SUMMARY

Several energy sources, including nuclear and coal, rely on steam turbines to generate electricity. Steam condensation is an integral part of this thermal cycle, and even a small improvement in this process can lead to significant economic savings. By promoting dropwise as opposed to filmwise condensation, heat transfer in the condenser can be improved. The promotion of dropwise condensation ultimately allows for a lower operational condenser cost or a reduction to the overall system size. Unfortunately, dropwise condensation is not permanent on most surfaces. During operation, the condensation regime shifts from discrete drops to a film. Recent advancements in micro and nano fabrication allow for the construction of highly non-wetting surfaces. These surfaces, termed superhydrophobic, may lead to greater mobility of the condensate drops, and a permanent state of dropwise condensation may be achievable. The proposed work will experimentally measure the heat transfer coefficient during dropwise condensation on various superhydrophobic surfaces. The superhydrophobic surfaces will be compared to a non-structured hydrophobic surface in terms of the heat transfer coefficient, as well as, the time required for transition to filmwise condensation. Furthermore, a numerical model will be developed to study the competing effects of conduction through condensed drops and the thermal diffusion in the solid substrate as a function of contact angle and drop size ratio. The proposed work will not only investigate whether superhydrophobic surfaces offer an enhancement to the heat transfer, but will also provide insight into the physical reason for this enhancement based on fundamental theory.