Thermal performance investigation of an oscillating heat pipe with external expansion structure used for thermal energy recovery and storage

Aiming to combining the strength of flexibility and adaptation of oscillating heat pipe (OHP) with specific application in the field of waste heat recovery and storage, an OHP with external expansion structure was designed and fabricated. The start-up characteristic, working status, overall thermal resistance, local thermal resistance and dispersion ratio for the local thermal resistances under different filling ratios (FR), working fluids and heat loads were revealed and compared experimentally. The results showed that for the OHP with water, it exhibits well start-up performance under wide range of FRs and is able to work effectively under wide range of FR at proper heat load. Meanwhile, it also shows well adaptability to heat load under proper FR. The OHP has not obvious difference for each branch in the heat transfer performance under wide working conditions. When filled with self-rewetting fluid (SRWF), it has smaller overall thermal resistance than the water case at specific range of heat load. Comparing to the case with water, the OHP with SRWF can show better uniformity in the heat transfer capacity for each branch under appropriate condition. However, the uniformity of branch does not always contribute to increasing the heat transfer performance.