In this study, experimental investigation is carried out to examine flow boiling heat transfer and hydrodynamic instability in boiler employing structured and unstructured minichannels for deionized water. The study compares boilers with unstructured surface and structured surface, consisting of circular pin fins, to assess their thermal and hydrodynamic performance. This study evaluates both local and average heat transfer coefficients, along with pressure drops, across varying mass flow rates of 50–93 kg/m 2 ·s under a constant heat flux of 46.91 kW m −2 . The experiments were conducted in lab-scale boilers consisting of a rectangular aluminum minichannel with a hydraulic diameter of 2.85 mm, dimensions of 270 mm in length, 30 mm in width and 1.5 mm in height. An inline circular pin fin configuration is used for the setup. The results demonstrate that the circular pin fin surface significantly enhances the boiling heat transfer coefficient, achieving about 70% higher than that on unstructured surface. At a mass flux of 50 kg/m 2 ·s, the local heat transfer coefficient reaches 78.19 kW/m 2 ·K for the structured surface compared to just 9.77 kW/m 2 ·K for the unstructured surface. In addition, on contrary to the unstructured surface, the structured surface exhibits a more stable and longer homogeneous nucleation regime at lower mass flux, which promotes uniform bubble formation and delay in transition to the slug flow regime. Circular pin fins surface also showed more steady pressure fluctuations, especially close to dry-out phase.
Alnaimat et al. (Fri,) studied this question.