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The thermal efficiency of gas turbine engines depends heavily on the cooling performance of the internal channels of turbine blades. In the present study, the effects of bidirectionally arranged ribs on the flow and heat transfer mechanism in a two-pass cooling channel are investigated numerically. The channel aspect ratio is kept constant at 1:2 (W: H), and the rib pitch-to-height ratio (P / e) is 10. Comparative analysis is performed for three different cross-sectioned (Square, triangular and Curved) ribs with Reynolds numbers ranging from 10,000-50,000. The results indicate that the bidirectional ribbed channel provided 69% better thermal performance compared to horizontal-only ribs due to its potential to induce secondary flow in both vertical and horizontal directions. The square and triangular ribs show similar characteristics, but the thermal performance of curved ribs drops by 11%. The pressure loss phenomenon is also lowest in the case of the curved ribs. The obtained Nusselt number and friction factor for all cases are normalized with the Dittus-Boelter correlation, Blasius correlation and the smooth channel. The detailed analysis of area-averaged normalized Nusselt number indicates that the best thermal performance occurs at the bend region due to the combined contributions of the ribs and the 180 ° turn. Furthermore, in terms of the overall thermohydraulic characteristics, the curved-bidirectional ribbed channel is noticed to have the best results with values of 1.38 and 1.25 for TEF o and TEF s respectively. • Numerical flow and heat transfer mechanisms of a bidirectional ribbed two-pass channel have been investigated. • Comparative analysis among three different types of rib cross-sections is generated. • Detailed analysis of the effects of rib arrangements on normalized Nu and f are presented. • Curved-bidirectional ribs show superior performance in terms of overall thermohydraulic characteristics. [ABSTRACT FROM AUTHOR]

As a phase change material, ice slurry has been successfully applied in HVAC&R systems due to its high energy storage density. The heat exchangers are the key equipment realizing energy conversion of ice slurry. In HVAC&R systems, U-tubes are frequently used in shell and tube heat exchanger. However, there are few studies on thermo-fluidic characteristics of ice slurry in U-tubes. Therefore, the thermo-fluidic characteristics of ice slurry in U-tubes are numerically studied in this paper using Euler-Euler approach. The results indicated that as enlarging the inlet ice content and velocity, the ice concentration distribution becomes more uniform along in vertical profile. Due to the secondary flow in bend section, the ice concentration decreases in the inner wall and increases in the outer wall as the inlet velocity increases; At the high Reynolds number, the inlet ice content and ice particle diameter have a more significant fluence on pressure drop (Δ p). The local heat transfer coefficient (h lo) in bend section exhibits a tendency of first increasing and then decreasing, with the maximum value of h lo occurs at θ = 90° of the bend section. Finally, a correlation is suggested between the average resistance coefficient (f ave) and local Nusselt number (Nu lo). • The melting process of ice slurry in U-tubes is investigated. • The factors affecting thermo-fluidic behavior of ice slurry in U-tubes are discussed. • This peak value of h lo is located within the bending section at an angle of θ = 90°. • The correlation of f ave and Nu lo in U-tubes is obtained for ice slurry. [ABSTRACT FROM AUTHOR]