Flow and Heat Performance of Microchannel Heat Sinks with Concave Cavities to Water-Cool Leds

The poor heat dissipation of LED light sources limits their applications in plant factories. Therefore, this paper proposes a microchannel heat sink (MHS) with concave cavities to develop a water irrigation system to water-cool LEDs. The influence of the concave cavity shape (circular, trapezoidal, and rectangular) on their flow characteristics and heat transfer performance was numerically studied by ANSYS Fluent 21.0 R1. MHS with corresponding concave cavities were manufactured, and an experimental platform was designed and built for verification. The results showed that the fluid velocity distribution in the microchannel was symmetric, and secondary flow was formed in the cavity. This resulted in the continuous destruction and reconstruction of the flow and thermal boundary layers, which contributed to heat and mass transfer in the microchannels. The pressure drop between the inlet and outlet of the MHS with concave cavities increased with the inlet flow rate. At the same inlet flow rate, the pressure drop between the inlet and outlet of the MHS with rectangular cavities was greater than that of the MHS with trapezoidal cavities. The pressure drop between the inlet and outlet of the MHS with circular cavities was the smallest, indicating that it had the best flow performance. The outlet temperature of the MHS gradually increased with the inlet flow rate. At the same inlet flow rate, the outlet temperature of the cooling water for the MHS with circular cavities was the highest, followed by trapezoidal cavities and then rectangular cavities. Thus, the MHS with circular cavities showed the best heat-transfer performance.