An oscillating heat pipe (OHP) is a two-phase thermal device used to move heat over fairly long distances while remaining small and more capable in different orientations than traditional heat pipes.
Physically, OHPs are configured as a continuous serpentine design in shapes that closely match the available space in the end device. Each path within the shape is narrow, on the order of 1-3mm in diameter, to allow the surface tension of the working fluid to form a series of liquid ‘slugs’ and vapor bubbles inside the partially evacuated device.
Figure 1: Cutaway Oscillating Heat Pipe. Alternating Slugs of Water & Vapor
OHPs are called oscillating heat pipes because of the way they function. Inside these pipes, the expanding and contracting vapor bubbles force the liquid slugs to move back and forth in a pulsating manner.
Key Benefits
Heat Transport: OHPs can transfer heat over several meters due to vapor pressure-based circulation, making them ideal for long-distance applications like spacecraft thermal management.
Compact Size/Light Weight: OHPs allow efficient heat transfer in complex configurations, offering more design flexibility. They can be integrated directly into metal thermal planes and have a higher Qmax per cross-sectional area, making them slimmer and lighter for aeronautical or wearable electronics.
Gravity Performance: OHPs outperform standard heat pipes in small tubes (1-3 mm) and maintain efficiency up to 1-1.5 meters against gravity, compared to 150mm for standard heat pipes.
Oscillating heat pipes are emerging as a viable option in thermal management, especially when space is limited, heat needs to be transported over longer distances, or when the heat sink operates against gravity. Though still in the early stages of commercialization and characterization, the initial results are promising. OHPs provide an innovative solution in scenarios requiring robust thermal management performance.
