Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.
In this work, a preliminary study related to the design and
manufacturing of a micro polymeric pipe for micro heat
exchangers was performed. Among possible polymeric
materials, a thermoplastic copolyester elastomer composed of
polybuthylene-terephthalate, as crystalline phase, and long
glycol chains, as the amorphous one (Hytrel® 6356, Dupont)
was selected, both unloaded and loaded with 7 % w/w carbon
powder. A microextrusion process was set up to obtain
microtubes and the thermo-mechanical characteristics of the
produced pipes were studied. Thermal properties of extruded
Hytrel® remained almost the same, in terms of melting
temperature (Tm ≅ 208 °C) and enthalpy change of fusion (ΔH
≅ 45 mJ/mg), although the material was C-loaded. The thermomechanical
tests performed on unloaded and C-loaded Hytrel®
microtubes at 25 and 70 °C (possible working temperature)
detected a considerable increase in the mechanical properties of
C-loaded Hytrel®, compared to the unloaded one. In particular,
a relevant improvement of the elastic modulus at 70 °C for the
C-loaded microtubes was observed, demonstrating a better
thermal stability at high temperature. Moreover, the fabrication
of a micro heat exchanger prototype and prteliminary tests with
different cooling fluids confirmed the possibility of using
Hytrel® for electronic applications, as a good thermal exchange
was evidenced.
