Single-Phase Convective Flows

Heat transfer in microchannel flow Single-phase convective flows in microchannels Single-phase forced convection in microchannels... 

Estimated by the convective coefficient of single-phase gas flow [Sleicher and Rouse, 1975]... 

M. S. Bhatti andR. K. Shah. "Thrbulent and Transition Flow Convective Heat Transfer in Ducts. Tn Handbook of Single-Phase Convective Heat Transfer, ed. S, Kaka9, R. K. Shah, and W. Aung, New York Wiley Interscience, 1987. 

Note that the tube contains a liquid before the bubbly flow regime and a vapor after the mist-flow regime. Heat transfer in those two cases can be determined using the appropriate relations for single-phase convection heat transfer. Many correlations are proposed for the determination of heat transfer... 

J. P. Hartnett, Single Phase Channel Flow Forced Convection Heat Transfer, in 10th International Heat Transfer Conference, vol. 1, pp. 247-258, Brighton, England, 1994. 

In this heat transport model, the radial heat transfer is represented by a Fourier-like law, using an equivalent radial thermal conductivity of the medium with flowing fluids 4r = A dT/dr. The bed radial effective thermal conductivity was expressed as sum of two terms—conductive contribution and convective contribution A -Aso+ gf In Hashimoto et al. [94] and Mat-suura et al. s [95] approach, the theory of single-phase gas flow... 

A very accurate and recent review of the main results on this topic has been published [10]. In that review it is demonstrated that the slip-flow regime has been much studied in the last few years from theoretical and experimental points of view. The gas rarefaction decreases the value of the convective heat transfer, as evidenced by the results quoted in Tab. 6, 9, 10 and 15. The convective heat transfer for rarefied gases in microchanneis depends on the kind of interactions between the gas and the walls in fact, these interactions determine the value of the finite temperature jump between walls and gas (see pressure-driven single phase gas flows). Rarefaction effects tend to influence the heat transfer for Knudsen numbers greater than 0.001. 

The boundary conditions that have to be used together with Eq. (3) can be found in pressure-driven single phase liquid flow and in pressure-driven single phase gas flows for the momentum equation and in convective heat transfer in microchannel for the energy balance equation. 

In the following sections, the experimental results which have been found in various studies of single-phase polymer flow in 1-D porous media will be discussed. Results will be referred to the convection-dispersion equation outlined above as a model for the flow. However, when there are deviations from this, the appropriate equations/models will be developed. In addition to discussing the macroscopic fit of the generalised convection-dispersion model for polymer transport in porous media, some aspects of the microscopic or physical basis of the phenomena under consideration will also be discussed. 

Designs of pressurized systems limit the heat removal to that determined when there is no bulk boiling. The flow is always subcooled, and the heat exchange is by single-phase (liquid) flow in the heat exchanger. Heat removal in normal and accident conditions can be set by the convective heat removal by natural circulation. 

New questions have arisen in micro-scale flow and heat transfer. The review by Gad-el-Hak (1999) focused on the physical aspect of the breakdown of the Navier-Stokes equations. Mehendale et al. (1999) concluded that since the heat transfer coefficients were based on the inlet and/or outlet fluid temperatures, rather than on the bulk temperatures in almost all studies, comparison of conventional correlations is problematic. Palm (2001) also suggested several possible explanations for the deviations of micro-scale single-phase heat transfer from convectional theory, including surface roughness and entrance effects. 

The data presented in the previous chapters, as well as the data from investigations of single-phase forced convection heat transfer in micro-channels (e.g., Bailey et al. 1995 Guo and Li 2002, 2003 Celata et al. 2004) show that there exist a number of principal problems related to micro-channel flows. Among them there are (1) the dependence of pressure drop on Reynolds number, (2) value of the Poiseuille number and its consistency with prediction of conventional theory, and (3) the value of the critical Reynolds number and its dependence on roughness, fluid properties, etc. 

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