Predictive model of convective heat transfer coefficient in bone micro-grinding using nanofluid aerosol cooling

摘要

In grinding, the convective heat transfer coefficient (CHTC) determines the heat transfer ratio and the grinding temperature, and it indirectly identifies the surface integrity. No effective method for calculating CHTC is available for aerosol cooling, and it still lacks the measuring equipment that accords with the actual condition of aerosol cooling. On this basis, the atomization mechanism of nanofluid aerosol cooling (NAC) was studied, the influence of jet parameters on the spray boundary was revealed, and the probability density of droplet size in the grinding zone was statistically analyzed. A theoretical model for the CHTC of NAC was developed on the basis of the analysis of the heat transfer coefficient of a single nanofluid droplet. Furthermore, a new method for measuring the CHTC of aerosol cooling was proposed, and the measuring equipment was designed and built. The measurement error of the measurement system was calculated, and results showed that the measurement error of the new measuring equipment is 0.044 (10~(-2) W/mm~2·K). Nanofluids were prepared by using medical nano-particles and normal saline, and the CHTC was calculated and measured. The results showed that the theoretical model error is 7.26%, which verifies the correctness of the theoretical model.