THERMO-HYDRAULIC CHARACTERISTICS OF ADDITIVELY MANUFACTURED MINI-CHANNELS

The aim of this work is to analyze the heat transfer, hydraulic resistance and thermo-hydraulic performance of a new type of heat exchange channels made by additive technology. The main factors affecting the quality of products and determining the heat transfer and hydraulic resistance of the channels are noted.  Well-known ratios for calculating hydraulic resistance and heat transfer are not suitable for such high roughness. Data on the AT resistance coefficient of the channels show that even at low Reynolds numbers there is a contribution of roughness. With increasing roughness, the intensification of resistance and heat exchange increases. The transition occurs at 700 < Re < 2000. Comparison of data on heat transfer augmentation and increase of hydraulic losses, as well as their thermo-hydraulic characteristics has been carried out. The hydraulic resistance coefficient of AT channels is significantly higher than the resistance coefficient of smooth channels. Heat transfer augmentation in wave-shaped channels is 2 times higher than augmentation in straight channels. Channels with pin fins allow to achieve a very high heat transfer augmentation (up to 8). Channels with internal grids provide high intensification, but have the highest hydraulic losses. The dependence of the Reynolds analogy factor on the resistance increase factor showed that the straight channels of all geometric forms fit on one dependence closed to the lower boundary line, and have a low hydraulic resistance. Data on channels with pin fins have a large spread. A number of points are above the upper boundary line, which refers to channels with low surface roughness.