Experimental Measurements of Fanning Friction Factors in Various Types of Additively Manufactured Compact Heat Exchangers

In recent years, the advancement of the additive manufacturing (AM) process has become popular in making very complex shapes, including compact plate-fin heat exchangers. This provides considerable flexibility in creating a complex geometry, is cost-effective, and eliminates a variety of manufacturing processes in a compact heat exchanger (CHE). CHEs are known to have a high heat-transfer area per unit volume greater than 700 m²/m³, which can be achieved by using high-density fins whose hydraulic diameters vary between 1 and 3 mm, which is much higher than that of conventional manufacturing components. This study aims to measure accurate pressure-drop values by estimating the fanning friction factor f across four types of CHEs produced by an AM process. Four types of CHEs were manufactured using AM techniques by varying their internal geometry (secondary surfaces). All four types of CHEs were subjected to pressure-drop measurements using air as the fluid by establishing dedicated experimental facilities. The friction factor f was estimated at various air mass flow rates by varying the Reynolds number in the laminar region up to 1800. The friction factors were found to be 1.5–3 times higher than the conventional manufacture of CHEs. In addition, an attempt was made to understand the difference between the surface topography of the AM process CHE heat exchanger and that of the computational fluid dynamics model. The information provided in this paper is very useful for CHE designers and researchers to understand the implications of surface roughness due to the AM process for CHEs.