EXPERIMENTAL HYDRAULIC PERFORMANCE STUDY OF A PRIMARY SURFACE RECUPERATOR WITH CROSS-WAVY MICROCHANNELS FOR PORTABLE MICROTURBINES

Portable microturbines with high power and energy densities are attractive candidates for mobile power sources. Due to the limitations of compressor pressure ratio and turbine inlet temperature, a compact and lightweight recuperator is the mandatory component of this type of microturbines to achieve high thermal efficiency. Typically, microchannels with thin wall thickness are used for heat transfer enhancement. However, the reduction in channel size may significantly increase the pressure drop of both fluids. Owing to the lack of existing experimental data for ultra-compact microchannel recuperators of portable microturbines, the hydraulic performance of a newly-designed primary surface recuperator with cross-wavy microchannels (CW-PSR) was experimentally studied. The 50 μm-thick heat transfer plates were used for the CW-PSR core, in which the hydraulic diameters of gas and air channels are 848.8 μm and 598.6 μm, respectively. Hence, the surface compactness of the CW-PSR prototype is about 2428 m2/m3. We tested the hydraulic performance of the CW-PSR both under hot and cold conditions with Reynolds numbers ranging from 320 to 980. The experimental results show that the pressure drops on both sides increase with increasing mass flow rate, while the hot conditions with high inlet temperature result in larger pressure drops. Besides, it was confirmed that the friction pressure drop in the heat transfer region accounts for more than 60% of the total pressure drop. Finally, a new correlation of friction factors for cross-wavy microchannels was obtained based on experimental results.