Material characterization and performance of additively manufactured high temperature heat pump screw compressor rotors
Industrial processes with high heat energy demand account for approximately two thirds of total industrial energy use globally. These processes are mostly fossil fuel driven and offer significant potential for efficiency improvements. High-temperature heat pumps (HTHPs) are one of the most promising technologies that can replace (or be integrated into) existing heating processes. However, most systems on the market do not exceed heat sink temperatures ranging between 150 °C and 175 °C. To exceed this range limit and to be able to cover a wider range of applications, new components and manufacturing technologies must be evaluated to enable sustained operations at high temperatures. This paper focuses on the design and manufacturing process of a twin-screw compressor by using selective laser melting (SLM) additive manufacturing process to produce the compressor rotors. The design target is to achieve a heat sink temperature of 200 °C with a temperature lift of 80 K. Therefore, material characterization tests were conducted with 3D-printed 18 Ni Maraging steel and 718 Inconel specimen. For both materials, specimens were printed in both horizontal and vertical build orientations to evaluate their material properties and compare them to a baseline material. Furthermore, the outcomes of the material tests were used in a coupled rotor-dynamics and fatigue model to simulate geometry deformation in a high-temperature environment, as found in an HTHP compressor. Based on the material test and simulation results, the best material and printing direction were selected, and the screw geometry was further optimized to enable efficient screw compressor operation at the design point of 205 °C discharge temperature.