Application of an anti-gravity oscillating heat pipe on enhancement of waste heat recovery

An anti-gravity oscillating heat pipe are introduced to enhance the waste heat recovery from an upper heat source to a lower object. A conceptual facility using an anti-gravity oscillating heat pipe as a core part of the heat conductor is set up for the recovery of waste heat from the upper high-temperature exhaust to preheat the diesel in a lower fuel tank. In order to verify this idea, a thermal experiment is conducted to investigate and compare the heat recovery performance of the conceptual facility based on four heat conductor designs. The results indicate that the current anti-gravity oscillating heat pipe with 35 turns and a filling ratio of 70% is able to effectively work under Bond number ranging from 0.814 to 0.986, exhibiting a much better heat-transfer performance along a distance of 0.83 m and only 58% weight relative to the pure copper with the same geometry. Significantly, the heat recovery efficiency of the conceptual facility using the anti-gravity oscillating heat pipe as the heat conductor is higher (about 1.66 times on average) than that using the traditional pure copper heat conductor, especially under a large heat load. Moreover, during the heat recovery process, the temperature uniformity of the diesel can be improved by increasing its effective thermal conductivity by filling a pure copper grating inside. This approach is also capable of enhancing the heat recovery efficiency of the anti-gravity oscillating heat pipe conceptual facility by an average of around 3.6% under the current experimental conditions.