Rib Arrangements Research Articles

Thermal-hydraulic performances and characteristics of hierarchical rib arrangements in serpentine cooling channels

Thermal-hydraulic performances and characteristics of hierarchical rib arrangements in serpentine cooling channels

Influences of submerged V-broken rib geometry on the hydrothermal performance of vortex and engulfment flow regimes within a T-channel

The current research presents a three-dimensional numerical study of detailed hydrothermal performance in a T-channel fitted with staggered V-broken ribs under laminar vortex and engulfment flow regimes (Re = 50 to 250) using CFD software tool FLUENT. Comprehensive parametrical investigations are executed to probe the influences arising from the geometrical parameters alterations of the V-broken ribs on the flow field and convective heat transfer characteristics in T-channel. A set of geometrical parameters involving, the orientation rib angles (θ = 30°, 45°, 60°), the pitch-to-outlet-channel width ratio (p/Wo = 1, 1.5, 2), the length-to-outlet-channel width ratio (l/Wo = 0.5, 0.75, 1), the height-to-outlet-channel height ratio (h/Ho = 0.2, 0.3, 0.4), and the staggered inclined rib arrangements (forward, backward, and mixed), are considered. With regard to all examined geometrical parameters, the presence of staggered V-broken ribs consistently enhances fluid mixing and convective heat transfer performance as compared with that without ribs. In addition, the findings illustrate that the V-broken ribs mounted on the bottom wall of the T-channel have approximately the same PEC at 45° and 60° orientation angles with a PEC of 2.23 at Re = 250. At Re = 250, the PEC improves by 40 % and 53 % in comparison to the standard T-channel for the 2 cm and the 4 cm of longitudinal pitch, respectively. Regarding, V-broken rib lengths of 1.5 cm and 1 cm, PEC shows similar trend and eventually reaches double, while the PEC for a 2 cm rib length is smaller than that of 1 and 1.5 cm. The results also exhibit that the smaller rib height of 2 mm gives higher PEC, approximately 2.15, in comparison to 3 mm and 4 mm. Finally, the backward V-broken rib arrangement provides the best PEC of the T-channel, around 2.42.

Topology optimization of regenerative cooling structures under high Reynolds number flow with variable thermo-physical properties

In the design of thermal protection system for hypersonic vehicles, the efficient convective heat transfer within regenerative cooling channels plays a critical role in maintaining their thermal performance. This study focuses on the topology optimization (TO) of the cooling channels that operate at high Reynolds number and have variable thermo-physical properties. A novel approach is introduced to enhance the density-based method by incorporating an effective artificial force correction and tabulating the temperature-dependent thermal properties. Several topology-optimized cooling layouts were generated to minimize the maximum temperature within the design domain while considering different power dissipation constraints. This confirms the validity of the proposed lumped correction term in momentum equation accounting both viscous and convective body forces. Regarding the thermal performance of the optimized layouts, the staggered arrangement of cellular ribs in the TO channel was found to induce multiple flow separations and promote turbulent mixing, thereby improving heat transfer efficiency and mitigating the thermal acceleration effect. Conjugate heat transfer calculations revealed that the optimal topology-optimized channel achieved a 24.3% improvement in overall thermal performance while being 15.3% lighter than the straight channel design. Furthermore, the optimal topology optimized layout consistently outperformed the straight channel design by 6.6% to 24.3% in terms of the overall thermal performance across a wide range of heat flux distribution and mass flow rate conditions. This investigation highlights the effectiveness of topology optimization in designing regenerative cooling structures featuring high Reynolds number hydrocarbon thermal fluid flow.

A comprehensive review of rectangular duct solar air heaters featuring artificial roughness

Abstract Solar air heaters (SAHs) are widely used solar thermal systems with applications in diverse sectors. However, its effectiveness is restrained by low convective heat transfer (HT) coefficients at the absorber plate, leading to inefficient HT, and the elevated temperature of the absorber plate causes significant heat losses, reducing thermal efficiency. This study addresses these challenges by introducing ribs or roughness on the absorber plate creating turbulence in the airflow, resulting in significant improvements. The research investigates various rib configurations, the influence of rib parameters, performance methods, and arrangements to evaluate their HT and friction characteristics. Among these rib configurations, a comparative analysis is done on various factors such as the Nusselt number ratio, thermal enhancement factor, friction factor ratio, and thermal efficiency to optimize distinct roughness parameters and rib arrangement patterns. This study also provides valuable recommendations from existing literature, offering insights into the effective design, prospects, and implementation of SAH systems.

Effects of turning vane on flow control and heat transfer in ribbed two-pass channel with varied rib patterns

Faced with the escalating cooling requirements of turbine blades, two-pass channels with ribs on the internal surfaces have been extensively employed to enhance internal wall heat transfer. Considering the potential to mitigate flow separation and pressure losses generated by channel curvature, in this study, a computational fluid dynamics approach based on the realizable k-ε turbulence model is employed to explore the effects of turning vane introduction on the flow and heat transfer characteristics of two-pass channels with varying rib configurations. The rib configurations are identified as NN, NP, PP and PN. “N” denotes the ribs rotated 45° clockwise relative to the flow direction, while “P” denotes the ribs rotated 45° counterclockwise. The results indicate that the introduction of turning vanes improves the flow uniformity in the downstream channel of the two-pass channel with N-patterned upstream ribs, enhancing inter-rib heat transfer in the downstream channel. It also strengthens the heat transfer performance at the bend region of the two-pass channel with P-patterned upstream ribs. Furthermore, the introduction of turning vanes results in a decrease in friction loss factor for two-pass channels with various rib arrangements at varying levels of Reynolds numbers. The reduction is more pronounced in the two-pass channel featuring N-patterned upstream ribs, with a maximum decrease of 18.6 %. In contrast, the decrease is only 5.2 % in the PP-patterned rib channel. Additionally, the thermal performance factor of NP-patterned and NN-patterned rib channels increases by 8.5 % and 8.7 % respectively after the insertion of turning vanes. However, the enhancement is limited in the PP-patterned and PN-patterned rib channels.

Aerodynamic optimization of high-rise building with façade ribs through CFD-based multi-objective optimization algorithm

Façade appurtenances is an effective aerodynamic optimization measure for alleviating the wind loads on high-rise buildings in modern cities, while the optimized layout of façade ribs necessary for practical engineering remains unclear. The conventional method through numerical simulations and wind tunnel tests can only obtain limited optimal schemes of ribs, the optimization process is time-consuming and laborious, an optimization algorithm can be used to effectively evaluate the optimal arrangement of façade ribs. In present study, a multi-objective optimization procedure coupling large eddy simulation (LES), back propagation neural network (BPNN), and non-dominated sorting genetic algorithm (NSGA-II) is applied to evaluate the optimal arranged parameters of façade vertical ribs. The optimization procedure can quickly identify the optimal location parameter b and extensional depth d of façade ribs that producing minimum wind loads acting on building and ribs. The findings indicate that there are complex non-linear relationships between the ribs arrangement parameters and the objective wind loads. The mean drag C‾d and fluctuating lift C'l of models of windward ribs and upstream sidewall ribs have opposite trend. The relationships between wind forces and arranged parameters of the downstream sidewall and leeward ribs are relatively complicated due to the vortex shedding. Genetic algorithm NSGA-II can effectively evaluate the optimal trade-off solution among multi-objective wind loads. The ranges of optimal layout parameters b/D and d/D are 0.14–0.17, 0.073–0.077, the ratio of b/d is about 2, and the optimal arrangement of façade ribs well balances the total wind forces on the model and wind forces on the ribs. The 3D numerical simulations demonstrate that the optimal layout of the ribs can considerably improve the flow structure and wind load, the maximum reduction ratio of the C‾d and C'l are achieved 25 % and 56 %, respectively. The obtained optimized layout parameters can provide reference for engineers when actually using the facade ribs.

Effects of bidirectional rib arrangements on turbulent flow structure and heat transfer characteristics of a two-pass channel for turbine blade internal cooling

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 TEFo and TEFs respectively.

Experimental and numerical investigation of jet impingement cooling onto a rib roughened concave internal passage for leading edge cooling of a gas turbine blade

Considered is thermal protection of the concave surface within an internal passage, which models the leading edge cavity of vanes or blades of stationary or aero engine gas turbines. Included along the internal surface are different arrangements of V-shaped ribs to further augment surface cooling heat transfer rates. Impingement jets are employed for the cooling, which are configured so that associated cooling air exits the cavity through a crossflow outlet and an array of staggered film cooling holes. The curved part of the asymmetric, concave target plate features a constant radius and connects to straight lines on the pressure and suction sides. Addressed are H/Djet values of 2.7 and 4.0, and Reynolds number Re values of 18,000, 24,000, and 30,000. A maximum crossflow configuration is utilized wherein the coolant flow exits the cooling passage through the film cooling holes and from one end of the passage, as the opposite end is blocked. Different surface configurations are investigated, including 4 V-ribs in four different positions, 8 V-ribs in one position, and a smooth surface of the leading edge cavity. Each V-rib geometry consists of a regular V-rib pointing upstream. A transient thermochromic liquid crystal (TLC) technique is employed to obtain spatially-resolved surface heat transfer data on the internal wall of the leading edge cavity. Resulting experimental heat transfer data are used to validate and verify CFD simulations. Employed for this purpose are steady-state 3D RANS simulations obtained using the OpenFOAM Version 7 numerical code with a kω-shear-stress-transport (SST) turbulence model. Experimentally-measured surface Nusselt number results indicate significant local enhancements adjacent to rib wakes, provided local crossflow velocity values are substantial. Local surface Nusselt number enhancements thus depend upon rib position, but local surface heat transfer increases are most strongly tied to magnitudes of local crossflow velocity. In contrast to these experimental results, CFD simulation results do not show significant variations as rib position is altered. The best thermal performance is associated with 4 V-rib arrangements in two positions, and 8 V-ribs in one position.

Multi-objective optimization of a hybrid nanofluid jet impinging on a microchannel heat sink with semi-airfoil ribs based on field synergy principle

With the increasing power density of electronic devices, improving the cooling performance of their heat sinks is an important aspect of heat transfer enhancement research. A novel jet impinging microchannel heat sink with semi-airfoil ribs (JIMCHS-SAR) is proposed. Hybrid Cu-Al2O3/H2O nanofluid is adopted as the coolant. Using the field synergy principle, the flow and heat-transfer characteristics of the hybrid nanofluid impinging on the JIMCHS-SAR are investigated by both single-factor analysis and multi-objective optimization. The effects of jet Reynolds number and hybrid nanoparticle concentration on the optimized JIMCHS-SAR are also evaluated. The results show that a bilateral symmetrical arrangement of the semi-airfoil ribs provides the best thermal resistance and the smallest field synergy angle. Using the optimal structural parameters of the JIMCHS-SAR obtained from multi-objective optimization can significantly improve its overall performance. The thermal resistance and pump power of the optimal JIMCHS-SAR are 1.080 K/W and 0.387 W, respectively. The maximum temperature of the JIMCHS-SAR bottom surface is 8.1 K less than that for a jet impingement microchannel flat plate heat sink. As Reynolds number increases from 6000 to 14,000 and hybrid nanofluid volume fraction increases from 0 to 2.0 %, the thermal resistance decreases from 1.185 K/W to 0.908 K/W, a decrease of 23.4 %, while the pump power increases from 0.22 W to 2.1 W, a nearly 10-fold increase.

Digitally Aided Analysis: A New Reading of the Cloister Vaults at Norwich Cathedral

ABSTRACT This article offers a new approach to analysing the medieval vaults of Norwich cathedral cloister, which at first appearance seem to be of a consistent design, yet detailed inspection and analysis reveals this not to be the case. Whilst previous scholars have recognised the presence of inconsistencies, their focus has been on chronology, patronage as well as the iconographic programme of the extraordinary range of sculpted bosses. Our approach is based on accurate digital surveying and analysis methods and comparison with similar data obtained from other sites. This enables us to understand the design of the cloister vaults in plan, including bay proportions and the nuances of the tierceron star arrangement of ribs. We then employ a representation technique termed the ‘middle plan’ to identify and analyse specific design runs and their breaks in a greater level of detail than previously achieved, including analysis of geometric data to explain different processes that were likely used to create the curvatures of individual ribs. In doing so, we have identified methods not previously described, which reveal the inventiveness of medieval masons faced with a series of complex constructional issues and enabling them to achieve a range of visual effects.

Performance evaluation and enhancement of turbulent flow and convective heat transfer characteristics for turbine blade internal cooling

For turbine blade internal cooling, the performance of turbulent flow and convective heat transfer in the cooling channel is numerically investigated via the computational fluid dynamics method, where the cooling channel adopts the combination of transverse rib arrangements and round-edged rib configurations or the combination of oblique rib arrangements and round-edged rib configurations. Under these two combination conditions, the simulation result shows that in the wide Reynolds number range of Re = 20 000–80 000, the heat transfer enhancement and the flow loss reduction, such as the larger normalized Nusselt number of Nu/Nu0 and smaller normalized friction factor of f/f0, are simultaneously realized by the oblique rather than transverse rib arrangement. In the oblique rib channel, the relationship between turbulent flow and convective heat transfer is for the first time revealed by the relationship between secondary vortices and turbulent kinetic energies. Based on the relation between secondary vortices and turbulent kinetic energies, the overall performance of turbulent flow and convective heat transfer for the oblique rib channel is first optimized by various normalized rib height, e/Dh, and rib spacing, p/e, and then evaluated by both overall performance factors of OPT1 and OPT2. Both OPT1 and OPT2 are larger at e/Dh = 0.062 and p/e = 15.00 in the wide range of e/Dh = 0.047–0.101 and p/e = 10.00–15.00. As a result of the comprehensive evaluation of OPT1 and OPT2, the combination of e/Dh = 0.062 and p/e = 15.00 is eventually employed by the oblique rib channel.

Numerical investigation and parameter optimization on a rib-grooved liquid-cooled plate for lithium battery thermal management system

To increase the effectiveness of liquid-cooled battery thermal management systems (BTMS) in electric vehicles, a unique liquid-cooled plate with a discrete, inclined, and alternating arrangement of ribs and grooves inside the plate was invented during this study. A numerical study was carried on to analyze the thermal performance between this rib-grooved liquid-cooled plate and a conventional straight-channel one. Firstly, a battery module's 1D/3D electrochemical-thermal coupled model was constructed to analyze the thermal performance in the case of actual electrochemical heat production. Then numerical results were obtained by solving this coupled model with different plates. The results indicated that ribs effectively equalize the flows between different channels and multiple longitudinal swirl flows are formed due to grooves, which improves the liquid-cooled system's temperature control performance with a small increase in pressure drop. The maximum battery temperature is 0.74 °C lower, the temperature standard deviation of the contact surface is 0.18 °C lower, and the pressure drop is 55.37 Pa higher in the BTMS with the rib-grooved liquid-cooled plate than it is in the conventional one. After that, an orthogonal design of experiments was used to investigate the effect of four features, including rib-groove tilt angle, column spacing, row spacing, and rib-groove length, on the thermal performance and energy consumption of the battery module. The optimum structure of the rib-grooved liquid-cooled plate is obtained through range analysis: the rib-groove inclination angle is 45°, the row spacing is 13.5 mm, the column spacing is 11.5 mm, and the rib-groove length is 9 mm. This research on the rib-grooved liquid-cooled plate offers a fresh concept that considerably enhances its capacity to regulate the temperature of the liquid-cooled BTMS.

Effect of cylindrical ribs arrangement in the cavity region of the microchannel heatsink with a fan-shaped cavity

Fan-shaped cavity microchannel heatsink with the combination of ribs is an effective configuration to dissipate large amounts of heat at the expense of lower pressure drop. However, the most effective location of circular ribs within a fan-shaped cavity which enhances the performance of a microchannel heat sink is still unknown. In this work, seven different structural units based on the ribs location in the cavity region such as ribs at the front of the cavities (RFC), at the back (RBC), at the centre (RCC), at the front and back (RFBC), at the left (RLC), at the right (RRC) and at the left and right (RLRC) are analysed for the range of Reynolds number from 100 to 500 and the results are compared with the microchannel with fan-shaped cavity only (MHFC) and plain rectangular microchannel heat sink on the basis of Nusselt number, interface temperature, pressure drop and performance factor. A notable finding of this study is identifying a rib as a disruption leading to the splitting of flow into two streams towards the arcuate region of the cavity and results in the enhanced mixing of the mainstream flow and the trapped fluid in the arcuate region. The maximum Nusselt number is exhibited by the RFBC with an increment of about 19% relative to the conventional centre location of the ribs in the cavity (RCC). At a lower Reynolds number, the Nusselt number of RLRC is lower than RCC and RBC however at Re > 300, the Nusselt number of RLRC is nearly equal to RCC whereas the minimum Nusselt number is associated with RRC and RLC among the microchannels having cavities and ribs. Along with the highest Nusselt number the largest value of pressure drop is also associated with RFBC whereas minimum pressure drop is accompanied by RRC and RLC.

Flow and heat transfer performance of microchannel heat sinks with circular concave cavities and ribs for water cooling LEDs

ABSTRACT The poor heat dissipation of LED light sources limits their applications in plant factories. This paper combines a microchannel heat sink (MHS) with circular concave cavities and ribs with the water irrigation system of an LED plant factory to develop water-cooled LEDs. By using this approach, four types of MHSs were designed: circular concave cavities (circular), circular concave cavities and single-sided ribs (circular-single), circular concave cavities and odd-symmetric ribs (circular-odd), and circular concave cavities and double symmetric ribs (circular-double). The influence of the arrangement of circular concave cavities and ribs on the flow and heat transfer performance was numerically investigated by ANSYS Fluent 21.0 R1. Corresponding MHSs with circular concave cavities and ribs were manufactured, and an experimental platform was built to experimentally verify the numerical results. The results showed that a circular concave cavity in the microchannel caused the fluid to form a secondary flow, which led to the continuous destruction and reconstruction of the flow and thermal boundary layer in the microchannel. This contributed to heat and mass transfer, while the presence of ribs altered the flow direction of the fluid and enhanced mass and heat transfer within the cavities. The pressure drop at the inlet and outlet of the MHS increased in the case of circular concave cavities and ribs as the inlet flow rate increased. Compared with MHSs with circular concave cavities, the ribs increased the pressure drop at the inlet and outlet. The inlet and outlet pressure drop of MHS with circular concave cavities and double-symmetric ribs was the highest, followed by MHS with circular concave cavities and odd-symmetric ribs, and the smallest was the MHS with circular concave cavities and single-sided ribs. As the inlet flow rate increased from 10 ml/min to 60 ml/min, the pressure drop between the inlet and outlet of the MHS with circular concave cavities increased from 22.54 Pa to 165.98 Pa (an increase of 143.44 Pa); the pressure drop of the MHS with circular concave cavities and single-sided ribs increased from 24.72 Pa to 187.31 Pa (an increase of 162.59 Pa); the pressure drop of the MHS with circular concave cavities and odd-symmetric ribs increased from 27.92 Pa to 212.12 Pa (an increase of 184.20 Pa) and that of the MHS with circular concave cavities and double symmetric ribs increased from 29.32 Pa to 221.21 Pa (an increase of 191.89 Pa). Under the same inlet flow rate and LED chip input power, the cooling water outlet temperature of MHS with circular concave cavities and double symmetric ribs was the highest, followed by MHS with circular concave cavities and odd-symmetric ribs, MHS with circular concave cavities and single-sided ribs, and MHS with circular concave cavities was the lowest. These results indicated that the heat transfer performance of MHS with circular concave cavities and double-symmetric ribs was the best, followed by MHS with circular concave cavities and odd-symmetric ribs, and MHS with circular concave cavities and single-sided ribs. The MHS with circular concave cavities had the worst heat transfer performance. The outlet temperature of the MHS with concave cavities and ribs reaches the highest value at the inlet flow rate of 30 ml/min. At this flow rate, the outlet temperature is 343.89 K for the MHS with circular concave cavities, 344.73 K for the MHS with circular concave cavities and single-sided ribs, 346.53 K for the MHS with circular concave cavities and odd-symmetric ribs; and 347.58 K for the MHS with circular concave cavities and double symmetric ribs.

Heat transfer enhancement of return channel by using rib turbulator for a new impingement cooling scheme

Impingement cooling method is widely applied to leading edge of turbine blade to ease thermal load. However, spent jet always develops into crossflow, which weakens cooling efficiency by deflecting the impingement direction of jet. An innovative impingement cooling structure can suppress the crossflow effect by drawing spent jet into return channel through return holes. This study further improves the heat transfer capability of the structure by introducing ribbed sidewall to the return channel. The effects of rib arrangements are investigated as the Reynolds number increases from 5000 to 15,000. The flow field and the heat transfer performance of the structure are analyzed numerically. The BSL turbulence model is utilized to conduct the simulation. The numerical results indicate that the ribs have a positive effect on improving heat transfer performance. The ribs disturbs the original flow in the return channel and increase the total pressure loss. The average Nusselt number on the sidewall of the return channel in the case with the optimal rib arrangement in this study is increased by 5.4% ∼ 10.4% compared to baseline value as the jet Reynolds number rises.

Thermal management for multi-cores chips through microchannels completely or incompletely filled with ribs

Microchannels have attracted significant attention in the thermal management of integrated circuits due to their small geometrical size and high heat transfer efficiency. Motivated by further improving the thermal management capacity of microchannels in multi-cores chips with lower pressure drop penalty, in this paper, a comparative investigation on four different configurations was conducted through numerical simulation for the Reynolds number ranging from 200 to 800 to analyze the comprehensive effects of filling mode and rib arrangement on the flow and heat transfer characteristics, including microchannel completely filled with aligned ribs (MCFAR), microchannel incompletely filled with aligned ribs (MIFAR), microchannel completely filled with staggered ribs (MCFSR) and microchannel incompletely filled with staggered ribs (MIFSR). Moreover, the entropy generation rate is used to estimate the irreversibility of flow and heat transfer based on the second law of thermodynamics. Finally, the performance evaluation criteria (PEC) is adopted to estimate the overall performance. The results show the flow patterns in the MIFAR and the MIFSR are different from those in the MCFAR and the MCFSR due to the incomplete filling mode, which could induce more dramatic disturbance and further break the downstream boundary layer, thus the heat transfer could be enhanced with a lower pressure drop penalty. The analysis of entropy generation rate indicates that entropy generated by heat transfer contributes the majority of the total entropy generation thus enhancing the heat transfer is a more important and effective approach in reducing the irreversibility. Among the four configurations researched, the microchannel MIFAR shows the best overall performance (PEC = 1.76) when Re = 400.

An extensive review on use of CFD simulation technique for assessment of performance of various rib geometries and arrangements in heated fluid ducts

An extensive review on use of CFD simulation technique for assessment of performance of various rib geometries and arrangements in heated fluid ducts

A COMPARATIVE STUDY OF CHANNEL COOLING ENHANCEMENT BY ANGLED, PARALLEL BROKEN, AND RHOMBUS PATTERNED RIBS

Heating and cooling of fluids play an important role in energy engineering, such as solar air heaters and the internal cooling of gas turbine blades. Heat transfer in the heat exchanger channels can be enhanced by ribs, which will also result in a significant decrease in coolant pressure. In our previous work, a novel bioinspired rib design with a rhombus-shaped pattern was proposed to enhance the channel cooling. The Nusselt numbers and flow characteristics are further compared to angled and parallel broken ribs in this work. It is interesting to find that the proposed channel with decreasing-height rhombus-shaped patterned ribs exhibits the best heat transfer performance. At the same time, the Nusselt number and friction factor are related to the Reynolds number in the studied range. The surface with rhombus-shaped patterned ribs shows greater thermal performance factors than that with angled ribs, while the surface with a decreasing-height rib arrangement has the highest thermal performance factor due to a better Coanda effect. This work confirms that the proposed ribs with decreasing height rhombus-shaped patterns are effective for enhancing the internal cooling of the channel.

Modeling of pressure losses in a cylindrical duct with rectangular ribs

AbstractIn order to improve the thermal performance of heat exchangers and air collectors, we insert various forms of artificial roughness, known as ribs, into the useful duct. These ribs promote the creation of turbulent flows and enhance heat transfer by conduction, convection and radiation.However, the introduction of these ribs leads to an increase in pressure drop, requiring higher mechanical power to pump the heat transfer fluid. This experimental study focuses on estimating, using empirical approaches, the pressure losses induced by rectangular ribs with an inclined top. The ribs are made from 0.4 mm galvanized sheet steel.An experimental set-up was designed to measure the head losses generated by the ribs, from the point of entry to the point of exit from the useful duct. Using the dimensional analysis method, correlations were established to evaluate head losses as a function of flow regime and rib geometry and configuration (including different geometries for rib arrangement over the configuration area).

Numerical research for the influence of cylindrical ribs and inclined mainstream on double wall cooling configurations

Gas turbine operates in high temperature environment, cooling technologies are applied for reducing the temperature of turbine blade, double wall cooling configuration is an effective cooling method. This paper proposed an investigation on double wall cooling configurations by computational fluid dynamics (CFD). Different cylindrical ribs were arranged on the different plates. Their cooling performances and flow field were analyzed, what's more, new rib arrangement, hole arrangement and spacing arrangement were proposed in the base of original arrangement, their cooling performances were compared. Finally, inclined mainstream is added for simulating gas impacting the inclined blade surface in real engine condition, the inclined angles were 30°, 45°, 60°. According to the results, ribs brought limit influence on the cooling effectiveness. More holes consumed extra 54 % coolant but only increase cooling effectiveness by 15 % under high blowing ratio. The inclined mainstream decreases cooling effectiveness by 67 % maximally. Under low coolant flow rate, cubic polynomial describes the correlation between cooling effectiveness and inclined angle, and under high coolant flow rate, linear polynomial is more suitable. Besides, offset arrangement shows better cooling performance under the inclined mainstream.