Thermally Enhanced Polyethylene Nanocomposites for Polymer Heat Exchanger Applications

Polymer-based heat exchangers may offer alternative to metal heat exchangers in multi-effect distillation units with improved resistance to corrosion, fouling and scale formation. However, the low-thermal conductivity (similar to 0.3 W/m K) of polymers is a bottleneck for their application in heat exchanger applications. Thermal conductivity, mechanical properties and wettability of a polymer can be enhanced through addition of graphene-based fillers. In this work, low-density polyethylene-nanocomposites with different loads of hybrid graphene-based fillers of different morphologies are prepared by melt mixing using different volume ratios. To investigate the effect of filler anisotropy on the nanocomposite thermal conductivity, the fillers, alignment was controlled through hot pressing and fabrication of multilayered structure. Our results indicate that similar to 21 vol.% of aligned expanded graphite-graphene hybrid has caused an increase in the thermal conductivity of low-density polyethylene from 0.29 to 5.78 W/m K corresponding to an enhancement of similar to 2000 and 580% over the conductivity of neat polymer and nanocomposite with same filler loading without filler alignment control, respectively. The stiffness of polyethylene was significantly improved, but the ductility was drastically reduced. The incorporation of 21 vol.% graphite-graphene hybrid to polyethylene has caused an improvement of Young's Modulus of almost 750%. The heat transfer studies were also carried out using plate type hot-water-to-cold-water poly(methyl methacrylate)-based heat exchanger. The experimental results show that the overall heat transfer coefficient of polyethylene-nanocomposite plate containing hybrid aligned filler was 3-4 times higher to that of neat polymer at different Reynolds number.