Experimental Research on Critical Heat Flux in Rectangular Channel with Femtosecond Laser-Modified Surface

As a type of laser modification method, femtosecond laser surface modification can fabricate microstructures on surfaces of of stainless steel, zironium alloy and nickel alloy, creating specific morphological features such as honeycomb patterns, grooves, and hump structures. These features significantly influence the heat and mass transfer efficiency as well as the thermal performance limits of heating surfaces. In order to verify the enhancement effect of femtosecond laser-modified surface on critical heat flux (CHF) under pressurized flow conditions, CHF experiments were conducted at pressures ranging from 2 to 4 MPa. The experimental results indicate that both the femtosecond laser-modified surfaces and conventional surfaces exhibit an increase in CHF with higher inlet mass flux and inlet subcooling, while CHF decreases with an increase in critical steam quality. The modified surfaces demonstrate technical potential for enhancing CHF, with hump and honeycomb structures showing the most significant improvement. Although all three surface types are hydrophilic, the degree of CHF enhancement varies. This difference is attributed to the varying capabilities of different microstructures in facilitating liquid cooling of overheated surfaces.