Friction Factor Research Articles

Experimental study on single-phase heat transfer performance of internal helically finned tubes covering low Reynolds number in turbulent flow

ABSTRACT This paper experimentally investigated the heat transfer performance of two internal helically finned tubes covering low Reynolds number in turbulent flow. A water-ethylene glycol mixture flowed inside and R134a boiled outside. The numbers of fin, the helix angles, and the ratios of fin height to diameter for the two test tubes were 38 and 60, 60° and 45°, and 0.0534 and 0.0222, respectively. The experimental Reynolds number was lower to 5400, covering the critical Reynolds number Re cr for turbulent flow. The data was divided into good and poor linearity regions by the modified Wilson plot method, which was much suitable for this case than that the data was treated as one region. The j factors showed ascending trend for Re below Re cr and descending trend for Re above Re cr. Enhancement factors of friction factor or j factor of the test tubes increased with increasing Reynolds number and eventually approached at the maximum for the Reynolds number above Re cr. The test tubes exhibited maximum efficiency indexes of 2.1 and 1.88, indicating superior overall performance compared to the majority of existing tubes. By utilizing the experimental data, a correlation was established basing on the critical Reynolds number, resulting in over 96% of the predicted errors falling within the range of ± 8%. This study has the potential to provide valuable insights for industrial implementation and the advancement of general correlation development.

Investigation of Sidewall and Reynolds Number Effects in a Ribbed Square Duct

This paper presents a comprehensive three-dimensional Direct Numerical Simulation (DNS) investigation of flow characteristics over a roughened wall in a duct, exploring bulk Reynolds number variations from 4400 to 13,200 and considering the influence of side walls. Notably, a significant increase in friction factor highlights heightened resistance to flow due to surface roughness, emphasizing the importance of considering surface conditions in engineering applications. The study reveals three recirculation zones in the streamwise direction, indicating intricate separation phenomena caused by the interaction between the ribbed wall and the flow. Furthermore, the presence of sidewalls creates two major vortices perpendicular to the flow direction, highlighting the complexity of the vortical structures in this configuration, crucial for predicting flow behavior and optimizing system performance. The study demonstrates that the influence of the Reynolds number on these vortices is not well-scalable with respect to outer units, in contrast with respect to smooth ducts. Investigating side-wall effects, increased turbulent production rate, and non-equilibrium turbulence along the side walls highlight the sensitivity of turbulent stresses to Reynolds number and side-wall proximity. In conclusion, the paper provides novel insights into the interplay between Reynolds numbers, roughened surfaces, and boundary conditions in turbulent flows, laying a foundation for a deeper understanding of the flow in duct with high roughness.

Machine learning based tool for the efficient estimation of geometric features of aggregated aerosol particles

While significant progress has been made in developing models for the formation and transport of aerosol aggregates, there is still a need for a simple, versatile tool capable of estimating intrinsic properties of aggregated particles. Scalar friction factor is an important parameter used extensively in the field of aerosol science. The scalar friction factor for non-spherical particles can be computed with the information on two geometric parameters, hydrodynamic radius (Rh) and orientationally averaged projected area (PA), depending on the momentum transfer regime. Although the existing methods for the estimation of these descriptors are efficient, many applications involve frequent estimation of these geometric descriptors, which can be time-consuming. We propose a Machine Learning (ML) based tool that can predict these descriptors using Fractal Dimension, pre-exponential factor, number of monomers and anisotropy factors as the input. An extensive database comprising fractal parameters, anisotropy factors, Rh, and PA is developed for testing and training the ML models. Five ML methods were assessed, with random forest (RF) identified as the most effective. The RF model demonstrated high accuracy in the testing phase, with R-squared value of 0.9875 for Rh and 0.9979 for PA, and average errors of 3.17% and 1.21% for Rh and PA, respectively. The predicted Rh and PA values were then used to estimate other relevant 3-dimensional properties such as mobility diameter, shape factor, and aerodynamic diameter, with the results indicating high accuracy of the prediction tool. Python-based tool offers ease of use, and can be easily integrated with other numerical codes.

Optimizing of a metal foam-assisted solar air heater performance: a thermo-hydraulic analysis of porous insert placement.

A numerical assessment of the heat transfer efficacy of a solar air heater (SAH) was carried out. The SAH is supplied with a porous metal foam layer to improve thermal mixing. Both the local thermal non-equilibrium (LTNE) and Darcy-extended Forchheimer (DEF) models were employed to forecast fluid and thermal transport within the partly filled SAH channel. The analysis was performed for various values of dimensionless foam layer lengths ( ), pore densities ( ), and Reynolds numbers ( ) at a fixed value of layer thickness ( ). Based on the position of the porous layer, three distinct arrangements, marked as Case 1, Case 2, and Case 3, were explored. Regarding the parameters examined, the findings indicate a definite improvement in the average Nusselt number ( ), but unfortunately, the friction factor also increases unfavorably. By reducing the length of the porous layer, a reasonable reduction in heat transfer rate and a significant decrease in pressure drop were noticed. The results showed about 26.64%, 48.73%, and 70.74% reductions in pressure drop by reducing the dimensionless foam length from 1 to 0.25, 0.5, and 0.75 respectively for at . On the other side, there are only about 11.05%, 23.11%, and 40.78% reductions in . The exhaustive analysis of the thermal performance of SAH was conducted using the thermal performance factor (TPF), which considers the trade-off between the SAH channel's potential for improved heat transmission and its cost for pressure loss. The TPF may reach a maximum of 2.82 compared to the empty channel when the metal foam layer is inserted with , for , and .

New formula of vegetation roughness height and Darcy–Weisbach friction factor in channel flow

Assessing the flow resistance caused by vegetation in rivers is a hot topic in the field of hydraulics and eco-hydrology. Based on mathematical experiments by first-order closure models, new roughness height of vegetation is proposed linked with the three factors that vegetation arrangement concentration, submergence ratio, and the ratio of width to height of vegetation. Besides, new Darcy–Weisbach friction factor is built for vegetated flow. Moreover, both collected and present experimental data are adopted for verification of the roughness height and friction factor. Compared with models from other research groups, results show that the new formulas proposed in this study have high accuracy for predicting vegetation resistance in ecological restoration and water resources management in rivers.

Thermohydraulic performance augmentation of triangular duct solar air heater using semi‐conical vortex generators: Numerical and experimental study

AbstractThermohydraulic performance augmentation using turbulence promotors is a commonly adopted technique in solar air heater (SAH) applications. This article presents the thermohydraulic performance augmentation of triangular duct SAH using semi‐conical vortex generators (SCVG) using computational fluid dynamics and experimental methodology for various flow Reynolds numbers ranging from 6000 to 21,000. An in‐depth parametric analysis is undertaken to establish the influence of flow attack angle, relative longitudinal pitch, relative transverse pitch and cone diameter of SCVG on the thermohydraulic performance as indicated by the thermohydraulic performance parameter (THPP). The results reveal that the SCVG generates longitudinal vortices and introduces flow impingement zones which significantly affects the flow and heat transfer characteristics of air heaters. Correlations for Nusselt number and friction factor are established, which predicts the performance outcomes with an average error of 6.74% and 4.46%, respectively. The optimal THPP is determined to be 1.74 using artificial neural network model and Bonobo Optimization algorithm. The SCVG produces THPP values well above unity for the entire flow Reynolds number range of 6000–21,000.

Analysis of exergy and heat transfer in a tube fitted with flapped V-baffles

Vortex generator is a device that shows promise in generating streamwise vortices that can be utilized for boosting the rate of heat transmission inside a cooling/heating system with a relatively smaller penalty in terms of friction loss. The primary goal of the current research is to maximize the comparative Nusselt number ratio (Nu/Nu0) to be as large as possible to lower the size of the system while keeping thermal performance as high as feasible to save more energy. Thus, in the current study, the impacts of inserting the flapped V-baffle vortex generator (FBVG) on the thermal effectiveness improvement of a round tube were experimentally investigated. At a fixed attack angle (α = 60°) and baffle blockage ratio (BR = b/D = 0.3), the geometrical behaviors of FBVGs placed periodically along two edges of a straight tape were six different flap angles (θ = 0°, 25°, 35°, 45°, 65° and 90°) and three ratios of baffle pitches (P/D = PR = 2.0, 1.5, and 1.0). The current V-baffles, which were positioned on both tape edges, were designed to reduce friction loss caused by interrupting the central core flow when placed on both tape sides. The measurement results focused on the friction loss and thermal behaviors, including exergy and entropy analyses for Reynolds number from 4750 to 29,270. In the findings, the Nusselt number and friction factor of FBVG at θ = 0° and PR = 1 are, respectively, up to 5.6 and 35.24 times larger than those of the smooth tube. The entropy generation (S˙gen′) seems to decline as θ and PR increase, with the smallest S˙gen′ found at θ = 0° and PR = 1 for lower Re. The FBVG has the greatest exergy efficiency (ηEx) at θ = 0° and PR = 1. To find the true benefits of FBVG, its thermal performance is estimated and seen to reach a maximum at about 2.44 with NuR = 4.65 at θ = 45° and PR = 1. The optimal scenario at θ = 25° and PR = 1 was preferred, however, since it yielded the largest NuR = 5.42 at TEF = 2.39.

Experiments On Gasketed Plate Heat Exchangers with Segmented Corrugation Pattern

Abstract Gasket plate heat exchanger (GPHE) is among the most used heat exchanger types, known for its high effectiveness and compact design. Its remarkable feature is the corrugated plate geometry, typically a Chevron pattern. This work aims to analyze another corrugation pattern, which has segments with different angles to the vertical. The strengths and weaknesses of the segmented plate are still unclear, as the studies on this pattern are scarce. To fill this gap, we experimentally assess the pressure drop and heat transfer in a GPHE composed of 31 segmented plates. The plates have four quadrants, and the combination of low-angle and high-angle plates can form up to six channel types. Pressure and temperature data are acquired in 144 sets of experiments. In the pressure drop results, we observe a considerable discrepancy between the two streams, which leads to a discussion of a relevant phenomenon: the elastic deformation of the plates. If the inner pressure of the streams is not equal, the pressure gradient causes the plates to deform and change the channel geometry. The stream with the higher pressure has its channels expanded, while the lower pressure channels will be strangled. This phenomenon is rarely reported in the literature and strongly affects the pressure drop. Moreover, we present friction factor correlations for six channel types using flow data. Based on the generalized Lévêque analogy in the heat transfer experiments, we argue that the plates' deformation also affects the heat transfer.

Numerical analysis of a solar air heater with offset transverse ribs placed near the absorber plate

Solar air heater (SAH) is used to convert readily available solar energy into useful thermal energy. Several studies have been conducted with different roughness elements on the absorber plate. However, study with ribs which are placed slightly above the heated plate, termed as offset transverse ribs, are still scant in the literature. Such study would explain the effect of flow between the ribs and the absorber plate on heat transfer augmentation in a SAH. With this objective a 2-D numerical study is performed here by solving steady RANS equations with RNG k−ɛ turbulence model. The effect of offset transverse ribs on heat transfer, pressure drop and thermal enhancement factor (TEF) is investigated. The geometrical parameters, such as, relative gap (α), relative height (β) and relative pitch (λ) are varied in the range of 0.0–0.045, 0.015 to 0.09, and 0.0333 to 0.1, respectively. The performance of SAH is evaluated on the basis of highest enhancement in relative Nusselt number (NuR/Nu) and thermal enhancement factor (TEF). A slight gap between the ribs and the absorber plate (α = 0.0075) is observed to yield better thermal performance than that for the attached ribs (α = 0). The maximum enhancement in NuR/Nu is found to be 1.52 for α = 0.0075. However, increasing the gap (i.e., α) prevents the flow reattachment with the absorber plate. Increase in rib height, on the other hand, is found to be more effective in heat transfer enhancement, but with a price of a significant enhancement in pressure drop. This leads to a reduction in the overall performance of SAH. Increment in pitch distance, however, reduces the enhancement in both Nusselt number and friction factor. By considering these three parameters, the highest TEF is found to be 1.042 for α=0.0075, β=0.030, and λ=0.0333 at Re equal to 13000. Finally, correlations for NuR and fR are derived as a function of the parameters investigated for helping the design of SAHs.

The effect of high values of relative surface roughness on heat transfer and pressure drop characteristics in the laminar, transitional, quasi-turbulent and turbulent flow regimes

This study investigated the effect of large values of relative surface roughness on the heat transfer and pressure drop characteristics using simultaneously measured heat transfer and pressure drop data. Experiments were conducted using a horizontal circular tube with a base inner diameter of 5 mm and length of 4 m. One smooth and two rough tubes, with relative roughnesses of 0.04 and 0.11, were tested at different constant heat fluxes between Reynolds numbers of 100 and 8 500. Water was used as the test fluid and the Prandtl number varied between 3 and 7. Contrary to the trend in the Moody Chart, a significant increase in laminar friction factors with increasing surface roughness was observed. Both the friction factors and Nusselt numbers as functions of Reynolds number showed a clear upward and leftward shift with increasing surface roughness across the different flow regimes. Furthermore, the boundaries between the flow regimes were the same for the pressure drop and heat transfer results. The width of the transitional flow regime was narrower for rough tubes and had a differing trend. The quasi-turbulent and turbulent flow regimes occurred at lower Reynolds numbers for increasing roughness. When investigating the relationship between heat transfer and pressure drop, it was found that an increase in surface roughness favoured heat transfer in the quasi-turbulent flow regime. This is useful for rough tubes as the quasi-turbulent flow regime onsets early with regards to the Reynolds number in tubes with large roughnesses.

Experimental investigation of the effects of graphene nano particle added water fluid on heat transfer in a smooth tube with double inserts

In this study, experimental studies were carried out to increase the performance of heat exchangers. The effects of two techniques (inserts and nanofluid) on thermohydraulic performance was investigated simultaneously. The twisted tape and the helically wire coil were originally created. The two separation ratios (0.1 and 0.05), the eight twisted tape pitch ratios (1.9/2.3/2.7/3 and 2.1/2.4/2.8/3.2), the four coil wire pitch ratios (0.8/1.2/1.5/1.6) and three weight fractions (0.5/0.75/1 %) for graphene-water nanofluids were used with the Reynolds number ranging from 5000 to 26,000. Experiments in which a coiled wire coil and twisted tape are used together have been found to increase both the heat transfer rate and the friction factor compared to experiments using distilled water in an empty tube. According to the results of all experiments, it was found that the highest heat transfer rate and friction factor were obtained with the model containing graphene-water fluid used at a weight fraction of 1 %. The highest performance evaluation criteria is found as 2.5 b y using the graphene-water mixture model with a wall separation ratio of 0.05, a twisted tape ratio of 2.1, a wire coil ratio of 0.8 and a 1 % weight fraction among all combinations.

Variable-dimension optimization study and design of internally finned helically coiled tubes heat exchangers based on numerical simulation and experiment

To improve the heat transfer in the helically coiled tubes, a novel type of internally finned helically coiled tube is proposed. The heat transfer and flow resistance characteristics of internally finned helically coiled tubes are investigated numerically. The empirical correlations to calculate the Nusselt number and friction factor of internally finned helically coiled tubes are summarized. The maximum relative error is not exceeding 18 %. To validate the empirical correlations, a test bench to evaluate the performance of internally finned helically coiled tubes heat exchangers is constructed, with a smooth helically coiled tubes heat exchanger as a comparison. The experimental results indicate that 94 % of the data exhibit a relative error of less than 30 % when compared to the fitting correlations. The heat transfer coefficient of the tube side is increased by approximately 30 %. Based on the validated correlations, a generalized variable-dimension optimization approach is proposed to solve the complex problem of optimizing the design of helically coiled tubes heat exchangers. Taking the area margin, heat transfer area and total cost, the structure of internally finned helically coiled tubes heat exchangers is optimized with different limitation. The optimization results show that the internally finned helically coiled tubes heat exchangers have better performance than smooth helically coiled tubes heat exchangers. A helically coiled tubes heat exchanger has been designed in an engineering project and significant improvements have been achieved in various performance indicators.

A case study on effect of twisting technique on heat transfer characteristics in a twisted oval helical tube

Efficient transfer of energy is an important issue addressed by numerous scholars in the literature and various methods have been proposed for enhancing the heat transfer efficiency in heat exchangers. Among many different heat exchangers, helical tubes are one of the most prevalent types of heat exchangers which have many applications in industry. In a case study, effect of twisting technique on the heat transfer in a helical tube with oval cross section has been investigated numerically and the results have been compared with simple circular cross section helical tube. Effect of cross section aspect ratio and twisting ratio in different flow Reynolds numbers has been considered. Results have been presented in terms of Nusselt number, friction factor, PEC, entropy generation and contours of velocity, streamlines and temperature. Results indicate that twisting technique can significantly enhance the heat transfer and all cases have PEC values of above unit which indicates superiority of this method. Also the velocity contours and streamlines indicate that using twisting technique result in higher mixing in the flow which is the reason for higher heat transfer characteristics in twisted oval helical tubes.

Thermal and hydraulic performance of volumetrically heated triply periodic minimal surface heaters

Advanced heat transfer surfaces, mainly Triply Periodic Minimal Surfaces (TPMSs) have great potential to increase heat transfer performance over traditional heat transfer surfaces due to their tortuous flow path and higher surface area-volume ratio. The emergence of additive manufacturing of nuclear fuel motivates experimental investigation of such advanced geometries in the context of a nuclear reactor core. This study employed a novel method to explore the performance of gyroid and diamond TPMS geometries. Volumetrically heated heaters were additively manufactured from conductive polymer filament, and airflow was used to simulate the convective heat transfer from the core within a nuclear reactor. The mass flow and volumetric generation rates were varied, local Nusselt number correlations were obtained using embedded thermocouples to measure the solid and fluid temperature, and friction factor correlations were developed using differential pressure measurements. The gyroid TPMS presented a friction factor 1.5 times higher than the diamond TPMS and 90 times that of the rod bundle. TPMS geometries showed Nusselt numbers 8–10 times higher than that of the rod bundle, also maintaining colder internal temperatures, which suggested that they could sustain 250–275 % higher power density than the rod bundle for a given centerline temperature. Hence, having the potential to greatly increase the safety margins and power output of a nuclear reactor core with similar volume.

Comparative examine of fluid pressure within microchannel through integrated cantilevers for microfluidic applications

This paper aims to explore the concept of a microfluidic pressure sensing mechanism across a microchannel, integrated with different structures of microcantilevers. Various structures of microcantilevers are integrated into a microchannel where laminar fluid flows and the microcantilever senses the fluid velocity and pressure. The different structures of the microcantilever include rectangular, T-shaped, and Pi-shaped designs, which are placed at the centre of the microchannel. The 2D microchannel has a length of 4000 μm and a height of 840 μm, while the microcantilever is positioned at a distance of 2000 μm from the inlet of the microchannel. The analysis of the fluid sensor is observed by plotting graphs of velocity, pressure, displacement of the microcantilever, Reynolds number, and friction factor with respect to the time domain. An inlet velocity of 8.33 µm/s is applied at the microchannel, and the fluidic sensor shows a significant change in the fluid characteristics, comparing them across all types of microcantilevers. The simulation results show that the T-microcantilever has a maximum displacement of 4.97 µm compared to other microcantilevers, with a maximum pressure of 1.58 Pa for the Pi-cantilever. The integrated device is suitable for healthcare applications, measuring fluid pressure in syringes, where the T-microcantilever proves to be more compatible than the other two microcantilevers (R-cantilever and Pi-cantilever). The design and simulation of the microfluidic pressure sensing process are conducted using the FEM tool COMSOL Multiphysics.

Optimization investigation for heat transfer enhancement of fins for plate-fin heat exchangers in cryogenic helium systems

In order to further improve heat transfer performance and high compactness of plate-fin heat exchangers (PFHEs) in cryogenic helium systems, a new type of perforated-serrated fins is proposed by combining traditional serrated and perforated fins. In this paper, the flow and heat transfer characteristics of helium in perforated-serrated fins and serrated fins channels at low-temperature are investigated using numerical simulations. The numerical model invokes the properties of low-temperature helium by NIST-Real-Gas-Model. Meanwhile, Colburn factor j, friction factor f and JF factor are qualitatively evaluated for pressure drop, heat transfer performance and thermo-hydraulic performance, respectively. The results show that new perforated-serrated fins have better heat transfer performance. The j factor of the new fins increases by 32.58% to 15.63% compared with serrated fins. The flow performance of perforated-serrated fins is slightly worse than that of serrated fins, but the overall thermo-hydraulic performance is better, especially at low Reynolds number. Compared with serrated fins, the JF factor of perforated-serrated fins is significantly higher and increase by 25.95% to 10.86%. The optimizing method of fins structure can be used in the actual design of PFHEs in cryogenic helium systems.

Development of correlations of Nusselt number and friction factor of solar thermal collector equipped with hybrid rib roughness

In this advanced and comprehensive research, a pioneering hybrid rib configuration, amalgamating arc and V-shaped ribs, is precisely engineered to delve into the complex synergistic effects between this cutting-edge rib design and the heat transfer and fluid flow behavior within a solar thermal collector (STC) specifically utilized for direct air heating. The focal point of this investigation is the impact of the rib pattern on pivotal performance indicators, notably the Nusselt number (Nu) and the friction factor (f). This specific rib roughness design emanates from an exhaustive analysis of a spectrum of non-dimensional roughness parameters: the arc angle (α), the attack angle (β), the relative positioning of the V ribs (D/w), the relative spacing of the ribs (p/e), and the rib height (e/D). These parameters are studied within defined ranges: 30̊‐60̊, 30̊‐60̊, 0.2–1, 8–12, and 0.023–0.043, respectively. The results of highlight a significant improvement in heat transport, as indicated by a significant increase in the Nusselt number (Nu), which has risen impressively by a factor of 3.08. Furthermore, this paper presents development of correlations for Nu and f, taking into account the roughness parameters of the hybrid ribs and the flow Reynolds number, in order to precisely forecast these key performance measurements.

Impact of Shape Factor on a Couple Stress Flow of a Ternary Hybrid Nanofluid over an Inclined Flat Plate when Non-Uniform Heat Source and Thermal Radiation are Significant: A Darcy-Forchheimer Model

Abstract The study of fluid flow over an inclined flat plate finds applications in a diverse range of engineering fields including aerodynamics, energy production and automotive design. This study theoretically investigates the steady and radiative flow of a ternary hybrid nanofluid (Water + TiO2 + CoFe2O4 + MgO) with couple stress, using the Darcy-Forchheimer model. The flow occurs through a tilted flat plate and is subjected to irregular heat source parameter and entropy generation. The problem’s equations have been transformed into a collection of ordinary differential equations (ODEs), which has been skillfully resolved using the bvp4c solver. Graphs are utilized to elucidate outcomes for two instances of shape components, namely platelet and spherical. An escalation in the couple stress parameter (S) is demonstrated to be inversely related to the fluid velocity, resulting in a drop. Specifically, when 0.5 ≤ S ≤ 3, the friction factor exhibits a decline, with rates of 0.306201851 (for Platelet shape) and 0.304466755 (for Spherical shape). An intriguing observation reveals an augmentation in the generation of entropy as the volumetric fraction of TiO 2 rises. Upon investigation, it has been determined that when the Eckert number (Ecn) increases within the range of 0 ≤ Ecn ≤ 0.3, there is a significant reduction in the Nusselt number. Specifically, the decline is measured to be 0.328685192 for the platelet shape and 0.308939422 for the spherical shape. The utility of the Forchheimer number in regulating the fluid’s motion has been unveiled.

Experimental investigation of the total flow resistance in emergent and submerged rigid canopy flows

In canopy flows, flow resistance mainly originates from vegetation drag and depends on vegetation characteristics and flow conditions. In the present study, a series of experiments were performed in various hydraulic scenarios with high stem Reynolds numbers (2641 ≤ Red≤ 17333) using relatively sparse rigid canopies, represented with four different dimensionless vegetation densities (0.0044, 0.0098, 0.0174 and 0.0392), on a smooth bed. A novel drag plate mechanism was developed to measure the total flow resistance due to the emergent and submerged vegetation arrays in a staggered pattern under subcritical flow conditions. Manning’s roughness coefficient and Darcy–Weisbach friction factor were adopted to represent the total flow resistance in the analyses. Simple empirical relationships based on roughness concentration and submergence ratio were derived to determine the total flow resistance parameters within a broad range of stem Reynolds numbers. Although relationships were proposed in a simple form to be used for direct practical applications, they show similar or better performance in the prediction of total flow resistance parameters than the existing equations in the literature, which require considerable computational effort. Additionally, analyses demonstrated that the results of the present study and those of similar studies regarding canopy flow resistance are in good agreement. Accordingly, the novel drag plate looks promising for measuring flow resistance due to vegetation and bed conditions similar to those in nature.

Exploring the combined influence of primary and secondary vortex flows on heat transfer enhancement and friction factor in a dimpled configuration twisted tape with double pipe heat exchanger using SiO2 nano fluid

The double-pipe heat exchanger has a wider application in food industries, chemical industries, and a wide variety of fields where heat transmission is necessary. This investigation focuses on optimizing heat transfer rates through active, passive, and combined approaches. Within the realm of passive methods, this study specifically examines the use of twisted tape additions in pipe flow. In this study, different factors like swirl flow, primary and secondary vortex flows caused by tape twist, and the presence of a V-cut on the tape are studied. These factors include heat transfer rate, friction factor, and the standard for judging the performance of a V-cut on the tape insert. Experiments have been conducted on a double-pipe heat exchanger with nanofluid silicon dioxide as the working medium. This study encompasses a Reynolds number range of 6000–14,000. Notably, investigations reveal that the introduction of a v-cut on the tape engenders a secondary vortex flow. The enhancement in the Nusselt number at the higher Reynolds number for the primary vortex was observed ineffective as the depth of cut increases. The friction factor is increased by 6.37 times for the e/c ratio, which equals 0.17 (tooth to the depth of the v cut) in comparison to smooth pipe, while the increase in heat transfer rate for the same is 87.73% for Re = 6000.