Investigation of heat transfer, pressure drop and performance in decaying swirl flow for different types and statements of axial swirl promoters

Investigation of Heat Transfer, Pressure Drop and Performance in Decaying Swirl Flow for Different Types and Statements of Axial Swirl Promoters In this study, heat transfer and pressure drop for turbulent swirl flow generated by swirl generators with 15° 30° 45° and 60 ° helical wing angles which were placed at different positions in a pipe with circular cross section and constant wall temperature were experimented. Instead of producing a circulating flow throughout the pipe, swirl generators were placed at position where the swirl effect decrease to obtain a periodic or nonperiodic swirl motion. 56 experiments measuring heat transfer and pressure drops were carried out by placing the swirl generators at 7 different positions, 4 different wing angles and 2 different wing numbers and Reynolds numbers between 3500 and 35000. In this study 3 different experimental setups were manufactured. In these experimental setups, the experiments of heat transfer and pressure drop, the flow observation experiments and the form resistance experiments were made. In the flow observation experiments, the flow area behind the swirl generator is observed and it was seen that the flow is a decaying swirl flow and that the swirl period decreases when the wing angle of the swirl generator decreases. In the experiments of form resistance, the form resistance coefficients of the swirl generators were determined by obtaining pressure measurements from the section where the swirl generator is placed. Moreover, the types and positions of effective swirl flow generator were determined by means of an exergy analysis. Wing angle islhemost significant parameter which effects heat transfer and pressure drop. An average increase of % 10 to % 100 in Nusselt number and an average increase of 2 to 49 times for the friction factor were obtained depending on the experiment type. It was determined that the most effective position of the swirl generator is the centre of the pipe and that the most effective wing angles are those which are lower than 30 °. At the swirl flow area, heat transfer coefficent and friction factor were mathematically modelled and expressions were derived. The harmony between the experimental results and the mathematical model is % 92 to % 99 for heat transfer results and % 86 to % 97 for the friction factor. Key Words : Decaying Turbulent Swirl Flow, Axial Swirl Generator, Augmentation of Heat Transfer, Exergy Analysis VI