In the aerospace industry, ceramic tiles are used for shuttle thermal protection systems. Large blocks of ceramic are used as an intermediate stage in the manufacturing process. These blocks are initially at a temperature of 900°C, but need to be cooled to 50°C before further processing can take place. There are two options to achieve this: active or passive convective cooling. Although both methods will achieve the desired results, there are cost and time issues that have to be considered. With passive convective cooling, the blocks are left to cool naturally in a large warehouse. This method takes more time and requires a large storage capacity. With active convective cooling, forced air is used to lower the temperature over a shorter period of time. This method takes less time, but demands the construction of costly cooling equipment. MapleSim, Maplesoft’s advanced multidomain simulation tool, can be used to create a cooling model to determine the best option.
The time required for the core of the block to cool to a temperature of 50°C, given changes in the dimensions of the block and other parameters, must be determined. Laboratory tests were not practical for exploring the entire parameter space, but could be used to calibrate a theoretical software model. A finite element method (FEM) modeling of the spatial temperature dynamics could be used, but this approach was expensive, required extensive operator training, and gave a level of detail that was not required. Ideally, a spatially discretized lumped parameter model that could be optimized to match experimental data could be created.
Using MapleSim, two models were created. The first model discretized the ceramic block along one spatial dimension. This approach is suitable if the heat loss from the sides of the block is negligible, and it was a reasonable assumption for the force-air cooling. Expanding on this model, a second model was created discretizing the block along three spatial dimensions. Sixteen vertical slices were used to represent the block, with each slice consisting of four segments. Parameters for the convective heat transfer coefficients for both active and passive cooling were used to fit the model to the experimental data.
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