utilization in the country, it is projected that, by the years 2010 and 2020, the total geothermal power installed capacity will increase to 500 MWe, respectively.Conference Object Citation - WoS: 1Citation - Scopus: 6Genetic Algorithm-Artificial Neural Network Model for the Prediction of Germanium Recovery From Zinc Plant Residues(Taylor and Francis Ltd., 2002) Akkurt, Sedat; Özdemir, Serhan; Tayfur, GökmenA multi-layer, feed-forward, back-propagation learning algorithm was used as an artificial neural network (ANN) tool to predict the extraction of germanium from zinc plant residues by sulphuric acid leaching. A genetic algorithm (GA) was used for the selection of training and testing data and a GA-ANN model of the germanium leaching system was created on the basis of the training data. Testing of the model yielded good error levels (r2 = 0.95). The model was employed to predict the response of the system to different values of the factors that affect the recovery of germanium and the results facilitate selection of the experimental conditions in which the optimum recovery will be achieved.