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Izmir, Turkey

Yaşar University is a university, in Izmir, Turkey on the Aegean Sea. The university faculty teaches in English, with programs at both the undergraduate and postgraduate level. Wikipedia.

The present study deals with modelling, analyzing and assessing the performance of greenhouse heating systems with earth-pipe-air heat exchangers (EAHEs) in closed loop mode. In this regard, an EAHE system is considered as an illustrative example. This system starts with the power plant, through the production of heat (EAHE), via a distribution system, to the heating system and from there, via the greenhouse air, across the greenhouse envelope to the outside environment. Exergy analysis method (the so-called low exergy or LowEx approach) has been and still being successfully used to design and evaluate sustainable buildings. It is applied to all components of this EAHE system for the first time to the best of the author's knowledge in this study. The overall energy efficiency value for the EAHE system studied is determined to be 72.10% while the overall exergy efficiency value is calculated to be 19.18% at a reference state temperature of 0 C. The exergy efficiency of the whole EAHE system decreases from 19.18% to 0.77% with the increase in the reference environment temperature from 0 to 18 C. The sustainability index values for the whole EAHE system decrease from 1.24 to 1.01 as the reference state temperature increases. © 2013 Elsevier B.V. Source

Hepbasli A.,Yasar University | Kecebas A.,Mugla University
Energy and Buildings | Year: 2013

This paper comparatively evaluates exergy destructions of a geothermal district heating system (GDHS) using both conventional and advanced exergetic analysis methods to identify the potential for improvement and the interactions among the components. As a real case study, the Afyon GDHS in Afyonkarahisar, Turkey, is considered based on actual operational data. For the first time, advanced exergetic analysis is applied to the GDHSs, in which the exergy destruction rate within each component is split into unavoidable/avoidable and endogenous/exogenous parts. The results indicate that the interconnections among all the components are not very strong. Thus, one should focus on how to reduce the internal inefficiency (destruction) rates of the components. The highest priority for improvement in the advanced exergetic analysis is in the re-injection pump (PM-IX), while it is the heat exchanger (HEX-III) in the conventional analysis. In addition, there is a substantial influence on the overall system as the total avoidable exergy destruction rate of the heat exchanger (HEX-V) has the highest value. On the overall system basis, the value for the conventional exergetic efficiency is determined to be 29.29% while that for the modified exergetic efficiency is calculated to be 34.46% through improving the overall components. © 2013 Elsevier B.V. Source

Tasdemir K.,Yasar University
IEEE Transactions on Neural Networks | Year: 2010

The self-organizing map (SOM) is a powerful method for manifold learning because of producing a 2-D spatially ordered quantization of a higher dimensional data space on a rigid lattice and adaptively determining optimal approximation of the (unknown) density distribution of the data. However, a postprocessing visualization scheme is often required to capture the data manifold. A recent visualization scheme CONNvis, which is shown effective for clustering, uses a topology representing graph that shows detailed local data distribution within receptive fields. This brief proposes that this graph representation can be adapted to show local distances. The proposed graphs of local density and local distances provide tools to analyze the correlation between these two information and to merge them in various ways to achieve an advanced visualization. The brief also gives comparisons for several synthetic data sets. © 2010 IEEE. Source

Kecebas A.,Mugla University | Hepbasli A.,Yasar University
Energy and Buildings | Year: 2014

The present study deals with analyzing, assessing and comparing conventional and advanced exergoeconomic analyses to identify the direction and potential for energy savings of a geothermal district heating system in future conditions/projections. As a real case study, the Afyon geothermal district heating system in Afyonkarahisar, Turkey, is considered while its actual operational thermal data on 8 February 2011 are utilized in the analysis, which is based on the specific exergy costing method. In this study for the first time, based on the concepts of avoidable/unavoidable and endogenous/exogenous parts, cost rates associated with both exergy destruction and capital investment of the geothermal district heating system are determined first, and the obtained results are then evaluated. The results indicate that the internal design changes play a more essential role in determining the cost of each component. The cost rate of unavoidable part within the components of the system is lower than that of the avoidable one. For the overall system, the value for the conventional exergoeconomic factor is determined to be 5.53% while that for the modified one is calculated to be 9.49%. As a result, the advanced exergoeconomic analysis makes more sense given the additional information in splitting process of the components. © 2013 Elsevier Ltd. All rights reserved. Source

Erbay Z.,Sudan University of Science and Technology | Hepbasli A.,Yasar University
Energy Conversion and Management | Year: 2014

Inefficiencies in an energy system can be quantitatively determined through conventional exergy analysis while sources of the irreversibilities and real improvement potential can be deducted using a relatively new method named as advanced exergy analysis. For the first time, an advanced exergy analysis is applied to a ground-source heat pump (GSHP) drying system used in food drying for evaluating its performance along with each component in this study. The results indicate that the most important system component is the condenser due to the design standpoint. The inefficiencies within the compressor could particularly be improved by structural improvements of the whole system and the remaining system components. Furthermore, the inefficiencies of other system components except for the condenser and the evaporator are mainly affected by the internal operating condition. Both the equipment design and system components' interactions of the condenser and the evaporator have a significant effect on their inefficiencies. The conventional and modified (advanced) exergy efficiency values are calculated to be 77.05% and 93.5%, respectively. © 2013 Elsevier Ltd. All rights reserved. Source

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