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Laminated polymer matrix carbon fiber composites have poor thermal conductivity in through thickness direction as all the conductive fibers are within the plane. One can increase the through thickness thermal conductivity by introducing conductive fibers in that direction or by modifying the form, direction and architecture of the fiber network. In this paper we conduct a parametric study using finite element analysis to investigate the relation between the local fiber architecture and its effective through-thickness thermal conductivity. The role of the fiber tow orientation, volume fraction and stacking sequence is explored. Unidirectional laminates containing fiber tows aligned in the same direction for all laminae exhibit higher through thickness thermal conductivity than the stacking sequence with other orientations. A conductive coating surface layer enhances the thermal conductivity of laminates independent of fiber orientation configuration. A geometric scalar parameter is proposed to correlate laminate through-thickness thermal conductivity with fiber tow stacking sequence. The influence of different boundary condition types on the through-thickness thermal conductivity is also assessed. [ABSTRACT FROM AUTHOR]

Abstract: Thermal transport mechanisms are investigated and characterized when highly conductive fibers are embedded across the thickness of a three-dimensional polymer composite. Different approaches are explored to enhance out-of-plane thermal conductivity and address measurement issues associated with this class of composites. An experimental setup was designed, fabricated and validated to measure through-thickness thermal conductivity. A corresponding finite element model of the setup was developed to characterize and gain further understanding of the thermal field in the measurement cell. An approach in which a conductive coating is applied on the surface of the composite to improve the through-thickness thermal conductivity of composites containing a small percentage of conductive fibers in the thickness direction is explored. A parametric study revealed that the thickness of the coating and the distribution of the conductive fibers play a crucial role in augmenting the heat transfer across the thickness of the polymer composite. [Copyright &y& Elsevier]

• Analytical solution of non-boiling heat transfer during droplet impact is obtained. • The analytical solutions are applicable to low velocity and low wall temperature. • Wall thermal effusivity can decide heat flux alone, but not the temperature drop. • Droplet property shows great and similar effect on heat flux and temperature drop. • Thermal effusivity is a decisive parameter and high thermal effusivity is preferred. Droplet impact process exhibits excellent heat and mass transfer characteristics. Analytical solution with simple explicit form and certain accuracy can clearly reflect the correlation of physical parameters, however the analytical study on droplet impact heat transfer is quite insufficient and limited to flow field analysis. In this paper, the analytical solutions of heat flux and temperature variation of droplet impact on heated wall in non-boiling regime were obtained based on boundary layer asymptotic matching method. Parameter analysis of thermophysical properties was conducted to explore the decisive properties of droplet and wall materials. The results showed that the analytical solutions are appropriate to predict non-boiling heat transfer at low impact velocity and low initial wall temperature. Parameter analysis showed that thermal effusivity is the decisive property rather than the thermal diffusivity. Wall thermal effusivity could independently determine heat flux, but should determine temperature variation together with wall thermal conductivity. Droplet thermal effusivity and Prandtl number were the decisive properties, however the effect of Prandtl number in reality can be ignored. Wall materials and droplet liquids with higher thermal effusivity showed higher heat transfer capacity. The importance of thermal effusivity was demonstrated and high thermal effusivity was preferred in future thermal management. [ABSTRACT FROM AUTHOR]