Browsing by Author "Dalkilic, A.S."

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The Effect of the Important Variables for the Design Novel Milli-Channel Cooling System on the Evaporator Performance by the Taguchi Method
(Springer Science and Business Media B.V., 2025) Koca, A.; Mustafaoglu, M.; Karakoyun, Y.; Dalkilic, A.S.
Optimizing controllable parameters is crucial to milli-channel cooling system design. This study investigates the heat transfer and hydrodynamic properties of a novel annular flow boiling process of water in milli-channels with better pulsation that passes through a rectangular cross section at a constant temperature. By optimizing system operating parameters and vapor and liquid recirculation, the main novelty in this suggested approach is the achievement of continuous thin-film (micron-sized) annular flow conditions. The 3D simulation model created by a 1D simulation technique has certain boundary restrictions to guarantee the existence of a thin layer of annular flow across the boiler’s whole surface. In Taguchi analysis, the signal-to-noise ratio is determined by using the following input parameters: the Reynolds number, the heated surface temperature, and the pulsatile character of fluid flow. According to the findings, the vapor quality in pulsatile flow is estimated to be 2% to 3% greater than in continuous flow. As thin-film thickness increases, wall temperature declines toward flow. Moreover, there is an approximate 2.5% increase in the mean heat transfer coefficients for pulsatile flow cases compared to continuous flow cases. Furthermore, the average vapor velocity in pulsatile flow is lower than that in continuous flow, according to an analysis of the velocity distributions for each reference zone. The average surface temperature at specified planes in pulsatile flow scenarios is ~ 0.5 K higher than continuous flow situations. © Akadémiai Kiadó Zrt 2025.
A New Hybrid Cfd Approach To Study the Impact of Forced Convection on Radiant Cooled Wall With Baseboard Diffuser Including Various Vane Angles
(Elsevier Masson s.r.l., 2025) Caliskan Temiz, M.; Bacak, A.; Camci, M.; Karakoyun, Y.; Acikgoz, O.; Dalkilic, A.S.
The current work examines the effect of forced convection on thermal comfort in a space, including radiant wall cooling and an innovative floor-level diffuser system. It examines the impact of various vane angles on thermal comfort in room air conditioning at 15°, 30°, 45°, 60°, and 75°, and employs experimental data to confirm a hybrid 3D computational fluid dynamics (CFD) model. A new floor-level diffuser system delivers air at temperatures between 18 °C and 22 °C, with supply air velocities of 5 m/s and 10 m/s measured at the exit side of diffuser while the supply water temperature is kept constant at 14 °C. In the hybrid 3D solution, experimentally derived convective heat transfer coefficients (CHTCs) for forced airflow are utilized. This is accomplished by merging a k-ω model with a hydronic radiant panel system that incorporates forced convection. The analysis examines temperature and velocity distributions, CHTCs on the radiant-cooled wall, and the PMV-PPD components. Results indicate that at a supply air velocity of 5 m/s, thermal comfort parameters do not satisfy PMV and PPD indices, except in proximity to the diffuser. Nevertheless, elevating the supply air velocity to 10 m/s ensures thermal comfort across the space, with the exception of regions next to the cooled wall surfaces. The examination of several vane angles indicated that a 45° angle yields the most advantageous thermal comfort conditions, irrespective of air velocity. The CHTC adjacent to the radiant wall is roughly 6 W/m2K at a velocity of 5 m/s and rises to 8 W/m2K at 10 m/s. The temperature disparity between the head and ankle regions at 5 m/s adheres to the 3 °C tolerance established by international standards. The study determines that a 45° vane angle ensures best thermal comfort, and the devised numerical method yields significant insights for the construction of analogous indoor settings. © 2025 Elsevier Masson SAS