Encyclopedia of Two-Phase Heat Transfer and Flow III

The following sections are included:

• Preface
• About the Editor-in-Chief
• List of Contributors
• Contents

This chapter presents the improved measurements, data reduction and models of two-phase flow and heat transfer in multi-microchannel evaporators. A state-of-the-art review is first presented, and then an experimental facility used for this study and the operating conditions are described. Three different refrigerants were tested in two test sections under various mass fluxes, heat fluxes, inlet subcoolings and outlet saturation temperatures. Afterwards, a new method for reducing the local heat transfer data is proposed, where a 3D inverse heat conduction problem is solved. The final part shows the results obtained. The results include (i) measurement and prediction of two-phase flow pressure drops, (ii) measurement and modeling of local heat transfer coefficients at steady-state, (iii) micro-evaporators wall temperature responses under transient heat loads and (iv) measurement of transient local heat transfer coefficients. It is found that the new pressure drop prediction method and the new flow pattern based local heat transfer model proposed in this study yield the best agreement with the present data with mean absolute errors (MAE) of 27.8% and 14.2%, respectively. It is worthwhile to highlight that the new heat transfer model predicts the local heat transfer data from the subcooled flow boiling regime all the way through to the annular flow regime.

Evaporation of refrigerant–oil mixtures inside smooth and microfin tubes are described. The flow patterns under different operating conditions are discussed. The heat transfer coefficient and pressure drop characteristics of refrigerant–oil mixtures flow boiling inside smooth and microfin tubes are analyzed. Some existing correlations for refrigerant–oil mixtures flow boiling inside smooth and microfin tubes are presented.

Convective condensation of refrigerant–oil mixtures inside smooth and microfin tubes are described. The heat transfer coefficient and pressure drop characteristics of refrigerant–oil mixtures during convective condensation inside smooth and microfin tubes are analyzed. Some existing correlations for convective condensation of refrigerant–oil mixtures inside smooth and microfin tubes are presented.

Evaporation of refrigerant–oil mixtures inside metal-foam filled tubes are described. The flow patterns under different conditions are observed and analyzed. Some existing correlations for refrigerant–oil mixture flow boiling inside metal-foam filled tubes are presented.

Nucleate pool boiling of nanorefrigerant and oil mixtures is described in this chapter. The effect of nanoparticle types (the spherical nanoparticles and cylindrical carbon nanotubes) on boiling heat transfer characteristics of nanorefrigerant and oil mixtures is investigated, and the effect of surfactant on the boiling heat transfer characteristics is analyzed. Some existing correlations are described and then some new correlations for pool boiling of these mixtures inside smooth tubes are presented.

The purpose of this chapter is to critically review all the literature on condensation in inclined tubes. This will include all the previous work conducted at different inclination angles, as well as recent experimental work of the authors, in terms of flow pattern observations and measurements of the heat transfer coefficients, pressure drops and void fractions at different inclination angles. Smooth circular tubes and internally microfinned tubes are considered, as well as the influences of condensation temperature and mass flux.

The following section is included:

• Index