Lattice Boltzmann study of nucleation site interaction and nucleate boiling heat transfer on a hybrid surface with multiple cavity-pillar structures

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Detail(s)

Original languageEnglish
Article number106860
Journal / PublicationInternational Journal of Thermal Sciences
Volume163
Online published1 Feb 2021
Publication statusPublished - May 2021

Abstract

In this work, nucleation site interaction and nucleate boiling heat transfer are studied on a hybrid rough surface, a surface with multiple cavities and a pillar on sides of each cavity, using a two-dimensional pseudopotential phase-change lattice Boltzmann method (LBM). To elucidate the effects of incorporation of pillars, the results of the hybrid rough surface are compared with a simple rough surface (a surface with multiple cavities). First, bubble nucleation, growth and departure processes are investigated above the simple and hybrid rough surfaces with three cavities and bubble interactions and their effects on cavity activation/deactivation at low superheat are discussed. The results showed a complete suppression of the central cavity at small pitch distance and left/right cavities at large pitch distance, which are caused by combined suppression effect of adjacent cavities and edge effects of the heater, respectively, for the simple rough surface. But, with the incorporation of pillars the heat transfer area is increased and the effects of induced flow are reduced, resulting in the activation of suppressed cavities, and thus, the higher heat flux is observed for the hybrid rough surface than the simple rough surface. The cavity suppression is also observed for unequal cavity depths or widths. The complete suppression of the central cavity occurs, when the central cavity is narrow or left/right cavities are deep. On the other hand, the highest heat flux is observed for the hybrid rough surface with central deep cavity and left/right shallow cavities due to the activation of all nucleation sites and additional heat transfer from the central deep cavity. Increasing pillar height or decreasing cavity-pillar spacing results in the stability and growth of residual bubbles to the next cycle without waiting periods, which increase the heat flux. Next, heat transfer in the nucleate boiling region is investigated by comparing saturated boiling curves obtained through simulations. The heat flux in the nucleate boiling including the critical heat flux (CHF) is higher for the hybrid rough surface than the simple rough surface. The heat flux also found to be increased in developing region of nucleate boiling, when pillar height is increased. The CHF increases with pillar height up to a certain height. But, with tall pillars at high wall superheats, the excessive nucleation of bubbles can also occur in the inter-pillar spacings, in addition to cavities, increasing the susceptibility of merger of closely spaced bubbles, which reduce the CHF.

Research Area(s)

  • Cavity, Lattice Boltzmann method, Nucleation site, Pillar, Pool boiling

Citation Format(s)

Lattice Boltzmann study of nucleation site interaction and nucleate boiling heat transfer on a hybrid surface with multiple cavity-pillar structures. / Ahmad, Shakeel; Chen, Jingtan; Eze, Chika et al.
In: International Journal of Thermal Sciences, Vol. 163, 106860, 05.2021.

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review