Numerical Investigation on Flow and Heat Transfer in a Lattice (Matrix) Cooling Channel

Abstract

Flow and heat transfer of lattice cooling channel are investigated numerically. Firstly, simulations are performed for two channels to reproduce the experimental results reported in open literatures. Based on the literatures, sub-channels consisting lattice network are designed with aspect ratio of near unity and crossing angle of 45 degrees. Predicted heat transfer patterns of primary surfaces have agreed qualitatively and quantitatively well with the experimental results. Cooling air turns mainly through turning at the end of each sub-channel. After impinging the sidewall, strong acceleration occurs at the entrance of the opposite sub-channel, which enhances local heat transfer. Based on the above discussions, the present study also compares heat transfer coefficient of all surfaces (rib + primary) surrounding the sub-channel. The highest local heat transfer coefficient is found at rib surfaces. Predicted flow pattern indicates that a longitudinal vortex is formed in parallel to the sub-channel after impinging the sidewall, and that transient flow from one to another side of the sub-channels keeps the core of the vortex. This transient flow substantially contributes to the heat transfer enhancement at the upper edge of a rib surface, and more than half of total heat flux transfers through the rib. It follows that, in designing lattice cooling channel, rib surfaces should also be treated as heat transfer surface. Moreover, the effect of sub-channel (or rib) inclination angle on flow and heat transfer is examined. Rib inclination angle strongly affects translation flow between the lower and upper sub-channels and impingement at the sidewall. Further experimental investigation is expected in the near future.

Study on Thermofluid Characteristics of a Lattice Cooling Channel

“…To understand the flow and heat transfer mechanism, flow visualization of the lattice cooling duct is needed; however, the complicated geometry makes it quite hard due to difficulty with optical access. Therefore, numerical investigations have been performed to discuss the flow characteristics [7][8][9][10][11]. Most predicted results have shown similar trends to those described by Khalatov and Nam [2]; however, prediction accuracy of the velocity field has never been quantitatively evaluated.…”

“…In Refs. [6] and [10], it is suggested that heat transfer from the side walls significantly contributes to the overall heat release. By comparing measured heat transfer coefficient distributions among three surfaces, the amount of contribution will be discussed.…”

Numerical investigation on heat transfer performance of matrix cooling channels for turbine trailing edges

“…Their research also shows that the matrix cooling channels with two inlet subchannels have higher heat transfer and lower pressure loss than those with four inlet subchannels. Hagari and Ishida 5 conducted numerical investigations on matrix cooling channels to examine the impact of rib inclination angle on the flow and heat transfer. The results show that a 27% increase of rib inclination angle leads to 30% increase in total heat flux by enhancing the translation between the subchannels and impingement at turning regions.…”