Experimental and numerical study of thermal performance of an additively manufactured microchannel heat exchanger

High-efficiency heat exchangers (HX) play a pivotal role in enhancing the thermal efficiency of micro gas turbines. This study presents an advanced microchannel heat exchanger which was specifically designed adopting a modular design concept. A unit of the heat exchanger was fabricated using additive manufacturing (AM), and steady-state thermal performance experiments were carried out under various operational conditions. The AM microchannel heat exchanger is characterized by wavy microchannels, and the corrugated primary walls are equipped with staggered micro-thickness supporting ribs spanning the height of the wavy microchannels, and the micro ribs work to increase the wetted area and achieve a uniform flow distribution within the microchannels. The AM heat exchanger exhibits compactness exceeding 1700 m²/m³, and industrial CT scanning reveals relatively high-quality except for the collapse of the peaks. Experiments show that the AM heat exchanger achieves a maximum heat transfer efficiency of 0.78 within the Reynolds numbers range of 200–600, and maintains a pressure loss below 3.0 % of the inlet total pressure, which shows about 88.9 % improvement in the average Nusselt numbers compared to conventional flat-plate heat exchangers. Numerical simulations further reveal the flow mechanisms behind the high thermal performance of the microchannel heat exchanger. Due to the regular flow fluctuations over the wavy walls and the flow guiding effects by the micro ribs along the wavy microchannels, the enhanced heat transfer is uniformly distributed across the channels. Apparent vortex structures are formed at the crests and troughs of the corrugated walls, and the sudden contraction at the inlet and expansion at the outlet contribute to additional pressure loss. Through comparing numerical simulations with the experimental data, it is evident that the inherent surface roughness of additive manufactured heat exchanger enhances heat transfer but also leads to greater pressure loss.