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EnginSoft - Conference Abstracts
EnginSoft International Conference 2009 |
Development of a Simplified Model for the Simulation of a Climatic Chamber Part1: Steady Case |
Ceccobello Michele - Angelantoni Industrie |
Abstract |
The project described by this paper is a long-term work Its aim is to simulate the behaviour, both from a fluid point of view and from thermal one, of every climatic chamber, either standard or special. A standard Angelantoni’s chamber was taken as reference case: it is the DISCOVERY 250. The reason for this choice is quite logic, for this kind of product a good set of robust data is available from testing department; it means a reliable tuning of the virtual simulation is feasible. The project foresee tree steps: steady case, transient case and implementation of a PID controller trough a FORTRAN external routine that should copy the logic of PLC of the actual chamber. Currently, the first step has been concluded, the description of the procedure and its results are the topics of this paper. The start point for the first step is the 3D model of the chamber from which a simplified and more functional new 3D model has been derived. The original model was details filled as the manufacturing department requires; the simplified model deals only with the internal volumes and the active and passive components: electrical heaters, evaporator/dehumidifier, fan, grids and all the details affecting the flow pattern inside the chamber. A very simplified model has been proposed for the axial fan in which the swirl motion has been implemented externally using an excel sheet. Evaporator, fan and grid have been modeled by porous sub-domains; fan as source of momentum, heaters and evaporator as sources of power, evaporator and grids as sources of directional losses and their characteristic curves have been put in the pre-processor as well the fan ones, the walls have been modeled with a global thermal coefficient. The solution strategy consists in two runs. In the first run the system is a closed system without any inlet or outlet, the momentum is given by the fan in which only the axial component of velocity is present; in this run all the characteristic curves are built-in; at the end of the run the overall mass flow evolving in the chamber is computed. In the second run the system becomes an open system, the fan sub-domain has been suppressed, in the inlet of the new configuration is used the mass flow computed in the previous run and a swirl motion is given by an external excel sheet. In this run power is given to the heaters and its surface temperature is fixed according to the testing department data, at steady condition. The results are: internal target temperature according to the actual model, good uniformity of temperature. In addition to the steady run a transient run has been done, putting the temperature profile of heaters in the pre-processing. The results were not realistic due to the lack of the model respect to the masses involving thermal inertia, but this is the target of the second step of the project. |
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