Second law analysis for nanofluid flow in mini-channel heat sink with finned surface: a study on fin geometries

In this numerical work, a second law analysis is carried out for the nanofluid flow and heat transfer in the mini-channel with finned surface. The mini-fins with various geometries, including trapezoidal, square, triangular, and sinusoidal, are located on the bottom surface of the mini-channel. The effects of mini-fins geometry, mini-fins number, Reynolds number, and solid volume fraction of nanoparticles on the temperature and velocity distributions, frictional and thermal irreversibilities, and Bejan number inside the mini-channel are studied. The numerical method is validated with the experimental data. The results show that the sinusoidal, triangular, square, and trapezoidal mini-fins generate up to 66.23%, 61.87%, 59.21%, and 57.80%, respectively, lower thermal irreversibility as compared with the smooth mini-channel. Among mini-fin geometries, the triangular mini-fins generate the maximum frictional irreversibility, while the trapezoidal mini-fins provide the minimum frictional irreversibility. The frictional irreversibility increases about 108.56%, while the thermal irreversibility decreases up to 46.33% as the mini-fin number increases from one to nine. The thermal irreversibility diminishes about 49% by boosting the Reynolds number from 100 to 500. Usage of nanofluid increases both frictional and thermal irreversibilities. Finally, the thermal irreversibility is a dominant term in the total irreversibility and the effects of frictional irreversibility can be ignored.