Thermal behavior of porous stainless-steel fiber felt saturated with phase change material

• Fiber felt saturated with paraffin can significantly reduced surface temperature.
• Dominant mechanism varied from heat conduction to convection with increasing porosity.
• Increase in porosity of the fiber felt augments the natural convection of the wax.
• Increase in porosity decreases effective thermal conductivity of fiber-foam composite.
• Surface temperature and interface moving rate increase in order of fiber diameter.

Integrating high thermal conductive porous media and high latent heat phase change materials (PCMs) is an efficient method for heat dissipation in passive cooling applications. In this study, the enhanced heat transfer performance of porous stainless-steel fiber felt saturated with paraffin as PCM was experimentally studied. The effects of the porosity and the fiber diameter on the surface temperature and the solid/liquid interface evolutions were investigated. The solid/liquid interface evolution was tracked using a digital camera. The increase in fiber felt porosity augmented the natural convection of the melted PCM and the moving rate of the solid/liquid interface, but reduced the effective thermal conductivity of the composite. The surface temperature and the moving rate of the interface increased with the fiber diameter. The measured surface temperature showed a good agreement with the interface shape and evolving rate. Two heat transfer mechanisms dominated the melting process, namely, the combined heat conduction and the natural convection of the inside fluid. The dominant heat transfer mechanism switched from combined thermal conduction to natural convection of the liquid wax as porosity increased. Furthermore, the effect of interfacial surface area exceeded that of the fiber felt permeability in the natural convection prevailed regime.