Rib Height Ratio Research Articles

Energy, Exergy, environmental and economic based experimental investigation of solar air heater using a novel arc rib geometry

To enhance the thermal efficacy of solar air heaters, the most efficient method is to disturb the viscous layer by roughening the surface using the artificial rib. In this research, a discrete apex-down arc-shape rib geometry on a roughened plate is used to examine the energy-exergo and economic- environmental based performance of solar air heater. By changing the Reynolds number from 3000 to 14,000 and maintaining a gap width to rib height ratio of 4, a relative height rib ratio of 0.045, and a pitch to rib height ratio of 10, the effects of arc rib angles of 30, 45, and 60 degrees are studied. The environmental exergy loss was determined to be substantial, between 70 % and 80 %. Maximum system to air exergy loss occurs at Reynolds number of 3000 with 5.64 W. At a temperature parameter of 0.0377 m2K/W, both the thermal and exergetic efficiencies are at their highest, at 77.60 % and 3.81 %, respectively. In comparison to a plate having a plain surface, the suggested apex-down discrete arc rib performs better based on energy payback time, usable yearly energy, and enviro-economic criteria. Finally, at rib angle of 30°, the conditions that optimize the heat transfer and energy payback time, energy cost, exergo-economic, and enviro-economic characteristic of the current artificially roughened geometry of solar air heater.

Numerical investigation of different transverse Rib shapes on thermal convection in a channel filled with nanofluid

With the growing interest in energy optimization, corrugated surfaces are arguably an excellent choice, finding applications in areas as diverse as heat exchangers, automobiles, building energy efficiency, and chemical reactors. However, due to the poor thermal properties of conventional fluids, heat transfer is limited. The introduction of nanoparticles into fluids is a promising solution to improve their thermal performance. This paper does a detailed numerical analysis of how different factors affect the forced convection heat transfer in a two-dimensional ribed channel. The shape of the ribs is one of the factors that are looked at, along with some new parameters like e/H, which is the ratio of rib height to channel height, and L2/P, which is the test section to the pitch between the ribs. The aim is to determine the optimum geometry that maximizes the Nusselt number while minimizing the pressure drop. The study also examines the effects of nanoparticle type and concentration on heat transfer and fluid flow characteristics. To this end, the continuity, momentum, and energy equations were solved with the finite volume method using the SIMPLE scheme with the k-ε turbulence model at different Reynolds numbers ranging from 4000 – 14,000. The results indicate that triangular ribs with ratios e/H = 0.15 and L2/P = 4 increase the Nusselt number by 63.3 % while reducing the pressure drop by 22 % compared with the other cases. The improvement in heat transfer in the water-SiO2 case was the greatest compared with the other nanofluids tested. Particle size fraction and Reynolds number increased the Nusselt number in ribbed channels by 20.7 % compared with water.

Preparation of Aluminum-Based Superhydrophobic Surfaces for Fog Collection by Bioinspired Sarracenia Microstructures.

Freshwater shortage is a growing problem. Inspired by the Sarracenia trichome fog-trapping and ultrafast water-transport structure, a series of hierarchical textured surfaces with high-low ribs with different wettabilities was prepared based on laser processing combined with dip modification. Through fog-collection performance tests, it was found that the samples with superhydrophobicity and low adhesion had the best fog-collection effect. In addition, it was observed that the fog-collection process of different microstructured samples was significantly different, and it was analysed that the fog-collection process was composed of two aspects: directional condensation and directional transport of droplets, which were affected by the low ribs number and rib height ratio. A design parameter was given to create the Sarracenia trichome-like structure to achieve a fast water transport mode. This study provides a good reference for the development and preparation of fog-collection surfaces.

Numerical study of cooling performance and flow characteristics of film hole-broken rib composite structure with squealer tip

The gas turbine blade tip might face substantial heat loads because of leakage flow between the blades and the casing. For blade tip cooling, a composite cooling structure with film holes and broken ribs is first used on GE-E3 blade in this work. The flow and cooling characteristics of the innovative structure are studied by numerical simulation under various blowing ratio (BR) conditions. Meanwhile, the impact of modifying both the rib angle and the rib height on the adiabatic film cooling effectiveness (AFCE) at the tip of the squealer is analyzed. According to the results, adding rib structures to the squealer tip can effectively regulate the paths of cavity vortices and kidney-shaped vortex pairs (KVP) at the tip. As a result, the averaged AFCE at the blade tip is improved. The notch pressure-side broken rib structure has good aerothermal performance, and the highest AFCE at BRs of 0.50, 1.00, and 1.50 basically occur under the “R60-100 %” condition (R60 refers to the rib structure of 60°, and 100 % is the ratio of rib height to notch depth), and the corresponding AFCE are 27.71 %, 26.00 %, and 32.47 % higher than those of the no-rib case, respectively. The corresponding AFCE increased by 27.71 %, 26.52 %, and 32.47 %, respectively, compared to the no-rib condition. The highest AFCE at a BR of 1.50 occurs at “R75-70 %“, which is a 38.20 % increase in AFCE compared to the no rib case. The improvement in AFCE is due to the difference in the flow of the cooling jets, which are subject to cavity vortices at different BRs. The analysis shows that the addition of ribs disrupts the formation of KVPs and weakens the influence of the cavity vortex, thus reducing the low AFCE region at the lower end of the tip groove and increasing the AFCE. However, due to the blocking effect of the ribs, the pressure loss at the blade tip is elevated. The proposed blade tip cooling structure is expected to provide new ideas for the next generation of advanced gas turbine cooling designs.

Experimental study on bending forming of AZ31 magnesium alloy equal curvature panel

Abstract The process parameters of bending forming for magnesium alloy panel are determined, and magnesium alloy panel bending tools are developed. The experimental research is completed, and several specifications of magnesium alloy panels are processed successfully, without cracks, rib buckling, or rib shoulder collapse defects. During the bending process of the magnesium alloy panel, the press height and rib height ratio have a significant effect on the microstructure of the panel. With the increase of press height and rib height ratio, the grain size decreases. The microstructure and properties of the magnesium alloy panel are improved and grains are refined. When the rib height ratio is 7/2 and press height is 7 mm, the minimum grain size at the rib of the panel is 15.6 µm and the minimum grain size at the skin surface is 17.2 µm.

Flow Performance Enhancement of a Fluidic Oscillator Through the Integration of Rectangular Ribs on Coanda Surface

Abstract Fluidic oscillators utilize internal flow dynamics to produce oscillatory fluid jets. The Coanda surface in the mixing chamber of a fluidic oscillator plays a critical role by facilitating controlled fluid manipulation through flow attachment and redirection. The mixing chamber pressure drop, jet oscillating frequency, and deflection angles are hence dependent on the geometry of the Coanda surface. In this study, the Coanda surface is modified by using rectangular ribs of different aspect ratios. The effects of ribbed Coanda surface on oscillating jet characteristics are computed numerically through two-dimensional unsteady Favre-averaged Navier–Stokes equations. The aspect ratio (ARribs), the ratio of rib height to rib base, is varied from 0.64 to 1.56 and air is used as a working fluid. An increase in the ARribs increases the jet oscillation frequency. The highest aspect ratio achieves an oscillation frequency of 820 Hz, contrasting with 355 Hz for the smooth case. On the other hand, the jet deflection angles are decreased as the aspect ratio increases. Interestingly the introduction of the ribs on the Coanda surface decreased the pressure drop in the oscillator. A decrease in pressure drop of 22% for an aspect ratio of 1.56 was achieved as compared to the smooth case. These results are attributed to the influence of the ribs on the formation of a separation bubble formed in the mixing chamber. The jet performance parameter, frequency-deflection-pressure ratio, was found to be 43% higher for ARribs of 1.56 as compared to the smooth case.

Numerical investigation of fluid flow and heat transfer characteristics of MWCNT-Al 2 O 3/H 2 O hybrid nanofluid flowing through a novel semi-arc ribbed square duct

This study carried CFD analysis to study the fluid flow and heat transfer characteristics of MWCNT- Al 2 O 3 / H 2 O hybrid nanofluid flowing through square duct equipped with novel semi-arc ribs. The turbulent flow simulations are performed at varying Reynolds numbers ( Re ) between 3,000 and 18,000 and nanoparticle volume concentration ( φ ) range of 1–4% for different rib parameters, namely relative stream pitch ratio ( X pr ) range from 2.67 to 3.67, Rib height ratio ( R hr ) range from 0.05 to 0.20, number of ribs ( n ) range from 1 to 4. Different performance indicators, such as Nusselt number ( Nu ), friction factor ( f r ) , and thermal hydraulic performance (THP) was examined to evaluate the system performance. The RNG k ‐ ε model was engaged to simulate turbulent nanofluid flow within the channel under constant temperature condition (T = 300 K). The findings indicated that the development of vortex flow and increased turbulence due to the effects of arcs can improve the heat transfer enhancement. The THP, Nu and f r were found to be highest for R hr = 0.15 , X pr = 3.34 , φ = 4 % , and n = 3 , yields to the best THP at 1.94.

Numerical Study on Flow Field and Heat Transfer Enhancement in a Cooling Channel With Novel Ribs Based on Battery Thermal Management System

Turbulent flow and heat transfer characteristics in a cooling channel with novel ribs have been numerically studied to improve thermal efficiency inside future electric vehicle batteries. In this study, the essential ratios of channel length, rib height, and rib pitch were all set to 6.67, 0.13, and 8.66, respectively. The realizable turbulent kinetic energy - epsilon model was used for the numerical simulation work under the Reynolds number varied from 10,000 to 50,000. The results showed that the heat transfer enhancement on a surface depended on the secondary flows due to the ribs. The enhancement of the wavy-winglet rib was approximately 9.8%−32% compared to other rib cases. Nevertheless, the improved heat transfer came at the expense of a higher pressure penalty. Above 29.7% of the friction factor for the wavy-winglet rib was obtained, compared to orthogonal ribs. In addition, the wavy-winglet rib gave the best thermal-hydraulic performance of the designs explored.

Experimental Study for the Enhancement of Thermal Efficiency and Development of Nusselt Number Correlation for the Roughened Collector of Solar Air Heater

Abstract The solar air heater’s thermal efficiency is relatively poor owing to the flat collector surface. This article’s primary objective is to increase the collectors’ thermal efficiency of rectangular ducts of solar air heater by adopting a novel V-shaped twisted rib element with staggering orientation. Experimentations are performed for various flow Reynolds numbers ranging from 3 k to 21 k, roughness pitch-to-rib height ratio ranging from 7 to 11, and staggering distance-to-rib height ratio between 2 and 6. Dispersion of Nusselt number over the collector surface is achieved through the liquid crystal thermography technique. Among the varied rib and flow constraints, it is observed that a maximum thermal performance enhancement index of 2.69 is observed, with the optimum value of the roughness parameter at a rib pitch-to-height ratio of 9 and a staggering distance-to-height ratio of 4. Mathematical correlation has also been developed using a regression model to estimate the Nusselt number in terms of non-dimensional roughness parameters. The percentage deviation between the Nusselt number attained from established relationships and the investigational results is found to be giving very satisfactory outcomes. The thermal efficiency of the smooth surface is recognized at 41.64% which increases for the roughened surface of twisted V-ribs to 73.63%. Hence employing twisted V-ribs as an artificial roughness element no doubt increases the Nusselt number, thermohydraulic performance enhancement index, and thermal efficiency, but it also exerts less frictional power of solar air heater.

Air Bubble Effect on Heat Transfer Enhancement in 90° Ribbed Parallel Channels Based on Photovoltaic-Thermal Collector Cooling

The effect of entrained air bubbles on heat transfer enhancement inside 90° ribbed parallel channels has been experimentally studied to improve electrical efficiency inside future solar panels. In this work, the Reynolds number was measured from 200 to 600. The essential ratios of channel aspect, rib height, and rib pitch were all set to 0.4, 0.18, and 10, respectively. The volumetric flow fraction for all test conditions varied from 0.0 to 0.5. The overall heat transfer distributions on the surface were captured using an infrared thermography camera. The main finding showed that the average heat transfer rate and the thermal performance gained beyond 25–81% and 7–82% compared with the smooth wall. In addition, the volumetric flow fraction of 0.5 at the Reynolds number of 200 became the best.

Radial envelope forming mechanism and process design method for cylindrical rings with thin wall and high web ribs

Cylindrical rings with thin wall and high web ribs (CRTWHWR) are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field. However, it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins, high web ribs and large size. In this paper, a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high performance. Firstly, the principle of radial envelope forming process is clarified. Then, an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle, i.e., CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single operation. Finally, a reasonable 3D FE model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively revealed. Through the FE simulation and experiments with material of plastic mud, a typical CRTWHWR with diameter of 300 mm, axial height of 192 mm, the maximum rib height of 25 mm, the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed, i.e., the ratio of the maximum rib height to the minimum rib thickness reaches 8.33, the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches 100. The above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.

Thermal behaviors and flow profiles in a square channel fitted with X–V modified ribs: A numerical analysis

A novel design of “X–V rib” turbulators is proposed to improve fluid blending and to perturb thermal boundary layer (TBL) in a heat exchanger (HX) duct. Better fluid blending and more highly disturbed TBL are the two important factors for the improvement of HX performance. Effects of X–V rib geometrical parameters including rib height ratios (b/H = 0.05–0.20), rib arrangements (V-tip pointing upstream called “V-Upstream (VU)” and V-tip pointing downstream called “V-Downstream (VD)”) and rib types (I, II and III) on air stream and thermal mechanisms are numerically investigated in a 3D model. The numerical model is solved with the finite volume method (a commercial code) and a commercial program. Laminar air flow (inlet conditions with Re = 100–2000) is a selected range of the present investigation. Firstly, the created numerical model for the ribbed duct is validated with two significant topics: 1. Plain duct validation and 2. Optimum grid elements (grid independence). The validated results show that the ribbed-duct model has great reliability to simulate air stream and thermal characteristics. According to the numerical results, the disturbed TBL is obviously found in all rib types. Moreover, it is observed that the core flow disturbance occurs and improves fluid blending. The outcomes from the present investigation point out that the knowledge about flow structure and thermal mechanism are important guidelines for the development of vortex turbulators and HX improvement. For the thermal assessments, it is found that the best Nusselt number ratio (Nu/Nu0) is 11.80 for the type III X–V rib with b/H = 0.20 in the VD-direction. Additionally, the maximum thermal enhancement factor within our investigated range is 3.48 at Re = 2000, b/H = 0.20, type II X–V rib in the VU-direction.

Heat transfer mechanism in ribbed twisted-oval tubes

This paper presents the fluid flow and heat transfer mechanisms in ribbed twisted-oval tubes. Simulations were conducted for a uniform heat-flux wall condition in turbulent flow (5000 ≤ Re ≤ 20,000). Optimal conditions were evaluated from the following parameter ranges: rib arrangement (vertical and horizontal); number of ribs, N = 1, 2, 4; rib height ratios, RR = 0.025–0.1; spiral depth ratios, DR = 0.05–0.14 and twist pitch ratios, PR = 1.5–5.0. It was determined that the ribbed twisted-oval tubes generated stronger swirl flow than a conventional twisted-oval tube, indicated by their greater turbulent kinetic energy. With increasing RR, DR and N, the turbulent kinetic energy significantly increased while the opposite trend was observed as PR became larger. The greater turbulent kinetic energy led to better fluid mixing between the core and near wall region, which directly varied with the heat transfer between the two regions. The optimal parameters that provided a maximal thermal performance factor (TPF), 1.32, were PR = 3.5, DR = 0.1, RR = 0.075, N = 4 and Re = 5000.

CFD Investigation of Thermo-hydraulic Performance in Rib Roughened Fin Under Forced Convection

Here, a for the purpose of investigating the thermo-hydraulic performance of, numerical simulation is performed. a fin with rib roughening and induced convection. The next paragraphs give the analysis. If we do numerical simulations under a variety of fluid flow situations and look at how they interact with one another, we might be able to obtain numerical information on the heat transfer and friction caused by a ribbed fin. We would need to examine how they interact in order to do this. There is a broad spectrum of rib pitch to rib height ratios (P/e) that are possible. it was feasible to gather data on fluid flow and temperature distribution in a validated numerical model by raising the Reynolds Number from 500 to 5000. These ratios were used to assess how effectively the model operated. To Charts that are based on the Nusselt Number and the friction factor are used in order to evaluate the thermal and hydraulic characteristics of rib-roughened fins. The findings from the rib roughened fin geometry are compared with those of a plain fin in order to determine the degree of efficiency that the test fin possesses in terms of eliminating heat from its base under operating conditions that are otherwise comparable to those previously described. This analysis was carried out to ascertain the degree of efficacy that the test fin possesses in terms of removing heat from its base. The ribbed fin’s P/e ratio of 6 contributes to the substantial increase in heat transport while also reducing friction.

Design optimization of prismatic rib turbulators in a rectangular channel based on multi-objective criterion

A multi-objective shape optimization of truncated prismatic ribs in a rectangular channel has been performed to optimize simultaneously, heat transfer and pressure loss. The numerical analysis was performed using Reynolds-averaged Navier-Stokes equations with eddy viscosity-based models for turbulence closure. The optimization was performed using multi-objective genetic algorithm technique, and the fitness functions for the objectives were obtained using surrogate modeling. Using literature survey and preliminary parametric analysis, three design variables related to prismatic ribs viz. ratio of rib-height (e) to hydraulic-diameter (Dh) of a rectangular channel, ratio of rib-pitch (p) to rib-height (e), and ratio of rib-height at end (ep) to rib-height at center (e) were selected. The augmentation Nusselt number (FNu) and friction factor (Ff) ratios were chosen as the multi-objective functions for heat transfer and pressure drop, respectively in the rectangular channel. Numerical analysis and multi-objective optimization have been done at fixed Reynolds number, Re = 42,500. Using the proposed optimization framework, Pareto-optimal front design (POD) signifies the trade-off between the obtained objective functions, and among them, five PODs have been chosen using K-means clustering technique. In the paper, results indicated that the POD which offer high blockage effect to the incoming flow lead to high heat transfer performance, but accompanied by greater pressure losses. The blockage effect is discussed using spatial flow and thermal patterns. An optimum design with a relative thermal performance enhancement of 168.60% compared with the reference design is reported.

Effect of Dimpled Rib with Arc Pattern on Hydrothermal Characteristics of Al2O3-H2O Nanofluid Flow in a Square Duct

The present work is concerned with the experimental analysis of the thermal and hydraulic performance of Al2O3−H2O nanofluid flow in dimpled rib with arc pattern in a square duct. The Alumina nanofluid consists of nanoparticles having a size of 30 nm. Reynolds number Renum studied in the square duct range from 5000 to 26,000. The nanoparticle volume fraction (ϕnp) ranges from 1.5% to 4.5%, the ratio of dimpled-arc-rib-height to print-diameter HAD/Pd ranges from 0.533 to 1.133, the ratio of the dimpled-rib-pitch to rib height PAD/HAD range from 3.71 to 6.71 and dimpled arc angle (αAD) range from 35° to 65°. The Al2O3−H2O-based nanofluid flow values of Nusselt number Nurs and friction factor frs are higher in comparison to pure water. The dimpled ribs in the arc pattern significantly improved the thermal-hydraulic performance of the investigated test section. The nanoparticle concentration of 4.5%, the ratio of dimpled arc rib height to print diameter of 0.933, the relative dimpled arc rib height of 4.64 and the dimpled arc angle of 55° deliver the maximum magnitude of the heat transfer rate. The maximum value of the thermal-hydraulic performance parameters was found to be 1.23 for Al2O3−H2O-based nanofluid flow in a dimpled rib with arc pattern square duct for the range of parameters investigated. Correlations of Nurs, frs and ηrs have been developed for the selected range of operating and geometric parameters.

Study on Shear-Lag Effect of Steel–UHPC Ribbed Slab Composite Structures Using Bar Simulation Method

Recently, Ultra-High Performance Concrete (UHPC) has attracted increasing attention in civil engineering. Numerous steel–UHPC composite structures have been constructed around the world. The proper consideration of the shear-lag effect has a significant influence on the safety of structures. In view of the shear-lag effect of steel–UHPC ribbed slab composite structure (SU-RSCS) in the elastic stage, a theoretical calculation model based on the bar simulation method is first developed. Then, the feasibility and accuracy of that are verified using both experimental data and numerical simulation. Moreover, many factors (including width-to-span ratio, the ratio of rib height to UHPC layer thickness, the ratio of rib width to rib spacing, and the number of transverse ribs) are parametrically investigated to further investigate the structural shear-lag effect using the proposed method. In addition, the orthogonal analysis is applied to determine the sensitivity of each parameter to the shear-lag effect. The parametric interactions are also considered. At last, the comparison between calculation results of the proposed method and specifications are discussed. The results show that the proposed approach can accurately predict the shear-lag effect on SU-RSCSs in the elastic stage. It is also found that the width-to-span ratio has a great influence on the structural shear-lag effect, while the number of transverse ribs has no significant influence on that.

Numerical investigation of fluid flow and heat characteristics of a roughened solar air heater with novel V-shaped ribs

Solar air heaters convert clean solar energy into useable heat and thus have a wide range of applications. Computational fluid dynamics (CFD) can aid in the design and development of solar air heaters with optimized thermal efficiency. A detailed numerical study was conducted to investigate the fluid flow and heat transfer characteristics of a roughened solar air heater with novel V-shaped ribs having staggered elements. Three-dimensional steady-state numerical simulations were performed using the k− ε Re-Normalisation Group (RNG) turbulence model, and results were found to be in excellent agreement with experimental data. The effect of rib spacing was studied through varying the rib pitch to rib height ratio P: e = 6–14, for Reynolds numbers (Re) in the range of 4000–14 000. A significant enhancement in the rib-roughened solar air heater's thermal performance was observed. It was also established that an increment in P: e from 6 to 10 increases the Nusselt number (Nu) for all Re values investigated. About 72.6% Nu enhancement was predicted for P: e = 10 at Re = 12 000. It was further observed that an increment in P: e from 10 to 14 decreases the Nu for all values of Re considered.

Jet impingement in a V-rib roughened solar air heater: an experimental approach

ABSTRACT The present research article is an experimental investigation of an impinging jet solar air heater with V-patterned ribs on a modified absorber plate. The study attempts to combine active-passive jet impingement techniques focusing on varying jet parameters and variation in the arrangement of the V pattern. The experimental trials are conducted by varying parameters as follows: streamwise pitch ratio of circular jets X s t / D h d from 0.35 to 0.50, the span-wise pitch ratio of circular jets Y s p / D h d from 0.79 to 0.94, and width ratio of V-patterned ribs w/W from 1 to 6. The geometrical parameter is kept constant, viz. angle of attack (α) = 60°, pitch ratio P/e = 10, and rib height ratio e / D h d =0.043. The range for Reynolds number is kept between 4000 and 16,600, and solar insolation was 1000 W/m2. The results indicated that jet impingement on the ribbed absorber plate enhances thermal and thermohydraulic efficiencies. The maximum reported Thermal-Hydraulic Performance in the present study was 3.301.

Effects of circumferential ribs on suppressing cross-flow and enhancing heat transfer in swirl cooling

This paper proposed a swirl chamber with circumferential ribs to avoid the impacting of cross-flow to jets, thus enhancing the penetration ability of jet and swirl cooling heat transfer intensity. To reveal the mutual effects between jets and cross-flow, the heat transfer features and flow structures under different Reynolds numbers of smooth swirl chamber and novel rib-roughened swirl chambers were studied and compared using 3D steady numerical analysis. The influence of rib height ratio on flow and heat transfer features was investigated further. The investigation revealed that for smooth swirl chamber, the cross-flow seriously weakened the heat transfer intensity. In contrast, the novel rib-roughened swirl chamber had an excellent suppression effect on cross-flow, thus greatly enhancing the penetration ability of jet and strengthening the swirl cooling heat transfer intensity. Under the Reynolds number of 10,500, for smooth swirl chamber, the peak number of circumferentially-averaged Nusselt number decreased from 80 to 58 from the first pitch to the last pitch. While for the case that rib height ratio is equal to 0.5, it increased from 80 to 120. In addition, the suppression effects of circumferential ribs on cross-flow increased when the rib height ratio increased, likewise the heat transfer enhancement effect. When the rib height ratio is less than 0.5, the Nusselt number ratio was larger than the friction factor ratio, while when the rib height ratio is larger than 0.5, the Nusselt number ratio was less than the friction factor ratio. The best thermal performance can be achieved when the rib height ratio was 0.5. Besides, the heat transfer enhancement effect of circumferential ribs was more significant under a higher Reynolds number in the studying range.