INFLUENCE OF USING STRAIGHT AND TWISTED ELLIPTICAL SECTION HEATER TUBES ON STIRLING ENGINE PERFORMANCE

Abstract

The heat transfer area of the heater tubes is a significant factor that deeply affects output power and thermal efficiency in Stirling engines. Alpha-type Stirling engine is concerned in this study. Circular section, elliptical section, twisted elliptical section tubes having twist ratios of 2, 3 and 4 are used as heater designs. 3D simulation model using SST K-ω turbulent model is used for simulating airflow through the hot cylinder, heater tubes, regenerator, cooler, and cold cylinder of the Stirling engine, during a complete engine cycle. The results showed that the elliptical section tubes are better than the circular section tubes. The maximum input energy rate, output work and thermal efficiency are achieved by using elliptical section with twist ratio of 2. These values are 4245.87 W, 1225.34 W and 29.55%, respectively with percentage increments of 5.2%, 7.47% and 3.76%, respectively relative to the circular section heater tubes.