Accurate prediction of two-phase frictional pressure gradients is crucial for operating two-phase flow systems within safe limits. However, existing correlations predict with high mean absolute errors (MAEs) especially for new low-GWP refrigerants, for instance, 53% for R1234yf and 41% for R32. To overcome this challenge, the present study developed a new correlation for frictional pressure gradient for mini/micro-channels applicable to both conventional and low-GWP working fluids. The correlation incorporates the effects of channel geometry, heat flux, inertial forces, and viscous forces through several dimensionless parameters including aspect ratio, heated-to-wetted perimeter ratio, boiling number, liquid-only Weber number, liquid-only Reynolds number, liquid-to-vapor density ratio, and two-phase Prandtl number. The amassed database consists of 3473 data points, of which 2882 are for circular and 591 are for non-circular cross-sectional geometries. The database encompasses flow boiling of 17 different fluids in single circular and non-circular mini/micro-channels of 0.529-8 mm hydraulic diameters with a mass velocity range of 33-2738 kg/(m2.s). This database is used to evaluate the predictive performance of 18 existing correlations. Following this assessment, a new universal correlation is developed using nonlinear optimization on the consolidated database. The new correlation accurately predicts both circular and non-circular channels with respective MAEs of 19.22% and 23.13%, and using the entire combined database yields an MAE of 19.88%.

Despite their critical importance to a wide range of space applications, experimental data and predictive tools for cryogenic pool boiling in microgravity remain extremely sparse. The present study develops a new correlation for cryogenic nucleate pool boiling under microgravity conditions to support the thermal design of space-based cryogenic systems. A consolidated database was assembled from the open literature, comprising 105 microgravity datapoints for LH2 (61 datapoints), LO2 (31), and LN2 (13) obtained from experiments conducted using drop towers, parabolic flights, and magnetic-field compensation techniques. The database spans a range of reduced-gravity and pressure conditions, with the gravity levels of a/g = 0.008–0.1 and pressures ranging from 0.099 to 0.35 MPa. Most of the data correspond to upward-facing heater orientations, with only limited datasets available for vertical and downward-facing configurations. Several widely used terrestrial correlations, along with the two principal microgravity correlations available in the literature, were evaluated against the consolidated database. The results indicate that most of these correlations lack generality and do not provide consistent accuracy across different cryogens. Guided by the parametric trends observed in the database, particularly the enhanced sensitivity to surface thermal conductivity and the need for a cryogen-sensitive fluid parameter, a new microgravity correlation is proposed. The formulation scales an Earth-gravity baseline nucleate boiling correlation using molar mass, wall thermal conductivity, and a gravity-scaling term. The proposed correlation predicts the consolidated database with an overall mean absolute error of 14.10%, with more than 85% of datapoints falling within ±30% error band. The results further indicate that, for cryogenic nucleate boiling, heat-transfer behavior under microgravity exhibits a weaker dependence on gravity level but an increased sensitivity to near-wall and interfacial transport processes, as well as to surface thermal properties.

This study builds upon the authors' prior work on cryogenic pool boiling, which established baseline heat transfer coefficient (HTC) correlations for nucleate boiling (NB), transition boiling (TB), and film boiling (FB), as well as correlations for the critical heat flux (CHF) and minimum heat flux (MHF). While the earlier work focused exclusively on baseline conditions, the present study extends those findings by incorporating the parametric effects of subcooling and key system characteristics, namely pressure, surface roughness, material, size, and orientation of the heated surface. Updated correlations for the boiling regimes and transition points were developed based on an expanded database compiled from the literature. The data revealed that the minimum dimension of the heated surface (Lc) has a significant influence on the FB HTC, as well as CHF and MHF when Lc is less than three times Taylor's most dangerous wavelength (lambda d), but approach asymptotic values beyond this threshold. For example, applying the effect of heated surface length in FB HTC reduces the MAE for LH2 from 33.71% to 12.77%. Moreover, surface roughness is found to strongly affect the NB regime, while exerting negligible impact on the other regimes. Specifically, the inclusion of a surface roughness multiplier in the NB correlation reduces MAE from 47.68% to 22.43% for rough surface data. Increasing the thermal conductivity of the heating surface enhances both the CHF and NB HTC but reduces the MHF. Due to the absence of direct contact between the liquid and the surface, the FB regime is largely unaffected by surface properties. Subcooling is shown to enhance heat transfer across all boiling regimes. To capture all these effects, multiplier functions were introduced to modify the previous baseline correlations for each boiling regime and transition points. The updated correlations demonstrate excellent agreement with experimental data and extend the applicability of the authors' previous models to realistic cryogenic boiling scenarios involving diverse configurations.

The modern world is shifting towards digitalization and miniaturization, leading to higher flux densities in electronic components and machines. However, conventional cooling methods, such as air-cooled smooth channels, are proving inadequate for removing the huge amounts of heat generated, thereby compromising the reliability and operational lifespan of electronic systems. This necessitates urgently exploring and analyzing modern techniques like microchannel cooling to improve its efficiency. This work uses ANSYS to conduct numerical simulations and investigates the heat transfer and flow behavior in a microchannel heat sink. The smooth channel is used to investigate and validate the flow behavior with the available literature. Moreover, a biomimetic design using trefoil cavity was mounted on different walls of smooth channels to see the performance improvement. The performance comparison of a smooth channel with a cavity channel was made by utilizing the heat transfer coefficient, Nusselt number, friction factor, pressure drop, thermal enhancement factor, thermal resistance, and thermal transport efficiency. The study reveals that adding trefoil cavities has improved the performance of the microchannel heat sink. Furthermore, it was observed that the addition of trefoil cavities to the base wall (MC-BWTC) has superior performance than that of side wall (MC-SWTC) and all wall trefoil cavities (MC-AWTC). Specifically, MC-BWTC increases the overall performance of smooth channel by 31 %, MC-SWTC by 21 %, and MC-AWTC by 17 %, respectively.

This study presents computational simulations and experimental validation of liquid nitrogen flow boiling under two gravity conditions: microgravity and Earth gravity. The primary objective is to evaluate the impact of gravity on two-phase flow behavior and heat transfer performance. A previously developed and validated multiphase CFD model -based on the Coupled Level Set Volume-of-Fluid (CLSVOF) method and augmented with additional momentum source terms -was employed to simulate cryogenic flow boiling in microgravity. In the first part of the study, microgravity simulations were performed at a mass velocity of 696 kg/m2 center dot s and three heat flux levels corresponding to 11 %, 23 %, and 45 % of the critical heat flux. Model validation was conducted using wall temperature data acquired during parabolic flight experiments. The simulation results demonstrated strong agreement with the experimental measurements, with a maximum temperature deviation of 3.3 K and a mean absolute error (MAE) of 1.33 % across tested conditions. In the second part of the study, the validated CFD model was employed to perform three additional simulations for vertical upflow under terrestrial gravity, using identical operating conditions. This allowed for a systematic assessment of gravitational effects. Direct comparisons were made between the microgravity and Earth gravity cases, focusing on key simulation outputs, including twophase flow contours, spatial fluid temperature distributions, axial wall temperature profiles, fluid vorticity fields, and mean velocity differences. The results highlight the influence of gravity on the thermal -hydraulic behavior of cryogenic flow boiling -effects that are otherwise extremely difficult to quantify or measure experimentally.

The present study addresses the limited availability of reliable data and predictive tools for transition boiling (TB) of cryogens and the lack of methods for predicting the wall temperature at the critical heat flux (CHF) point (TCHF) during saturated pool boiling from flat surfaces. A thorough literature review was conducted which identified six existing TB correlations but none for TCHF. To fill this gap, extensive steady-state cryogenic fluid data from global sources were compiled, focusing on saturated pool boiling under Earth gravity. Two databases were amassed: one for TCHF (200 datapoints for clean and 36 for treated surfaces) and another for TB (133 datapoints for clean surfaces). The existing TB correlations performed poorly against the consolidated database. Since TB is affected by both the CHF and minimum heat flux (MHF) points, accurate correlations for heat flux and temperature at both points are essential. The authors' recent work has already provided correlations for heat fluxes at the CHF and MHF points, and wall temperature at the MHF point. This study introduces a new predictive method for TCHF and utilizes it to predict the heat transfer coefficient (HTC) in the TB regime. The new correlations show very good predictive accuracy with mean absolute errors (MAEs) of 10.71 % and 14.84 % for TCHF and the TB HTC, respectively. Additionally, the present study emphasizes the need for further experiments to expand the cryogenic database, covering more cryogens and broader ranges of operating conditions.

Constructing a complete and continuous boiling curve is a very challenging endeavor because correlations have historically been developed in individual studies only for specific boiling regimes or transition points, often using different fluids and operating conditions. The present study tackles systematically the complexities of this endeavor by relying on predictive correlations recently developed by the present authors for all individual pool boiling curve regimes and transition points for cryogenic fluids. It is shown how, by integrating the previous correlations and correcting for any discontinuities between correlations, a continuous saturated pool boiling curve can be constructed across the entire range of wall superheats and heat fluxes for all cryogens. The predicted boiling curves are validated against experimental data for key cryogens such as liquid helium, liquid hydrogen, and liquid nitrogen across varying pressure ranges. The critical heat flux is shown to decrease with increasing surface orientation angle, measured from horizontal upward facing, and this effect becomes more pronounced with increasing pressure. The heat transfer coefficient in both the nucleate boiling and film boiling regions increases with increasing pressure, but this trend, especially for nucleate boiling, is less evident at very high pressures. Reinforcing published trends, the decrease in the nucleate boiling heat transfer coefficient near the critical heat flux point is clearly captured, especially for cryogens with relatively high saturation temperatures, such as liquid oxygen and liquid methane. Additionally, the presented methodology shows the wall superheats for the critical heat flux and minimum heat flux points decrease with increasing pressure, excepting very high pressures. Overall, the methodology for generating the complete boiling curve for cryogens is validated over broad pressure ranges, up to 75 % of critical pressure (p = 0.75pc).

This study addresses the critical need for a reliable database for the minimum heat flux (MHF) point in saturated pool boiling of cryogens. Relying on a comprehensive review of the relatively sparse published literature, a key objective of the study is to amass a MHF database, which is then used to investigate influences of various parameters on MHF, assess the accuracy of published correlations, and develop new correlations specifically tailored to cryogenic fluids. By applying stringent point-by-point evaluation criteria, 165 data points for MHF point temperature ( T min ) and 158 data points for MHF point heat flux ( q" min ) are aggregated, comprising this study's "Consolidated Database" for MHF. This database includes data for liquid helium (LHe), liquid argon (LAr), liquid hydrogen (LH2), 2 ), and liquid nitrogen (LN2) 2 ) and boiling from clean as well as treated (coated or oxidized) surfaces. A total of 9 correlations for T min and 10 for q" min are evaluated for accuracy against the new Consolidated Database. Leveraging insights from prior correlation results and trends from the new Consolidated Database, new universal correlations are formulated for both T min and q"min. min . The new correlation for T min features Mean Absolute Errors (MAEs) of 9.05 % for clean surfaces and 7.7 % for treated surfaces. Similarly, the new q" min correlation shows MAEs of 21.50 % for clean surfaces and 25.22 % for treated surfaces. While the new correlations represent a significant advancement in the development of predictive tools for cryogens, this study points to a need for more comprehensive experimental investigation of heat transfer aspects of cryogens, which will undoubtedly further improve the robustness and accuracy of the new correlations.

The present study is motivated by the absence of a comprehensive pool film boiling database for cryogenic fluids. Amassing such a database is deemed essential for the thorough evaluation of existing models and correlations, simultaneously laying the groundwork for the development of new advanced predictive methodologies. To address this research gap, a Consolidated Cryogenic Pool Film Boiling Database was meticulously compiled, encompassing 1,209 data points for heat transfer coefficient (HTC) from flat surfaces across various orientations, from horizontal (θ = 0°) to vertical (θ = 90°). The exhaustive database enabled a comprehensive evaluation of prior models and correlations, revealing significant errors, particularly for elevated superheat conditions. In response, a finely tuned universal correlation for all cryogenic fluids is proposed, surpassing the predictive capabilities of its predecessors. The inclusion of a radiation term in the correlation contributes to its superior performance, especially in scenarios involving elevated temperatures, resulting in a Mean Absolute Error (MAE) of 12.94 % for the entire database, with 91.07 % of predictions falling within ±30 % of the data, and 98.92 % within ±50 %. Furthermore, outstanding performance is realized for specific orientations, with MAEs of 15.47 %, 7.92 %, 3.78 %, and 11.59 % for orientations θ = 0°, 30°, 60°, and 90°, respectively. This achievement situates the new correlation as a robust tool for thermal design and performance assessment across a diverse spectrum of devices and systems, also marking a significant advancement in understanding of cryogenic pool film boiling heat transfer phenomena.

This study proposes using novel ogive-shaped ribs and cavities to enhance the thermal performance of a microchannel heat sink (MCHS). A three-dimensional conjugate numerical model was employed to investigate the impact of these modifications, i.e., ogive shape ribs and cavities, on the hydro-thermal performance of MCHS in laminar flow regime (Reynolds number 100-1000). The results show that flow separation occurs on the trailing edge of ogive ribs, promoting convective heat transfer by disrupting the boundary layer and enhancing fluid mixing on the downside of ogive ribs due to the formation of recirculation zones. Conversely, stagnant zones are created inside the ogive cavity due to very low fluid local velocity which results in a decrease of local Nusselt number. The study reports a 41.34% maximum improvement in Nusselt number for MCHS with ogive ribs on side channel walls and a maximum thermal enhancement factor of 1.42 for MCHS with ogive ribs on the bottom channel wall.

This study proposes the use of symmetrical ogive-shaped ribs on the walls of microchannel heat sinks (MCHS) to improve their thermal performance with minimal pressure drop. The ribs are arranged in three different configurations: ribs attached to all channel walls (MC-SAWR), ribs attached to side channel walls (MC-SSWR), and ribs attached to the bottom channel wall (MC-SBWR). Numerical investigations are conducted using the laminar conjugate heat transfer model to study the flow and heat transfer characteristics of the MCHS. The augmentation entropy generation number and thermal enhancement factor criterion are used to quantify the overall hydrothermal performance of the MCHS. The results show that the inclusion of symmetrical ogive-shaped ribs improves the Nusselt number of MCHS. The MC-SAWR configuration shows the highest Nusselt number improvement of 13–50% compared to the smooth MCHS over the Reynolds number range of 100–1000. Additionally, the MC-SAWR configuration shows a maximum reduction of 58% in the total entropy generation rate as it has the smallest augmentation entropy generation number value of 0.42. In terms of the thermal enhancement factor criterion, the MC-SSWR configuration shows the highest performance at Reynolds numbers below 400, but the MC-SAWR configuration outperformed the MC-SSWR configuration at Reynolds numbers above 400. Therefore, the MC-SAWR configuration is the best configuration that provides high cooling performance.

In this study, 3D numerical conjugate heat transfermodeling is used to investigate the thermal and hydraulic characteristics of the microchannel heat sink (MCHS) with different configurations of novel ogive shape ribs on channel walls. It was found that new proposedMCHS configurations with ogive ribs have a high Nusselt number as compared to the smoothMCHS because ogive ribs enhance the heat dissipation between channel walls and fluid by continuously interrupting the thermal boundary layer development. MCHS configuration with ogive ribs mounted on bottom wall improves the Nusselt number of smooth MCHS by 1.13-1.87 times, while MCHS with ogive ribs mounted on both side walls and MCHS with ogive ribs mounted on bottom channel wall improve Nusselt number by 1.12-1.70 and 1.08-1.59 times, respectively, at Re 100-1000. In terms of thermal enhancement factor criterion, the MCHS with ogive ribs on side walls shows superior performance at Re 100-300 and has the highest thermal enhancement factor. While MCHS with ogive ribs on bottom wall outperformed other configurations in terms of thermal enhancement factor at Reynold number> 300. Amaximum thermal enhancement factor of 1.42 is reported for MCHS with bottom wall ribs ogive at Re = 1000.

Since the fossil reserves are depleting day by day, the trend of modern energy sector is going towards renewable energy. The demand of solar power plants is therefore at the peak nowadays across the globe. However, the construction of these plants is extremely dependent on feasibility study to estimate the real solar potential before installing it in any region. To evaluate the solar energy potential of Peshawar region in Pakistan, Ground-based global horizontal irradiance (GHI) and direct normal irradiance (DNI) were compared with satellite-based model SUNY. Ground measurements were done at the University of Engineering and Technology Peshawar (UET Peshawar) with the help of pyranometer and shadowband irradiometer. Comparison of the data showed that there was a maximum difference of 42.90% in ground and satellite-based GHI in the month of December. Minimum difference in GHI was found for the month of March that was −3.83%. Moreover, ground-based GHI was overestimated in the month of February, March, and April, while in rest of the months, satellite values of GHI exceeded the ground measurements. Similarly, maximum difference of 55.86% was found in the month of November between ground and satellite-based DNI while minimum difference of −3.34% was seen in DNI in the month of March between the two data. Furthermore, satellite-based DNI was underestimated in the months of February, March, and April while in rest of the months it was overestimated compared to ground measurements. In addition to this, correlation of ground and satellite-based GHI and DNI showed R2 value of 0.8852 and 0.4139, respectively. The results of this study revealed that the difference between ground measurements and satellite values was considerable and hence real time measurements are necessary to properly estimate solar energy resource in the country.

In this article, a numerical technique based on polynomials is proposed for the solution of one and two-dimensional time-fractional Burgers equation. First, the given problem is reduced to time discrete form using θ-weighted scheme. Then, with the help of Lucas and Fibonacci polynomials the given PDEs transformed to system of algebraic equations which is easy to solve. The proposed algorithm is validated by solving some numerical examples. Despite this, convergence analysis of the scheme is briefly discussed and verified numerically. The main objective of this paper is to show that polynomial based method is convenient for 1D and 2D nonlinear time-fractional partial differential equations (TFPDEs). Efficiency and performance of the proposed technique are examined by calculating L2 and L∞ error norms. Obtained accurate results confirm applicability and efficiency of the method.

The sustainability and economic development is intertwined with the energy consumption and conversion processes. To suffice the ever-increasing demand of energy consumption amid environmental concerns, energy conservation and recovery along with the harnessing of renewable energy has been mandated by the policy regulators. In any energy conversion process, heat exchangers are vital operation component and has been part of any energy conversion process since the Nineteenth century. However, due to the increased energy demand, requirement of high efficiency and space and material constraints, the need for miniaturized light-weight heat exchangers with adequate heat transfer characteristics persists. Traditional heat exchangers are outdated because of its large space requirements and comparatively less heat removal rate. The miniaturized micro channel heat sink (MCHS) with tubes of about less than 1 mm have a tremendous potential to further enhance the heat transfer performance. However, its simple design doesn’t cope with the modern requirements of heat removal. Therefore, many researchers have tried to improve its performance using different techniques. The present study reviews some of the most important techniques applied to MCHS. These techniques include, coolant types used in MCHS, MCHS shapes, flow conditions, numerical methods used for this research, and materials used to manufacture MCHS. Moreover, some recommendations have been given to provide opportunities to researchers for future aspects.

The present study aims to investigate the performance of microchannel heat sink via numerical simulations, based on the first and second law of thermodynamics. The heat transfer and flow characteristics of rectangular microchannel heat sinks have been improved by adding six different types of surface enhancers. The cross-sections include rectangular, triangular, and hexagonal-shaped ribs and cones. The cones have been created from the same cross-sections of ribs by drafting them at an angle of 45° orthogonal to the base, which is expected to decrease the pressure drop, dramatically. The performance of ribs and cones has been evaluated using different parameters such as friction factor, wall shear stress, entropy generation rate, augmentation entropy generation number, thermal resistance, and transport efficiency of thermal energy. The results of the present study revealed that the novel effect of coning at an angle of 45° reduces frictional losses (Maximum pressure drop reduced is 85%), however; a compromise on thermal behavior has been shown (Maximum Nusselt number reduced is 25%). Similarly, the application of coning has caused a significant reduction in wall shear stress and friction factor which can lead to reducing the pumping power requirements. Moreover, triangular ribs have more ability to transfer thermal energy than rectangular and hexagonal ribs. Furthermore, it has been examined in the present study that the trend of total entropy generation rate for triangular ribs decreases up to Re = 400 and then increases onwards which means that thermal losses are more significant than frictional losses at lower Reynolds number. However, frictional losses dominate over thermal losses at higher Reynolds numbers, where vortex generation takes place, especially in triangular ribs.

The aim of this paper is to numerically analyze the hydrothermal behavior of different cross-sectional geometries of microchannel heat sinks (MCHSs) and conduct a comparative analysis of traditional and non-traditional designs using ANSYS Fluent. It is expected that the proposed design discussed in this paper will improve the performance of MCHSs by maximizing the cooling capability and minimizing the thermal resistance and entropy generation rate, thus leading to better energy efficiency. The channel designs include a rectangular microchannel (RMC), a circular microchannel (CMC), an elliptical microchannel (EMC), a trapezoidal microchannel (TMC), a hexagonal microchannel (HMC), and a new microchannel (NMC) which has a plus-like shape. The discussed geometry of the NMC is designed in such a way that it maximizes the cross-sectional area and the wetted perimeter of the channel, keeping the hydraulic diameter constant (D-h = 412 mu m). The performance of various channels is compared on the basis of pressure drop, wall temperature, thermal enhancement factor, thermal resistance, thermal transport efficiency, and entropy generation rates. It has been observed that the NMC is capable of cooling effectively and it can achieve a minimum wall temperature of 305 K, thus offering the lowest thermal resistance (R-th), irreversible heat loss, and entropy generation rate. Moreover, the NMC has achieved the highest value of the thermal enhancement factor, i.e., 1.13, at Re = 1,000. Similarly, it has the highest thermal transport efficiency of almost 97 % at Re = 1,000, followed by the TMC and the RMC. Overall, the NMC has achieved the best performance in all aspects, followed by the RMC and TMC. The performance of the EMC, the CMC, and the HMC was found to be the worst in this study.

Traditional cooling technologies are now become inadequate for electronic chips cooling due to their size reduction and increase in generated heat flux. Microchannel heat sink (MCHS) is promising candidate due to its superior cooling performance than its competitors. The aim of this study is to investigate the hydrothermal performance of MCHS with novel trefoil shape ribs. The three configurations of trefoil shape ribs considered in this study are: MC-AWTR (all wall trefoil ribs), MC-SWTR (side wall trefoil ribs), and MC-BWTR (base wall trefoil ribs). The performance of MCHS is evaluated on the basis of thermal enhancement factor, thermal resistance, transport efficiency and entropy generation at Re=100-1000. The results predict that addition of trefoil ribs to walls of smooth microchannel significantly improve its thermal performance at cost of pressure penalty. Nusselt number and average heat transfer coefficient tends to increase with rise in Reynolds number while thermal resistance and entropy generation reduces. Highest pressure drop occurs for MC-AWTR configuration due to more obstruction of the fluid flow. MC-SWTR configuration has highest thermal enhancement factor among all configurations while MC-AWTR has lowest due to large pressure drop penalty at all Reynold numbers. So, overall MC-SWTR shows superior performance than any other considered trefoil rib configuration.

In the present study, hydrofoil ribs made from NACA 2412 profile were mounted in a novel way at all walls of microchannel heat sink with various configurations to improve its thermo-hydraulic characteristics. The various configurations include comparison between staggered and aligned arrangements, and the variation of rib spacing between two consecutive hydrofoils (Sr = 0.2–0.6 mm) at a constant cord length (Cr = 0.4 mm). The study was performed with the help of commercially available computational fluid dynamics tool, ANSYS Fluent. The performance of various configurations were compared with each other and with smooth channel using parameters like friction factor (f), Nusselt number (Nu), and overall performance is determined by thermal enhancement factor ( $\eta$ ). The results of this study showed that the best performance is achieved by the configuration where rib spacing becomes equal to cord length (Sr = 0.4 mm). Moreover, it has been observed in this study that staggered configuration performed better than aligned configuration.

The present study investigates the thermo-hydraulic characteristics of a microchannel sink with novel trefoil Shaped ribs. The motivation for this form of rib shape is taken from the design of lung alveoli that exchange oxygen and carbon dioxide. This study has been conducted numerically by using a code from the commercially available Fluent software. The trefoil shaped ribs were mounted on the centerline of different walls of the microchannel in three different configurations. These consisted of base wall trefoil ribs (MC-BWTR), sidewall trefoil ribs (MC-SWTR), all wall trefoil ribs (MC-AWTR) and smooth channel (MC-SC) having no ribs on its wall. The streamline distance between the ribs was kept constant at 0.4 mm, and the results were compared by using pressure drop (∆p), Nusselt number (Nu), thermal resistance (Rth) and thermal enhancement factor (η). The results indicated that the addition of trefoil ribs to any wall improved heat transfer characteristics at the expense of an increase in the friction factor. The trends of the pressure drop and heat transfer coefficient were the same, which indicated higher values for MC-AWTR followed by MC-SWTR and a lower value for MC-BWTR. In order to compare the thermal and hydraulic performance of all the configurations simultaneously, the overall performance was quantified in terms of the thermal enhancement factor, which was higher than one in each case, except for MC-AWTR, in 100 < Re < 200 regimes. The thermal enhancement factor in the ribbed channel was the highest for MC-SWTR followed by MC-BWTR, and it was the lowest for MC-AWTR. Moreover, the thermal enhancement factor increases with the Reynolds number (Re) for each case. This confirms that the increment in the Nusselt number with velocity is more significant than the pressure drop. The highest thermal enhancement factor of 1.6 was attained for MC-SWTR at Re = 1000, and the lowest value of 0.87 was achieved for MC-AWTR at Re = 100.