Numerical Study of Condensation Process in Semi-Circular Mini-Channels for the Printed Circuit Heat Exchanger

Abstract

Printed circuit heat exchanger has been recognized as a perspective mini-channel heat exchanger. Semi-circular cross-section is designed here due to the special manufacture technology. However, there is a lack of related investigations on condensation process in mini-channels with semi-circular cross-section. In this paper, corresponding three-dimensional numerical simulations are presented. The horizontal straight channels with radius of 1 mm and 1.222 mm, and length of 250 mm are considered as the geometric models. Constant mass flux (317 kg/m2 s) and wall temperature (310 K) are applied as the boundary conditions. Heat transfer and flow characteristics are conducted by comparing to that in common circular channel with identical wetted perimeter. The effect of placing direction and surface wettability are present as well. The results show that the liquid film in the semi-circular channel is more uneven compared to that in the circular channel. The liquid is accumulated in corners because of surface tension, and this brings worse heat transfer to the semi-circular channel further. Besides, the placing direction has little influence on heat transfer with the variation range of heat transfer coefficient within 4% in the present conditions. The influence of surface wettability can be neglected for the larger tube.