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Abstract: Experiments on flow boiling of water are carried out for a rectangular vertical channel with dimension 0.86×2.0mm2 (width×depth, hydraulic diameter d h =1.2mm). The Confinement number Co ∗ for the investigated range of operating parameters is about 2.2. So, applying the criterion Co ∗ >0.5 for microchannels, the investigated channel has to be classified as “micro”. Investigations of heat transfer, pressure drop and flow pattern were carried out for different mass and heat fluxes and their relationships were analysed. [Copyright &y& Elsevier]

Visualization experiments were carried out for nucleate pool boiling of propane and iso-butane on a horizontal smooth tube and two kinds of structured enhanced tubes. Some bubble dynamic parameters were measured. Comparisons were made between the smooth tube and the enhanced tubes for bubble growth rate, departure diameter, frequency, active site density, rise velocity and latent heat transfer. The effects of physical properties on the bubble dynamics are discussed. The present experimental results are compared with the model of Haider and Webb, relatively good agreement is found for enhanced surfaces. The augmentation mechanisms of heat transfer from structured enhanced tubes are also discussed. [Copyright &y& Elsevier]