In heat exchangers and liquid cooling devices the thermal conductivity of the liquid is an important factor in their design. Recently it has been shown that adding small amounts of nanoparticles to the liquid can significantly increase the thermal conductivity of the fluid [1]. This study investigates the thermal conductivity of diamond nanofluid. The nanofluid is HPLC grade water with 1% by volume diamond nanoparticles that are 5-50 nm in diameter. The thermal conductivity was measured by the transient hot-wire method. In order to verify the experimental measurement, the thermal conductivity of pure water (HPLC grade) was conducted and the measurement error is 3.6%. The experimental results show that the diamond nanoparticles can enhance the thermal conductivity of nanofluid. At an ambient temperature of 21 °C, the thermal conductivity for nanofluid was determined to be 1.00 W/m-K comparing with the thermal conductivity of 0.60 W/m-K for pure water (HPLC grade). Therefore, the nanofluid provides a significant increase in thermal conductivity. Utilizing this nanofluid, an oscillating heat pipe was developed and tested. Experimental results showed that when the oscillating heat pipe is charged with diamond nanofluids, the increase in heat transport capability can be significant and highly dependent on the operating temperatures.

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