Progress of Research on Oscillating Heat Pipes by High Efficiency Precision Machining Technology Research Institute

introduction

Efficient grinding technology was developed in the 1980s and is known as the pinnacle of modern grinding technology. High-efficiency grinding technology for the further development of high-speed grinding and slow-feeding deep-cut grinding technology, with high grinding and feed speed, large grinding depth, so it improves while maintaining high grinding surface quality The material removal rate is 100-1000 times. These characteristics make high-efficiency grinding technology widely used in the efficient processing of aerospace difficult materials such as titanium alloys. However, there are surface burn problems in efficient grinding.

The film boiling theory explains the cause of sudden burns: when the heat flux density in the grinding arc is lower than the critical heat flux density of the coolant, the coolant is maintained in the nucleate boiling state, and the grinding heat is taken out of the arc by the cooling liquid. The cutting temperature is maintained at around 120 °C. When the heat flux density exceeds the critical heat flux density, the coolant melts in a film state, and the gas film hinders the coolant from effectively grinding the tropical arcing zone, causing a sudden increase in the grinding temperature and causing the grinding burn. On the one hand, the film boiling theory of coolant reasonably explains the cause of sudden burns during high-efficiency grinding; on the other hand, considering the critical heat flux density as an unchangeable physical parameter restricts the further development of high-efficiency grinding technology.

However, the critical heat flux density can be further increased by the forced arc heat transfer in the grinding arc region, and increasing the critical heat flow surface density means increasing the material removal rate. Based on this idea, a slotted grinding wheel with a radial water jet wheel was proposed to change the state of the coolant to increase the critical heat flux density. However, these methods require high pressure casting of a large amount of coolant which is toxic to the human body and the environment. This is contrary to the green manufacturing concept pursued by modern processing.

Summary of results

The heat pipe group directed by Professor Fu Yucan has made some progress in the study of the heat transfer mechanism of the oscillating heat pipe. Through the experimental study of the oscillating heat pipe unit and revealing the influence of the geometry, operating parameters and physical parameters of the oscillating heat pipe on its heat transfer mechanism, it is found that the flow pattern and motion form of the internal working medium of the oscillating heat pipe with the increase of the heat flux density The change is the nature of the change in the heat transfer performance of the oscillating heat pipe. As the heat flux density increases, the two-phase flow manifold is transformed by a bubble flow-plug flow-transition flow-annular flow, and the manifold is oscillated from a "single pendulum" - bubble generation and expansion oscillation and circulation flow - commutation cycle Flow - one-way circulation flow. Based on the heat transfer variation law of the oscillating heat pipe, the inner diameter of the oscillating heat pipe is determined to be 3 mm and the working medium is acetone for the oscillating heat pipe for the grinding wheel. The research results are published in "International Journal of Heat and Mass Transfer" "Experimental investigation of thermal performance of the oscillating heat pipe for the grinding wheel".

Graphic guide

Figure 1 Schematic diagram of oscillating heat pipe grinding wheel

Figure 2 Two-phase manifold change

Figure 3 manifold and motion changes

Figure 4 Reflow phenomenon

About the Author

Qian Ning, Ph.D. student, research interests: high-efficiency grinding technology, heat pipe technology, heat and mass transfer;

Fu Yucan (communication author), professor, doctoral tutor, research interests: high efficiency, ultra high speed grinding technology, adaptive processing technology;

Zhang Yuwen, Professor (University of Missouri), doctoral tutor, research interests: heat pipe technology, heat and mass transfer, nanofluid;

Chen Jiajia, Ph.D., research interests: efficient grinding technology, heat pipe technology;

Xu Jiuhua, professor, doctoral tutor, research interests: high-performance cutting / grinding technology, super-hard abrasive tool technology.