Oscillating heat pipes (OHPs) consist of a simple long capillary tube that is formed into many turns and partially filled with a working fluid. When the tube diameter is less than the capillary length, liquid 'plugs' and vapour 'bubbles' are formed. When the temperature difference between the two ends of the hot evaporator and cold condenser exceed a certain threshold, the plugs and bubbles begin to oscillate spontaneously back and forth. The amplitude of oscillations can be very strong and the liquid plugs penetrate into both the condenser and evaporator. As a result of this process, heat is thus transferred by latent heat transfer by exploiting this simple approach, the thermal resistance of an oscillating heat pipe can exceed that of the metal alone. Our patented device examined within this proof of concept activity combines oscillating heat pipe with a thermal pyroelectric harvester which generates small levels of power from the thermal oscillations to provide an additional sensing or low power generation to the OHP. While the OHP is used to remove heat and to provide cooling of the system, the rapid temperature fluctuations in the OHP (which are in Hz range) are simultaneously transformed into electrical charge to sense and monitor the OHP or power other low power electronics such as self-powered/wireless sensors. Potential applications include small scale systems, such as that used in the thermal management of microprocessors, mobile computing devices, cooling of batteries and LED lighting. Larger electronic systems also require cooling and include voltage transformers and current rectifiers, since most of the modern electronics require a direct current (DC). Solar panels and batteries also benefit from oscillating heat pipes thermal management since an increase in temperature significantly reduces the efficiency and lifetime of the devices. The ability to provide a combination of cooling and self-powered sensors that can inform the conditions of the heat pipes or local environment. Prototype devices were manufactured and evaluated in terms of cooling performance and power generation.
