Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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20192

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Department: search.filters.department.İzmir Institute of Technology. Energy Systems EngineeringPublisher: search.filters.publisher.Elsevier

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  • Article
    Citation - WoS: 33
    Citation - Scopus: 42
    Thermodynamic Assessment of Downhole Heat Exchangers for Geothermal Power Generation
    (Elsevier, 2019) Yıldırım, Nurdan; Parmanto, Slamet; Akkurt, Gülden Gökçen
    Downhole heat exchanger is a device to extract heat from geothermal fluid. While it is widely used for heating purposes, its use for power generation has not been reported. The aim of this study is to examine the feasibility of power generation from a 2500 m deep existing geothermal well with high temperature gradient and insufficient flowrate by using a downhole heat exchanger. For this purpose, a thermodynamic and an economic evaluation model are developed by the use of Engineering Equation Solver software. Additionally, the parametric studies have been carried out to identify the effects of insulation, geothermal well conditions, geometry of downhole heat exchanger, mass flowrate and type of working fluids on the performance of downhole heat exchanger system. Consequently, work output of the best alternative is computed as 2511 kW(e) with 64 kg/s mass flowrate of R-134a for 2500 m-deep downhole heat exchanger having inner pipe diameter of 0.127 m. Electricity generation cost and simple payback time are calculated as 46 $/MWh and 2.25 years, respectively. The obtained results showed that the downhole heat exchanger system can be a feasible alternative for wells with very low geothermal flowrate to generate power. (C) 2019 Elsevier Ltd. All rights reserved.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 11
    The Relation Between Thermal Comfort and Human-Body Exergy Consumption in a Temperate Climate Zone
    (Elsevier, 2019) Turhan, Cihan; Gökçen Akkurt, Gülden
    Human body exergy balance calculation method gives minimum human body exergy consumption rates at thermal neutrality (TSV = 0) providing more information on human thermal responses than other methods. The literature is lacking the verification of this method in various climatic zones. The aim of this study is to investigate the relationship between thermal comfort and human body exergy consumption in a temperate climate zone. A small office building in Izmir Institute of Technology campus, Izmir/Turkey, was chosen as a case building and equipped with measurement devices. The occupant was subjected to a survey via a mobile application to obtain his Thermal Sensation Votes. Objective data were collected via sensors and used for predicting occupant thermal comfort and for exergy balance calculations. Under given conditions, the results show that Thermal Sensation Votes are generally zero at a T-i range of 21-23 degrees C and, are mostly lower than Predicted Mean Votes in summer while the opposite is observed in winter. Predicted Mean Votes at minimum Human Body Exergy Consumption rates were on slightly warm side while Thermal Sensation Votes are zero. It means that for given case, the HBexC rate calculation gave a better prediction of the environmental parameters for the best thermal comfort. (C) 2019 Elsevier B.V. All rights reserved.