The　single-phase　flow　and　heat　transfer　behaviors　of　SiC　and　Al2O3　nanoparticles　dispersed　in　water　were　studied　experimentally　in　a　multiport　minichannel　flat　tube　(MMFT).　The　volume　concentrations　of　the　two　nanofluids　ranged　from　0.001%　to　1%.　Their　effective　particle　sizes,　thermal　conductivities,　and　viscosities　were　also　measured.　Results　indicated　that　these　nanofluids　as　a　working　fluid　could　enhance　heat　transfer　but　increase　pressure　drop　and　the　Nusselt　number　by　up　to　85%.　The　two　nanofluids　exhibited　a　common　optimal　volume　concentration　of　0.01%　for　heat　transfer.　Effective　particle　size　was　also　found　to　have　a　significant　effect　on　heat　transfer.