Characteristics of thermal convective flow of near-critical CO2 fluid in microchannels

Lin Chen, Xin Rong Zhang

Research output: Contribution to conferencePaper

Abstract

Near-critical/supercritical fluids have been widely proposed in chemical extraction and synthesis, micromanufacturing and also heat transfer apparatus, etc. Fluid near its gas-liquid critical point is dense and much expandable. The critical diverges are very important for both hydrodynamic study and heat transfer applications of industry. The current paper reports a series of systematic investigations into the near-critical CO2 convective flow and heat transfer in microchannels. Careful numerical procedures and theoretical studies are carried out by modified Navier-Stokes equations, energy and near-critical CO2 fluid state equations. The numerical method has been refined and the characteristics of such near-critical fluid configuration in microscales are systematically explored with sudden application of boundary heat fluxes. It is interestingly found that strong near-critical vortex flows can happen for a relative wide range of initial and input conditions. Transitions from vortex mixing flow to buoyancy convections are found during the microchannel spatial scaling. Theoretical analysis shows that the basic Kelvin-Helmholtz instability applies to the current microchannel instability evolution. The specific boundary thermal-mechanical perturbation process (with hot boundary stratification and expansion) serves as the origin of current instability phenomena. The near-critical fluctuations and multi-time scale analysis show that different from traditional acoustic Piston Effect in closed systems, thermal-mechanical effects dominates the convective structures for the current open channel configurations. Characteristics of the transition phenomena, convection structure, onset threshold, heat transport relations, and possible applications in micro-engineerings are also presented in this paper.

Original languageEnglish
Publication statusPublished - 2014 Jan 1
Externally publishedYes
Event15th International Heat Transfer Conference, IHTC 2014 - Kyoto, Japan
Duration: 2014 Aug 102014 Aug 15

Other

Other15th International Heat Transfer Conference, IHTC 2014
CountryJapan
CityKyoto
Period14/8/1014/8/15

Keywords

  • Convection
  • Heat transfer
  • Microchannel
  • Nonlinear thermal fluid phenomena
  • Stability
  • Thermodynamics

ASJC Scopus subject areas

  • Mechanical Engineering
  • Condensed Matter Physics

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  • Cite this

    Chen, L., & Zhang, X. R. (2014). Characteristics of thermal convective flow of near-critical CO2 fluid in microchannels. Paper presented at 15th International Heat Transfer Conference, IHTC 2014, Kyoto, Japan.