The Effects of Degrees Subcooing and Operating Time on Spray Cooling Heat Transfer Performance Using Nanofluids As Coolant

摘要

Using Al_2O_3-water nanofluid as coolant, this study investigates the influences of different degrees subcooling and operating time on the spray cooling heat transfer performance. The experiment adopts nanofluids of four different degrees subcooling (i.e., 0°C, 10°C, 20°C and 30°C) and four different spray operating times (i.e., 10, 20, 30 and 40 hours). Results show that spray cooling heat transfer performances of various-subcooling nanofluids are ranked from superior to inferior as follows: 20°C, 10°C, 0°C and 30°C. Moreover, the results also show that the spray operating time has a negligible effect on the heat transfer performance when q"≤200 W/cm~2. However, heat transfer coefficient decreases with increasing spray operating time when q">200 W/cm~2. The SEM images confirm that at a higher surface heat flux, the deposition of Al nanoparticles on the test surfaces and the deposition amount increases with an increasing spray operating time and then decreasing the heat transfer performance.