A computational procedure for analysis of the melting, burning and flame spread of polymers under fire conditions is presented. The method, termed particle finite element method (PFEM), combines concepts from particle-based techniques with those of the standard finite element method (FEM). The key feature of the PFEM is the use of an updated Lagrangian description to model the motion of nodes (particles) in the thermoplastic material. Nodes are viewed as material points which can freely move and even separate from the main analysis domain representing, for instance, the effect of melting and dripping of polymer particles. A mesh connects the nodes defining the discretized domain where the governing equations are solved using the FEM. An incremental iterative scheme for the solution of the nonlinear transient coupled thermal-flow problem, including radiation, loss of mass by gasification and combustion is used. Examples of the possibilities of the PFEM for the modelling and simulation of the melting, burning and flame spread of polymers under different fire conditions are described.


Keywords: melting, dripping, polymers, particle finite element method (PFEM).

Knowledge of a material thermal conductivity is essential in several engineering applications. This material property serves also as a measure of the quality of manufactured materials. Nowadays, a lot of effort is directed into development of non-destructive, fast and reliable measurement techniques. In the works of Adamczyk et al. [1] and Kruczek et al. [10], a new in situ conductivity measurement technique for an anisotropic material was developed. This method, due to its rapidity and nondestructive character, can be embedded in a manufacturing process. However, despite many advantages, the developed measuring technique has some drawbacks corresponding to the applied mathematical model, which is used for determining the material thermal conductivities. It neglects the effect of heat losses due to radiation and convection phenomena on the calculated values of thermal conductivities. In this work, the computational fluid dynamic (CFD) modeling was applied to estimate heat losses due to radiation and convection. The influence of omitting the radiative and convective heat transfer on the predicted temperature field and calculated thermal conductivities was investigated. Evaluated numerical results were compared against experimental data by using the developed in situ measurement technique for the thermal conductivity of anisotropic materials.


Keywords: thermal conductivity, in-situ method, CFD, radiation, natural convection.

The work deals with thermal-hydraulic analyses of a pressurized water reactor containment response to accidents caused by a rupture of primary circuit. The in-house system computer code HEPCAL-AD and CFD ANSYS Fluent have been coupled for these simulations. The aim of this work is verification of possible ways of the codes coupling. The assessment of each method has been done by comparing the computational results with experimental data obtained from testing rigs of the AP-600 reactor containment cooling system. Additional simulations of a loss-of-coolant accident (LOCA) have been carried out as well, and compared with outcomes of the AP-600 reactor simulator.


Keywords: reactor containment, thermal-hydraulic analysis, lumped parameter code, CFD code, coupling.

A model integrated meshless solver (MIMS) tailored to solve practical large-scale industrial problems is based on robust meshless methods strategies that integrate a native model-based point generation procedures. The MIMS approach fully exploits strengths of meshless methods to achieve automation, stability, and accuracy by blending meshless solution strategies based on a variety of shape functions to achieve stable and accurate iteration process that is integrated with a newly developed, highly adaptive model generation employing quaternary triangular surface discretization for the boundary, a binary-subdivision discretization for the interior, and a unique shadow layer discretization for near-boundary regions. Together, these discretization techniques provide directionally independent, automatic refinement of the underlying native problem model to generate accurate adaptive solutions without need for intermediate user intervention. By coupling the model generation with the solution process, MIMS addresses issues posed by ill-constructed geometric input and pathologies often generated from solid models in the course of CAD design.


Keywords: meshless methods, heat transfer, large-scale problems.

The key issue in designing borehole heat exchangers (BHE) is the long-term performance of the ground source heat pump (GSHP) systems. The performance directly reflects economic profitability and depends on a large number of parameters including rock formation, the construction of the borehole heat exchangers, working parameters (circulation rates) and thermal load. The objective of the paper is to perform a realistic long-term (up to 10 years) analysis of the ground system to show possible degradation of efficiency over time. A mathematical model of the heat transfer in a borehole heat exchanger and the surrounding area has been constructed for parameters of the currently running experimental system. The long-term performance of the ground source heat pump system is evaluated.


Keywords: borehole heat exchangers, reservoir engineering, heat pumps systems, geoenergetics.

The main objective of this paper is to recognise the heat transfer phenomena between an infant placed in a radiant warmer and the surrounding environment. The influence of the parameters in the computational time during different physical phenomena in heat transfer is studied. This model can be also used in future work to improve radiant warmer efficiency. A complete 2D and 3D numerical simulation was carried out using commercial code ANSYS Workbench- ANSYS Fluent. The analysis involved the fluid flow, convection and radiation heat transfer as well as turbulence modeling, although moisture phenomena were omitted. The experiments were completed to validate a numerical solution.


Keywords: numerical analysis, radiant warmer, radiation, premature infant, CFD, heat transfer, fluid mechanics.