Experimental and Numerical Investigations of Thermal Contact Conductance for Cylindrical and Flat Surfaces

Abstract

Thermal Contact Conductance (TCC) is highly random phenomena and plays a significant role in evaluating heat transfer across the joints for maintaining temperature limits in spacecraft payloads. TCC varies with type of contact, shape of joining surfaces, pressure, interface temperature and hardness of materials. Estimating the correct value of TCC for every particular case requires experimental investigation. Numerical model which can cover a wide range of parameters affecting TCC is the dire need of the time.TCC for cylindrical joints with heat transfer in radial direction is not yet explored extensively. Assuming the values of TCC in cylindrical coupling used for calculating the amount of heat transfer through cylindrical components in space application results into overdesign or underdesign. Establishment of experimental test setup in ambient condition has been carried out to find the range of TCC for cylindrical joints in radial direction. The study involves bare joint as well as joints with different Thermal Interface Materials (TIM) used to enhance the heat transfer between two surfaces. Among T-pli 220, indium foil (100\mu m) and chotherm (400\mu m), the least temperature drop at interface was found for T-pli 220 in laboratory conditions. Further, numerical model for the cylindrical surface contact in radial direction can be developed.A novel approach to develop a numerical model for flat-flat surfaces is explored. This study aims towards development of numerical model for most of the flat surface joints using random number. Unique random profile is generated to imitate the surface at the joint. The contact algorithm and area in contact of two joining surfaces is based on the deformation of softer material. Temperature distribution over entire geometry is obtained by solving two dimensional steady state heat conduction equation. Optimization of numerical model for flat joint at different real life application conditions based on experimental investigation is required. Further, the same numerical model for flat-flat surfaces can be extended for cylindrical surfaces.