Experiments are conducted to analyze the influence of turbulence and secondary flows on heat transfer and CHF in sub-cooled flow boiling. Inserts creating turbulence and stationary vortices are placed below a vertical channel with a heated wall and upward flow direction with flow velocities up to 1.2 m/s. The boiling chamber is of square shape with inner dimensions of 40 × 40 mm2. Boiling regimes range from onset of nucleate boiling up to fully developed film boiling. Influence of the inserts is measured for varying flow velocities and subcooling from 4 K to 27 K. Flow parameters are measured with Particle Image Velocimetry (PIV). A decay of nearly isotropic turbulence within only few diameters is observed, while stationary swirls exhibit longer penetration depths. Boiling experiments are conducted with unsteady heating with a low boiling hydrocarbon (dodekafluoromethylpentanone) as working fluid. Results from boiling experiments show a positive influence of the inserts on the boiling process, increasing with higher subcooling and flow velocities.

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