عمار فاخر عبد الواحد الشوكي

Abstract – Film cooling represents one of the important game-changing technologies that has allowed the achievement of today’s high inlet turbine temperature to get high-efficiency gas turbine engines. Shear Stress Transport (SST) K-ω was performed to investigate the flow structures and the development process of vortices in different sections (rectangular, hexagonal and circular) of a stationary gas turbine at blowing ratio equal to (0.5, 1.0, 1.5 and 2.0), while the jet film cooling hole angles equal to (90°, 60°, 45° and 30°). It was observed that higher freestream turbulence improves adiabatic effectiveness and heat transfer coefficient for the corrugation film cooling holes design and specially enhancement at holes angle equal to 30° with twisted angle equal to 360° and rectangular corrugation shape. Results show the effectiveness enhancement range of 20.1%-69.3%of the smooth film cooling hole. Numerical calculation of film cooling effectiveness is validated with reported numerical and experimental results.

Abstract – An experimental study has been conducted to study the heat transfer characteristics within corrugation film cooling holes of different cross section area square, rectangular and circular. The experiments investigation for this paper have been performed using a thermal IR camera, and the flow field has been analyzed by numerical calculation using a commercial code (FLUENT) was utilized and the SST k- ω turbulence model. The effect of blowing ratio (0.5, 1.0, 1.5 and 2.0) and twisted film cooling holes angles (90°, 180°, 270° and 360°) were also considered. A duct flow enters into a twisted film cooling hole in a cross direction. For the corrugation film cooling hole, it is observed that the reattachment of separated flow and the vortices within the hole enhance considerably the heat/mass transfer around the holes entrance region. Results showed that the twisted film cooling holes performed better than the cylindrical hole. Also, the film cooling effectiveness and heat transfer coefficient for the corrugation holes were strongly affected by the angle of twisted film cooling holes of the corrugation hole. Results show the heat transfer enhancement range of (1.5-2.7) time of smooth film cooling holes. Experimental and numerical calculation of film cooling effectiveness is validated with pervious experimental results.

Abstract – This paper investigates a new method of film cooling using swirling coolant flow through a rectangular twisted film cooling holes with spiral corrugated tube. Two different air flows with different temperatures were used in this study. Throughout the investigation, blowing ratio varied from 0.5 to 2.0 for several configurations of rectangular twisted angle of 0°, 90°, 180°, 270° and 360°. The results of cooling effectiveness obtained were compared against a standard untwisted tube. Results show that the overall thermal effectiveness improved significantly when the temperature difference between the air flows is at 25 degrees. Such improvement is supported by heat transfer enhancement that obtained from 19.7% to 57.4%. Based on these findings, the study concludes that using a specific geometry of film cooling holes with twisted configuration may result in an improve the convective heat transfer coefficient.

Abstract – This paper investigates a new method of film cooling using swirling coolant flow through a rectangular twisted film cooling holes with spiral corrugated tube. Two different air flows with different temperatures were used in this study. Throughout the investigation, blowing ratio varied from 0.5 to 2.0 for several configurations of rectangular twisted angle of 0°, 90°, 180°, 270° and 360°. The results of cooling effectiveness obtained were compared against a standard untwisted tube. Results show that the overall thermal effectiveness improved significantly when the temperature difference between the air flows is at 25 degrees. Such improvement is supported by heat transfer enhancement that obtained from 19.7% to 57.4%. Based on these findings, the study concludes that using a specific geometry of film cooling holes with twisted configuration may result in an improve the convective heat transfer coefficient.

The heat transfer is a very interesting field for economical, functional and environmental reasons; it is almost related to each aspect of human lives. Therefor, the enhancement of such field is quite essential. Passive heat transfer represents is the soul of heat transfer enhancement due to the merits of simplicity, cheap and good enhancement with acceptable pressure drop. Corrugation is a method involved within the passive techniques of enhancement, it is important and being adopted in a wide range of applications like a nuclear reactor cooling, refrigeration, heat exchangers, and other industrial applications. The current article presents an extensive review of numerical and experimental studies on heat transfer enhancement, which covers the laminar and turbulent flow regions in the corrugations, especially in corrugated tubes. This paper dealt with 95.74% of papers published in corrugated tubes for different applications to offer one article representing a database stop for the designers and authors whom concerning and dealing with heat transfer enhancement in corrugated tubes.

Various techniques have been tested on heat transfer enhancement to upgrade the involving equipment, mainly in thermal transport devices. These techniques unveiled significant effects when utilized in heat exchangers. One of the most essential techniques used is the passive heat transfer technique. Corrugations represent a passive technique. In addition, it provides effective heat transfer enhancement because it combined the features of extended surfaces, turbulators and artificial roughness. Therefore, A Computational Fluid Dynamics was employed for water flowing at low Reynolds number in spiral corrugated tubes. This article aimed for the determination of the thermal performance of unique smooth corrugation profile. The Performance Evaluation Criteria were calculated for corrugated tubes, and the simulation results of both Nusselt number and friction factor were compared with those of standard plain and corrugated tubes for validation purposes. Results showed the best thermal performance range of 1.8–2.3 for the tube which has the severity of 45.455 × 10−3 for Reynolds number range of 100–700. The heat transfer enhancement range was 21.684%–60.5402% with friction factor increase of 19.2–36.4%. This indicated that this creative corrugation can improve the heat transfer significantly with appreciably increasing friction factor.