Determination of convective heat transfer coefficient in human femur bone drilling in the presence of normal saline and evaluation of effective parameters in it

This research has analyzed the drilling process in the human femur bone in order to determine the heat transfer coefficient and investigate the occurrence or non-occurrence of thermal necrosis. 3D drilling simulation have carried out in natural with air and force convection with normal-saline and the analysis performed for three feed rates of 50, 100 and 150mm/min at rotational speeds of 500, 1000 and 2000 rpm. The results show that in the natural cooling state, the highest generated heat is equal to 4J at 50mm/min and 500rpm while the lowest value of generated heat is 1.65J at 150mm/min and 2000rpm. The maximum difference of the average heat transfer coefficient with the experimental results is %12.5, which represents a good accuracy of the present results. The results in this state also show that the average heat transfer coefficient at 100 and 150mm/min is %55 and %29.1 more, respectively, and it is %5 less at 50mm/min rate, compared to the constant value of 20w/m2.k which is considered in the previous researches. Thermal necrosis occurs under all conditions of the natural cooling. In the force cooling, the highest average heat transfer coefficient with normal_saline is 150mm/min at a rotational speed of 2000rpm, which is equal to 3650w/m2.k and in all conditions, the bone temperature has not exceeded the temperature limit of thermal necrosis