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A mathematical and a numerical approach to model the injection mold filling stage is presented. The approach is based on a Generalized Eulerian Lagrangian (GEL) formulation. In purely Lagrangian formulations the solution is obtained at mesh points which follow the local fluid velocity. On the other hand, in Eulerian formulations the mesh is fixed and the solution is obtained at fixed spatial locations. In injection molding different parts of the flow domain are best analyzed by one but not both formulation methods. The Generalized Eulerian Lagrangian formulation combines the advantages of both formulations: In the same flow problem but different regions the GEL formulation allows the selective application of an Eulerian, Lagrangian, or a mixture of the two formulations. In this work the melt is described using the White-Metzner constitutive relation and results are shown and discussed for the filling of a cavity from a single gate and from a fully open end under different process conditions.

Highlights • The start-up plane Poiseuille flow of a Bingham fluid is considered. • The analytical expression for the velocity in the core is given. • The analytical solution is extended to include the velocity in the yielded zone. • Strict bounds on the validity of the analytical solution are provided. Abstract The start-up flow of a Bingham plastic in a channel is considered and Safronchik's solution [1] for the initial evolution of the yield surface and the core velocity is revisited. Stricter time bounds for the validity of the above solution are derived and the solution is extended to include the velocity profile in the evolving yielded zone. Comparisons are made with another approximate solution derived under the assumption that the velocity in the yielded zone is parabolic adjusting with the evolving yield surface. This approximation performs well for small values of the yield stress, or, equivalently, for large values of the imposed pressure gradient. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the potential of a small-scale, combined-cooling-heating-and-power system, consisting of a 1 MW e gas turbine subsystem coupled to a 0.5 MW e photovoltaic (PV) subsystem for application in Cyprus. The proposed system is completely autonomous, without any interconnections to a central power grid. To allow maximum utilization of the electricity generated by the PV subsystem, an electrolyzer unit is coupled to the system to convert excess renewable electricity to hydrogen. The generated hydrogen is injected to the natural gas supply for the gas turbine. For the generation of useful cooling and heating, the system recovers heat from the flue gas exiting the gas turbine; the recovered heat is supplied to a heat-activated absorption chiller/heater to generate cooling or heating. An electric chiller/heater is integrated to the system to supplement thermal energy when necessary. The thermal energy is supplied to nearby buildings through a district energy network. The annual average primary energy ratio of the proposed system is 0.806. For an assumed system lifetime of 20 years, the lifecycle cost of the proposed system is 11.12 million USD, resulting to a unit cost of electricity at 0.06 USD/kWh, which is a 62% reduction of the current cost in Cyprus. The results of the parametric study suggest that the economic performance of the proposed system is highly dependent on price fluctuations of the unit cost of natural gas, while the specific cost of the electrolyzer unit is also critical. The proposed system could become an important candidate for power and thermal energy generation in Cyprus as a measure to reduce the presently high cost of electricity. [ABSTRACT FROM AUTHOR]