Experimental study on the forming of rectangle- & V- channels interconnected boiling enhancement structures

In this paper, a rectangle- & V-channels interconnected boiling enhancement structure was manufactured by ploughing-extrusion and multi-tooth planing processes based on copper strips with 0.5mm in thickness. The rectangle channels are 0.5mm in width, 0.4mm in depth and 1mm in pitch. While in the opposite surface, the V-channels are 0.6mm in depth, 40° in groove angle and 0.48mm in pitch. These rectangle channels and V-channels are perpendicular and inter-connected. Wavy fins are at the fringe of V-channels. Micro pores are formed in the intersect site where theses two kinds of channels meet which are about 0.2mm in length, 0.1mm in width and have irregular fins around it. The final thickness of this structure is about 0.7mm. The “pore-channel-fin” structures are advantageous for enhancing the nuclear boiling so can be widely used in thermosyphon, capillary pump loops, loop heat pipes and other two-phase heat transfer devices. The parameters of the employed ploughing-extrusion tool are: the major forming angle (γ0) is 30°, the minor forming angle (γ0′) is 20°, the edge inclination angle (Xγ) is 45°, the major extrusion angle (β) is 25°, and the minor extrusion (β′) angle is 16°. Experiments show that the ploughing-extrusion depth has the greatest influence on the formation of micro pores. Only when the sum of the planing depth (Dp) and ploughing-extrusion depth (Dp-e) surpass the thickness of copper strip to a certain value, the cracks would appear. The bigger the sum is, the larger the cracks extend, and the bigger the formed pores are. When the ploughing-extrusion tool goes through the rectangle channels, the metal in V-channels could flow upward and downward along the forming faces of the tool and forms the fins at the bottom of rectangle channels and the fringe of V-channels, while- after the tool departing from the rectangle channels, the metal could only flows upwards results that the fins at the fringe of V-channels are higher. So the final fringes of V-channels are wavy fin structures, which are advantageous for enhancing boiling further.