GCTG New Cooling Pulsating Heat Pipe Technology (CLPHP) for Extreme Operating Conditions (Vibration and Elevated Temperature Environments)

In NSF Phase I, GCTG developed an innovative two-phase cooling technology with micro-channel Closed Loop Pulsating Heat Pipes (CLPHPs), that was tested and proven to handle the thermal challenges of advanced electronics with multiple distributed power source configurations in various orientations while reducing energy consumption.   This DARPA Small Business Innovation Research Phase II project employs a CLPHP, a unique serpentine micro-geometry with specific features machined inside a thin ceramic or metallic plate combined with an environmentally friendly two-phase coolant. As CLPHPs are wickless and pumpless, they operate in vertical, inclined, horizontal and inverted orientations, which is ideal for portable and mobile military and commercial applications. The performance of the Gen 1 CLPHP was experimentally compared with competing advanced cooling devices in the NSF Phase I project. Phase I proved that the Gen 1 CLPHP generated its characteristic instabilities caused by vapor bubbles forming, growing, flowing and condensing to move fluid and heat more efficiently than the main competitors, vapor chambers and traditional heat pipes that require wicking structures.  The CLPHP oscillations create much faster coolant flow rates than legacy technologies, increasing the cooling capacity. The NSF Phase I tests demonstrated 2.5 times better cooling performance per unit volume versus the vapor chambers. Various materials and new enhanced designs (Gen 4 CLPHP) will be evaluated in the DARPA Phase II testing plan under extreme operating conditions (high temperature and vibration) and compared to the competing technologies. The thin CLPHPs are planned for integration into various mobile military applications exposed to harsh conditions, to provide increased cooling capacities and battery energy savings in compact form factors.  GCTG CLPHPs are a cost-effective, environmentally friendly, disruptive technology uniquely suited to meet the cooling challenges of the new generation of mobile electronics in harsh conditions, able to function at their highest performance level. Compared to commercial applications, where the peak temperature is 90-95°C based on an ambient of 25°C, the harsh military applications will explore high ambient temperatures (up to 49°C) and higher junction temperatures (115 – 125°C).  The commercial applications heat dissipation targets were 20-30W in this compact (0.85 mm thick) form factor, with a thermal resistance of 2.3 – 2.7°C/W, much lower than comparable volume vapor chambers (3.1 – 3.5°C/W).  The heat dissipation target for harsh military applications with high vibrations and elevated ambient temperature is 50-70W and a target thermal resistance of 1.5 – 1.6°C/W. A novel mini-fin structure will be added to the condenser and with forced convective conditions, the thermal resistance will be reduced by over 30% while increasing the maximum cooling power by over 60%.  The goal is to meet/exceed these key performance parameters.