TY - GEN
T1 - Study of coalescence-induced jumping droplets on biphilic nanostructured surfaces for thermal diodes in thermal energy storage systems
AU - Zhu, Y.
AU - Tso, C. Y.
AU - Ho, T. C.
AU - Chao, Christopher Y.H.
N1 - Funding Information:
The funding for this research is provided by the Hong Kong Research Grant Council via Collaborative Research Fund (CRF) account C6022-16G and General Research Fund (GRF) account 16202517, and also the City University of Hong Kong StartUp Fund via the account code of 9610411.
Publisher Copyright:
Copyright © 2020 ASME
PY - 2020
Y1 - 2020
N2 - Thermal energy can be better harvested and stored by integrating thermal diodes with thermal energy storage systems. Among different types of thermal diodes, jumping-droplet thermal diodes exploiting superhydrophilic and superhydrophobic surfaces yield greater thermal rectification performance (i.e. diodicity) due to high latent heat. However, the condensation heat transfer and coalescing-jumping droplets are restricted by the ability of water to nucleate on the superhydrophobic surface, leading to a limited maximum jumping height, finally resulting in degradation of diodicity of the thermal diode. To solve this problem, we propose coating hydrophilic bumps on the superhydrophobic surface which can provide preferable nucleation sites, forming a new type of nanostructured surface, called biphilic surface. This work aims to investigate coalescence-induced jumping droplets on biphilic surfaces to enhance diodicity of phase change thermal diodes. Our experimental results show that the jumping height and jumping volumetric flux of the coalescence-induced jumping droplets on a biphilic surface are enhanced by 42% and 254% compared to those on a superhydrophobic surface, respectively. Based on the jumping droplet results, a mathematical model for diodicity is built. 244% improvement can be achieved in the thermal diode with an optimized biphilic surface as compared to that with a superhydrophobic surface, which provides an effective strategy to improve the diodicity of a phase change thermal diode and an alternative approach to enhance the energy harvesting and storage capability in thermal energy storage systems.
AB - Thermal energy can be better harvested and stored by integrating thermal diodes with thermal energy storage systems. Among different types of thermal diodes, jumping-droplet thermal diodes exploiting superhydrophilic and superhydrophobic surfaces yield greater thermal rectification performance (i.e. diodicity) due to high latent heat. However, the condensation heat transfer and coalescing-jumping droplets are restricted by the ability of water to nucleate on the superhydrophobic surface, leading to a limited maximum jumping height, finally resulting in degradation of diodicity of the thermal diode. To solve this problem, we propose coating hydrophilic bumps on the superhydrophobic surface which can provide preferable nucleation sites, forming a new type of nanostructured surface, called biphilic surface. This work aims to investigate coalescence-induced jumping droplets on biphilic surfaces to enhance diodicity of phase change thermal diodes. Our experimental results show that the jumping height and jumping volumetric flux of the coalescence-induced jumping droplets on a biphilic surface are enhanced by 42% and 254% compared to those on a superhydrophobic surface, respectively. Based on the jumping droplet results, a mathematical model for diodicity is built. 244% improvement can be achieved in the thermal diode with an optimized biphilic surface as compared to that with a superhydrophobic surface, which provides an effective strategy to improve the diodicity of a phase change thermal diode and an alternative approach to enhance the energy harvesting and storage capability in thermal energy storage systems.
KW - Biphilic Nanostructured Surface
KW - Coalescing Jumping Droplets
KW - Condensation Heat Transfer
KW - Thermal Management
KW - Thermal Rectification
UR - http://www.scopus.com/inward/record.url?scp=85091842172&partnerID=8YFLogxK
U2 - 10.1115/ES2020-1703
DO - 10.1115/ES2020-1703
M3 - Conference article published in proceeding or book
AN - SCOPUS:85091842172
T3 - ASME 2020 14th International Conference on Energy Sustainability, ES 2020
BT - ASME 2020 14th International Conference on Energy Sustainability, ES 2020
PB - American Society of Mechanical Engineers(ASME)
T2 - ASME 2020 14th International Conference on Energy Sustainability, ES 2020
Y2 - 17 June 2020 through 18 June 2020
ER -