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The third generation enhanced heat transfer technologies, such as three-dimensional fin and dimple, are still important means of improving energy efficiency and will continue to be challenging issues. This paper concentrates on the analysis of the condensation heat transfer performance of an edge-shaped finned-tube fabricated by extrusion-ploughing process. Experimental results show that the overall heat transfer coefficient increases with increases of volumetric flow rate of cold water and heat flux whereas the shell side heat transfer coefficient decreases with volumetric flow rate and heat flux increasing. At the similar volumetric flow rate, the shell side heat transfer coefficient of the edge-shaped finned-tube is 4-6 times larger than that of the smooth tube. At the similar volumetric flow rate, the shell side heat transfer coefficient of edge-shaped finned-tube increases with ploughing depth increasing. At the same temperature difference between wall and vapor, the shell side heat transfer coefficient is also higher than what had been reported in the literature. [ABSTRACT FROM AUTHOR]

In order to ensure the normal work of electronic product, the thermal management is of key importance. Miniature loop heat pipe (mLHP) is a promising device of heat transfer for electronic products. Cu-water nanofluid with different concentration is used as working material in mLHP. Experiments are conducted to investigate its heat transfer performance. The heat flux owing to thermal diffusion is calculated. It is found that this heat flux and the boiling temperature are non-monotonic function of concentration of nanoparticle. Turning concentration appears at about 1.5 wt%. Differential equation of thermal diffusion produced by micro movement of nanoparticle is established in this paper. Average speed formula for nanoparticles is derived and slope of the curve of phase equilibrium is obtained. Based on the theoretical research in this paper, enhanced heat transfer mechanism of nanofluid is analyzed. The facts that heat flux owing to thermal diffusion and boiling temperature are all associated with nanoparticle concentration are also well explained with the aid of the derived theory in this paper. [ABSTRACT FROM AUTHOR]