Abstract

Serpentine channels are a common feature seen in heat exchanger geometries. For example, they are present in midchord regions of gas turbine blades to prevent material failure at high turbine inlet temperatures. Due to their serpentine nature, these channels contain 180 degree turns or Ubends. These Ubends are responsible for nearly 20% of the pressure drop in such channels. A topology optimization method has been used in the current study to optimize the shape of a baseline Ubend for minimum pressure drop, at a Reynolds number of 17,000. TO uses a variable permeability approach to design an optimum flow-path by manipulation of solid blockage distribution in the flow path. The pressure drop across the channel was lowered by 50% when compared to a standard Ubend channel profile from literature. Postprocessing was performed to extract the flow-path and run a forward simulation in STAR-CCM+ after remeshing with wall refinement. A 3D printed model of the TO shape and benchmark Ubend was created using ABS as the printing material, to confirm the results of the turbulent fluid TO, which is a relatively untouched topic in current TO literature. Experimental results showed deviation from CFD by about 5%. Comparison of the TO optimum was carried out with an in-house parametric shape optimization using surrogate model based Bayesian optimization and a similar shape optimization study from literature. Higher reduction in pressure drop was seen in case of the TO geometry when compared to the benchmark and the BO cases.

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