Friction Factor Enhancement Research Articles

Influence of pitch and height of pentagonal ribbed absorber plate of solar air heater for performance enhancement with environmental analysis

Installation of corrugations on the absorber plate of a solar air heater (SAH) improves its performance. Pentagonal ribs were used as artificial corrugations on the SAH absorber, which is used in an indirect solar dryer. The impact of Reynolds number, Re (4000–22000), corrugation pitch, P (25–200 mm), corrugation height, e (4–20 mm), and corrugation angle, α on the performance of SAH was analyzed by estimating the Nusselt number (Nu), friction factor (f), Nu ratio, f ratio, and thermo-fluidic enhancement index (Etf). Seventeen models were generated in ANSYS DesignModeler. 133 simulations were performed to obtain the optimum pitch (set-1 and 3 simulations) and the optimum height (set-2 simulations) values. Environmental analysis of the SAH was performed by computing the energy payback period (Epb), and CO2 mitigation for a lifetime of 20 years. The Nu increased and the f fell with a rise in Re value. Compared to smooth SAH, the pentagonal ribbed SAH produced a 60–149 % increase in Nu. The highest Etf of 1.839 was obtained at P = 25 mm, e = 7 mm. The proposed optimal dimensions of the pentagonal rib are; e = 7 mm (e/D = 0.05), P = 25 mm (P/e = 3.57), and corrugation angle, α = 18.64°. The Epb and CO2 mitigation are 0.174 years and 57.34 tons, respectively. A comparison of the results with the literature data showed that the present results are acceptable.

Experimental Investigation for Enhancement of Heat Transfer and Friction Factor Through Using V-pattern Ribs Along with Semi-circular Perforated Manner

Experimental Investigation for Enhancement of Heat Transfer and Friction Factor Through Using V-pattern Ribs Along with Semi-circular Perforated Manner

Enhanced heat transfer in sandwich heat transfer unit with metal foam: A numerical investigation

In this study, a novel configuration of a sandwich heat transfer unit (SHTU) is proposed, characterized by the partial filling of metal foam on both sides of the fin. The thermal–hydraulic characteristics of the SHTU are investigated numerically using the local non-equilibrium method and Forchheimer-Brinkman extended Darcy model, and compared with those of traditional flat plate-fin heat transfer unit (PHTU). The effect of geometrical parameters, mass distribution of fin and metal foam, and morphological parameters of metal foam on the characteristic of SHTU was explored. Compared to PHTU the Nusselt number of SHTU increases by 13.1% and 27.6%, while the friction factor increases by 6.2% and 33.1% at Reynolds numbers of 100 and 900, respectively. At a Reynolds number of 500, as the filling ratio increases from 0 to 0.95, the Nusselt number, friction factor, and comprehensive thermal performance enhancement increase by factors of 10, 20, and 3, respectively. When the foam fraction increases from 0.30 to 0.90, the thermal performance enhancement improves by 4–5 times within the investigated range. The impact of porosity (ε) and pore density (ω) on the performance of SHTU is not monotonic. The optimal ω was observed to be in the range of 15–20 PPI, while the optimal ε was found between 0.90–0.92.

Optimizing of heat transfer and flow characteristics within a roughened solar air heater duct with compound turbulators

AbstractThermal systems for solar air heating have been widely used in both industrial and residential contexts, and are essential for converting and recovering solar energy. Thermal performance in solar air heaters (SAHs) can be improved through the repetitive application of artificial roughness to the surfaces. This research work includes a numerical evaluation of SAH performance with artificial rough surfaces made up of combined transverse trapezoidal ribs and chamfered grooves. The ANSYS Fluent software version 2023 R1 was used to simulate SAH with varying relative roughness pitch (), relative roughness heights (), and Reynolds number (). The RNG model was chosen to forecast an enhancement in Nusselt number (), friction factor (), and thermohydraulic performance factor (TPF) for the proposed roughness. Out of multiple roughness parameters analyzed, it was determined that the compound turbulator with and , were the most effective. The TPF for this scenario was determined to be 2.12 at . Finally, a numerical based empirical correlations for and in terms of Re, , and were developed.

Analysis of nanofluid and nano-enhanced phase change material (NEPCM) in a heat exchanger for thermal management of electronic devices

Thermal management of high-power electronic devices is essential to control their enormous heat generation, which is usually the cause of their damage. Scientists have found several solutions for cooling electronic devices, but a counter-current heat exchanger has never been used. In the same context, numerical research on the thermal performance of a proposed new cooling system based on a counterflow heat exchanger combined with a heat sink is conducted in this article. Cu-H2O nanofluid, n-Docosane nano-enhanced phase change material, and water were selected as coolants, and they are compared in terms of temperatures, Nusselt number, heat transfer coefficient, pressure drop, friction factor, and performance enhancement coefficient using a two-phase mixture transient model based on Finite Volume method. Two cases of the proposed system are studied to find the optimal distance between heat exchanger pipes and the hot surface. Results are compared with previous experimental data to demonstrate that the system under study is accurate. They revealed that integrating the heat exchanger with the heat sink using Cu-H2O nf as a coolant maintained the hot surface temperature below 308 K with improved heat transfer by 31.22% compared to water. 0.25 mm is the optimum distance to find the highest thermal performance of the cooling system.

Twisted tape inserts in parabolic trough solar collectors: Assessment of Energy, Exergy, and Environmental impacts

The parabolic trough solar collector is a solar technology extensively employed to focus and harness solar energy for diverse heating purposes. One effective technique to enhance its thermal performance involves the insertion of swirl generators within its absorber tube. In this research, experimental investigation on performance enhancement of parabolic trough solar collector using single twisted tape and dual twisted tape insert across Reynolds number values ranging from 1,000 to 9,000 is performed. Collector efficiency, Nusselt number, friction factor, performance improvement factor, and exergy efficiency are examined for single twisted tape inserts with pitch to width ratios (y/w) of 1, 1.5, 2, 2.5, and 3, and dual twisted tape inserts with y/y0 ratios of 2, 3, and 4. Maximum enhancement in collector efficiency is reported at the lowest flow rate for both inserts. The single twisted tape insert with pitch to width ratio of 1 and the dual twisted tape insert with a pitch ratio of 2 exhibit the most notable enhancements in the evaluated performance parameters. Specifically, at lower flow rates (Re < 4400), the dual twisted tape insert (y/y0 = 2) outperforms the single twisted tape insert (y/w = 1). This dual twisted tape insert configuration provides a thermal efficiency enhancement of 14 %, while the Nusselt number and friction factor enhancement are found to be 372 % and 1600 % compared to bare tube. Additionally, the exergy efficiency exhibits a peak increase of 20.8 % at the lowest flow rate using the dual twisted tape insert (y/y0 = 2). This improvement translates to an annual CO2 reduction between 1.53 tons/year offering a highest enviro-economic benefit of 22.19 US dollars per year.

Effect of Upwind and Downwind Directions of Right-Trapezoidal Winglet-Vortex-Generators in a Solar-Air-Heater

Two directions of right-trapezoidal winglet vortex generators, namely, upwind and downwind directions, were numerically investigated to understand how they affect the thermo-hydraulic performance of the heat exchanger in a solar air heater. The results showed that the Nusselt number, friction factor, and thermal enhancement factor were higher when the vortex generator was installed in an upwind direction. This was because of the magnitude and the position of the airflows’ velocity. That is, faster airflows were induced in the region adjacent to the absorber plate when the vortex generator was installed in the upwind direction. As a result, high convection rates occurred and then increased the overall convective heat transfer rates of the solar air heater. Therefore, Nusselt number and thermal enhancement factor were higher. Nevertheless, the faster airflows also caused increased form drags due to vortex generator blockage, resulting in higher friction factor.

An experimental investigation of the convective heat transfer augmentation in U-bend double pipe heat exchanger using water-MgO-Cmc fluid

One of the major problems of using nanofluids in heat exchange applications is the forming and deposition of nanoparticles on the inner surface of the heat exchanger. In this paper, Water-Cmc fluid is used as a surfactant for nanoparticles to prevent deposition and congregation. The pressure drops and heat transfer in U-bend double pipe heat exchanger based on water-MgO-Cmc fluid, are examined. Nanoparticles of Magnesium Oxide (MgO) and Carboxymethyl Cellulose (Cmc) are used with pure water as a base fluid. The experimental rig and procedures are designed to facilitate various operational conditions such as flow rate, volume concentration of MgO particles and weight concentration of Cmc particles. Furthermore, convective heat transfer coefficient, heat exchanger effectiveness, pressure drop, friction factor, under different conditions, are measured. The results demonstrate convective heat transfer coefficient of U-bend double pipe heat exchangers is enhanced by 35% for 1 MgO vol.% and 0.2 Cmc wt.% compared to base fluid (Water-Cmc). It is concluded that pressure drops are directly proportion to the increase of MgO nanoparticles at same Cmc concentration by 23% at 0.2 wt.%. Whilst, friction factor of the system is inversely proportion to the increase of volumetric flow rate of water-MgO-Cmc fluid. An increase in MgO nanoparticle concentration increases the friction factor, hence maximum friction factor enhancement by 38% for MgO concentration of 1 vol.%. The effectiveness of heat exchanger is slightly increased by 8% with increase of MgO concentration and flow rate. Finally, thermo-physical characteristics of water-MgO-Cmc fluid at various temperatures, are measured

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.

Parametric study on thermal performance augmentation of TiO2/water nanofluids flowing a tube contained with dual counter twisted-tapes

The study of compound heat transfer enhancement technique using dual counter twisted tapes (DCTs) together with TiO2/water nanofluids was carried out. The dual twisted tapes in form of counter-swirl tape arrangement were utilized at three twist ratios (y/w = 1.5, 2.0 and 2.5). TiO2/water nanofluids having three different volume concentrations (φ = 0.05, 0.10 and 0.15 %) were employed as the testing fluids. The results indicated that heat transfer rate, friction factor and thermal enhancement index rose with decreasing tape twisted ratio and elevating nanofluid concentration. The TiO2/water nanofluids applied in the present work offered higher Nu than pure water (the base fluid) by 7.3–10.0 %. The application of DCT with the smallest y/w of 1.5 and TiO2/water nanofluids with the largest φ of 0.15 vol% led to the highest thermal enhancement index (TEI) of 1.53, under the same pumping power criteria. Additionally, the k-nearest neighbor (k-NN) and artificial neural network (ANN) were developed to predict the thermal enhancement index (TEI). It was found that the k-NN and ANN models provided maximum R2 values of 0.919 and 0.992 f, respectively.

Experimental Analysis of the Improvement of Heat Transfer in Tube Heat Exchangers via Passive Flow Generators Using Wire Coil Inserts

Abstract Due to their high performance and low-cost demands, internally treated tube heat exchanger surfaces are one of the passive heat transfer enhancements that have caught the industry&amp;#39;s attention. At bulk temperatures of 30 &amp;#176;C, an experiment for the insertion of 1 mm and 0.5 mm wire coils with a constant pitch length of 8 mm was carried out in this study. The results on the improvement of heat transfer, including the velocity profile, Nusselt number, friction factor, and thermal enhancement efficiency, were significant. Based on a lower surface temperature recorded beyond the uncertainty value, the results demonstrated an improvement in heat transfer for smaller diameters of wire coil inserts. Interestingly, this improvement is concentrated at low Reynolds numbers, indicating that there may be a point at which an increase in wire thickness does not necessarily result in an equivalent improvement in heat transfer. For both wire thicknesses, a Nusselt number increase of up to 5 times was observed. The friction factor penalty, however, varies depending on the wire thickness, with a higher magnitude (3.2-fold increase) obtained for 1mm as opposed to a 1.8-fold increase for the lower counterpart. This distinction results in the 0.5 mm coil insert gaining better overall performance with an average of 2.2 for the thermal performance ratio, further solidifying the advantage of this technique for enhancing heat transfer in conduits.

Experimental investigation on effect of perforated double V-cut twisted tape on thermo-hydraulic characteristics of heat exchanger tube

ABSTRACT To enhance overall thermal performance factor of tubular heat exchanger, use of twisted tape has been very effective. Twisted tape creates turbulence in the flow which enhances rate of heat transfer and friction factor. Present experimental study aims to limit this penalty of increase in friction factor and achieve high thermal performance factor. For this, present article analyzes the effect of different design modifications in twisted tape on thermo-hydraulic performance of heat exchanger tube. Different inserts, i.e. Simple Twisted tape (STT), Double V-Cut Twisted Tape (DVCTT) and Perforated Double V-Cut Twisted Tape (PDVCTT), of varying twist ratio (TR) 3, 4 and 5 are considered for the investigation. Further design modification such as V-cut with width of cut (wc) 5 mm, depth of cut (dc) 4 mm, and perforation of 5 mm diameter is produced in twisted tape. Water is used as the working fluid for the study. Data pertaining to Nusselt number and friction factor is collected for the analysis in turbulent region where Reynolds number varied from 4000 to 16,000. Maximum enhancement in Nusselt number and friction factor is recorded 2.44 times and 3.71 times of plain tube respectively at Re = 4000 in case of TR = 3. Further PDVCTT leads to maximum decrement in Nusselt number and friction factor 3.83% and 27.35% when compared with DVCTT. Maximum thermal performance obtained is 1.71 in case of PDVCTT with TR of 3 at Re = 4000.

Hydrothermal and entropy generation performance of convergent tubes with various dimple shapes

This paper introduces a comprehensive study on the hydrothermal and entropy generation performance of convergent tubes designed with different dimple shapes. The effects of the dimple shape on the flow characteristics (heat transfer and friction) are investigated using validated computational fluid dynamics (CFD) numerical modelling and simulation tools. Inside convergent tubes with different dimple designs, turbulent flows are subjected to a continuous heat flux of 40 kW/m2. Dimpled tube geometries of different diameter ratios (DR) were built within ANSYS-Fluent software (V2022 R2). Four different dimple shapes were investigated: (a) spherical, (b) cylindrical, (c) conical, and (d) stepped-conical. These dimple shapes were examined to investigate the optimal configuration with the best hydrothermal and entropy generation performance. A comparison is made against the baseline straight smooth tube case. The main performance indicators for comparison are Nusselt number (Nu), friction factor (f), and thermal enhancement factor (TEF), calculated for different Reynolds numbers, Re = 3000 to 40,000, and at different diameter ratios, DR = 1 to 2. In addition, thermal, viscous, and total entropy components, the Bejan number (Be), the enhanced entropy generation ratio (Ns,en), and the irreversibility distribution ratio (φs) are evaluated based on the selected geometrical configurations. The results showed that the dimple shape significantly affects the hydrothermal and entropy generation characteristics of convergent tubes. The best average value of the TEF was attained by convergent tubes with stepped-conical dimple shapes at DR = 1.75, which represents a 7.81% increase over the reference smooth tube (the maximum TEF value is 1.3243 at Re = 3000 and DR = 1.25). Furthermore, the minimum levels of Ns,en were achieved by tubes with stepped-conical dimples, with average reductions of 36.92% over the studied Re range. The study provides valuable insights into the design and optimization of convergent tubes with various dimple shapes for various applications.

Numerical investigations on optimised shell designs of a U-tube heat exchanger

Previous researchers focused on enhancing the heat transfer rates of heat exchangers using developments on the tube-side components. Nevertheless, the performance of the shell side has been overlooked in all previous studies. Therefore, this study aims to investigate the heat transfer performance, pressure drop, friction factor, exergy, and performance enhancement criteria (PEC) of a heat exchanger due to the geometrical modification on a cylindrical shell. Three modified shell designs were proposed using SolidWorks software: Twisted-square shell model (TSSM), Mirrored-square shell model (MTSSM), and Corrugated-square shell model (CSSM). Their thermofluid performance is simulated using ANSYS-Fluent software at different Reynold's numbers (46941 ≤ Re ≤ 89616). Results have revealed that TSSM attained the highest heat transfer coefficient, with a 24.4% enhancement at Re = 55,476, followed by the MTSSM with 23.1% and TSSM with a 22.1% increment at Re = 81,081. Moreover, the MTSSM showed the most significant improvement in effectiveness, with a 24.64% advancement, followed by the TSSM with a 22.35% at Re = 81,081. Furthermore, the pressure drop experienced by the MTSSM and CSSM was found to be lower than the cylindrical shell and the TSSM at all Re, with the highest reduction of 16.25% and 15.89% by the CSSM at Re = 55,476 and 46,941, followed by the same model at Re = 72,546 and 64,011 with a 15.15% and 15.13% decrement, leading to potential cost savings in terms of lower pumping and operating expenses compared to the TSSM and cylindrical model. On the other hand, the TSSM showed an increment in the pressure drop with the highest increment of 9.94% and 8.82% at Re = 64,011 and 46,941 compared to the cylindrical model. Besides, the friction factor of both the CSSM and MTSSM was found to be much lower compared to the cylindrical shell model with the highest decrement of 16.25% and 15.98% in the CSSM at Re = 55,476 and 46,941 and 13.17% and 12.85% at Re = 81,081 & 46,941 in the MTSSM, and nonetheless increment in the TSSM with the highest increment of 9.94% and 8.82% at Re = 64,011 and 46,941 respectively. However, the TSSM still provides superior heat transfer performance even at its lowest Re = 46,941 with a lower pressure drop compared to the highest Re = 81,081 in the cylindrical shell, indicating that the TSSM can be used at Re ≤ 46,941 and still provides better heat transfer performance than the highest Re applied in the cylindrical shell, resulting in a lower operating and pumping cost to circulate the fluid through the shell. These outcomes demonstrate the positive impact of the optimised shell modifications on the overall efficiency and cost-effectivenessofthesystem.

Effect of particle size on second law of thermodynamics analysis of Al2O3 nanofluid: Application of XGBoost and gradient boosting regression for prognostic analysis

In this study, the current research delves into the influence of nanoparticle size on turbulent forced convective heat transfer, entropy generation, and friction factor. The investigation focused on three different sizes (30 nm, 50 nm, and 80 nm) of Al2O3 nanoparticles (NPs) suspended in a water-based nanofluid (NF) with a 1 vol% concentration flow in a circular tube. The nanoparticles (NPs) were characterized using various characterization techniques. The stability and pH of the NF were determined, and its viscosity (VST) and thermal conductivity (TC) were measured at a temperature of 60 °C. Heat transfer experiments were conducted with varying particle sizes and Reynolds number (Re), maintaining a fluid inlet temperature of 60 °C. The results indicated that the NF containing 30 nm particles exhibited higher VST and TC compared to the other samples and the base fluid. The maximum enhancement in Nu for Al2O3 (30 nm) and Al2O3 (80 nm) NFs is 60.7 and 18.5 % greater than that of base fluid, respectively. The maximum and minimum total entropy generation (Sgen,T) value of 0.499 and 0.286 observed for base fluid and Al2O3 NF (30 nm), respectively at low Re. The highest friction factor enhancement for Al2O3 NF (30 nm) exceeded by 9.4 % compared to the base fluid, and the maximum thermal performance factor observed for Al2O3 NF (30 nm) was 1.57. Finally, regression analysis was employed to establish correlations for estimating Nu and friction factor values. Prognostic models were developed using two sophisticated machine learning algorithms, XGBoost and Gradient Boosting Regression (GBR). Both models demonstrated exceptional prediction abilities, achieving over 99 % accuracy rates based on the experimental data.

Friction Factor and Heat Transfer Enhancement of Hybrid Nanofluids in a Heated Circular Tube

Friction Factor and Heat Transfer Enhancement of Hybrid Nanofluids in a Heated Circular Tube

Numerical Simulation and Application of a Channel Heat Sink with Diamond Ribs

This paper presents a channel radiator with ribbed ribs and primarily investigates the fluid flow and heat-transfer characteristics of the channel radiator. A three-dimensional numerical simulation of the radiator’s pressure-drop and heat-transfer process was conducted using the finite volume method. A comparison between the experimental data and the simulation results demonstrates that the simulation in this paper is accurate, with a maximum error not exceeding 5%. Furthermore, the radiator was further subjected to geometric parameter studies, principally including the height ratio between the fins and the channel, the fin angle, and the spacing between the fins. The thermal resistance, Nusselt number, friction factor, and heat-transfer enhancement factor were calculated. The results indicate that if the geometric parameters are selected appropriately, the heat sink will enhance heat-transfer performance within an acceptable pressure drop. When the Reynolds number is greater than 507.5, the height ratio of 25%, the rib angle of 135°, and the rib spacing of 2.5 mm can be given priority. This heat sink is used in PCR devices, and experimental results show that the novel channel heat sink can meet the heat dissipation requirements of the TEC during the PCR process.

Experimental investigations on heat transfer enhancement in a double pipe heat exchanger using hybrid nanofluids

Abstract Heat exchanger (HE) is an instrument that facilitates the operation of HE between two fluids that are at various temperatures. Double-pipe HEs are used in many organizations because of their low installation, design, maintenance costs, flexibility, and their suitability for high pressure applications. Heat transfer (HT) augmentation techniques (passive, active or compound techniques) are used in heat exchangers to reduce the HT surface area, to increase HT capacity and to reduce pumping power. Passive augmentation techniques are much cheaper and do not involve any external power input. They aim to improve the effective surface area, the residence time of the HT fluid and its thermal conductivity by the usage of nanofluids. Nanofluids are used for cooling applications in organizations, transportation, nuclear reactors, electrical and electronic devices and for biomedical applications. Hybrid nanofluids have higher thermal conductivity, low PD and frictional losses and pumping power as compared to the mono nanofluids. In this present work, experiments are conducted in a double pipe HE using TiO2, and SiC-water nanofluids by varying the volume concentration and cold fluid mass flow rate ranging from 17.5 to 34.5 lpm by making constant hot fluid mass flow rate. Further, experiments are conducted using TiO2–SiC/water hybrid nanofluids. Influence of nano and hybrid nanofluids on the overall HTC and friction factor are experimentally investigated. From the experiments, TiO2–SiC/water hybrid nanofluid with nanoparticle ratio TiO2:SiC = 1:2 is found to be optimum as the heat transfer enhancement is more with less improvement in friction factor. The overall heat transfer, and friction factor enhancement is 22.92 %, and 11.20 % higher respectively when compared with base fluid for TiO2:SiC = 1:2.

Mini-channel cooling system for solar PV Panels with hybrid magnetic nanofluid and magnetic field

This study delves into the interplay between magnetic fields, heat transfer, and fluid behavior within a 3D mini-channel. Exploring the effects of a magnetic field on a hybrid nanofluid (Fe3O4–TiO2) under varying intensities (1000–2000 Gauss) and positions. Using numerical simulations (finite volume method), key parameters like Nusselt number (Nu), Friction factor (f), and Thermal Enhancement Factor (TEF) have been analyzed to uncover how magnetic fields and nanofluids interact in complex geometries. Results showed that the application of a magnetic field significantly enhanced heat transfer performance, with a maximum Nusselt number enhancement of 230%. Moreover, it was shown that greater magnetic field intensities were associated with elevated friction factors, whereas friction factors exhibited a declining trend as Reynolds numbers increased. The thermal enhancement factor initially increased with Reynolds numbers, but declined after reaching a peak. However, higher magnetic field strengths mitigated this decline, intensifying heat transfer enhancement effects reaching a maximum of 2.18 at 2000G magnetic field. These findings provide quantitative insights into the effectiveness of magnetic fields in enhancing heat transfer in Fe3O4–TiO2 hybrid nanofluids.

Impact of nanoparticles loading to a novel hybrid TiO2-CNTs/water nanofluid on thermal performance enhancement

This present work investigated the thermal characteristics and hydrodynamics behavior of TiO2-CNTs/water hybrid nanofluids for laminar and turbulent conditions. Assuming hybrid nanofluids as Newtonian fluids, simulation-based evaluation was conducted using a single-phase approach. Various nanoparticles loading and Reynolds number were employed to characterize the observed hybrid nanofluids’ convective heat transfer coefficient and friction factor. The ratio between heat transfer performance and pressure drop enhancement was analyzed to understand thermal performance. Constant heat flux of 6500 W/m2 and low nanoparticle concentration from 0.10 to 0.20 vol.% were applied in this simulation. The results revealed that adding CNTs nanoparticles did not significantly affect friction factor enhancement at very low concentrations due to their good tribological properties. For the thermohydraulic characteristics, the observed hybrid nanofluids were better than those of water. The thermal performance factor magnitudes of hybrid nanofluids were above 1.0 even though they did not have significant magnitudes at very low concentrations, 1.01 and 1.07 for laminar and turbulent flow, respectively.