Numerical study on heat transfer of Stirling engine heater tube with rectangular micro-ribs

Numerical simulations were carried out to study the heat transfer and friction characteristics for Stirling engine heater tubes with three-dimensional internal extended micro-rib. During the numerical simulations, phase angle in a cycle ranged from 0 degrees to 360 degrees. The results represent that the friction factor (f) increased with micro-rib length (L) and micro-rib height (H) for enhanced tube within the range of parameters in this study. For the micro-rib heat tube ofL = 60 mm andH = 0.9 mm, thejwas equal to 1.44 and the average Stanton numberStwas significantly improved up to 1.287 compared to smooth tube, the friction factor f was also increased by almost 2.32. The outlet pressure from 0.7 Mpa to 1 Mpa with the cosine change is presented as the phase angle increases. Therefore the benefits are apparent for micro-rib heat tube in Stirling engine.