Experimental Investigation and Comparison of the Thermal Performance of Additively and Conventionally Manufactured Heat Exchangers

Abstract

Air heat exchangers (HXs) are applicable in many industrial sectors because they offer a simple, reliable, and cost-effective cooling system. Additive manufacturing (AM) systems have significant potential in the construction of high-efficiency, lightweight HXs; however, HXs still mainly rely on conventional manufacturing (CM) systems such as milling, and brazing. This is due to the fact that little is known regarding the effects of AM on the performance of AM fabricated HXs. In this research, three air HXs comprising of a single fin fabricated from stainless steel 316 L using AM and CM methods—i.e., the HXs were fabricated by both direct metal printing and milling. To evaluate the fabricated HXs, microstructure images of the HXs were investigated, and the surface roughness of the samples was measured. Furthermore, an experimental test rig was designed and manufactured to conduct the experimental studies, and the thermal performance was investigated using four characteristics: heat transfer coefficient, Nusselt number, thermal fluid dynamic performance, and friction factor. The results showed that the manufacturing method has a considerable effect on the HX thermal performance. Furthermore, the surface roughness and distribution, and quantity of internal voids, which might be created during and after the printing process, affect the performance of HXs.

Experimental Investigation of Pressure Drop Performance of Smooth and Dimpled Single Plate-Fin Heat Exchangers

“…The Reynolds number can be used to characterise the inertial and viscous properties of a moving fluid [24], where it can be calculated using the equation given below that has been adapted from Vafadar, Guzzomi and Hayward [25].…”

Experimental Investigation of Additively Manufactured High-Temperature Heat Exchangers

“…However, no information is provided on hydraulic diameters and the relative surface roughness. Vafadar et al [12] investigated additively and conventionally manufactured fin elements and also find increased pressure losses of the additively manufactured variants, with no clear trend in the heat transfer. It is argued that the increased surface roughness results in better heat transfer, but the increased porosity of the material leads to lower thermal conductivity and thus again to lower overall performance.…”

Aerothermal Characterisation of Surface Heat Exchangers for Turbofans

“…One of the main outcomes of their study is the importance of a careful design for an adequate interaction between the exchanger and the fluid. Besides, as previously commented, the finishing of additively manufactured heat exchangers generally gives rise to a poorer aerodynamic efficiency [29,30].…”

“…One of the main disadvantages though of this type of manufacturing is the impact of the finishing. Vafadar et al [29] compared the performance of three pairs of different geometries built by milling and direct metal printing, discovering that the surface finishing plays a key role in the results and finding more discrepancies as the air mass flow increases. Saltzman et al [30] were able to improve the heat removal by up to 14% by testing an additive manufactured heat exchanger, but with a decrease in its aerodynamic performance, almost doubling the induced pressure drop.…”