Composite materials with enhanced conductivities

The authors have analyzed the isotropic thermal/electrical conductivities of two types of specially structured composite materials. Closed-form results have been obtained for predicting the conductivities of the composites, and the accuracy has been verified by FE simulations. The obtained results in this paper are compared to the relevant theoretical predictions and experimental measurements. It has been demonstrated that the type-I composites have achieved a conductivity that is almost the same as the highest possible theoretical upper limit, and the type-II composites have a conductivity significantly greater than the experimental results of conventional isotropic composite materials

The elastic properties and yield strengths of low-density honeycombs and open-cell foams

This chapter aims to briefly review the main theoretical and finite element simulation results on the elastic properties and yield strengths of regular hexagonal honeycombs, Kelvin open cell foams, random irregular Voronoi honeycombs and open-cell foams, and discuss about their deformations mechanisms. The book chapter further introduces the effects of other parameters such as the degree of cell regularity, imperfection of defects, cell size, solid volume fraction and material distribution, on the elastic properties and yield strengths of these cellular materials. Voronoi honeycombs and open cell foams can be related to their mechanical properties

District heating and cooling optimization and enhancement – towards integration of renewables, storage and smart grid

District heating and cooling (DHC) systems are attracting increased interest for their low carbon potential. However, most DHC systems are not operating at the expected performance level. Optimization and Enhancement of DHC networks to reduce (a) fossil fuel consumption, CO2 emission, and heat losses across the network, while (b) increasing return on investment, form key challenges faced by decision makers in the fast developing energy landscape. While the academic literature is abundant of research based on field experiments, simulations, optimization strategies and algorithms etc., there is a lack of a comprehensive review that addresses the multi-faceted dimensions of the optimization and enhancement of DHC systems with a view to promote integration of smart grids, energy storage and increased share of renewable energy. The paper focuses on four areas: energy generation, energy distribution, heat substations, and terminal users, identifying state-of-the-art methods and solutions, while paving the way for future research

Size-dependent and tunable elastic and geometrical properties of nano-structured hierarchical cellular materials

The basic building blocks of nano-structured hierarchical cellular materials are nano-sized wires or plates. Due to the effects of surface elasticity and the initial stress/strain, their bending, torsion, stretching and transverse shear rigidities are not only size-dependent, but also tunable and controllable over a large range. Based on the closed form results of the bending, torsion, stretching and transverse shear rigidities of nanowires [1, 2] and nano-plates [3,4], the analytical results for the size-dependent and tunable elastic and geometrical properties are obtained for the first order nano-sized regular honeycombs [4,5]and open-celled foams[6], and the similar results are obtained for the first order nano-sized random irregular Voronoi honeycombs[7] and random Voronoi open-celled foams by computer simulation. Further, the size-dependent and tunable elastic and geometrical properties are obtained for nano-structured hierarchical and selfsimilar regular and irregular honeycombs and open-celled foams. The obtained results indicate that some very interesting and much desired elastic and geometrical properties, which do not exist in conventional cellular materials, become possible in their nano-structured hierarchical counterparts