Heat transfer and thermal–hydraulic evaluations of cross-circular grooved rectangular flow ducts depending on rectangular baffle design parameters

Abstract

The cross-grooved rectangular flow ducts are largely used for plate heat exchangers. In this work, so as to better the heat transfer in cross-grooved rectangular ducts with circular grooves, rectangular baffles were located in the flow duct, and the influences of the rectangular baffle angles and heights on the features of heat transfer were numerically performed in detail. Equations of Navier–Stokes and energy were resolved by employing a program of Ansys-Fluent with k–ε turbulence model as steady and three-dimensional. Air employed as working fluid has a temperature of inlet 293 K while the circular groove’s wall temperature is 373 K. Rectangular baffles have various angles of 30°, 60°, and 90°, and heights of 0.25 H, 0.5 H, and 0.75 H. The mean Nusselt number (Num), temperature, turbulence kinetic energy (TKE), pressure, and PEC (Performance Evaluation Criterion) number of the flow duct with rectangular baffles were evaluated by comparing it with the cross-circular grooved channel non-baffle. Besides, the contours of velocity, turbulence kinetic energy, temperature, and velocity vector were exhibited for the cross-circular grooved rectangular channels with different baffle angles and height arrangements. Results were matched with experimental and numerical outcomes of the study found in the literature, and it was observed that they were fairly coherent. For Re = 6000, the number of Num increases by 180.48% in the duct with a 90° angle and 0.75 H baffle height compared to the duct non-baffle, and for 30° baffle angle, the PEC value at 0.25 H baffle height is 66.88% higher than that in the 0.5 H. Graphical Abstract Compared to the temperature contour distribution in the non-baffle state, the temperature gradient increases due to the turbulence intensity created by the inserting of baffles to the circular grooved ducts. When the baffle height is increased to 0.75 H, the increase in fluid temperatures toward the end of the ducts is the clearest evidence of this situation. Thus, while cooling increases in circular grooves, the temperature gradient in the duct above the circular grooved section gets better, especially in the case of 0.75 H height and 90° baffle angle. Temperature distribution contours of the ducts for non-baffle and with baffle of 90° angle and 0.75 H height for Re = 6000.