Between 75-90% of the world’s electricity is generated by steam cycles. Each steam cycle relies on liquid-vapor phase change of the working fluid in both a boiler and a condenser, representing potential areas for efficiency improvement. For example, improving condensation heat transfer performance in a steam-cycle-based power plant by an order of magnitude can yield a 1-2% improvement in overall electrical generation efficiency, potentially saving billions of dollars each year by reducing fuel requirements and, correspondingly, reducing power plant emissions. We develop techniques to enhance both boiling and condensation heat transfer with a focus on robust, scalable solutions.
- Scalable Graphene Coatings for Enhanced Condensation Heat Transfer
D.J. Preston, D.L. Mafra, N. Miljkovic, J. Kong, E.N. Wang
Nano Letters, 15(5), 2015
- Electrostatic Charging of Jumping Droplets
N. Miljkovic, D.J. Preston, R. Enright, E.N. Wang
Nature Communications, 4(2517), 2013
As computers become increasingly powerful, the need to keep them cool during operation has arisen as a critical issue. Specifically, the mean time to failure for a computer chip is exponentially related to its operating temperature, and squeezing more and more transistors into small areas has increased the heat fluxes that need to be dissipated in these systems, requiring lower thermal resistances and higher heat transfer performance. Phase-change cooling, often in the form of heat pipes, has been implemented in most modern laptops – and some cell phones – to dissipate this heat. We research both evaporation and condensation, as well as transport of the working fluid from the condenser back to the evaporator (usually by wicking), to push the limits of thermal management and enable high-powered computing.
- Gravitationally-Driven Wicking for Enhanced Condensation Heat Transfer
D.J. Preston, K.L. Wilke, Z. Lu, S.S. Cruz, Y. Zhao, L.L. Becerra, E.N. Wang
Langmuir, 34(15), 2018
- Porous Cu Nanowire Aerosponges from One-Step Assembly and their Applications in Heat Dissipation
S.M. Jung, D.J. Preston, H.Y. Jung, Z. Deng, E.N. Wang, J. Kong
Advanced Materials, 28(7), 2015
Potentially useful energy is wasted, on a massive scale, in many forms, from mechanical, to electromagnetic, to thermal. For example, as soldiers walk from location to location, their footsteps could be used to charge personal electronics instead of simply being dissipated as sound and thermal vibrations. Another example, in power generation, is wasted thermal energy: the condenser in a steam cycle rejects potentially usable heat to the environment. In prior work, we have demonstrated generation of electricity from a thermal gradient using “jumping droplets” on a superhydrophobic surface inside of a heat pipe; as droplets jump from one surface to another during heat transfer, they carry an electrical charge that builds up and can be used. We will focus on capture and conversion of wasted energy – of all types – in future work.