Heat transfer and flow characteristics of intermittent oscillating flow in tube

Motions of piston and displacer in ideal Stirling cycle is non-sinusoidal and rise-dwell-fall-dwell. However, heat transfer and flow characteristics of present oscillating flow are based on sinusoidal motions. In this work, heat transfer and flow characteristics of intermittent oscillating flow with intermittent ratio = 1 in tube were numerically studied. The model was firstly validated based on literature's empirical equations for sinusoidal oscillating flow. Then, heat transfer and flow characteristics of intermittent and sinusoidal oscillating flows were simulated and compared. The simulation results showed that the total heat transfer coefficient and pressure drop in intermittent oscillating flow were 14.6% lower and 0.83% higher respectively compared to those in sinusoidal oscillating flow. The curves of pressure drop were nearly the same in sinusoidal and intermittent oscillating flows with removal of stagnation periods. Besides, velocity distributions in two oscillating flows were also investigated. The simulation results showed that the "velocity loop" in two oscillating flows occurred at the same time and the changing amplitudes of wall's velocity over central axis's velocity in "velocity loop" were nearly the same.