Effect of Vertical Mini-Fins on External Condensation Heat Transfer

The purpose of this research is to experimentally study how vertical mini-fins affect the overall heat transfer on a solid surface under external condensation conditions. Filmwise condensation is a major factor when designing steam condensers for thermoelectric power plants. These plants currently account for 40% of freshwater withdrawal and 3% of freshwater usage in the United States. Filmwise condensation averages five times lower heat transfer coefficients than those present in dropwise condensation. Due to the elevated nucleation rates in thermoelectric power plant condensers, filmwise condensation is the dominant condensation regime. The film thickness is directly proportional to the condenser’s overall thermal resistance on a surface under filmwise condensation. This research investigates the potential of mini-fins to mitigate the onset and effect of filmwise condensation, thus reducing thermal resistance and maximizing heat transfer. The overall heat transfer is determined by measuring the temperature gradient across aluminum test sections. The experimental setup was designed to control the cooling load, pressure, and steam quality in order to measure the temperature gradient under steady state conditions. By comparing the overall heat transfer of surfaces with different mini-fins, the optimal surface geometries can be found. Preliminary results show that mini-fins can improve the overall heat transfer ratios. Future work will introduce other mini-fin shapes, as well as focus on investigating the most efficient heat fluxes for each mini-fin.