Refinement of the thermal analysis of the gearbox taking into account the thermal conductivity of the joint

The existing method for calculating the operating temperature of the gearbox housing is clarified by taking into account the thermal conductivity coefficient of the contact, the value of which depends on the materials used for the housing and frame, the finish of the supporting surfaces and their area, as well as on the tightening force of the screws that pull the housing to the frame. An example of calculating the temperature of the housing of a worm gear is given. Keywords: gearbox, heat sink, heat transfer coefficient, thermal conductivity coefficient of contact, thermal conductivity coefficient of materials, roughness parameter. [email protected]

Experimental Study of VACNT Arrays as Thermal Interface Material

In order to improve thermal interface material (TIM), vertically aligned carbon nanotube (VACNT) arrays were synthesized by the chemical vapor deposition method, and then transferred by dipping in hydrofluoric acid (HF acid) solution to get a free standing VACNT array. Different TIM samples with sandwiched structures were fabricated by inserting the free standing VACNT arrays between two copper plates with and without bonding materials. The laser flash analysis method was applied to measure the overall thermal conductivity of these samples. Results show that: compared with two copper plates in direct contact, thermal conductivity of samples only with VACNT arrays as TIM can be enhanced about 142%–460% depending on the thickness of VACNT arrays. Conventional TIM made up of thermal paste (TG-550 with thermal conductivity of 5 W/mK) and a thermal pad (TP-260 US with thermal conductivity of 6 W/mK) was used as a bonding material between copper plates and VACNT arrays, thermal conductivity has been shown to further improve with the highest values at 8.904 W/mK and 10.17 W/mK corresponding to the different bonding materials and different thicknesses of VACNT arrays used. Results also show that the thicker the VACNT array is when used as a TIM, the lower the overall thermal conductivity of the corresponding samples. This lower thermal conductivity caused by more defects in amorphous carbon of thicker VACNT arrays and lower density of the corresponding sandwiched samples.