Aerosol nucleation and growth in a laminar flame or a gas-phase reaction jet were considered in the free-molecular regime. A two-dimensional, axisymmetric, discrete-sectional model was developed based on a species equation. Parabolic conservation equations resulted from the formulation of the governing equations in boundary layer form, neglecting axial diffusion and axial thermophoretic velocities. The source terms of the equations included monomer formation by gas-phase chemical reaction, and growth or reduction by coagulation and condensation among all aerosol particles. A binomial expansion was used to approximate the collision rate. The equations were linearized by Newton's method and solved with a block tridiagonal solver. The results of the model exhibited reasonable agreement with an aerosol size distribution measured by dynamic light scattering. Spatial transport processes that could influence the aerosol dynamics included convection, diffusion, and thermophoresis. Their impact on the development of the aerosol and its distribution in the flame was investigated; thermophoresis was found to have the greatest impact on the spatial distribution of aerosol mass, although the amount of aerosol was not affected significantly. AEROSOL SCIENCE AND TECH

The innovative system for shaping plastic pipes combines the advantages of computerized numerical control (CNC) pipe bending, established for metal pipes, with the thermofixing known for plastics. According to the principle of rapid prototyping, no complex bending tool shapes are required, but each bend is formed separately on the universal bending head. The bending process consists of forming, heating and cooling. In order to achieve the shortest possible cycle times, dielectric heating is used. Tests have shown that a new machine concept is necessary due to the plastic pipes and that conventional horizontal CNC bending cannot be used. It will also be shown that the design and layout of the universal bending head is possible with a suitable polymeric material. For this purpose, the acting forces were estimated and general requirements were formulated for the material. In addition, this material selection was limited by determining the dielectric properties under operational conditions. As a result, a polyetheretherketone (PEEK) type could be selected as a suitable material. The design of the bending head is based on mechanical and thermal simulations with this PEEK.

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