Additive Manufacturing Methods to Make High-Heat-Flux Heat Sinks

• Main Author: Ramaraju, Ram Gopal Varma
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Energy; High Temperature Physics; Mechanical engineering
• ISBN: 9798368427423

Cold plates with internal flow passages were made by placing 3D printed polyvinyl alcohol (PVA) parts in channels machined in the plates, spraying metal over the polymer, and then dissolving the polymer. Aluminum and copper plates with coolant channels were made and found to have significantly lower thermal resistances than commercial cold plates. Properties for a sprayed metal layer to adhere to a polymer substrate were identified, including substrate roughness, substrate temperature during spraying and the thermal coefficients of expansion of the metal and polymer.Surface features such as pin fins and channels were deposited directly on heat-generating surfaces using thermal spray deposition. Tests were done by cooling a 1 cm2 copper surface with a surface heat flux of 50-450 W/cm2. The thermal resistance of the heater surfaces decreased resulting in heat transfer coefficients up to 50 kW/m2K. These features increased the heat transfer area by 45% and distributed cooling liquid uniformly without introducing any thermal contact resistance, unlike conventional heat sinks.Nozzles with an array of water jets were 3D printed using polymer to impinge water jets over a high heat-flux surface. Experiments were done to measure convective heat transfer from a copper surface with a surface area of 0.142 cm2 emitting heat fluxes of 50 to 900 W/cm2 while varying the water flow rate from 0.1 to 1.0 L/min. Heat transfer coefficients as high as 150,000 W/m2K were measured during impingement cooling.