다이아몬드 나노유체의 열전달 및 기관윤활특성

Abstract

Engine lubricating oil requires a high performance of lubrication because of the extreme condition during combustion process in a cylinder.

Diamond nanofluids containing diamond nano-particles have a good heat transfer and lubricating characteristics compared with other nanofluid containing other nano-particles. For the reason, diamond nanofluids have been considered as one of the measure for enhancing lubricating performance of engines.

This study tested heat transfer and lubricating characteristics of diamond nanofluids.

Thermal conductivities of diamond nanofluids containing 0.1, 0.3, 0.5, and 1.0vol% nanodiamond particles in DI water, ethylene glycol, and ethyl alcohol are enhanced compared with those of DI water, ethylene glycol, and ethyl alcohol without nano-powder.

Especially, thermal conductivity is increased up to 23% at 1.0vol% of nanofluid suspended in DI water.

Convective heat transfer characteristics of diamond nanofluids are tested in the conditions of 0.1, 0.3, and 0.5vol% suspended in DI water, various Reynolds number, and the inlet tempertures of 25℃ and 50℃. As the result, the higher temperature is the higher convective heat transfer coefficient is.

Lubricating characteristics of diamond nanofluids containing 0.1, 0.3, 0.5 and 1.0wt% of nanoparticles in a commercial engine oil are tested in a diesel engine driven by an electric motor. As a result, the friction torque and the shaft vibration are reduced with suspended diamond nano-powder increase.