Nanoscale Thermophysics and Transport in Liquid-Vapor Phase Change Processes
Funded by NSF, the Hass Sustainable Products and Solutions Program, UC Berkeley Blum Center, CITRIS, the endowment for the A. Richard Newton Chair, and DOE through the U.S.-China Clean Energy Research Center (CERC).
Nano-structured surfaces for enhanced water spray cooling of power system condensers
Water spray cooling of steam power plant air-cooled condensers is often used as a means to compensate for increased electrical demand or high ambient air temperature. Over the past year we have successfully developed a system in our laboratory to fabricate nanostructured surface coatings on metallic substrates that can enhance water droplet evaporation heat transfer on heat exchanger surfaces. The surfaces are ZnO nanowire coatings that we are currently growing on a copper substrate with different wire lengths and spacing. The resulting surfaces are superhydrophilic, which causes impinging water droplets to rapidly spread into a thin liquid film on the nanostructured surface. This results in very rapid and efficient heat removal from the surfaces of the condenser as the film evaporates. We are specifically interested in this type of coating because the thermal-growth fabrication process can be scaled up to coat large metal surfaces in heat exchangers. Use of this type of surface coating to enhance heat transfer can significantly improve the efficiency of the power plant. It can also reduce water consumption for spray cooling, which is critically important for power plants located where water resources are scarce. We are also exploring the Leidenfrost transition to film boiling for these surfaces to better understand the physics of surface wetting effects on water quenching of metal forgings and castings.
Our work in this area is particularly noteworthy because we appear to be the first to develop the capability to manufacture this type of coating on copper surfaces, and we are working to develop this type of superhydrophilic coating technology on surfaces of aluminum and other metals used in heat exchangers for power plant condensers, air conditioners and other important applications.
Asynchronously-Cooled Thermal Energy Storage for Enhanced Power Plant Air-Cooling Systems
Research is supported by recently-obtained funding from ARPA-E
On the basis of initial modeling we proposed to ARPA-E a development plan for a high tech asynchronous cooling system that includes a compact air pre-cooler (to reduce inlet air temperature to a power system steam condenser) coupled to a unique (cold) thermal energy storage (TES) that operates over a range of daytime temperatures and is recharged at night by an asynchronous cooling unit. This shifts the daytime peak heat rejection load to nighttime hours to increase power-plant efficiency and output. With “smart” controls for pre-cooler bypass and TES operation, it is integrated with (a) an air cooled condenser (ACC), and (b) an air-to-water closed loop heat exchanger (AWHX) as a dry retrofit to existing wet cooling. The heat exchangers are to be optimized for air- and liquid-side heat transfer enhancement, and fabricated with low cost materials and advanced manufacturing. This project has been funded by ARPA-E, and we are initiating work on this project this summer (2015). The Carey UC Berkeley team will lead the heat transfer and pressure drop modeling and design analysis and development of the TES unit and the asynchronous cooling (air-cooled) heat exchanger. The optimized designs of the TES unit and the asynchronous cooling heat exchanger will be developed through a joint effort of the UC Berkeley team and researchers at Texas A&M. The UC Berkeley team will also collaborate in assessment of test data for a prototype to be developed by industrial collaborators at Boeing and Evapco.
Trash to Tiles
This project is funded by NSF, the Big Ideas competition at Berkeley, a USAID Global Development Fellowship, and the Blum Center InFEWS program
Trash to Tiles (T3) is a research project founded in November 2017 to repurpose plastic waste in Uganda into construction products by designing an energy efficient manufacturing process to fuse plastic waste with locally available fillers. We are exploring creating roofing tiles, pavers, gutters, and other construction products. T3 is developing technology to fill the gap between capital-intensive, industrialized plastic manufacturers and low-tech NGOs struggling to expand. Uganda faces an 8 million unit housing shortage, so building materials are in high demand. In the pilot market of Gulu, Uganda, T3 created prototypes and confirmed market demand through 200 interviews with consumers. A plastic collection center will be established in Gulu to provide a consistent stream of waste plastic, clean up the community, prevent unhealthy burning of waste plastic, and provide income generation opportunities for locals. In partnership with Gulu University, T3 is building an extruder and designing a manufacturing process for creating construction products from plastic waste. An exergy analysis of an industrialized plastic roofing tile manufacturer in Kampala, Uganda was completed as a baseline for understanding the process.