Boiling heat transfer in mini-channels: influence of the hydraulic diameter

International audienceThe present experimental study shows how the reduction of the hydraulic diameter affects the heat transfer coefficientfor a boiling flow in mini-channels. Flat aluminium multipart extruded tubes composed of parallel rectangular channelswith hydraulic diameters 0.77 and 2.01 mm were used with refrigerant Rl34a. It was shown that the reduction of thehydraulic diameter increased the heat transfer coefficient and favored dry-out, probably because of the thinning of theliquid layer due to the bubble confinement. However it was found that the quality averaged heat transfer coefficientwas still greater than what would be obtained in macro-tubes