@article{MandalMannaBiswasetal.2026, author = {Mandal, Dipak Kumar and Manna, Nirmal K. and Biswas, Nirmalendu and Rudra, Tansu and Kumar, Rajesh and Benim, Ali Cemal}, title = {Enhanced heat transport in magneto-nanofluidic thermal systems: adiabatic block effects in grooved channels and ANN modeling}, series = {International Journal of Thermofluids}, volume = {31}, journal = {International Journal of Thermofluids}, publisher = {Elsevier}, issn = {2666-2027}, doi = {10.1016/j.ijft.2025.101515}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-60127}, year = {2026}, abstract = {This study investigates heat transfer enhancement in magneto-nanofluidic systems through the strategic placement of adiabatic blocks in grooved channels. Using CuO-H2O nanofluid in a bottom-heated channel with circular expansion, we examine the complex interactions between forced convection, magnetic fields, and uoyancy effects. Through systematic numerical analysis, we explore the combined influences of Rayleigh, Reynolds, and Hartmann numbers on thermal performance. Our findings reveal significant heat transfer enhancement (up to 137 \%) under optimal conditions, particularly with vertical magnetic field orientation at Re = 100 and Ha = 30. The results demonstrate how adiabatic blocks modify flow structures, with larger blocks diminishing vortex intensity while elevated Ra generates secondary vortices that interact with primary circulations. Magnetic field effects show notable dependence on orientation, with vertical fields generally promoting better heat transfer than horizontal configurations. To complement the numerical analysis, we develop a predictive model using Artificial Neural Network (ANN) for Nusselt numbers across various operating conditions, achieving over 99 \% accuracy. The integrated computational-ANN approach offers significant advancements in optimizing thermal systems in various areas, ranging from electronics cooling to microfluidic devices.}, language = {en} } @article{ShajahanBenim2026, author = {Shajahan, Mohamed Iqbal and Benim, Ali Cemal}, title = {Granular PCM based heat sink for electronics thermal management}, series = {Applied Thermal Engineering}, volume = {286}, journal = {Applied Thermal Engineering}, publisher = {Elsevier}, issn = {1359-4311}, doi = {10.1016/j.applthermaleng.2025.129336}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-59649}, year = {2026}, abstract = {This study investigates aluminum heat sinks integrated with GR42 phase change material (PCM), aiming to enhance thermal inertia and stabilize device temperatures. This is important, since the increasing miniaturization and performance demands for electronic devices have led in a growing need for advanced thermal management systems capable of handling rapid transient loads. The novelty of the work lies in examining different heat sink layouts that optimize the heat dissipation capabilities of GR42 PCMs while minimizing size and weight for electronic cooling. The experimental testing was conducted using three configurations, namely no fin, circular fin and hexagonal fin, with three input powers (4 W, 8 W, and 12 W). The experimental results show that the hexagonal-fin heat sink, surface area is 25 \% more than circular fins, exhibited superior thermal performance without significant variation in input power. Notably, the hexagonal-fin heat sink achieved the desired set point temperature of 55 ◦C in 33 \% less time than the circular-fin design and 45 \% less time than the heat sink without fins. Furthermore, the peak temperatures increased up to 21 \% for circular fins. During the charging cycles, the enhancement ratios vary from 72 \% and begin to narrow to 25 \% during discharge cycles. The hexagonal-fin configuration also exhibited superior melting dynamics, completing the phase transition 44 \% faster at higher input power than the circular fins, and established a thermal deviation of nearly 51 \% less than finless heat sinks. These findings underscore the critical role of fin geometry and PCM integration in achieving uniform temperature distribution and improved energy storage efficiency. Overall, the hexagonal-fin heat sink with GR42 PCM shows strong potential as a passive cooling solution for low-power portable electronic devices.}, language = {en} } @article{MandalGuptaBiswasetal.2025, author = {Mandal, Dipak Kumar and Gupta, Kritesh Kumar and Biswas, Nirmalendu and Manna, Nirmal K. and Santra, Somnath and Benim, Ali Cemal}, title = {Optimization of hybrid solar chimney power plants (HSCPPs): A review of multi-objective approaches}, series = {Applied Energy}, volume = {396}, journal = {Applied Energy}, publisher = {Elsevier}, issn = {0306-2619}, doi = {10.1016/j.apenergy.2025.126214}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-54199}, pages = {25}, year = {2025}, subject = {Erneuerbare Energien}, language = {en} } @article{BiswasMandalMannaetal.2025, author = {Biswas, Nirmalendu and Mandal, Dipak Kumar and Manna, Nirmal K. and Benim, Ali Cemal}, title = {Thermomagnetic convection and entropy generation in a hybrid nanofluid filled wavy-walled cavity heated non-uniformly}, series = {Archives of Thermodynamics}, journal = {Archives of Thermodynamics}, publisher = {Polish Academy of Sciences}, issn = {1231-0956}, doi = {10.24425/ather.2025.154182}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-52344}, pages = {61 -- 81}, year = {2025}, abstract = {In this work, thermomagnetic convection and irreversibility production in a hybrid nanofluid-filled wavy-walled porous thermal system containing a semi-circular heated bottom is presented. Both the sidewalls of the enclosure are cooled and undulated with varying undulation numbers. The lower wall is partially undulated following a semi-circular-shaped object and is heated isothermally. The horizontal walls are insulated. The cavity is occupied with Cu-Al2O3/water-based hybrid nanofluid and porous substances under the impact of the evenly applied horizontal magnetic field. This work significantly contributes to the existing research rendering an exhaustive understanding of the hydrothermal flow-physics as well as irreversibility production of a hybrid nanofluid in the cavity having surface undulation. The Galerkin weighted finite element method is utilized to solve the mathematical model. The hydrothermal performance of the thermal system is considerably influenced by various pertinent factors such as Darcy-Rayleigh number, Darcy number, Hartmann number, and number of undulations. The wall undulations have a critical role in altering the hydrothermal performance. Heatlines are used to analyse heat transport dynamics from the protruded hot surface to the heat sink. The protruded heater wall induces the formation of a hot upward plume in the nearest fluid layers. The flow divides into two parts forming a pair of circulations due to symmetrical cooling at the sidewalls. The flow behaviours are significantly dampened by increasing the Hartmann number. The associated total entropy generation is also demonstrated. This study contributes to the existing domain knowledge and provides insights for designing and optimizing similar thermal systems.}, subject = {W{\"a}rme{\"u}bertragung}, language = {en} } @article{BenimCicek2023, author = {Benim, Ali Cemal and {\c{C}}i{\c{c}}ek, Ayd{\i}n}, title = {Comparative analysis of water and carbon dioxide injection for the thermohydraulics of an EGS project in Dikili Geothermal Field, T{\"u}rkiye}, series = {Bulletin Of The Mineral Research and Exploration}, volume = {171}, journal = {Bulletin Of The Mineral Research and Exploration}, publisher = {Maden Tetkik ve Arama Genel M{\"u}d{\"u}rl{\"u}ğ{\"u}}, issn = {0026-4563}, doi = {10.19111/bulletinofmre.1288731}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-49115}, pages = {91 -- 105}, year = {2023}, abstract = {A comparative numerical analysis of the thermohydraulics of an enhanced geothermal system (EGS) project in T{\"u}rkiye in Dikili area is presented. The fractured granodiorite is modelled as porous media, utilizing the numerically suggested data of other authors for the corresponding hydraulic characteristics. As the heat transmission fluid, two different mediums are alternatively considered. These are the more classical medium, water and the supercritical Carbon Dioxide (sCO2). Transient calculations are performed for a time period of twenty years, comparing the temporally developing results obtained for water and sCO2 with each other. Based on modeling parameters and assumptions, higher production temperatures are observed with sCO2, in comparison to water, implying an advantage for sCO2 usage as a working fluid in EGS. This is accompanied by the further advantage of a lower pressure drop for sCO2. On the other hand, the temperature advantage is relativized by the lower specific heat capacity of sCO2 causing a decrease in the production thermal power. In general, the present re found to be encouraging for a further and more detailed analysis of the employment of sCO2 as working fluid in EGS.}, subject = {Numerische Str{\"o}mungssimulation}, language = {en} } @article{BaşaranBenim2024, author = {Ba{\c{s}}aran, An{\i}l and Benim, Ali Cemal}, title = {Development of Correlations Based on CFD Study for Microchannel Condensation Flow of Environmentally Friendly Hydrocarbon Refrigerants}, series = {Energies}, volume = {17}, journal = {Energies}, number = {7}, publisher = {MDPI}, issn = {1996-1073}, doi = {10.3390/en17071531}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-46398}, pages = {21}, year = {2024}, abstract = {A CFD simulation of the condensation flow of R600a and R290 within microchannels was conducted to explore the effect of mass flux, hydraulic diameter, and vapour quality on heat transfer rate and pressure drop. Data obtained from CFD simulations were used to develop new heat transfer and pressure drop correlations for the condensation flows of R600a and R290, which are climate-friendly refrigerants. Steady-state numerical simulations of condensation flow of refrigerants were carried out inside a single circular microchannel with diameters varying between 0.2 and 0.6 mm. The volume of fluid approach was used in the proposed model, calculating the interface phase change using the Lee model. The CFD simulation model was validated via a comparison of the simulation results with the experimental data available in the literature. It is found that the newly developed Nu number correlation shows a deviation, with an Ave-MAE of 11.16\%, compared to those obtained by CFD simulation. Similarly, the deviation between friction factors obtained by the newly proposed correlation and those obtained by CFD simulation is 20.81\% Ave-MAE. Widely recognized correlations that are applicable to the condensation of refrigerants within small-scale channels were also evaluated by comparing newly developed correlations. It is concluded that the newly proposed correlation has a higher accuracy in predicting the heat transfer coefficient and pressure drop. This situation can contribute to the creation of a sustainable system via the use of microchannels and climate-friendly refrigerants, like R600a and R290.}, subject = {Druckabfall}, language = {en} } @article{YalcınkayaDurmazTepeetal.2024, author = {Yal{\c{c}}{\i}nkaya, Orhan and Durmaz, Ufuk and Tepe, Ahmet {\"U}mit and Benim, Ali Cemal and Uysal, {\"U}nal}, title = {Heat and Flow Characteristics of Aerofoil-Shaped Fins on a Curved Target Surface in a Confined Channel for an Impinging Jet Array}, series = {Energies}, volume = {17}, journal = {Energies}, number = {5}, publisher = {MDPI}, issn = {1996-1073}, doi = {10.3390/en17051238}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-46387}, pages = {21}, year = {2024}, abstract = {The main purpose of this investigation was to explore the heat transfer and flow characteristics of aero-foil-shaped fins combined with extended jet holes, specifically focusing on their feasibility in cooling turbine blades. In this study, a comprehensive investigation was carried out by applying impinging jet array cooling (IJAC) on a semi-circular curved surface, which was roughened using aerofoil-shaped fins. Numerical computations were conducted under three different Reynolds numbers (Re) ranging from 5000 to 25,000, while nozzle-to-target surface spacings (S/d) ranged from 0.5 to 8.0. Furthermore, an assessment was made of the impact of different fin arrangements, single-row (L1), double-row (L2), and triple-row (L3), on convective heat transfer. Detailed examinations were performed on area-averaged and local Nusselt (Nu) numbers, flow properties, and the thermal performance criterion (TPC) on finned and smooth target surfaces. The study's results revealed that the use of aerofoil-shaped fins and the reduction in S/d, along with surface roughening, led to significant increases in the local and area-averaged Nu numbers compared to the conventional IJAC scheme. The most notable heat transfer enhancement was observed at S/d = 0.5 utilizing extended jets and the surface design incorporating aerofoil-shaped fins. Under these specific conditions, the maximum heat transfer enhancement reached 52.81\%. Moreover, the investigation also demonstrated that the highest TPC on the finned surface was achieved when S/d = 2.0 for L2 at Re = 25,000, resulting in a TPC value of 1.12. Furthermore, reducing S/d and mounting aerofoil-shaped fins on the surface yielded a more uniform heat transfer distribution on the relevant surface than IJAC with a smooth surface, ensuring a relatively more uniform heat transfer distribution to minimize the risk of localized overheating.}, subject = {Beschaufelung}, language = {en} } @article{Benim2024, author = {Benim, Ali Cemal}, title = {Investigation into the Computational Analysis of High-Speed Microjet Hydrogen-Air Diffusion Flames}, series = {Fire}, volume = {7}, journal = {Fire}, number = {9}, publisher = {MDPI}, issn = {2571-6255}, doi = {10.3390/fire7090314}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-46345}, pages = {23}, year = {2024}, abstract = {High-speed microjet hydrogen-air diffusion flames are investigated computationally. The focus is on the prediction of the so-called bottleneck phenomenon. The latter has been previously observed as a specific feature of the present flame class and has not yet been investigated computationally. In the configuration under consideration, the nozzle diameter is 0.5 mm and six cases with mean nozzle injection velocities (U) between 306 m/s and 561 m/s are considered. The flow in the nozzle lance is analyzed separately to obtain detailed inlet boundary conditions for the flame calculations. It is confirmed by calculation that the phenomenon is mainly determined by the transition to turbulence in the initial parts of the free jet. The transitional turbulence proves to be the biggest challenge in predicting this class of flames, as the generally available turbulence and turbulent combustion models reach the limits of their validity in transitional flows. In a Reynolds-Averaged Numerical Simulation framework, the Shear Stress Transport model is found to perform better than alternative two-equation models and is used as the turbulence model. By neglecting the interactions between the turbulence and chemistry (no-model approach), it is possible to predict the morphology of the bottleneck flame and its dependence on U qualitatively. However, the position of the bottleneck is overpredicted for U \< 561 m/s. The experimental flames in the considered U range are all attached to the nozzle. This is also predicted by the no-model approach. The Eddy Dissipation Concept (EDC) used as the turbulence combustion model predicts, however, lifted flames (with increasing lift-off height as U decreases). With the EDC, no bottleneck morphology is observed for U = 561 m/s. For lower U, the EDC results for the bottleneck position are generally closer to the measurements. It is demonstrated that accuracy in predicting the bottleneck position can be improved by ad hoc modifications of the turbulent viscosity.}, subject = {Turbulenzmodell}, language = {en} } @article{RueckertIbrarAhmedetal.2024, author = {R{\"u}ckert, Frank Ulrich and Ibrar, Burhan and Ahmed, Arslan and Allweyer, Benjamin and H{\"u}bner, Dirk and Klinger, Friedrich and Knaus, Hermann and Benim, Ali Cemal}, title = {Fluid flow and heat transfer of a novel passive cooling system for gearless wind turbines with a power range of 3-12 MW}, series = {Energy}, volume = {312}, journal = {Energy}, publisher = {Elsevier}, issn = {0360-5442}, doi = {10.1016/j.energy.2024.133478}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-46594}, year = {2024}, abstract = {Today, the gearless horizontal axis wind turbines are mainstream in wind energy industry. High demands of electric power led to bigger systems and active cooling reduces the overall efficiency of the turbines. Passive cooling systems have been examined for the first time for a gearless wind energy generator with power range of 3-12 MW. With further developed heat conductors, it is possible to operate a wind generator in a larger power class with passive cooling components. This is accompanied by enormous cost savings due to elimination of costs for active cooling elements such as the use of fans, pumps, and heat exchangers. An additional factor is the significant reduction in necessary maintenance due to the minimized incidence of corrosion and wear. Design of the cooling fins and an ideal position of the generator within the housing of the wind turbine has been objectives. Mandatory is that maximum temperatures of the generator fins should stay under 155 °C, which could be reached with several designs for different heat exchanger geometries.}, subject = {Windturbine}, language = {en} } @article{BaşaranBenim2024, author = {Ba{\c{s}}aran, An{\i}l and Benim, Ali Cemal}, title = {Condensation Flow of Refrigerants Inside Mini and Microchannels: A Review}, series = {Applied Sciences}, volume = {14}, journal = {Applied Sciences}, number = {7}, publisher = {MDPI}, issn = {2076-3417}, doi = {10.3390/app14072988}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-46358}, year = {2024}, abstract = {Nowadays, the demand for obtaining high heat flux values in small volumes has increased with the development of technology. Condensing flow inside mini- and microchannels has been becoming a promising solution for refrigeration, HVAC, air-conditioning, heat pumps, heat pipes, and electronic cooling applications. In these applications, employing mini/microchannels in the condenser design results in the working fluid, generally refrigerant, undergoing a phase change inside the mini/microchannels. On the other hand, the reduction in the hydraulic diameter during condensation gives rise to different flow regimes and heat transfer mechanisms in the mini- and microchannels compared to the conventional channels. Therefore, the understanding of fluid flow and heat transfer characteristics during condensation of refrigerant inside mini- and microchannels has been gaining importance in terms of condenser design. This study presents a state-of-the-art review of condensation studies on refrigerants inside mini- and microchannels. The review includes experimental studies as well as correlation models, which are developed to predict condensation heat transfer coefficients and pressure drop. The refrigerant type, thermodynamical performance, and compatibility, as well as the environmental effects of refrigerant, play a decisive role in the design of refrigeration systems. Therefore, the environmental impacts of refrigerants and current regulations against them are also discussed in the present review.}, subject = {Kondensation}, language = {en} }