Continuous Rib Research Articles

Enhancing recuperators performance in supercritical CO2 Brayton cycle of solar power plants through ribbed heat transfer plates

Sixteen diverse combinations of ribbed heat transfer plates (HTPs), comprising continuous and discontinuous rib configurations, are investigated as potential replacements for traditional smooth HTPs in both the low-temperature recuperator (LTR) and high-temperature recuperator (HTR) of supercritical CO2 Brayton cycles. The findings indicate that the impacts of the introduced HTPs are more significant under the operating conditions of the LTR than those of the HTR. Generally, the incorporation of denser ribs at the upstream sections of both the hot and cold flow paths leads to a significant enhancement in j-factor values. On the hot side of the LTR, these increases exceed 60%, while on the cold side, they surpass 40%. It is also observed that variations in rib pitch exert a more substantial influence on thermal performance compared to alterations in rib length. When comparing non-uniform rib patterns, it is found that the use of ribs with variable lengths increases f-factor values, whereas the design of HTPs with variable rib pitches decreases these values. The design of HTPs with a non-uniform arrangement of rib pitch yields the best overall performance in the LTR. The performance index values for the hot-side and cold-side of this model reach 1.39 and 1.26, respectively.

Numerical investigation of the flows and heat transfer characteristics of internal cooling channels with separated ribs in gas turbine blades

Gas turbine engines play a crucial role in numerous industrial domains, including power generation, aviation, and marine propulsion. One of the major challenges in designing gas turbine engines is managing the high temperature generated by the combustion process. Internal cooling is a commonly used technique to maintain the temperature of critical components, such as turbine blades, within a safe operating range. Rib turbulators are widely used in internal cooling systems to enhance heat transfer performance by promoting turbulence in the fluid flow. Nevertheless, the existence of a continuous rib within the cooling channel can result in elevated temperatures near the rib section, potentially diminishing the overall system efficiency. In response to this challenge, a new rib turbulator design, denoted as the “separated rib,” has been introduced to mitigate the high-temperature zone. Through the utilization of the passing-gap design in the separated rib configuration, the coolant flow passes through the gap, effectively eliminating the region of extreme heat and augmenting the secondary flow. Consequently, it results in a notable enhancement of heat transfer performance within the ribbed channel. The numerical simulations are performed by solving three-dimensional (3D) Reynolds-averaged Navier–Stokes equations using the commercial software ANSYS CFX. The working fluid is steam, and the heat transfer performance is evaluated in terms of the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). The results show that the separated rib configuration has approximately 17.3% higher Nusselt number than the original ribbed configuration when the Reynolds number (Re) changes from 5000 to 60 000. The separated rib configuration consistently shows higher TPF values between about 1.6 and 1.9 than the original rib configuration, where TPF is smaller than 1.35. Furthermore, the heat transfer correlation related to the Reynolds number was developed to predict heat transfer performance. The heat transfer correlations align closely with the numerical simulation results, showing about 17.4% and 34.3% improvements in Nu and TPF, respectively, for our newly designed system compared to the old version.

Enhanced heat transfer of supercritical n-decane in cooling channels with triangular ribs for regenerative cooling

• A continuous ribbed channel is designed to enhance the cooling capacity. • The channel can provide up to 2.04 times superior heat transfer performance. • The insertion of ribs enhances the uniformity of buoyancy distribution. • The triangular rib channel improves axial temperature uniformity. • The mechanism of generating vortices in the slot is analysed. Regenerative cooling is regarded as an effective method for managing the heat of scramjet combustors, and the design of cooling channels is critical for removing more heat from the engine. A continuous triangular rib channel was proposed. The effects of rib position, height, and pitch on the heat transfer performance were investigated using Fluent 18.0. The SST k –ω turbulence model was used to study the thermal behaviour of supercritical n-decane in channels and showed good agreement with the experimental data. Results show that the insertion of triangular ribs at the bottom and top can reduce the bottom wall temperature by 243.8 K in the studied case. The triangular rib channel can provide up to 2.04 times superior heat transfer performance. The continuous triangular ribs significantly reduced axial temperature inhomogeneity. Local streamlines were studied to demonstrate the influence of rib parameters on the flow and heat transfer processes. A local heat transfer enhancement occurs when the rib has a large inclination. For the studied conditions, the generation of vortices was carefully evaluated, and it was found that the generation of vortices in the slot was related to the value of h / p .

Printnervi – Design and Construction of a Ribbed Floor System in the Digital Era

Ribbed floor systems, which include ribbed slabs and columns, are used extensively to enhance the structural performance of buildings. With the emerging topology optimization and advanced manufacturing techniques, the material usage and construction process of the ribbed floor systems can be improved significantly to achieve higher efficiency and sustainability. This paper presents a digital design and construction process for ribbed floor systems that combines a modified topology optimization method for ribbed slab design with a hybrid digital fabrication process for large-scale concrete casting. This new approach is tested through digital design and physical realization of a large-scale ribbed floor unit as proof of concept. The topologically optimized result and the constructed unit are compared with a famous historical floor system designed by Pier Luigi Nervi. The paper shows that the proposed design method, based on the bi-directional evolutionary structural optimization framework, can generate a slab design with a continuous rib layout and with higher structural stiffness. The paper also demonstrates that 3D printing of formworks for casting ribbed slabs and complex-shaped columns is feasible and sustainable. The new process presented in this paper can be used to design and construct a wide range of structures while minimizing material usage and labor cost.

Numerical Simulation of Flow and Heat Transfer of a Discontinuous Single Started Helically Ribbed Pipe

In the present study, the turbulent flow field and the heat transfer in a single started helically ribbed pipe with a discontinuous rib are investigated. A large-eddy simulation (LES) technique is applied in a pipe section with cyclic boundary conditions. The aim of this study is to explain and further analyze the findings from the heat transfer measurements at such complex structures with the help of detailed flow simulations. The simulation results are validated with measurements at a Reynolds number of Re = 21,100 and a Prandtl number of Pr = 7 with water as fluid. The comparison clearly shows that the current method delivers accurate results concerning average flow field, turbulence quantities and local heat transfer. The results demonstrate that the applied method is capable of correctly simulating flows with heat transfer in complex three-dimensional structures. The overall heat transfer performance of the helically ribbed pipe with a discontinuous rib is compared to a smooth pipe and a continuous rib configuration. The impact of the interruption of the rib structure on pressure drop and heat transfer are analyzed in detail.

Performance assessment of double-pass parallel flow solar air heater with perforated multi-V ribs roughness — Part B

ABSTRACT After analyzing the effect of perforation in a single pass solar air heater in part A, an experimental comparative study was performed on a Double Pass Parallel Flow Solar Air Heater (DPPFSAH) roughened with continuous and perforated multi-V rib roughness. In DPPFSAH, for perforated rib roughness, the gain in Nu/Nus, f/fs, and Thermo-hydraulic performance parameter (THPP) for W/w = 6 are 8.33, 9.09, and 2.97, respectively. While for continuous rib for W/w = 6 the values of Nu/Nus, f/fs, and THPP are 5.93, 10.83, and 1.82, respectively, as compared to the smooth plate. The results strongly support the application of perforation in artificial roughness.

Heat transfer and fluid flow analysis of sinusoidal protrusion rib in solar air heater

Three dimensional (3D) simulation has been carried out to study the heat transfer and fluid flow phenomenon of sinusoidal protrusion rib (SPR) in solar air heater (SAH). The performance of SPR model has been compared with continuous transverse sinusoidal rib (CTSR) model for roughness pitch 10 mm, 14 mm and 18 mm. The thermohydraulic performance (THP) value of SPR model is obtained very near to the THP value of CTSR model whereas it has been observed that at roughness pitch 10 mm in the range of Reynolds number 5000–10,000, THP value for SPR model is greater than that of CTSR model. The optimal Computational Fluid Dynamics (CFD) results of SPR model has been validated with experimental results of SPR model. The variation of experimental results with CFD results for Nusselt number and friction factor are found 6.53% and 4.11% respectively. The thermal efficiency of SPR model has been found 69% at Re 15,000 in the range of Reynolds number investigated.

Numerical investigation of the flow field and heat transfer characteristics for upstream continuous and truncated ribs

AbstractTo verify the applicability of upstream ribs in film cooling, the present numerical study examines heat transfer characteristics and flow field for ribs located upstream of the film hole. Five ribs including bilaterally truncated ribs, centrally truncated ribs, and continuous ribs are explored with the smooth case at two blowing ratios and fixed crossflow Reynolds number. The results show that the film cooling effectiveness of cases with ribs outperforms the case without rib at a low blowing ratio. Centrally truncated ribs and continuous ribs provide superior cooling effectiveness than bilaterally truncated ribs and smooth cases. The introduction of ribs makes the distribution of the heat transfer coefficient (HTC) uneven after the hole. Among these, centrally truncated ribs increased the HTC, while bilaterally truncated ribs reduce the HTC in the far hole area at a high blowing ratio. It is found that anti‐kidney‐shaped vortex pairs are generated between two adjacent jets for centrally truncated rib cases, while they are generated in front of the jets for bilaterally truncated rib cases. For continuous rib, the impingement of the mainstream gas on the jet leads to a reduction in strength of the kidney‐shaped vortex, which allows the coolant to form a better coverage.

Experimental and computational investigation for 3-D duct flow with modified arrangement ribs turbulators

A combined numerical and experimental study is conducted to test the heat transfer enhancement and friction factor characteristics for a rectangular duct fitted with three cases of ribs turbulators: continuous ribs, intermittent-continuous-intermittent ribs, and intermittent ribs. Experiments are conducted within a turbulent flow for Reynolds numbers values varied from 10000 to 35000, pitch ratio equal to 5 and height ratio of 0.33. The numerical study carried out using ANSYS FlUENT17.2. The turbulence is modeled by using k-? model. The results showed that the case of intermittent ribs provide the highest over performance factor while the continuous ribs indicate less overall performance factor among the considered cases. In addition, the results show that the highest values of the friction factor are marked from the case of intermittent ribs and then the case of intermittent-continuous-intermittent ribs followed by continuous rib case. The continuous rib case showed the lowest friction factor.

Triplet therapy (continuous ribociclib, everolimus, exemestane) in HR+/HER2− advanced breast cancer postprogression on a CDK4/6 inhibitor (TRINITI-1): Efficacy, safety, and biomarker results.

1016 Background: The combination of CDK4/6 inhibitor (CDK4/6i) + endocrine therapy (ET) provides consistent improvement in PFS and response rates compared with single-agent ET as first- or subsequent-line therapy in HR+, HER2− advanced breast cancer (ABC), but the optimal regimen postCDK4/6i progression, including the role of continued CDK 4/6 blockade, is unclear. Methods: TRINITI-1 is a Phase I/II, open-label trial (NCT02732119) of triplet therapy: ribociclib (RIB; CDK4/6i) + everolimus (EVE; mTORi) + exemestane (EXE; ET) in men or postmenopausal women with HR+, HER2− ABC that progressed on prior CDK4/6i and up to 3 lines of therapy (≥ 1 ET and ≤ 1 chemotherapy regimen). Phase I determined RP2D; Phase II assessed efficacy/safety of RIB 300 or 200 mg + EVE 2.5 or 5 mg + EXE 25 mg/day. Here we present the first results in the entire patient population who received this triplet regimen and the correlation of biomarkers with outcomes. Results: As of October 24, 2018, 95 patients were evaluable (ET refractory and postCDK4/6i) in Phases I (n = 17) and II (n = 78). Continuous RIB + EVE + EXE demonstrated clinical benefit at week 24 in 39 patients (41.1%), exceeding the predefined primary end point threshold (> 10%). ORR was 8.4% by investigator assessment, median PFS was 5.7 months, and 1-year PFS was 33%. AEs were consistent with known safety profile of RIB, EVE, and EXE. Most common AEs were neutropenia (all grades, 41.7%; grade 3/4, 31.3%), stomatitis (41.7%; 3.1%), and fatigue (35.4%; 1.0%). No grade 3/4 QTc prolongation was noted. ctDNA genotyping revealed patients with certain tumor alterations, eg ESR1, had shorter median PFS vs wild-type: 3.5 vs 6.9 mo (HR 1.76, 95% CI 1.01–3.05). Additional genomic results, including PIK3CA, will be presented. Conclusions: TRINITI-1 met its primary efficacy end point and is the first trial to demonstrate clinical benefit and tolerability of continuous triplet therapy with ET + mTORi + CDK4/6i in patients with ET-refractory HR+, HER2− ABC postCDK4/6i progression. Tumor genomic profile might impact the clinical outcome with triplet therapy and warrants additional research to guide rational therapy selection. Clinical trial information: NCT02732119.

Investigations on thermo-hydraulic performance of broken arc rib in a rectangular duct of solar air heater

In present paper, solar air heater duct having aspect ratio 12 roughened with broken arc rib has been investigated. The broken arc is formed by creating symmetrical gap in continuous arc with gap width equal to roughness height. It has been planned to investigate the influence of position of gap in arc rib on Nusselt number as well as on friction factor. For this purpose, five broken arc rib roughened plates having relative gap position ranging 0.2–0.8 have been investigated for values of Reynolds number 2000–16000. The remaining roughness parameters like relative roughness height, arc angle, and relative roughness pitch were taken as 0.043, 30o and 8 respectively. The presence of broken arc ribs enhanced the Nusselt number, friction factor and thermo-hydraulic performance up to 2.37, 2.55 and 1.94 respectively, compared to smooth duct. The results of ducts roughened with broken arc rib and continuous arc rib have been compared under similar flow conditions. The effect of gap in continuous arc rib on the flow pattern has also been observed using ANSYS Academic Research CFD 15.0.

Film cooling performance and flow characteristics of internal cooling channels with continuous/truncated ribs

To better evaluate the application of ribs in gas turbine blade cooling, this numerical study reports on the effects of ribs mounted on the internal cooling channel wall on external adiabatic film cooling performance. The numerical model is validated against available experimental data. For fixed mainstream and cooling flow Reynolds numbers, three ribs including the continuous rib, centrally truncated rib and laterally truncated rib at two blowing ratios (i.e., 0.5 and 1.0) are considered. At lower blowing ratio, results show that the cases with three distinct ribs provide approximately identical cooling effectiveness but significantly outperform the case without ribs. The superiority regarding laterally averaged adiabatic cooling effectiveness is 17–157%. However, at higher blowing ratio, the cases with ribs are inferior to the case without ribs, showing an inferiority of 21–68%. Further, at higher blowing ratio, the case with continuous ribs exhibits a 12–45% higher localized cooling effectiveness relative to other ribbed cases. It is found that cooling effectiveness deteriorates with the increase of spiral intensity of the coolant flow inside the film hole. Lower spiral intensity leads to a better covering of target wall by the coolant and thus results in better cooling effectiveness. The distinct relative merits among the cases at different blowing ratios are explored based on the aforementioned dominant mechanism.

Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with broken arc ribs

In present experimental investigation, solar air heater duct with aspect ratio 12 roughened with broken arc rib has been investigated. The broken arc was formed by creating symmetrical gap in continuous arc. To investigate the influence of roughness parameters of broken arc rib on Nusselt number as well as on friction factor, thirty-seven broken arc rib roughened plates having relative roughness pitch (P/e), relative gap width (g/e), relative gap position (d/w), relative roughness height (e/Dh) and arc angle (α) varying from 4 to 12, 0.5 to 2.5, 0.2 to 0.8, 0.022 to 0.043 and 15° to 75° respectively, have been investigated for Reynolds number range of 2000–16,000. Keeping similar flow conditions, results of broken arc rib roughened duct have been compared with smooth and continuous arc rib roughened ducts. The maximum increase in Nusselt number and friction factor over that of continuous arc rib roughened duct was 1.19 and 1.14 times respectively. The corresponding values over that of smooth duct were 2.63 and 2.44 times respectively. Experimental results of heat transfer and friction in flow have also been correlated in terms of flow and roughness geometry parameters.

Effect of rib roughness pitch on thermal and thermo-hydraulic performance of a solar air heater roughened artificially with arc rib having gap

This experimental study on a solar air heater having absorber plate roughened artificially by providing roughness in the form of arc ribs having gap was carried out in the Department of Mechanical Engineering, Punjab Agricultural University, Ludhiana, India to study the effect of relative roughness pitch on thermal and thermohydraulic performance as well as to compare the performance of arc rib with gap roughened solar air heater with that of continuous arc rib roughened solar air heater. The roughness geometry parameters included relative roughness height of 0.043, angle of attack of 30 degree, relative gap position of 0.80, gap-width equal to the width of the rib and five values of relative roughness pitch ranging from 4 to 12 for flow Reynolds number range of 2000 to 16,000. The Nusselt number and friction factor were found to be more for relative roughness pitch value of 10 as compared to other values of relative roughness pitch. Thermo-hydraulic performance of solar air heaters roughened by arc with gap and continuous arc roughness geometries were found to be 1.91 times and 1.78 times respectively as compared to that of solar air heater having smooth absorber plate due to generation of turbulence in laminar sublayer region. However, improvement in thermo-hydraulic performance of solar air heater roughened by arc with gap geometry over continuous arc rib roughened solar air heater was attributed to generation of a region of turbulence on downstream side of the gap.

Nusselt number and friction factor correlations for solar air heater duct with broken V-down ribs combined with staggered rib roughness

Artificial roughening of a broad wall of solar air heater leads to significant enhancement in heat transfer besides comparable rise in friction losses. This paper presents the outcome of experimental study on heat transfer and fluid friction characteristics of solar air heater duct roughened with broken V-down rib combined with staggered rib piece. Experimental data were collected on a high aspect ratio rectangular duct by varying the Reynolds number from 3000 to 17 000, relative gap position (s′/s) 0.2–0.8, relative staggered rib position (p′/p) 0.2–0.8, relative staggered rib size (r/e) 1–2.5, for the fixed values of relative roughness pitch (p/e) of 10, relative roughness height (e/Dh) of 0.043, relative gap size (g/e) of 1, and angle of attack (α) of 60°. The effect of flow Reynolds number and roughness parameters on Nusselt number and friction factor has been explored and the results are compared with continuous V-down rib roughened duct and smooth duct under similar flow conditions. Correlations for the Nusselt number and friction factor as a function of Reynolds number and roughness parameters have been developed.

Investigations on thermo-hydraulic performance due to flow-attack-angle in V-down rib with gap in a rectangular duct of solar air heater

In this investigation, thermo-hydraulic performance of rectangular ducts roughened with a new configuration of ‘V-down rib having gap’ on one wide wall is determined. Small symmetrical gap equal to rib height is created at the centre of both legs of V of continuous V-down rib. The duct has aspect ratio (AR) of 12 and the Reynolds number (Re) ranged from 3000 to 15,000. To simulate the indoor testing of solar air heater, the roughened side of rectangular duct is heated with constant heat flux electric heater while the other sides are insulated. The roughness has relative roughness height of 0.043 and relative roughness pitch of 8. Five rib roughened plates having flow-attack-angle (α) from 30° to 75° have been tested. The thermo-hydraulic performance parameter based on equal pumping power (η), friction factor (f) and Nusselt number (Nu), were found to be highest for α=60°. The results obtained at α=60° were compared with those of continuous V-down rib for same rib-roughness parameters.

Heat Transfer and Friction Factor Correlations for Rectangular Solar Air Heater Duct Having 60° Inclined Continuous Discrete Rib Arrangement

The heat transfer coefficient between the absorber plate and air can be considerably increased by using artificial roughness on the underside of the absorber plate of the solar air heater. An experimental study has been carried out for enhancement of heat transfer coefficient of a solar air heater having roughened air duct provided with artificial roughness in the form 60° inclined discrete rib. Increment in friction factor by provided with such artificial roughness element has also been studied. The effect of system parameters such as relative roughness height (e/D), relative roughness pitch (P/e) and relative gap position (d/W) have been studied on Nusselt number (Nu) and friction factor (f) with relative gap width (g/e) 1 and Reynolds number (Re) varied from 4105 to 20526. Considerably enhancement in heat transfer coefficient has been achieved with such roughness element. Using experimental data correlations for Nusselt number and friction factor have also been developed for such solar air heaters, which gives a good agreement between predicted values and experimental values of Nusselt number and friction factor. Research Article British Journal of Applied Science & Technology, 1(3):67-93, 2011 68

Heat transfer and friction factor of discrete V-down rib roughened solar air heater ducts

In this paper, results of experimental investigation on heat transfer and friction in rectangular ducts roughened with a new configuration of “discrete V-down ribs” on one broad wall are presented. The discretization of V-down rib is done by providing small symmetrical gap equal to rib height in both legs of V-shape. The rectangular duct has width-to-height ratio of 12 and the Reynolds number ranged from 3000 to 15 000. The roughened wall is uniformly heated while the remaining three walls are insulated. These boundary conditions correspond closely to those found in solar air heaters. The rib roughness has height-to-hydraulic diameter ratio of 0.043, angle of attack of 60°, and pitch-to-height ratio of 10. The relative gap position was varied from 0.20 to 0.80. The effects of gap position on Nusselt number and friction factor have been discussed and results compared with continuous V-down rib roughened duct and smooth duct under similar flow and boundary conditions to investigate the enhancement in Nusselt number and friction factor. The maximum enhancement in Nusselt number and friction factor has been obtained at relative gap position of 0.65 and is of order of 2.88 and 3.03 times of that of the smooth duct, respectively. The thermohydraulic performance of solar air heater provided with such rib roughness is considerably enhanced.

An experimental study of the flow and heat transfer between enhanced heat transfer plates for PHEs

The flow and heat transfer between inclined discrete rib plates for plate heat exchangers have been experimentally studied. Dye injection method is used to visualize the flow structures. The visualization results show that front vortex, rear vortex and main vortex are formed between the plates. The rib parameter influence is also studied using visualization method. The pressure drop and heat transfer between the inclined discrete rib plates as well as that between inclined continuous rib plates and smooth plates are also measured. The measured results show that the inclined discrete rib plate can enhanced heat transfer 20–25% at the same pumping power compared with the commonly used inclined continuous rib plates.

Detailed measurement of heat/mass transfer with continuous and multiple V-shaped ribs in rectangular channel

Abstract Effects of aspect ratio on heat/mass transfer were investigated in rectangular channels with two different V-shaped rib configurations, which are continuous V-shaped rib configuration with a 60° attack angle, and multiple (staggered) V-shaped rib configuration with a 45° attack angle. The square ribs were attached on the test section in a parallel manner. A naphthalene sublimation method was used to measure the local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices were generated in the channel, and high transfer region was formed at the center of the ribbed walls. However, for the multiple V-shaped rib configuration with 45° attack angle, asymmetric secondary flow patterns were generated due to its geometric features, resulting in uniform heat/mass transfer distributions. The effect of channel aspect ratio was more significant for the continuous 60° V-shaped rib than for the multiple 45° V-shaped rib configuration.