Thermal performance of heat pipe drill: A new simulation model for heat pipe

It is well known that drilling is one of the most difficult metalwork cutting operations, not only from the viewpoint of manufacturing process, but also from the thermal management point of view of the drill. For the drilling process, due to its long time continuous metal-to-metal friction between drill tip edge and work piece, a significant amount of heat is generated on the interface, which is in a confined space compared to other machining processes, such as cutting or milling. This makes it very difficult to keep the temperature of drill tip under a certain but acceptable range since the coolant is unable to penetrate deep enough into the hole. Also, based on the environmental considerations and the cost reduction requirement, the conventional flooding coolant method become highly inefficient and expensive due to high maintenance costs. A new approach, dry drilling method (i.e., no coolant is employed during the drilling process) is investigated in this study. In dry drilling, we used heat pipe technology to accomplish the goal of efficient heat removal from the drill tip. It is heat pipe's unique and excellent advantages such as, high reliability, supreme equivalent thermal conductivity, flexible adaptability and so forth, that make it possible for dry drilling by combining the drill and heat pipe. From the numerical simulation viewpoint of heat pipe drill, how to correctly model the heat pipe in the drill is one of the crucial tasks because it will directly influence the accuracy of the simulation results. So far, there are few different kinds of simulation models for heat pipe drill and each of them works well in some kinds of special situations. The present paper studied and compared these different simulation models of heat pipe and then proposed a general, simple but robust and more accurate approach to simulate the heat transfer process in the heat pipe drill. Furthermore, this kind of the heat pipe model can be used in many other heat pipe applications.