Browsing by Author "Ekren, Orhan"

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Citation - WoS: 168
Citation - Scopus: 211
A key review of wastewater source heat pump (WWSHP) systems
(Elsevier Ltd, 2014) A. Hepbasli; Emrah Biyik; Orhan Ekren; Huseyin Gunerhan; Mustafa Araz; Ekren, Orhan; Araz, Mustafa; Hepbasli, Arif; Gunerhan, Huseyin; Biyik, Emrah
Heat pumps (HPs) are part of the environmentally friendly technologies using renewable energy and have been utilized in the developed countries for years. Wastewater is seen as a renewable heat source for HPs. At the beginning of the 1980s waste (sewage) water source heat pumps (WWSHPs) were widely applied in North European countries like Sweden and Norway and partially applied in China. In the past two decades the WWSHP has become increasingly popular due to its advantages of relatively higher energy utilization efficiency and environmental protection. The present study comprehensively reviews WWSHP systems in terms of applications and performance assessments including energetic exergetic environmental and economic aspects for the first time to the best of the authors' knowledge. In this context a historical development of WWSHPs was briefly given first. Next wastewater potential and its characteristics were presented while a WWSHP system was introduced. The previously conducted studies on WWSHPs were then reviewed and classified in a tabulated form. Finally some concluding remarks were listed. The COP values of the reviewed studies ranged from 1.77 to 10.63 for heating and 2.23 to 5.35 for cooling based on the experimental and simulated values. The performance assessments are mostly made using energy analysis methods while the number of exergetic evaluations is very low and has not been comprehensively performed. It is expected that the comprehensive review here will be very beneficial to those dealing with the design analysis simulation and performance assessment of WWSHP systems. © 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 7
Citation - Scopus: 8
Design of microcontroller-based decentralized controller board to drive chiller systems using PID and fuzzy logic algorithms
(SAGE Publications Ltd, 2020) Yalcin Yalcin Isler; Savaş Şahin; Orhan Ekren; Cüneyt Güzeliş; Isler, Yalcin; Ekren, Orhan; Guzelis, Cuneyt; Sahin, Savas
This study deals with designing a decentralized multi-input multi-output controller board based on a low-cost microcontroller which drives both parts of variable-speed scroll compressor and electronic-type expansion valve simultaneously in a chiller system. This study aims to show the applicability of commercial low-cost microcontroller to increase the efficiency of the chiller system having variable-speed scroll compressor and electronic-type expansion valve with a new electronic card. Moreover the refrigerant system proposed in this study provides the compactness mobility and flexibility and also a decrease in the controller unit’s budget. The study was tested on a chiller system that consists of an air-cooled condenser a variable-speed scroll compressor and a stepper driven electronic-type expansion valve. The R134a was used as a refrigerant fluid and its flow was controlled by electronic-type expansion valve in this setup. Both variable-speed scroll compressor and electronic-type expansion valve were driven by the proposed hardware using either proportional integral derivative or fuzzy logic controller which defines four distinct controller modes. The experimental results show that fuzzy logic controlled electronic-type expansion valve and proportional integral derivative controlled variable-speed scroll compressor mode give more robustness by considering the response time. © 2022 Elsevier B.V. All rights reserved.
Doğrusal Tip Manyetik Soğutma Sistemi Tasarımı ve Performansının Deneysel Olarak İncelenmesi
(2018) Mehmet Akif Ezan; Ahmet YILANCI; Emrah BIYIK; Orhan EKREN; Ekren, Orhan; Yılancı, Ahmet; Ezan, Mehmet Akif; Bıyık, Emrah
Bu çalışmada manyetokalorik etkinin ısıtma-soğutma amacıyla kullanımına yönelik deneysel bir çalışma sunulmuştur. Çalışma kapsamında tasarlanan ve oda sıcaklığı civarında çalışan manyetik soğutma sistemi performansı incelenmiş ve deneysel çalışma sonuçları verilmiştir. Deneysel manyetik soğutma sisteminde manyetokalorik malzeme olarak gadolinyum kullanılmıştır. Manyetokalorik malzemenin plaka ve toz şeklinde kullanıldığı yeni bir rejeneratör tasarlanarak doğrusal hareketli manyetik soğutma sisteminde çalıştırılmıştır. Sistemde ısı transfer akışkanı olarak %10 etanol-su karışımı kullanılmıştır. Tasarlanan sistem ile 0 76 Tesla manyetik alan altında teorik çalışmalarda5 °C deneysel çalışmalarda yaklaşık 2 °C sıcaklık düşüşü elde edilmiştir.
Citation - Scopus: 1
Evaluation of fuel production technologies by using renewable energy for smart cities
(Elsevier, 2022) Celal Hakan Canbaz; Orhan Ekren; Banu Yetkin Yetkin Ekren; Vikas Kumar; Ekren, Orhan; Canbaz, Celal Hakan; Kumar, Vikas; Ekren, Banu Y.
Fuels that are environment-friendly resources play a vital role in the development of economies. Each fuel resource has intensive however inadequate specifications in terms of security sustainability capacity to compete with other sources. Although oil and gas resources lead the way of fuel production due to their low cost alternative sources such as wind and solar renewable energy and nuclear energy have also gained popularity forcing the technological development of fuel production technologies. Hydrogen is a source for the production of energy by using any energy resource. In this chapter we investigate the latest fuel production technologies providing energy outputs from renewable energy resources for their usage in smart cities. We study the role of renewable resources under the current dynamics of the global energy market situation as well as the effects of fuel production technologies to increase the efficiency and sustainability for the future of smart cities. This review includes a broad spectrum that spans from the technical energy resources literature with very comprehensive research by using SCOPUS database to nontechnical but renowned resources including journals and other publications including raw data as well as forecasts and opinions that respected experts have performed. Specifically solar and wind production technologies as well as future forecasts compared with the conventional fuel resources are reviewed comprehensively. By that we aim to shed a light on the current status of fuel production technologies in renewable energy resources and their usage in smart cities. © 2022 Elsevier B.V. All rights reserved.
Citation - WoS: 31
Citation - Scopus: 32
Experimental exergetic performance evaluation of a novel solar assisted LiCl-H2O absorption cooling system
(ELSEVIER SCIENCE SA, 2014) Tuncay Gunhan; Orhan Ekren; Vedat Demir; Arif Hepbasli; Aytunc Erek; Arzu Sencan Sahin; Sahin, Arzu Sencan; Demir, Vedat; Ekren, Orhan; Gunhan, Tuncay; Hepbasli, Arif; Erek, Aytunc
This study proposes a novel solar assisted absorption cooling (SAAC) system and performs its exergetic analysis and assessment. The system was designed constructed and tested in Izmir Turkey. Water was used as refrigerant in the system. The performance of the whole system along with its main components was assessed through exergy analysis method. The results obtained gave the exergy destruction rate the exergy efficiency in various forms the relative irreversibility and sustainability index in both charging and discharging processes. A parametric study was also undertaken to investigate the effect of the various dead (reference) state temperatures ranging from 30 degrees C to 42 degrees C with an interval of 4 degrees C on the entire system efficiency. In this context the exergy efficiency of the whole system varied between 13.1 and 43.2% as the dead state temperatures increase from 30 degrees C to 42 degrees C. The highest relative irreversibility values of 66.1% and 34.6% belonged to the solar collectors and the absorption chiller in charging and discharging processes at a dead state temperature of 34 degrees C respectively. (C) 2013 Elsevier B.V. All rights reserved.
Citation - WoS: 100
Citation - Scopus: 117
Heat exchanger applications in wastewater source heat pumps for buildings: A key review
(ELSEVIER SCIENCE SA, 2015) Oguzhan Culha; Huseyin Gunerhan; Emrah Biyik; Orhan Ekren; Arif Hepbasli; Culha, Oguzhan; Ekren, Orhan; Hepbasli, Arif; Gunerhan, Huseyin; Biyik, Emrah
Wastewater heat recovery applications are becoming widespread in energy saving applications. A sustainable and low emissions operation in air conditioning and heating processes is achieved by harvesting the otherwise wasted energy in wastewater through specially designed heat exchangers lying at the core of heat pumps. This combined system is called wastewater source heat pump. In this study a review of wastewater heat exchangers in wastewater source heat pump applications is presented and wastewater heat exchangers are classified in detail based on multiple features including utilization and construction methodology. Also the potential of wastewater types of wastewater source heat pumps and their applications are briefly discussed. (C) 2015 Elsevier B.V. All rights reserved.
Citation - WoS: 19
Citation - Scopus: 20
Numerical analysis of a near-room-temperature magnetic cooling system, Analyse numérique d'un système de froid magnétique proche de la température ambiante
(Elsevier Ltd, 2017) Mehmet Akif Ezan; Orhan Ekren; Cagri A.S. Metin; Ahmet Yilanci; Emrah Biyik; Salih Murat Kara; Ekren, Orhan; Yilanci, Ahmet; Kara, Salih Murat; Ezan, Mehmet Akif; Biyik, Emrah; Metin, Cagri
In this study for a near-room-temperature magnetic cooling system a decoupled multi-physics numerical approach (Magnetism Fluid Flow and Heat Transfer) is developed using a commercial CFD solver ANSYS-FLUENT as a design tool. User defined functions are incorporated into the software in order to take into account the magnetocaloric effect. Magnetic flux density is assumed to be linear during the magnetization and demagnetization processes. Furthermore the minimum and maximum magnetic flux densities (Bmin and Bmax) are defined as 0.27 and 0.98 respectively. Two different sets of analyses are conducted by assuming an insulated cold heat exchanger (CHEX) and by defining an artificial cooling load in the CHEX. As a validation case experimental work from the literature is reproduced numerically and the results show that the current methodology is fairly accurate. Moreover parametric analyses are conducted to investigate the effect of the velocity of heat transfer fluid (HTF) and types of HTF on the performance of the magnetic cooling system. Also the performance metrics of the magnetic cooling system are investigated with regards to the temperature span of the magnetic cooling unit and the cooling load. It is concluded that reducing the cycle duration ensures reaching lower temperature values. Similarly reducing the velocity of the HTF allows reducing the outlet temperature of the HTF. In the current system the highest temperature spans are obtained numerically as around 6 K 5.2 K and 4.1 K for the cycle durations of 4.2 s 6.2 s and 8.2 s respectively. © 2017 Elsevier B.V. All rights reserved.
Özgün Güneş Fotovoltaik/Isıl (Pv/T) Destekli Bir Atıksu Isı Pompası Sisteminin Tasarımı, Kurulumu ve Deneysel Araştırılması
(2016) Çulha, Oğuzhan; Hepbaşlı, Arif; Bıyık, Emrah; Ekren, Orhan; Araz, Mustafa; Öztop, Hakan Fehmi; Gunerhan, Huseyin
In this research project, it was aimed at designing and constructing a hybrid Photovoltaic/Thermal (PV/T) solar-assisted wastewater source heat pump (WWSHP) and evaluating its performance through various energetic and exergetic analysis methods. The WWSHP system consisting of three (a HP, a WW and an end-user) cycles was installed at Yasar University, Izmir, Turkey. Within the scope of the project, a total of 18 experiments was conducted and recorded to assess the performance of the system using various analysis methods such as energy, exergy, exergoeconomic, exergoenvironmental, low-exergy (lowex) methods. A three-dimensional design of different WW heat exchangers (WWHEs) was made at various geometries and lengths while their performance, fluid and heat transfer tests were modeled using computational fluid dynamics (CFD) method. A dynamic model of the heat pump system was also developed using system identification methods, and was used within the model predictive controller to estimate the system’s response to control actions. The results indicated that the overall COP and exergy efficiency values of the system were in the range of 1.85-5.89 and 3.39% and 20.71% , respectively. The PV/T unit accounted for the biggest exergy destruction, followed by the compressor and the fan-coil unit. The fan-coil unit caused a decrease in the overall COP and exergy efficiency values due to the higher energy consumption and higher exergy destructions. The exergy efficiency and flexibility factor values from the primary energy transformation to the building envelope were determined to be 5.66% and 14.51% through the lowex analysis, respectively. Based on exergoeconomic and exergoenvironmental analysis results, the exergoeconomic factor values were obtained to be larger than 0.5 for the system components excluding the fan-coil unit and the PV/T system while the exergoenvironmental factor values were obtained to be smaller than 0.5 for the system components excluding the condenser and the pumps.