Development of a semi-empirical thermal conduction estimation model for dry metal-metal contacts

This thesis aims to investigate the effects of contact pressure and type of deformations on the thermal contact conductance(h’) for dry metal-metal contacts. Also, an attempt is made to develope a thermal contact conductance estimation model for the same. The materials used in this thesis are metals (aluminium and tin). Several experiments are performed on two different test setups. The first setup is situated in the process and energy department[P&E] of TU Delft where tin material is used to investigate deformation effects on h’ with respect to contact pressure ranging till 4MPa. The sample is in a shape of a wire with a diameter 2mm and placed between two copper cylinders for evaluating h’. The second setup is situated in Philips Engineering Solutions [PES] where flat aluminium samples are used with different roughness under high contact pressures (up to 25MPa). Later, the results from both experimental setups are compared to the prediction from literature models to brief their general applicability. The increase in contact pressure over a surface roughness, first deforms a surface elastically and then plastically. Plastic deformation increases the actual contact area and conducts more heat than elastic with sample contact pressure. Oxide layer formation over time is critical for aluminium surfaces and so aging may cause differences in contact conduction. In conclusion, there is a large difference between the experimental results and prediction by literature models. Only when a lot of effort is put in keeping orientation exactly the same, reproducibility is good, rest the thermal contact conduction is irreproducible. The development of an entirely new semi-empirical model is very complex. There is a need to be aware of validity ranges of thermal contact conductance literature models as they quickly deteriorate outside their application ranges and the usage of available models should be done critically. The real contact area plays a major role in estimating
Mechanical Engineering | Energy, Flow and Process Technology