Experimental Analysis on Microchannels with Different Cross-Sectional Shapes for Internal Cooling Applications

The use of additive manufactured microchannels for gas turbine cooled components is considered a promising approach to enhance the internal cooling efficiency. On the other hand, the evaluation of heat transfer and pressure loss characteristics is complicated by the fact that several manufacturing choices can affect the as-built geometry and surface roughness, thus making it difficult to predict their performance with simple relations. Moreover, the evaluation of the channels characteristic dimension must be carried out through complex processes and the distinction between channel shape and its intrinsic roughness is in general a nonambiguous aspect. The possibility to adopt micro-channels with noncylindrical cross-sectional shapes introduces an additional degree-of-freedom. This article builds on a previous one, where a procedure to retrieve the characteristic dimension was developed and tested on cylindrical microchannels; the method was based on a differential flow check, allowing to by-pass the direct geometrical investigation. In this, the methodology is applied to microchannels with various cross-sectional shapes, to assess its capabilities. The results are discussed, especially in terms of performance scaling capabilities, and compared to the ones achieved from the conventional approach based on geometrical inspection. The results showed that the approaches returned slightly different values of the characteristic dimension and, in turn, of the quantitative values of the parameters of interest. Nevertheless, the same conclusions and performance were achieved, as far as the comparative analysis of different coupons and the scaling capability are concerned.