Feasibility investigation of experimental visualization techniques to study subcooled boiling flow

• Feasibility study of two-phase flow parameters by visualization techniques.
• Experimental practices for accurate measurements of subcooled flow boiling parameters.
• Data analysis procedures to minimize the uncertainty induced by density gradients and boiling bubbles.
• Subcooled flow boiling was successfully studied with simultaneous PTV/shadowgraphy techniques.
• Accurate liquid and vapor measurements of subcooled flow boiling by means of simultaneous PTV/shadowgraphy.

The purpose of this study is twofold: (1) to explore the feasible implementation of whole-field visualization techniques such as infrared thermometry, particle tracking velocimetry, and high speed shadowgraphy to study subcooled boiling flow through a vertical square channel with a single heated wall and (2) to provide subcooled boiling flow experimental measurements based on the methodology developed in this work. To fulfill the first objective, a series of sensitivity studies and uncertainty analyses was performed, from which recommendations for the proper implementation of these visualization techniques for the study of two-phase flows are given. The purpose of the second objective is to provide reliable information that can be used for the validation of CFD simulations and for the improvement and development of turbulence models under subcooled boiling conditions. Unique in the presented experimental results is the whole-field simultaneous measurement of turbulence characteristics for both the liquid and gas phases and for their interactions. These measurements were made under transitional conditions from a single phase flow region to a two phase boiling flow condition. The presented experimental results provide whole-field, multi-scale measurements that can help improve the accuracy of descriptions of the boiling phenomena.