A novel micro-channel heat sink with trapezoid drainage for enhancing condensation heat transfer of dielectric fluid

This study experimentally investigates the condensation of dielectric fluid HFE-7100 in a micro-channel heat sink with the hydraulic diameter of 1.21 mm. Tests are conducted at a fixed pressure of 110 kPa, with vapor mass quality (x_in) ranging from 0.1 to 0.9, mass fluxes (G) from 150 to 250 kg·m⁻²·s⁻¹, inclined angle (θ) from −90° to +90°. A novel trapezoid drainage design is proposed to enhance the condensation heat transfer by effectively entraining condensation film. When G is lower than 200 kg·m⁻²·s⁻¹, the two phase heat transfer coefficient (h_tp) for the trapezoid drainage design exceeds the conventional rectangular micro-channel heat sink by 10–26% while the corresponding pressure drop is about 22–45% lower. When G is increased to 250 kg·m⁻²·s⁻¹, the drainage design can still dramatically decrease the pressure drop, however, it shows a negative effect on h_tp when the x_in is greater than 0.2. With inclined arrangements, the pressure drop would dramatically increase due to gravity effect. Besides, at the conditions of θ = −45° and −90°, the trapezoid drainage channel can improve the h_tp by 43–45% when G is lower than 200 kg·m⁻²·s⁻¹. On the contrary, with the arrangement of θ = +45° and +90°, the trapezoid drainage channels may decrease the h_tp by 8–15%. This phenomenon is especially pronounced at a high x_in. In addition, the heat transfer enhancement and deterioration are both analyzed based on stress distribution at vapor phase and condensation film.