Liquid Film Flow Characterization in Microfluidic Oscillating Heat Pipes Using Particle Image Velocimetry

Due to continuous reduction of the size yet increased performance of electronic systems, increased heat generation has been a critical issue. To solve this issue, oscillating heat pipes (OHP) have emerged as an effective cooling solution. OHPs are preferred in some scenarios over conventional heat pipes as the latter lose their efficiency when the device thickness decreases below 2-3 mm. OHPs operate on the basis of a two-phase system of vapor and liquid. The interaction between the liquid and vapor creates a thin film region between the vapor bubble and the walls of the oscillating heat pipe, whose role is currently not well understood. Therefore, this study focuses on the investigation of the thin film region. Thermocouples and particle image velocimetry are used for analyzing the temperature profile and fluid flow patterns across the thin film region. The OHP is fabricated using standard photolithography and deep etching, where microchannels are etched in a silicon wafer with a glass wafer bonded on top. Ethanol is used as a working fluid. The study provides valuable insights into the role of thin films in heat transport processes, which will be significant to better understand the fundamental mechanisms and improve the effectiveness of OHPs.