Numerical simulation on heat transfer enhancement of free piston Stirling engine heater with composite cross section mini channels

Integral fin with micro-channels have been widely used in small free piston Stirling engines heater due to their high heat transfer rate, low flow loss, and high machining accuracy. A beta-type free piston Stirling engine heater with composite cross section mini channels(CCSMH) is designed for heat transfer enhancement applying to solar dish power generation system. Investigation on heat transfer performance of the heater under oscillating flow is carried out by CFD method, which is compared with smooth annular tube heater. The influence of geometry parameters on the performance of heat transfer and pressure loss is investigated. A improved performance evaluation criteria PEC is proposed for the condition of equal flow velocity to evaluate the enhanced heat transfer performance of the heater. The results show that the maximum value of the comprehensive performance evaluation index PEC can reach 3.14, the maximum mean pressure drop increment of CCSMH compared with the smooth tube heater is 38.4 Pa, which is much lower than the minimum pressure of 2.3 MPa and can be neglected.