Basic Research of Thermal Transfer Simulations

Abstract

The article summarizes basic research into thermal transfer simulations. Problems of thermal influence in mechanical systems are solved there. The first steps focus on matching simple heat-transfer samples with CAE software. Simple cases are performed in a real environment. Thermal values are measured. Cases are also solved using CAE software tools. Solutions are compared. CAE solutions are matched to real values. CAE results are verified or refuted. There are many differences between the options in the solvers, there are steady states and transient-run possibilities, etc. Software tools like Nastran, etc. need many coefficients to solve the problem. This procedure is able to identify specific conditions, fits the solver to the specific sample and performs CAE simulations to get real, verified results. For example, passive radiators heated by an induction heater are used for real tests. Temperature fields are measured by thermal camera and structural deformations by measuring displacement. These values are used in simulations and solved by finite elements method. Simulations are performed in Siemens NX10 software, supported by solvers Nastran, MAYA, and NX Multiphysics. Results are compared and matched in the simulation to acquire a more precise solution in the following steps All these steps are processed to get characteristics of thermal transfer simulation which will be useful in difficult examples of simulation machines, machine tools etc.Keywords: heat load; thermal flow simulation; FEM Verifying of thermal loadA simple simulation of the heat load was performed in the first part of the research. A small iron cylinder was heated by a high frequency induction heater. The cylinder was heated from 25°C to nearly 250°C as you can see on the Fig.1. The heat load was turned on for 60 seconds, and then it was cooled by radiation and natural convection. The temperature of the cylinder was logged by a thermocouple. The temperature was monitored in relation to time. Thermal fields were monitored by a thermal camera. The thermal camera was used to verify the optimum homogeneous warming. Four measurements were made. Three measurements of a cylinder with diameter 25 mm and 30 mm high are performed. Effective emissivity was guaranteed by paint with guaranteed emissivity (e = 0.95). This effect was simulated. Derivation of the measured curve provided the loading characteristic. The same loading characteristic is used in the simulation. That obtains two views, measured and simulated, as you can see in the Fig. 1. The results of the experiments are shown in the graphs Figs. 2. Heat load was measured in the experiment. Measuring determined heat load 219 W. For equivalent simulation was estimated heat load 220 W. Then was computed convection heat exchange. Measured exchange was 16.3 W and simulated heat exchange less, about 14 W. Cooling losses were calculated by derivation of curves in Fig. 2. -0578 -

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