Energy Systems Engineering / Enerji Sistemleri Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4752

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Citation - WoS: 11
Citation - Scopus: 13
Assessment of Thermal Comfort Preferences in Mediterranean Climate a University Office Building Case
(Vinca Inst Nuclear Sci, 2018) Turhan, Cihan; Gökçen Akkurt, Gülden; 03.10. Department of Mechanical Engineering; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
This study aims at evaluating the perceived thermal sensation of occupants with respect to thermal comfort standards, ASHRAE 55 and ISO 7730, for office buildings located in Mediterranean climate. A small office building in Izmir Institute of Technology Campus Area, Izmir, Turkey, was chosen as a case building and equipped with measurement devices to assess thermal comfort of occupants with respect to predicted mean vote and actual mean vote. Both objective and subjective measurements were conducted. The former included indoor and outdoor air temperature, mean radiant temperature, relative humidity and air velocity that were used for evaluating the thermal comfort of occupants. Oxygen concentration which can play an additional role in thermal comfort/discomfort, health and productivity of the office occupants, was also measured. Furthermore, occupants were subjected to a survey via a mobile application to obtain subjective measurements to calculate actual mean vote values. Based on objective and subjective measurements, the relationships among the parameters were derived by using simple regression analysis technique while a new combined mean vote correlation was also derived but this time by using multiple linear regression model. Neutral and comfort temperatures were obtained using indoor air temperature and actual mean vote values which were calculated from subjective measurements. The results showed that neutral temperature in the university office building was 20.9 degrees C whilst the comfort temperature range was between 19.4 and 22.4 degrees C for the heating season. By applying new comfort temperatures, energy consumption of the case building located in Mediterranean climate, can be reduced.
Citation - WoS: 8
Citation - Scopus: 10
Auditory Event-Related Potentials Demonstrate Early Cognitive Impairment in Children With Subclinical Hypothyroidism
(Walter de Gruyter GmbH, 2019) Çatlı, Gönül; Kocaaslan Atlı, Sibel; Olgaç Dündar, Nihal; Bayazıt, Onur; Evirgen Esin, Nur; Erdoğan, Uğraş; Dündar, Bumin Nuri; 01. Izmir Institute of Technology
Background: The aim of this study was to examine the cognitive functions of children with subclinical hypothyroidism (SH) and healthy children with the use of auditory event-related potentials (AERPs) and neuropsychological tests. Methods: Twenty children aged between 8 and 17 wars, diagnosed with SH, and 20 age-matched healthy controls were included in this study. A classical auditory oddball paradigm was applied during the electroencephalography (EEG) recordings, and event-related potentials (ERPs) were evaluated between the 0.5- and 20-Hz frequency intervals. P1, N1, P2, N2 and P3 amplitudes and latencies were measured in Fz, FCz, Cz, CPz, Pz and Oz electrodes. Additionally, a number of neuropsychological tests evaluating the reaction time and various cognitive functions were carried out. Results: In children with SH, P3 amplitudes in FCz, Cz and CPz electrodes were significantly lower than those in controls (p <0.05). In addition to this, the P1N1 and N1P2 peak-to-peak amplitude values were also found to be smaller for children with SH than controls (p <0.05). With regard to the neuropsychological tests, no significant difference was observed between the SH and control groups on any of the cognitive test parameters, reaction time or correct response rates. Conclusions: In the present study, while children with SI I did not differ from controls with respect to their cognitive functions evaluated via neuropsychological tests, cognitive differences were detected via electrophysiological investigations. This result implies that implicit changes in cognition which are not yet overtly reflected on neuropsychological tests may be detected at an early stage in children with SH.
Citation - WoS: 1
Citation - Scopus: 1
Energy and Exergy Analysis of a Geothermal Energy Sourced Hot-Air Drying System
(Inderscience Enterprises, 2023) Helvacı, Hüseyin Utku; Keleş, Nazlı; Gökçen Akkurt, Gülden; 01. Izmir Institute of Technology; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering
A geothermal energy-sourced drying system was tested for the thin-layer drying process of tomato slices at air temperatures of 40 degrees C, 50 degrees C and 60? and velocities of 0.5 m/s and 1.5 m/s to investigate system performance in terms of the first and second laws of thermodynamics. The energy and the exergy efficiency of the system were found to be 6.6% and 22.31%. The energy utilisation and energy utilisation ratio were calculated in the range of 1.271 kW-5.102 kW and 9.644%-39.56%, respectively. The exergy destruction, exergy efficiency and improvement potential of the drying chamber varied between 0.0198 kW-0.2621 kW, 59.74%-81.95% and 0.00486 kW-0.07396 kW, respectively.
Citation - WoS: 6
Citation - Scopus: 9
Impact of Climate Change on Indoor Environment of Historic Libraries in Mediterranean Climate Zone
(Inderscience Enterprises, 2019) Turhan, Cihan; Durmuş Arsan, Zeynep; Gökçen Akkurt, Gülden; 02.02. Department of Architecture; 03.10. Department of Mechanical Engineering; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology; 02. Faculty of Architecture
Most historic library buildings house valuable paper-based collections that are kept in unconditioned environments. This vulnerable cultural heritage is expected to be highly affected by climate change in the future. In this study, indoor microclimate of an unconditioned historic library, Necip Pasa Library (Izmir, Turkey) is analysed for existing conditions and future climate data. The measured and predicted indoor microclimate data from 'present' till 2080s are used to determine possible chemical degredation risk on library collection and human comfort. Comparison of periodic results of future climate data indicates an increase in temperature that could cause both an increase in chemical degredation risk on the library collection and a decline in thermal comfort conditions. Mitigation of climate change effects on library collection and human comfort requires taking some actions such as adding light and adaptive mechanical solutions.
Stochastic 1-D Reactive Transport Simulations To Assess Silica and Carbonate Phases During the $co_2$ Reinjection Process in Metasediments
(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2024) Erol, Selçuk; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
One proposed method to mitigate carbon emission is to mineralize the $CO_2$ in deep geothermal reservoirs while mixing the coproduced CO2 with the effluent fluid for reinjection. The injection fluid temperature fluctuates due to the mixing process between CO2-charged water and the effluent fluid, and compressor interruptions change the thermodynamic conditions that influence the fluid- rock interaction in the reservoir. Mineral dissolution or precipitations are associated with changes in permeability and porosity that affect the flow and, eventually, the lifespan of the reservoir. A combined stochastic–reactive transport simulation approach is useful for inspection purposes. Moreover, the stochastic algorithm validates the deterministic reactive transport simulation and demonstrates the time evolution of a chemically reacting system in the reservoir. This study examines a range of injection temperatures between 80 °C and 120 °C to evaluate silica and calcite precipitation along a flow path. One-dimensional (1-D) reactive transport and compartment- based stochastic reaction-diffusion-advection Gillespie algorithms are carried out. The 1-D model represents a reservoir feed zone of around 2300 m. Two common metasediment rock types are evaluated for inspection. The first one is the muscovite schist, which has approximately 60% quartz, and the second is the quartz schist, consisting of roughly 90% quartz. The stochastic method can be applied more effectively if the chemical system is completely defined with proper reaction rates as a function of temperature. The mixing ratio of the coproduced $CO_2$ over the effluent fluid is around 0.0028. Simulation results show that $CO_2$ is partially sequestrated as calcite within the first 10 m of the entrance to the reservoir and plugs the pores completely in the muscovite schist scenario. Chalcedony and α-cristobalite precipitate as secondary minerals evenly along the flow path. $CO_2$ injection into a quartz schist layer is more appropriate for geochemical interactions below 120 °C.
Citation - WoS: 1
Citation - Scopus: 1
Thermodynamic Re-Assessment of a Geothermal Binary Power Plant Operated in a Moderate-Temperature Geothermal Field
(Inderscience, 2023) Özcan, Zeynep; Gökçen Akkurt, Gülden; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
An existing organic rankine cycle power plant which uses isobutane as working fluid is re-evaluated for different working fluids. The plant is first modelled by EES software; then the model is simulated for different working fluids obtaining heat transferred through the heat exchanger, net work output, energy and exergy efficiencies, and mass flowrate of the working fluid. Two parametric studies are conducted to evaluate the thermodynamic performance of the plant under a range of turbine inlet temperature (130°C–155°C) and geothermal resource temperature (152°C–161°C) for each working fluid. The study reveals that the highest cycle energy and exergy efficiencies are observed for R-152a at any geothermal resource temperature. R-152a resulted with 13.1% and 58.2% cycle energy and exergy efficiency, respectively at operation condition, whilst the lowest efficiency and net work output is calculated under n-butane presence.
Citation - WoS: 7
Citation - Scopus: 8
Update for Reactive Transport Modeling of the Kızıldere Geothermal Field To Reduce Uncertainties in the Early Inspections
(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2023) Erol, Selçuk; Akın, Taylan; Akın, Serhat; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The development of carbon capture and storage techniques has become essential to reduce and mitigating CO2 emissions to the atmosphere. CarbFix1 and CarbFix2 projects carried out in Iceland demonstrated that the emissions of waste CO2 gas from geothermal power plants can be captured and mixed with the effluent geofluid and subsequently injected back into the geothermal reservoir. This experience gained in the CarbFix projects expanded into other geothermal fields around Europe, and one of the demonstration sites is the geothermal field in Turkey, Kızıldere. This paper focuses on the results of an updated study on early field evaluations with reactive transport simulations. In the new three-dimensional numerical model, the geological formations and fault zones were updated according to the well-logs data. Based on the tracer tests performed in the field, the anisotropic permeabilities between the wells were evaluated and imposed into the model. Geofluid chemistry, mineral components, and the volume fractions used as input in the simulations are modified depending on the performed laboratory experiments on the metamorphic schists taken from the geothermal site (i.e. X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning-electron microscope (SEM), and batch reactor tests). Different thermodynamic databases such as Lawrance Livermore National Laboratory (LLNL) and Thermoddem databases were tested using PHREEQC and TOUGHREACT programs for consistency with experiments. The thermodynamic conditions and the geofluid-rock-CO2 interactions prevent the mineralization of CO2 in the reservoir. This outcome differs from CarbFix projects in terms of the carbonization process, but the CO2 injection is still reliable with solubility-trapping in a geothermal reservoir to partially mitigate the emission. Roughly, 200 kt of CO2 in 10 years can be safely injected into the geothermal reservoir. According to the new analysis, the ratio of magnesium, sodium, and potassium varies in solid solution series of feldspars and clay minerals as albite end-member and montmorillonite/illite end-members, respectively. The evaluations of solid solution reactions are relatively limited in the law of mass action approach used by PHREEQC and TOUGHREACT. © TÜBİTAK.

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