Experimental Investigation of the Thermal Performance and Pressure Loss in Additively Manufactured mini-channels

Abstract: Industrial gas turbines reach temperatures of 1500-2000K at high rotational velocities which means that much effort is spent on the design of an efficient cooling system. With the recent advances of the additive manufacturing (AM) industry, new design opportunities have open up for many industries and applications, including the design of cooling systems. However, a significant surface roughness will be present in AM components compared to traditionally manufactured components. An increased surface roughness inside a channel will affect both the heat transfer and pressure loss. The performance of AM channels are therefore not fully known and needs to be examined experimentally on the actual material to fully capture the effects of the increased surface roughness. The aim with this project is to experimentally investigate the thermal performance and pressure losses experienced in AM channels due to surface roughness. This was done by using a Steady State Heat Transfer rig which was assembled and verified. AM and aluminium test channels were mounted in a copper block which was insulated and heated up by electrical heaters. The test channels were then subjected to an air flow of constant mass flow. Temperature and pressure measurements were made at the inlet and outlet together with mass flow measurements and copper block temperature measurements. The Nusselt number and Darcy friction factor were used to evaluate the heat transfer and pressure losses experienced in the channels. The results showed that the heat transfer and friction factor increased significantly for the AM channels compared to smooth channels. Both the heat transfer and friction factor increased when the relative roughness of the channels increased. This project was executed at Siemens Energy in Finspång at the Fluid Dynamic Laboratory and is a part of the work of obtaining thermal performance data for mini-channels manufactured by AM.