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The purpose of this paper is to augment heat transfer rates of traditional rib-elements with minimal pressure drop penalties.

The novel geometries in the present research are conventional cylindrical ribs with rounded transitions to the adjacent flat surfaces and with modifications at their bases. All turbulent fluid flow and heat transfer results are presented using computation fluid dynamics with a validated v2f turbulence closure model. Turbulent flow characteristics and heat transfer performances in square channels with improved ribbed structures are numerically analyzed in this research work.

Based on the results, it is found that rounded transition cylindrical ribs have a large advantage over the conventional ribs in both enhancing heat transfer and reducing pressure loss penalty. In addition, cylindrical ribs increase the flow impingement at the upstream of the ribs, which will effectively increase the high heat transfer areas. The design of rounded transition cylindrical ribs and grooves will be an effective way to improve heat transfer enhancement and overall thermal performance of internal channels within blade cooling.

The novel geometries in this research are conventional cylindrical ribs with rounded transitions to the adjacent flat surfaces and with modifications at their bases. The combination of cylindrical ribs and grooves to manipulate the turbulent flow.

The fluid flow in a rotating channel is obviously different from that in a stationary channel due to the existence of Coriolis force, which, in turn, enhances the heat transfer on the trailing side and reduces the heat transfer on the leading side. The purpose of this paper is to study various rib configurations combined with channel orientation on heat transfer and frictional loss in a rotating channel.

In the present study, the k-ω SST model was used as the turbulence model. The fluid flow direction in the channel is radially outward. The angle between the rotation axis and leading side is 45°. The channel aspect ratio (W/H) is 2, the blockage ratio (e/D_n ) is 0.1 and the pitch ratio (P/e) is 10. The Reynolds number is fixed at 10,000 and the rotation number varies from 0 to 0.7. Angled ribs, reversed angled ribs, standard V-shaped ribs and outer-leaning V-shaped ribs, are examined.

It is found that the reversed angled rib configuration and the outer-leaning V-shaped rib configuration display better heat transfer performance than the V-shaped ribs in rotating condition, which is in contrast to stationary condition. At the leading side, the reversed angled rib and the outer-leaning V-shaped rib show better performance in recovering the heat transfer recession due to the negative effects of the Coriolis force.

In the present study, the fluid is incompressible with constant thermophysical properties and the flow is steady.

The results of this study will be helpful in design of ribbed channels internal cooling for turbine blade.

The results imply that the rib configuration combined with channel orientation significantly impacts the heat transfer performance in a rotating channel. The reversed angled rib and the outer-leaning V-shaped rib show better heat transfer performance than standard V-shaped ribs, especially at high Rotating numbers, which is in contrast to stationary condition. The outer-leaning V-shaped rib has a relatively good heat transfer uniformity along the widthwise direction.

The pin fin is applied into a Lamilloy cooling structure which is broadly used in the leading edge region of the modern gas turbine vane. The purpose of this paper is to investigate effects of the layout, diameter and shape of pin fins on the flow structure and heat transfer characteristics in a newly improved Lamilloy structure at the leading edge region of a turbine vane.

A numerical method is applied to investigate effects of the layout, diameter and shape of pin fins on the flow structure and heat transfer characteristics in a newly improved Lamilloy structure at the leading edge of a turbine vane. The diverse locations of pin fins are Lp = 0.35, 0.5, 0.65. The diameter of the pin fins varies from 8 mm to 32 mm. Three different ratios of root to roof diameter for pin fins are also investigated, i.e. k = 0.5, 1, 2. The Reynolds number ranges from 10,000 and 50,000. Results of the flow structures, heat transfer on the target surface and pin fin surfaces, and friction factor are studied.

The heat transfer on the pin fin surface gradually decreases and then increases as the location of the pin fins increases. Increasing the diameter of the pin fins causes the heat transfer on the pin fin surface to gradually increase, while a lower value of the friction factor occurs. Besides, the heat transfer on the pin fin surface at a small root diameter increases remarkably, but a slight heat transfer penalty is found at the target surface. It is also found that both the Reynolds analogy performance and the thermal performance are increased compared to the baseline whose diameter and normalized location of pin fins are set as 16 and 0.5 mm, respectively.

The models provide a basic theoretical study to deal with nonuniformity of the temperature field for the turbine vane leading edge. The investigation also provides a better understanding of the heat transfer and flow characteristics in the leading edge region of a modern turbine vane.

This is a novel method to adopt pin fins into a Lamilloy cooling structure with curvature. It presents that the heat transfer of the pin fin surface in a pin-fin Lamilloy cooling structure with curvature can be significantly increased by changing the parameters of the pin fins which may lead to various flow behavior. In addition, the shape of the pin fin also shows great influence on the heat transfer and flow characteristics. However, the heat transfer of the target surface shows a small sensitivity to different layouts, diameter and shape of pin fin.

The purpose of this paper is to numerically study the influence of wall conduction on the heat transfer of supercritical n-decane in the active regenerative cooling channels.

A horizontally placed rectangular pipe with a solid zone and another one without a solid zone were used. A drastic variation of thermo-physical properties was emphatically addressed. After the verification of mesh and turbulence models comparing with the experimental results, a mesh number of 4.5 M and the low Reynolds number SST k-ω turbulence model were chosen. The solution of the governing equations and the acquisition of the numerical results were executed by the commercial software FLUENT 2020 R1.

The numerical results indicate that there is a heat transfer deterioration (HTD) potential for the upper wall, lower wall and sidewall with the decrease of mass flux. Due to wall conduction, the distribution of the fluid temperature at spanwise-normal planes becomes uniform and this feature also takes advantage of the relatively uniform transverse velocity. For the streamwise-normal planes, the low fluid temperature appears close to the upper wall at the region near the sidewall and vice versa for the region near the centre. Undoubtedly, the secondary flow at the cross-section plays a crucial role in this process and the relatively cool mainstream is affected by the vortices.

This study warns that the wall conduction must be considered in the practical design and thermal optimization due to the sensibility of thermo-physical properties to the heat flux. The secondary flow caused by the buoyancy force (gravity) plays a significant role in the supercritical heat transfer and mixed convection heat transfer should be further studied.

In this study, numerical simulations are performed to compare the adiabatic film cooling effectiveness and reveal the difference of film cooling mechanisms of two models with the same geometries and cross-section areas of film holes’ exits at three typical blowing ratios (M = 0.5, 1 and 1.5). The two models are an elliptical model and a cylindrical model with 90° compound angle, respectively.

Three different cases are considered in this work and the baseline is the model with a cylindrical film hole. The same boundary conditions and a validated turbulence model (realizable k-ε) are adopted for all cases.

The results show that both the elliptical and cylindrical models with 90° compound angle can enhance the film cooling effectiveness compared with the baseline. However, the elliptical model performs well at lower blowing ratios and in the near region at each blowing ratio because of the wider width of the film hole’s exit. The cylindrical model with 90° compound angle provides better film cooling effectiveness in the further downstream area of the film hole at higher blowing ratio because of the less lift-off and better coolant coverage in the larger x/D region along the mainstream direction.

Overall, it can be concluded that although the elliptical and cylindrical models with 90° compound angle have identical hole exits, the different inlet direction and cross-sectional geometry affect the flow structures when the coolant enters, moves through and exits the hole and finally different film cooling results appear.

The study aims to focus on rotation effects on a ribbed channel of gas turbine blades for internal cooling. The combination and interaction between secondary flows generated by angled rib geometry and Coriolis forces in the rotating channel are studied numerically.

A radially outward flow passage as an internal cooling test model with and without ribs is used to perform the investigation. Aspect ratio of the passage is 1:1. Square ribs with e/Dh = 0.1, p/e = 10 and four various rib angles of 90°, 75°, 60° and 45° are configured on both the leading and trailing surfaces along the rotating duct. The study covers a Reynolds number of 10,000 and Rotation number in the range of 0-0.15.

Nusselt numbers in the ribbed duct are 2.5 to 3.5 times those of a smooth square duct, depending on the Rotation number and rib angle. The maximum value is attained for the 45° ribbed surface. The synergy angle between the velocity and temperature gradients is improved by the angled rib secondary flows and Coriolis vortex. The decrease of the synergy angle is 8.9, 13.4, 12.1 and 10.1 per cent for the 90°, 75°, 60° and 45° ribbed channels with rotation, respectively. Secondary flow intensity is increased by rotation in the 90° and 75° ribbed ducts and is decreased in 45° and 60° ribbed cases for which the rib-induced secondary flow dominates.

The primary motivation behind this work is to investigate the possibility of heat transfer enhancement by vortex flow with developing turbulence in the view point of the field synergy principle and secondary flow intensity.

The purpose of this paper is to study the effects of dimple geometries and arrangements on the heat transfer enhancement in a dimple jacketed heat exchanger.

For the purpose of this paper, with the experimental validated numerical model, this paper carries out numerical simulations of both single dimples with different geometries and the whole dimple jacketed heat exchanger with different dimple arrangements. For a single dimple, its secondary vortex flow, temperature differences and the pressure drop performance for different geometries are analyzed. For the whole dimple jacketed heat exchanger, the heat transfer and pressure drop performances are investigated by comparing the no dimple, triangular and rectangular dimple arrangements.

Results show that dimples can improve the heat transfer efficiency compared with conventional jacketed heat exchanger, and specific geometries and arrangement of dimples for better heat transfer performance are figured out.

This paper considers both dimple geometries and arrangements, which can be useful for further applications in specific integrated devices or similar applications.

This study aims to clarify the mechanism of film hole location at the span-wise direction of an internal cooling channel with crescent ribs on the adiabatic film cooling performance, three configurations are designed to observe the effects of the distance between the center of the ellipse and the side wall(Case 1, l = w/2, Case 2, l = w/3 and for Case 3, l = w/4).

Numerical simulations are conducted under two blowing ratios (i.e. 0.5 and 1) and a fixed cross-flow Reynolds number (Re_c = 100,000) with a verified turbulence model.

It is shown that at low blowing ratio, reducing the distance increases the film cooling effectiveness but keeps the trend of the effectiveness unchanged, while at high blowing ratio, the characteristic is a little bit different in the range of 0 = x/D = 10.

These features could be explained by the fact that shrinking the distance between the hole and side wall induces a much smaller reserved region and vortex downstream the ribs and a lower resistance for cooling air entering the film hole. Furthermore, the spiral flow inside the hole is impaired.

As a result, the kidney-shaped vortices originating from the jet flow are weakened, and the target surface can be well covered, resulting in an enhancement of the adiabatic film cooling performance.

The purpose of this study is to enhance the thermal performance in the labyrinth channel by different ribs shape. The labyrinth channel is a relatively new cooling structure to decrease the temperature near the trailing region of gas turbine.

Based on the geometric similarity, a simplified geometric model is used. The k − ω turbulence model is used to close the Navier–Stokes equations. Five rib shapes (one rectangular rib, two arched ribs and two trapezoid ribs) and five Reynolds numbers (10,000 to 50,000) are considered. The Nusselt number, flow structure and friction factor are analyzed.

Nusselt number is tightly related to the rib shape in the labyrinth channel. The different shapes of the ribs result in different horseshoe vortex and wake region. In general, the arched rib brings the highest Nusselt number and friction factor. The Nusselt number is increased by 15.8 per cent compared to that of trapezoidal ribs. High Nusselt number is accompanied by the high friction factor in a labyrinth channels. The friction factor is increased by 64.6 per cent compared to rectangular ribs. However, the rib shape has a minor effect on the overall thermal performance.

This study is useful to protect the trailing region of advanced gas turbine.

This paper presents the flow structure and heat transfer characteristics in a labyrinth channel with different rib shapes.

This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing.

Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed.

It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance.

The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.