Yazar "Ceviz, Mehmet Akif" seçeneğine göre listele

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    Analysis of thermal energy storage in batch processes using phase change materials
    (Springer, 2025) Kaya, Nur Efsan; Ceviz, Mehmet Akif; Afshari, Faraz; Mandev, Emre; Koksal, Huseyin
    Batch reactors are widely utilized in the chemical, pharmaceutical, and food industries due to their simplicity, ease of operation, and maintenance. However, efficient energy management remains a key challenge, especially for systems operating under intermittent conditions. While phase-change materials (PCMs) offer potential for improving energy efficiency by storing and reusing waste heat, integrating heat storage within reactors can compromise their volume and design. This study introduces a novel approach by designing and experimentally testing a PCM heat battery positioned outside the reactor to reduce energy consumption cost in batch processes. By focusing on peak load shifting, the PCM heat battery stores thermal energy during off-peak periods, reducing operational costs and enhancing energy efficiency. The results indicate that energy operating costs can be significantly reduced with a PCM heat battery. Specifically, utilizing the PCM battery under a three-time tariff allows for the efficient use of energy stored at night, reducing the energy cost per batch process by approximately 8%, from 1.72 TL ($0.041) to 1.59 TL ($0.037) for facilities starting operations at 08:00. Furthermore, the findings suggest potential applications in systems like solar energy and highlight the benefits of peak load shifting, offering a sustainable and cost-effective solution for energy management in batch processing.
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    Comparative thermal and hydraulic performance of Type-22 panel radiators under continuous and pulsating flow
    (Pergamon-Elsevier Science Ltd, 2026) Koksal, Huseyin; Ceviz, Mehmet Akif; Muratcobanoglu, Burak; Mandev, Emre
    Pulsating water-side flow has been proposed as a radiator control strategy to enhance heat emission at low supply temperatures, yet device-level studies rarely quantify thermal gains together with hydraulic costs under matched baselines. This study experimentally investigates the coupled thermal and hydraulic response of a PCCP Type-22 panel radiator operated under continuous and on-off pulsating flow regimes. A dedicated test loop was developed using a temperature-controlled hot-water tank (50 degrees C setpoint) and an Arduino-based driver to impose repeatable pulsation, while measuring inlet/outlet temperatures, instantaneous flow rate, pump electrical energy, and spatiotemporal surface temperatures via infrared thermography. The results show that increasing the continuous flow rate provides the highest absolute heat output, but at the cost of increased pumping energy. In contrast, pulsating operation improves the thermal-hydraulic balance by increasing heat delivery relative to the reference case while reducing pump energy consumption. Among the tested pulsating cases, short-period pulsation produced the most favorable behavior by maintaining a warmer and more spatially stable radiator surface. Longer off-periods promoted deeper surface cooling, reduced the effective emitting area, and weakened the thermal benefit of pulsation. Infrared thermography confirmed that the pulsation period strongly affects surfacetemperature uniformity and temporal stability. Overall, short-period on-off pulsation emerges as the most favorable operating mode when the objective is to increase heat delivery while lowering pumping energy in PCCP-type radiators.
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    Enhanced freshwater production in prism-type solar stills using a fresnel lens system with comprehensive energy-exergy and cost analysis
    (Springer Heidelberg, 2026) Ceviz, Mehmet Akif; Koksal, Huseyin; Afshari, Faraz; Muratcobanoglu, Burak
    This study presents the development and performance evaluation of a novel prism-type solar still integrated with a Fresnel lens concentration system designed to concentrate solar radiation on an external spiral heat exchanger. Experimental investigations were conducted under two different saline water flow rates of 0.05 and 0.1 kg/min. The performance of system was comprehensively analyzed in terms of fresh water yield, thermal efficiency, exergy efficiency, and economic viability. The heated saline water and resultant vapor were directed into the prism-shaped condensation chamber, where condensation occurred efficiently. The experimental results demonstrated that lower saline water flow rates led to higher water temperatures and enhanced evaporation rates, thereby increasing freshwater productivity. In contrast, higher flow rates resulted in greater accumulation of saline water within the basin, reducing the evaporation rate and thus lowering overall productivity. The proposed design uniquely combines geometric enhancement via a prism-shaped condensation chamber with solar concentration through a Fresnel lens, enabling a dual-effect improvement in energy absorption and condensation efficiency, an approach not previously reported in the literature for solar desalination systems. The system achieved thermal and exergy efficiencies of 22.95 and 15.50%, respectively, at a saline water flow rate of 0.05 kg/min, producing 92 g of clean water in 60 min. Furthermore, the cost analysis conducted indicated a cost of $0.2546 per liter for this scenario.
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    A novel ignition timing strategy to regulate the energy balance during the warm up phase of an SI engine
    (Elsevier, 2023) Koksal, Huseyin; Ceviz, Mehmet Akif; Yakut, Kenan; Kaltakkiran, Galip; Ozakin, Ahmet Numan
    The warm up characteristics of an engine have a significant impact on engine performance and exhaust emissions. In SI engines, the light-off performance of the catalytic converter is also important. One of the methods used to shorten the light off time of the catalytic converter is to retard the ignition time. When the ignition time is retarded, the temperature of the exhaust gases increases. However, in this case, the warm up performance of the engine itself may be adversely affected. In this study, firstly, the effects of ignition timing on the energy balance during the warm up period in an SI test engine were revealed. Then, a novel ignition timing strategy was proposed in order to increase the temperature of the exhaust gases, and not to reduce the engine performance. The novel ignition timing strategy working on the principle of sequentially advanced and retarded ignition at certain intervals during the warm up period provides several advantages. When the novel ignition strategy is applied, the energy loss through the exhaust gas was increased up to 7.2% for several operating conditions, while the reduction in engine performance is eliminated. Moreover, 20% reduction in NO emission has been achieved.