Purpose and main features of the subsystem ASONIKA-T. Subsystem ASONIKA-T can operate in standalone mode or as part of ASONIKA in combination with other subsystems. Subsystem ASONIKA-T is designed to automate the modeling of thermal processes such as micro assemblies, radiators, heat-removing bases, hybrid-integrated modules, power cordwood structure, cabinets, racks, and atypical (arbitrary) structures electronics. You can use the machine for the analysis of thermal processes the following types of model structures: plate unit housing, modular design, cluster design.
The subsystem, during the design of electronic structures, allows to implement the following design objectives:
– to identify the average temperatures of blocks, printed circuit assemblies and materials bearing structures, as well as the air volume inside the electronic structures;
– to make changes to the electronic structure in order to achieve acceptable thermal conditions;
– to choose the best option in terms of structural thermal work regimes from several existing conceptual options;
– to justify the need and the evaluate the efficiency of additional electronic protection from thermal influences;
– to create, if necessary, an effective program for testing electronic models and prototypes on the thermal effects (in thechoosing problems of the most information tested influences, the choice of sensors and their installation location in the most heat-loaded places, etc.).
The subsystem allows you to simulate the stationary and non-stationary thermal modes of electronics. There is the possibility of taking into account the causes of non-stationary thermal conditions: a change in time of ambient temperature, time variation of the heat capacity of electronic components, the time variation of the heat capacity of structural elements, etc.
There is a possibility of integrating the work of electronics in different conditions: in vacuum and in air, both at normal and at reduced pressure. It is possible to account for different cooling conditions: natural or forced convection, heat, air cooling, the use of heat sinks, etc.
ASONIKA-T subsystem’s service software includes a database with geometric and thermo-physical reference parameters of electronic components and construction materials, graphical input of initial data for structures graphical output of results.
Simulation of thermal processes in electronic structures using ASONIKA-T subsystem. For the simulation session, the following background information is required:
– sketch or drawing of the electronic bearing structure;
– thermo-physical material parameters of the considered design;
– heat generation output in the lower-level hierarchy structures that are within the structure under consideration. Output consist of mounted electronic components in them;
– cooling conditions (boundary conditions) design.
The first stage of constructing a thermal processes model (TPM) of electronics module is that the product is divided into conditional isothermal volumes. Electronic component, an element of product design can be shownin the form of these isothermal volumes, which is necessary to determine the temperature, air volume inside the unit, the environment, a set of elements of the product, the entire electronics unit, element parts, and etc. The partition depends on the structure of the calculated object, on the required accuracy of thecalculation temperature, on the assumptions made when considering the heat transfer processes in the product, and etc. Main difficulty is finding the allocation of points in the product, in which the accuracy of modelinghasbeen savedand at the same the complexity of the TPM (the number of nodes) would remain within reasonable limits. To do this, first idealize (simplify) the processes of heat transfer in the product:
– ignore the minor types of heat transfer in the product design (ie, discard irrelevant thermal connection between the nodes of TPM);
– justify and accept conditional insulated these or those groups of bodies (parts, elements). Conditionally an isothermal volume, including several bodies, called the «hot zone».
Next to build TPM electronic block among these conventional isothermal volumes, volumes that are in thermal interaction are allocated. These include:
– bordering single Solid State volumes (conduction);
– volumes, that interact through layers of air (free convection in a confined space);
– volumes that are in the radioactive heat transfer (radiation);
– volume of the solid and the volume of the surrounding air (convection);
– contact volumes of two solids (contact thermal conductivity), etc.
In the ASONIKA-T subsystem, TPM is represented by a topological TPM, which isrepresented as an undirected graph. Vertices (nodes) of the graph modelingstructure’srelatively insulated elementary volumes (they correspond to structural elements and components of electronics structure, or fragments).The branches (edges) of the graph represent the heat flow between the volumes of relatively insulated structures in TPM.ASONIKA-T subsystem provides the ability to automatically form TPM standard structures, for non-standard structures there is a graphical user interface in which the user builds himself a topological TPM.
ASONIKA-T subsystem has the ability of taking into account the thermal interactions, and hence the possibility of applying the types of the TPM branches.
Based on of the topological TPM, a system of nonlinear algebraic equations (SNAE) is formed for stationary thermal process or a system of ordinary differential equations (SODE) for transient thermal process. To solve systems of equations, the designer sets the boundary conditions which corresponding to the conditions of electronic operation. The backward differentiation formula (BDF) is used to solve SODE, the fixed point iteration method is used to solve SNAE. To solve systems of linear algebraic equations (SLAE), which include SODE and SNAE (at each time step and / or at each iteration of nonlinearities), the LU decomposition method is used with the symbolic factorization and also taking into account the matrix sparsity of thermal conductivities.
After the TPM was created, the calculations are carried out.According to the results the user is able to obtain various textual and graphical information. The data is displayed for both stationary calculation in the form of a temperature tables in the model nodes and for the nonstationary calculation in the form of a temperature dependency graph in the model nodes on the time and temperature table in the time intervals in the model nodes.
The work is submitted to the International Scientific Conference «Actual problems of education», Greece (Crete), October, 17-24, 2013, came to the editorial office оn 20.03.2013.