Opportunities in Nanoengineered Surface Designs for Enhanced Condensation Heat and Mass Transfer

Recent advancements in surface nanoengineering have spurred intense interests in their implementation for enhancing condensation heat transfer. When appropriately designed, nanoengineered surfaces not only lead to highly efficient transport mechanisms not achievable with conventional dropwise condensation, they also demonstrate the possibility of augmenting condensation of low surface tension fluids widely used in industry. These advantages are further enhanced by the development of highly scalable nanofabrication methods, which enable the potential transition from laboratory-scale prototypes to real-world industrial applications. In this review, we discuss the progress, opportunities, and challenges of enhancing condensation heat and mass transfer with nanoengineered surfaces. This article provides an overview of the recent developments in micro/nanoscale coating and structure fabrication techniques and performs a thorough comparison of their condensation performance, elucidating the complex interfacial transport mechanism involved. Surface structuring methods that are durable, scalable and low-cost are essential attributes for large-scale industrial implementation. Here, the methods used to improve surface durability and demonstrations of nanostructure-enhanced meter-scale condensers are presented. Limitations are discussed and the potential techniques to overcome these challenges are summarized. Given the recent development of metal additive manufacturing technology and its growing relevance in manufacturing processes, we end this review by providing our perspectives on the opportunities in enabling surface nanostructuring of metal additive manufactured materials and the potential of nanometric-millimetric co-design optimization for the development of next-generation additively manufactured condensers.

An acoustic emission source localization approach based on time-reversal technology for additive manufacturing

The metal additive manufacturing process can inevitably lead to a great temperature gradient in the workpiece. Therefore, the thermal stress deformation and defects seriously affect the processing quality. In this paper, an array acoustic probe is designed on the base plate with the consideration of the time reversal technology. Corresponding simulations is implemented, which are designed to verify the ability of detecting and positioning the workpiece stress release acoustic emission signal. The simulation results demonstrate that the proposed method can position and monitor the random acoustic emission.