Title: Thermal Energy System Engineering at the Extremes: Supercritical CO2 Power Cycles and Dropwise Condensation
Of the ~100 Quads of energy use in the USA, 2/3 are applied thermally for heating and fuel. The remaining 1/3 is used for electricity production, from which 2/3 are rejected as waste heat. This heat rejection accounts for 41% of USA fresh water withdrawals. To more sustainably use these energy and water resources, underlying heat transfer processes must be advanced, and transport-level gains must be propagated to the system scale. This seminar will present our work to characterize and engineer thermal-fluid energy systems in two themes: 1. Supercritical CO2 Power Cycles and 2. Dropwise Condensation.
- Supercritical CO2 (sCO2) power cycles are an emerging technology that can offer greater efficiency and reduced cooling water use compared with steam (Rankine) and gas turbine (Brayton) systems. Because of the complex property trends of supercritical fluids, new heat transfer models and compact heat exchanger designs are needed. We have partnered with Siemens Energy and Oak Ridge National Lab to develop a techno-economically optimized fully-additively manufactured heat exchanger design for sCO2 power cycles. This design has been verified at the ~25 kW scale, and is targeted to enable microgrid-scale combined cycle power plants with efficiency >50%.
- Dropwise condensation (DWC) can yield an order-of-magnitude improvement in heat transfer performance compared with the more conventional filmwise mode. DWC is of particular interest for power generation and water desalination, for which it can offer system-level efficiency gains. Recent advances in surface engineering offer pathway for implementation at relevant scales. However, the startup process of DWC on an initially dry surface is not well understood. We have conducted highly time-resolved heat transfer measurements of DWC initialization at high heat fluxes, and identified distinct phases of behavior. These transient heat trends can inform practical DWC system engineering.
Alex Rattner is an Associate Professor of Mechanical Engineering at Penn State University and the principal investigator of the Multiscale Thermal Fluids and Energy Lab. He received the 2016 Frederick A Howes Scholar award in computational science and an NSF CAREER grant (2017-2022). His research expertise includes waste heat recovery, absorption refrigeration, supercritical CO2 power cycles, spacecraft thermal management and power systems, and experimental and computational multiphase flow heat and mass transfer.