Steady and Unsteady Flow in a Heated Capillary

The forced fluid flow in heated micro-channels with a distinct evaporation front is considered. The effect of a number of dimensionless parameters such as the Peclet, Jacob numbers, and dimensionless heat flux, on the velocity, temperature and pressure within the liquid and vapor domains has been studied, and the parameters corresponding to the steady flow regime, as well as the domains of flow instability are delineated. An experiment was conducted and demonstrated that the flow in microchannels appear to have to distinct phase domains one for the liquid and the other for the vapor, with a short section of two-phase mixture between them. 

The investigations of fluid flow in micro-channels may be divided in two groups (1) single-phase flow, and (2) evaporative two-phase flow. The first was intensively investigated beginning from the pioneer work by Tukermann and Pease (1981). Two-phase flow is much less understood. 

Fluid Flow, Heat Transfer and Boiling in Micro-Channels Springer 2009 

Peles et al. (1998) and Khrustalev and Faghri (1996) considered two-phase laminar flow in a heated micro-channel with distinct evaporating meniscus in the frame of quasi-one-dimensional and two-dimensional models. 

Below the system of quasi-one-dimensional equations considered in the previous chapter used to determine the position of meniscus in a heated micro-channel and estimate the effect of capillary, inertia and gravity forces on the velocity, temperature and pressure distributions within domains are filled with pure liquid or vapor. The possible regimes of flow corresponding to steady or unsteady motion of the liquid determine the physical properties of fluid and intensity of heat transfer. 

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Peles YP, Yarin LP, Hetsroni G (2001) Steady and unsteady flow in a heated capillary. Int J Multiphase Flow 27 577-598... 

Morris SJS (2003) The evaporating meniscus in the channel. J Fluid Mech 494 297-317 Peles YP, Yarin LP, Hetsroni G (2000) Thermohydrodynamic characteristics of two-phase flow in a heated capillary. Int J Multiphase Flow 26 1063-1093 Peles YP, Yarin LP, Hetsroni G (2001) Steady and unsteady flow in a heated capfllary. Int J Multiphase Flow 27 577-598... 

Peles el al. (2000) elaborated on a quasi-one-dimensional model of two-phase laminar flow in a heated capillary slot due to liquid evaporation from the meniscus. Subsequently this model was used for analysis of steady and unsteady flow in heated micro-channels (Peles et al. 2001 Yarin et al. 2002), as well as the study of the onset of flow instability in heated capillary flow (Hetsroni et al. 2004). 

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