▎ 摘　　要

Utilizing nanofluids is a suitable method to improve the performance of microchannel heat exchangers. Moreover, graphene quantum dots nanofluid, as a novel nanofluid with its unique features, can be a proper choice for employment in heat exchangers. In this article, for the first time, a graphene quantum dots nanofluid is employed as the working fluid of a microchannel heat exchanger. For this purpose, the graphene quantum dots nanofluid at concentrations of 0-0.5% and Reynolds numbers ranging from 50 to 200 is utilized as the hot fluid, while pure water with a Reynolds number of 100 is considered as the cold fluid. The problem-solving approach is the 3D numerical method based on the finite-volume technique. Moreover, temperature-dependent thermophysical properties are assumed for the hot and cold fluids. The results reveal that at Reynolds numbers of 50 and 100, utilizing the nanofluid greatly improves the heat transfer rate for a slight increase in the pressure drop, so that in the case of using the 0.5% nanofluid at Reynolds number of 50, the heat transfer rate improves 14% for only an 8% increase in the pressure drop. However, at Reynolds numbers of 150 and 200, the use of the nanofluid imposes a large pressure drop on the system. Based on the obtained results, utilizing the graphene quantum dots nanofluid at Reynolds numbers of 50 and 100 is suggested since the heat exchanger performance enhances, while at Reynolds numbers of 150 and 200, using the nanofluid is not recommended due to the high pressure drop penalty.