Ribbed Side Research Articles

A convection-enhanced flow field with height-changing ribs for redox flow batteries

Serpentine flow fields with flat ribs can effectively improve the performance of redox flow batteries. However, the marginal pressure difference between adjacent channels near the end side of ribs in conventional designs leads to weak convection in the regions, increasing the local concentration overpotential. This problem will be exacerbated in scaled-up redox flow battery stacks due to enlarged under-rib regions near the end side of ribs. In this work, two modified serpentine flow fields with height-changing ribs are proposed to adjust the electrode compression ratio at the under-rib region, thereby enhancing the convection in the electrode near the end side of ribs. Therefore, the active species are distributed more uniformly, resulting in an improved battery performance. Specifically, the uniformity of V2+, the energy efficiency and the system efficiency of the vanadium redox flow batteries with the ramp ribs are improved by 21 %, 2.7 %, and 2.7 % respectively compared with that of the conventional flat ribs, at the current density of 200 mA cm−2, the flow rate of 3.4 mL min−1 cm−2, and the active area of 117 cm2.

Deformation mechanism of gob‐side entry at top coal caving mining face: A numerical study

AbstractTo investigate the significant deformation of the surrounding rock within the dynamic pressure zone of the gateroad, this study utilized the tailgate of the 1506 longwall face in Anyang Coal Mine as the engineering context. A combined approach of field measurement and numerical analysis was employed to explore the deformation and failure mechanisms of the surrounding rock under dynamic pressure. The findings indicate that before the exploitation of the 1506 longwall face, there was a notable reduction in stress across the floor and immediate roof, with minimal stress concentration observed in the coal pillar and the entity rib side. The plastic zone surrounding the tailgate was limited, suggesting a high degree of stability in the entry's surrounding rock. However, during the extraction of the 1506 longwall face, the tailgate, extending 60 m ahead of the working face, was subjected to dynamic pressure, leading to a marked increase in stress within the floor, coal pillar, and immediate roof. Stress concentration was more pronounced on the entity rib side than on the pillar rib side. This resulted in significant fissuring and severe deformation of the entry's surrounding rock. The primary failure mechanism involved damage to both the roof and floor corners, with the severity of damage escalating alongside the stress in the surrounding rock. This culminated in the failure of roof corner bolts and anchor cables, thereby compromising the stability of the entry within the dynamic pressure zone.

Fatigue behavior of orthotropic composite bridge decks without cutout at rib-to-floorbeam intersection

The composite bridge panel consisting of an orthotropic steel deck with no extended cutout at the rib-to-floorbeam (RF) intersection and an ultra-high performance concrete (UHPC) rigid layer was proposed, which can simplify the manufacture process and enhance economic benefit. Refined finite element models were established to analyze the stress response of fatigue-prone details, and the approach of variable thickness rib was proposed to achieve an infinite fatigue life. The effect of critical geometric parameters on fatigue performance of RF joint was further investigated, and the parameter combinations with infinite fatigue life were determined. The results show that the rib-to-deck (RD) joint indicates infinite fatigue life, and the stiffness of panel meets the requirements of specification. There is a significant stress raiser at RF joint, and Dong's structural stress reveals that the surface stress at rib side is dominated by bending stress. The effects of the thicknesses of UHPC layer and deck plate on the stress are not significant. Increasing the thickness of the rib belly as well as decreasing the floorbeam thickness and spacing can reduce the stress range of rib side at RF joint, and the 10 mm thick floorbeam is preferable. The UHPC layer can be 50 mm if the rib with variable thickness is utilized, while the UHPC is required to be 60 mm and the floorbeam spacing is 2.5 m if the rib with uniform thickness is adopted.

Effects of full internal bulkheads on fatigue behaviors of orthotropic steel decks

To investigate the effects of full internal bulkheads (FIBs) set inside the ribs on the fatigue behaviors of rib-to-floorbeam (RF) details, rib-to-deck (RD) details, and cutout details in orthotropic steel decks (OSDs) and determine whether new fatigue-prone details will be produced, a field monitoring test was conducted, and OSD models with and without FIBs were developed. The study found that in the OSD with FIBs, the stress amplitudes of the RF-F (RF weld on the floorbeam side) and RF-W (RF weld at the rib wall) details were significantly higher than those of the RF-R (RF weld on the rib side) detail, which were more prone to fatigue problems. The FIBs combine the floorbeam with the ribs, which can significantly enhance the in-plane stiffness of the ribs and make the floorbeam function as a solid-web beam rather than a Vierendeel beam. The stress transmission paths at the RF connection are changed by FIBs—particularly at the RF-W and cutout details. The FIBs cause significant improvements at the RF and cutout details but do not affect the stress response of RD details. The RF and cutout details have infinite fatigue life, with the local stiffness enhanced by the FIBs, but the RD details have a finite fatigue life, as the FIBs are far from the RD details. The rib-to-bulkhead (RB) details have the maximum stress at the bottom of the ribs, where the stress outside the rib is higher than that inside, indicating that the fatigue assessment of RB details can be conducted using the stress measured outside the ribs.

Stress Behaviors at Rib-to-Floorbeam Weld and Cutout Details under Controlled Truck Loading

The rib-to-floorbeam (RF) connection is the most complicated joint in orthotropic steel decks (OSDs), where four fatigue-prone details are created, i.e., the RF at the rib side (RF-R), RF at the floor beam side (RF-F), RF at the rib wall (RF-W), as well as the floor beam cutout detail. In order to clarify the behavior of those details under the passage of trucks, a controlled truck loading test and finite element analysis (FEA) are performed at various typical transverse loading locations on a newly built long-span cable-stayed bridge. The research finds that, in the bridge transverse direction, stresses at the four details presented significant local effects. Only when these details are underneath the deck plate covered by the wheel patch a notable stress can be produced at these details. In the bridge longitudinal direction, the wheel loading effect at the four details can be discerned only when the wheels load on the deck supported by their adjacent floor beams. The results find that, under wheel loading, the stress ranges at the RF-R, RF-F and Cutout details are compressive, while the stress at the RF-W detail is in tension. The riding-rib-wall loading is the most critical transverse loading location for the RF and Cutout details, and the RF-W is the most critical fatigue detail in the RF connection. The FEA indicates that, due to offset of wheel loads, floor beams may suffer from severe out-of-plane bending, while ribs may experience notable warping and distortion. Under the passage of the tandem axles, the individual axle cannot be identified, and only one stress cycle is produced at the four details.

ЭКСПЕРИМЕНТАЛЬНОЕ МОДЕЛИРОВАНИЕ ТЕПЛООБМЕНА В ТЕПЛОВЫДЕЛЯЮЩИХ СБОРКАХ БЫСТРЫХ РЕАКТОРОВ В АВАРИЙНЫХ РЕЖИМАХ В УСЛОВИЯХ ЕСТЕСТВЕННОЙ КОНВЕКЦИИ

The results of experimental studies of heat transfer carried out at the State Research Center RF - IPPE on models of fuel assemblies in cores and screens of fast reactors BOR-60, BN-350, BN-600, BN-800 (the relative pitch of the fuel element simulators varied in the range 1.04≤s/d≤1.24) with natural and mixed convection of liquid metal coolants, which are the basis for the development of design codes. Model fuel assemblies of fast reactors contain 37 fuel elements (fuel rod simulators) located in a triangular lattice and enclosed in a hexagonal cover. The elements were heated with nichrome heaters, which ensure a constant heat flux on the inner surface of the elements and along the length of the heat generation. The central, lateral and corner elements are rotary. On their surface, 12 chromel-alumel thermocouples each in covers made of X18H9T steel (diameter of the cover 0.8-0.5 mm, diameter of thermoelectrodes 0.2 mm) are embedded, measuring the coolant temperature in the collectors of the models, as well as in each cell at the exit from the bundles. The spacing of the elements is carried out using wire coils; variants of smooth fuel rod simulators are also used. Experimental studies on model fuel assemblies revealed regularities in the formation of temperature fields in fuel elements and coolant. Natural convection manifests itself in the region of low velocities, promotes fluid mixing between channels, leveling the uneven heating of the coolant in the cross section of the fuel assembly, and reduces the azimuthal non-uniformity of the temperature of the wall fuel elements in the fuel assembly. The results of experimental studies show that the effect of natural convection manifests itself in the range of Pe<10 (Re<2000) numbers in gratings with relative steps (s/d<1.05) and in wide bundles (s/d<1.3 to a greater extent in bundles of smooth fuel rods in comparison with bundles of ribbed fuel rods. The introduction of displacers into the peripheral channels of a fuel assembly does not fundamentally change the nature of the temperature field in a fuel assembly as compared to the version of the geometry of a fuel assembly without displacers. An attempt was made to generalize the experimental data using the Gr*Pr criterion, where Gr* is the modified Grashof number calculated from the local heat flux on the heat exchange surface and the axial coordinate measured from the beginning of heat generation. In the dependences DTwmax = f(Gr*Pr2) at Pe<100 or ribbed side elements and Pe<10 for smooth side elements, two regions of DTwmax change in the Gr*Pr2 growth function are observed - first, DTwmax ncreases to a certain “limiting” value characteristic for fixed Pe, and then - a drop in DTwmax at large values of the parameter Gr*Pr2. As the Peclet number increases, the “limiting” value of DTwmax hifts to the region of larger values of Gr*Pr2; and at Pe=370 or ribbed elements and Pe=26.5; 100 or smooth elements, the limiting value of DTwmax is not achieved in the investigated range of the Gr*Pr2 parameter variation. For smooth side elements, the limiting values of DTwmax are approximately the same for different Pe numbers and amount to DTwmax≈10.

Predicting Maximal Costal Cartilage Graft Size for Laryngotracheal Reconstruction.

Current methods of assessing rib cartilage dimensions for laryngotracheal reconstruction (LTR) are inexact, making surgical planning difficult. The purpose of this study was to determine the most appropriate rib for costal cartilage graft LTR to minimize the number of ribs harvested and improve surgical outcomes. Retrospective review. Computed tomography imaging of chest scans in 25 children aged 1 to 18 years was evaluated. The lengths and widths of medial and lateral cartilaginous segments of ribs 4 to 7 were measured bilaterally. Right and left cartilaginous rib dimensions were compared using a two-sample t-test. Linear mixed-effect regression was performed to develop models quantifying the relationship between rib size and patient height, rib side, and rib number. Regression analysis established strong models for medial rib length (R2 =0.89) and for medial and lateral rib width (R2 =0.71, 0.77, respectively). There was no difference in rib dimensions across chest sides. Rib length and width increased with child height. Total cartilaginous rib length increased from superiorly to inferiorly, primarily due to an increase in the dimensions of the medial portion of each rib. Cartilaginous rib lengths and widths were associated with patient height, with taller children having longer ribs. Inferior ribs were longer than superior ribs, suggesting that inferior ribs may be preferred for LTR. There was no difference in cartilaginous rib length across chest side. Results may help surgeons with preoperative planning. NA Laryngoscope, 132:1682-1686, 2022.

Structural optimization of rib-to-crossbeam joint in orthotropic steel decks

In orthotropic steel decks (OSDs), the rib-to-crossbeam joint is the most complex joint. When dealing with the intersection of the rib to the crossbeam, the prevailing approach is to design a cope hole in the crossbeam web. Nevertheless, the stress concentration induced by rib distortion makes this joint a fatigue-prone detail. Furthermore, the weld connecting the rib and the crossbeam heavily relies on the manual welding, which leads to high fabrication costs. In this paper, the possibility of canceling the cope hole is discussed. Calculation results of different modeling methods using solid elements and shell elements are first compared with experimental results. Then, several design parameters of an OSD without cope holes are investigated adopting the hot spot stress method. Based on the results of the parametric analyzes, optimized dimensions of the rib-to-crossbeam joint without cope holes are selected. The comparison of the models with and without cope holes is performed. Fatigue life assessments are conducted based on the influence surfaces of reference points predefined around the rib-to-crossbeam joint. Research results reveal that the most critical position for the rib-to-crossbeam joint without cope holes is at the curvature on the rib side. The radius of rib has a local influence on the points at the curvature. A larger radius could effectively lower the maximum stress range. The fatigue performance of the rib-to-crossbeam joint depends on the distribution of the tire load. Considering less fatigue-prone locations and reduced fabrication costs, the overall performance of the optimized rib-to-crossbeam joint without cope holes is better.

Static energy absorption capacity of grid stiffened composite plates

This paper presents an experimental study on the energy absorption capacity of iso-grid and ortho-grid stiffened composite plates under transverse loading. The 3-point bend test has been performed to investigate the energy absorption behavior of grid stiffened composite plates. The test results show that energy absorption capacity up to failure is improved when the load is applied on the rib side. The ortho grid stiffened structure shows a higher energy absorption capacity after failure when loaded at the rib side. The main failure modes in grid stiffened composite plates are rib fracture, matrix cracking and delamination over the skin.

Research on characteristics of flow boiling and dryout inhibition of rifled tube

The two-fluid three-flow field mathematical model is used to carry out the numerical simulation of heat transfer characteristics of steam-liquid two-phase flow in dryout and post-dryout region of the rifled tube. The absolute vorticity flux and intensity of the secondary flow are introduced to quantitatively characterize the heat transfer enhancement. The results show that, compared with smooth tube, the rifled tube can greatly reduce the rise of wall temperature and have a significant effect on dryout inhibition. The cross-section wall temperature of rifled tube presents a periodic distribution. The wall temperature at the intersection of the root and rib side is higher due to the fluid retention. After the dryout occurs, the wall temperature is higher than other locations due to the continuous liquid film on the crest being torn. The secondary flow strength and heat transfer enhancement degree of fluid in rifled tube increase with the increase in axial height. The absolute vortex flux, intensity of the secondary flow and absolute value of the vorticity in main flow direction can reflect the degree of fluid disturbance caused by internal thread.

Performance enhancement of a triple-tube heat exchanger through heat transfer intensification using novel crimped-spiral ribs and nanofluid: A two-phase analysis

This research attempted to analyze a triple-tube heat exchanger (TTHE) fitted with innovative crimped-spiral ribs to enhance thermal efficiency. The crimped-spiral rib was placed on the top of the internal tube, and the water–alumina nanofluid was employed as the hot fluid within the ribbed side, whereas the two other fluids were pure water. The numerical solutions were performed through the two-phase mixture method, while the turbulent flow was modeled via the Reynolds Stress Model (RSM). The overall heat transfer coefficient (U), heat transfer rate, effectiveness, and performance index enhanced remarkably by using the nanofluid. The greatest increment in the U and effectiveness reached around 44.91 and 41 %, respectively, by the increment of the volume fraction by 0.02. The crimp intensity had an appreciable contribution to the thermal performance. The main mechanism was stronger swirl flow generated by the crimped-spiral rib that yielded boundary layer destruction. The heat transfer capability was increased via the rib pitch decrement and rib height increment. The performance index showed great values even at low volume fractions, which manifested the great merit of the implemented refinements. The thermal attributes were investigated at the first of the result section and then, the hydraulic characteristics were researched.

Comparison of Bone Remodeling Between Collum Femoris-Preserving Stems and Ribbed Stems in 1-Stage Bilateral Total Hip Arthroplasty.

BackgroundThis study examined a cohort of patients who underwent bilateral THAs. CFP prostheses and ribbed prostheses were each used on both sides. We assessed the midterm clinical, radiological, and bone remodeling outcomes around prosthesis of these patients.Material/MethodsFrom January 2009 to January 2013, 53 patients were enrolled in our study. We clinically evaluated all patients by recording Harris hip and Oxford hip scores. Some radiological indicators of the femoral prosthesis position were measured. Periprosthetic bone remodeling was assessed via bone mineral density (BMD) measurements.ResultsThe mean preoperative HHS of the CFP group and ribbed group were no significantly different (P=0.570). The neck-shaft angle in the ribbed group was significantly greater than in the CFP group (P<0.001). The CFP group had a greater offset (P<0.001). There was no significant difference in leg-length discrepancy (P=0.727) or Engh score between the 2 groups at the last follow-up (P=0.858). The preoperative BMD was increased at the last follow-up in Gruen zones 3 and 5 (P<0.05) and decreased in Gruen zones 1 and 7 (P<0.05) on the CFP side. BMD was increased in Gruen zone 4 (P=0.007) on the ribbed side. Pearson correlations and rate of complications were not significantly different.ConclusionsBoth the CFP and ribbed stem significantly improved the preoperative HHSs and OHSs. The bone remodeling of the CFP stem was more concentrated in the middle and distal regions of the prosthesis, while that of the ribbed stem was more concentrated in the proximal portion of the prosthesis.

Squeezing failure behavior of roof‐coal masses in a gob‐side entry driven under unstable overlying strata

AbstractThis paper endeavors to reveal the squeezing failure mechanism of roof‐coal masses and its correlation with the movement of the roof strata. An integrated method incorporating field instruments and numerical modeling was conducted. The borehole camera detection revealed that the development degree and scope of cracks in the roof strata on the coal pillar side are significantly larger than that on the panel rib side, and the fracture line of the main roof occurred above the coal pillar. A rigorous modeling procedure verified the borehole camera detection results and also found that the vertical and horizontal displacement of the roof‐coal mass exhibited asynchronous development characteristics at various heights. Subsequently, a comprehensive control strategy was proposed to prevent the squeezing failure behavior of roof‐coal masses in DUOS gob‐side entry. This study provides a basis for understanding the squeezing failure behavior of roof‐coal masses, and the proposed control strategy can potentially be applied in other similar mining projects.

Microscopy of composite materials based on carbon fibre

The work is devoted to a composite material consisting of carbon fibres in a carbon pitch-based matrix. Due to its high wear and heat resistance, this material is widely used in aviation brake systems. Two samples with different impregnation of fibres were studied. It is shown that their tribological properties are different. A complex method of microscopy (optical, scanning electron, and scanning probe microscopies) was used to study the friction surface and inner structure of the samples. In the sample with the best properties, the fibres have a regular ribbed side surface, fibre bundles are located parallel to the friction surface, matrix around the fibres has a denser structure. It is also shown that in this sample wear rates of the fibres and the matrix are the same. Thus, a small change in the production process leads to a noticeable change in the structure, which determines the operational properties.

RESEARCH ON PROPAGATION CHARACTERISTICS AND REINFORCEMENT METHOD OF PENETRATING CRACK AT RIB-TO-DIAPHRAGM WELDED JOINTS IN STEEL BRIDGE DECK

The rib-to-diaphragm welded joints in the deck of an orthotropic steel bridge is most prone to fatigue cracking. A FE model was established and fracture mechanics was used to study the reinforcement effect of angle steel reinforcement methods on the penetrating crack at fatigue vulnerable details. Based on the finite element model corresponding to a full-foot segment fatigue test model, a penetrating fatigue model was established for the cracks in rib-to-diaphragm welded joints, and the reinforcement effect was evaluated on two reinforcement techniques:bolted angle steel and the bolted steel plate beside a longitudinal rib. The results indicate that:the fatigue cracks at the welded joint in the rib-to-diaphragm of a steel bridge deck expand into a certain length and will develop into penetrating cracks, the deformation of the crack surface under stress conditions is complicated, the fatigue crack propagation characteristics of the inner and outer side of longitudinal ribs are not the same, and as the crack propagation progresses, the cracking mode of the crack tip will be dominated by composite cracking. The existing research results show that:the bolted angle steel reinforcement method can well inhibit the longitudinal rib and diaphragm connection details of the vulnerable part with the fatigue crack type I cracking. Therefore, the short crack propagation can be well suppressed. However, the reinforcement effect on penetrating fatigue cracks extended in a composite type in this detail is not as good as the short crack that have not penetrated the web; the reinforcement method of the half U rib steel plates bolted to the outside of longitudinal ribs can effectively reduce the equivalent stress intensity factor of penetrating fatigue cracks, and stay below the crack propagation threshold after reinforcement. It shows that the reinforcement method has a good reinforcement effect on penetrating fatigue cracks.

Fatigue behavior of orthotropic steel bridge stiffened with ultra-high performance concrete layer

As a novel cement based material, the ultra-high performance concrete (UHPC) has been recently used in reinforcing steel bridge decks. In this paper, an orthotropic steel bridge (OSB) stiffened with UHPC layer is modeled via the finite element submodel technique. The stress responses of fatigue-prone details under wheel loads are obtained, and the fatigue performance is also evaluated. The stress tendencies observed by the finite element models are compared to the stress response data from field measurements. It is observed that an application of 45 mm thick UHPC layer on the OSB deck can reduce the stress range at deck side of rib-to-deck (RD) joint by up to 70.9%, achieving an infinite fatigue life. However, the stress ranges for the other three details are still significant, including the stress range at rib side of RD joint (with both membrane and bending stresses), the stress range on rib wall at weld end of rib-to-floorbeam (RF) joint (with both rotational and Poisson's effects), and the stress range at floorbeam side of RF joint (due to the in-plane deformation and out-of-plane twist). To reduce such significant stress ranges in achieving infinite fatigue life of the bridge under high traffic volume, the critical influencing parameters on the stress ranges are studied and selected for fatigue design.

Effect of a ribbed surface on the water transfer characteristics of a porous plate

Porous plates are commonly used in the external humidification devices employed in proton exchange membrane fuel cells. In this study, the effect of a ribbed surface on the water transfer characteristics of a porous plate is investigated experimentally to elucidate the process by which heat and mass is transferred from a high-temperature, high-humidity gas (wet air) through porous media to a low-temperature, low-humidity gas (dry air). Experimental results show that a porous plate with ribs can promote the water transfer between the two gases and that the water transfer ability of the plate is markedly improved when the ribbed side is oriented toward the humidified gas.

Numerical study on mechanical and adhesive splices for ribbed GFRP plates used in concrete beams

A new concrete beam design, comprising concrete core and glass fiber reinforced polymer (GFRP) ribbed side plates has been developed. Plate splicing is made by using a mechanically fastened or adhesively bonded spliced form through end ribs. This paper presents the development, calibration, and application of comprehensive finite element models for the hybrid beam. The models incorporate material and geometric nonlinearities along with bond-slip interfacial relations. Interfacial behavior at the plate-to-plate splice, whether adhesively bonded or mechanically fastened, as well as plate-concrete interface are considered. Parametric study was performed to examine the effects of fastener spacing and adhesive coverage length of the 4 mm thick GFRP plates. It was shown that the ultimate strength of beams with adhesively bonded splices was 28% higher than the beams with unbonded splice (i.e. without any adhesive or fasteners). Decreasing fastener spacing from 47 to 3.8 times the fastener diameter resulted in increasing ultimate load by about 20%. No further reduction in load occurs beyond fastener spacing larger than 47 times the diameter. The beam stiffness at service load is not affected by the fastener spacing or the adhesive coverage length.

A numerical modeling study on the influence of catalyst loading distribution on the performance of Polymer Electrolyte Membrane Fuel Cell

In this study, the effects of different non-uniform catalyst loading distributions that vary in both lateral and longitudinal directions on the performance of Polymer Electrolyte Membrane Fuel Cell (PEMFC) were numerically examined in detail. A two-phase, multi-component, transient and three-dimensional model was employed for simulating the performance of the cathode half-cell of the PEMFC. At the first step, the best longitudinal catalyst loading distribution was found. At the second step, several lateral distributions were superimposed to the noted longitudinal catalyst loading distribution and the performance of the PEMFC was evaluated for each distribution. Numerical results showed 3.1% enhancement for the longitudinal catalyst loading distributions; while 8% improvement was observed with a non-uniform catalyst loading distribution in both longitudinal and lateral directions. Results indicated that when lateral distribution is employed, liquid water saturation in the rib side is reduced. In the best longitudinal distribution, the ratio of platinum loading in longitudinal direction was 1.857 and the ratio of platinum catalyst from the center region of the catalyst layer to the rib side is varied in a wide range. In the case of the noted ratio more than 30, the enhancement in the PEMFC performance was insignificant. Finally, the effect of catalyst loading distribution was investigated on the polarization curves. It was found that the catalyst loading distribution is most effective at the high current densities while it has a minor effect at low current densities.

Investigation of heat transfer augmentation and friction factor in triangular duct solar air heater due to forward facing chamfered rectangular ribs: A CFD based analysis

The rib provided over absorber plate can improve the performance of solar air heater (SAH). The effect of forward chamfered ribbed absorber plate is studied in the present article. Two new roughness parameters named as rib aspect ratio (e/w) and rib chamfered height ratio (e′/e) has been defined and their influence on the performance of triangular duct SAH is simulated using commercial ANSYS software for fixed range of Reynolds number (Re) which varies from 4000 to 17000. The e/w, relative roughness height (e/D) and e′/e ranges from 0.24 to 1.5, 0.018 to 0.043 and 0 to 1.0, respectively. The ribbed side of duct is heated with constant heat flux of 1000 Wm-2. The three-dimensional model of SAH is developed for the analysis and results are simulated using finite volume approach. The numerical methodology is validated by comparing predicted results with the available results and a close match is seen between friction factor (f) and Nusselt number (Nu). A remarkable change in f and Nu value is observed by varying both Re and roughness parameters. The maximum increase in Nu is observed in case of e/w, e/D and e′/e value of 1.5, 0.043 and 0.75, respectively, at Re value of 17000 and it is of the order of 2.88. The maximum increase of friction penalty is seen in case of e/D value of 0.043 which is of the order of 3.52 times the without ribbed duct at Re value of 4000. With the help of numerically predicted results, a generalized correlation is developed for Nu and f.