Thermal performance analysis of axial-rotating oscillating heat pipe and its prediction model based on grey system theory

Oscillating heat pipes (OHP) have attracted much attention in thermal management due to its high heat transport capacity and simple structure. OHP also have the potential to transfer heat under rotational conditions, while research on OHP heat transfer performance under a system rotation is still insufficient. The thermal performance of a single closed loop OHP under a centrifugal acceleration due to an axial rotation is here experimentally investigated. This OHP is then treated as a grey system, since the complexity of the internal physical processes is very high and only a limited amount of experimental data is available. The grey system theory, which analyzes an uncertain system with small samples and poor information, is used to provide a novel path of modeling the thermal performance of two-phase systems. The results show that the heat transfer characteristics of an OHP filled with methanol improve with the increase of centrifugal acceleration and heat flux. The data are then modeled by a GM(1,1) grey model to simulate and predict the heat transfer coefficient. The errors range from 3.36% to 16.6%, and the prediction of the performance is satisfying. A case study of applying the prediction model in designing abrasive-milling tool with OHP inside to enhance heat transfer is conducted. It shows that the grey system prediction model provides a reliable guidance for the engineering application of the OHPs.