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ABSTRACT
Nanoparticle jet mist cooling (NJMC) is an effective solution to prevent heat injuries in clinical neurosurgery bone grinding. A simulation study on temperature field of microscale bone grinding was performed to discuss the effect of nanoparticle size on heat convection during this cooling method by the dynamic heat flux density model. Such dynamic heat flux density model was established through real-time acquisition of grinding force signals. Results showed that given the real-time dynamic heat flux, workpiece surface temperature changes with time. Nanofluids using 30 nm nanoparticles show the largest heat convection coefficient (1.8723 W/mm2 · K) and the lowest average surface temperature followed by nanofluids of 50, 70, and 90 nm nanoparticles successively. An experimental verification using fresh bovine femur was conducted with 2% (volume fraction) of different sizes of Al2O3 nanoparticles. The simulated temperature under dynamic heat flux comes close to the actual measured temperature. Under testing conditions, temperature under mist cooling is 33.6°C, temperatures under NJMC using nanofluids (30, 50, 70, and 90 nm) are 21.4, 17.6, 16.1, and 8.3% lower, respectively. This result confirmed the positive correlation between the average workpiece surface temperature and nanoparticle size. Experimental results agreed with theoretical analysis, verifying the validity of theoretical modeling.