Numerical Study on Spreading and Vaporization Process of Liquid Nitrogen Droplet Impinging on Heated Wall

Liu Wang, Yue Ding, Yinan Qiu, Yunxing Yu, Junlong Xie and Jianye Chen ()
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Liu Wang: School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Yue Ding: School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Yinan Qiu: State Key Laboratory of Technologies in Space Cryogenic Propellants, Beijing 100028, China
Yunxing Yu: School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Junlong Xie: School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Jianye Chen: School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Energies, 2022, vol. 15, issue 22, 1-20

Abstract: Micro-structured surfaces can affect heat transfer mechanisms because of enlarged specific surface areas. However, employing the Leidenfrost effect during liquid nitrogen (LN 2 ) droplet cooling of a heated micro-structured surface possessing a fin with a spacing much smaller than the diameter of the droplet has not yet been explored. In the present work, a direct numerical simulation (DNS) is carried out to investigate heat transfer mechanisms of the LN 2 droplet, whose diameter is sufficiently larger than the structured spacing of fin, impinging on a micro-structured surface with variable velocities. For a comparative study, a smooth surface is also employed in numerical simulations. The spreading mechanisms and vaporization behavior of the droplet along with liquid film morphology at various conditions are investigated. Results show that a smaller fin size inhibits LN 2 in entering into the grooves between the fins and left the surface untouched by the droplet completely, and eventually, a thinner liquid film is spread out in contrast to the smooth surface. Notably, at a low Weber number, the droplet can be shrunk or even rebounded away from the wall after impinging on the wall. The fastest vaporization behavior for both surfaces, namely smooth and micro-structured, is obtained at a Weber number of 180. Additionally, an effective heat transfer upon the micro-structured surface is observed at a low impinging velocity of the droplet.

Keywords: spray cooling; liquid nitrogen; droplet impingement; vaporization; direct numerical simulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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