Terms Of Pressure Drop Research Articles

A methodology to reduce the computational effort in 3D-CFD simulations of plate-fin heat exchangers

The analysis of a plate-fin heat exchanger performance requires the evaluation of key parameters such as heat transfer and pressure drop. In this regard, Computational Fluid Dynamics (CFD) can be proficiently adopted, at the design stage, to predict the performance of plate-fin heat exchangers. However, these last are often characterized by a complex geometry, such as in the case of plate exchangers with turbulators, leading to a huge computational effort, which often exceeds the available resources. In this study, a numerical methodology for the simulation of plate heat exchangers is proposed, to bypass the limits imposed by the computational cost. The methodology relies on the simulation of a minimal portion of the exchanger (two plates, one per fluid) characterized by periodic boundary conditions (that mimic the presence of several layers). The total heat exchanged is obtained simply multiplying the calculated heat transfer by the number of plate couples composing the device. Moreover, the two plates allow to calibrate porous media which are adopted to rebuild (in a simplified version) the two fluid circuits of the whole exchanger and obtain the overall pressure drop across the device for both the hot and cold fluids.The proposed approach is validated against experimental data of an oil cooler for automotive application, that is a plate-fin heat exchanger characterized by the presence of turbulators. The numerical outcomes are compared to the experiments in terms of pressure drop and heat transfer for a wide range of volumetric flow rates. Particular attention is devoted to the mesh sensitivity and the adopted computational grid minimizes the number of cells (and, thus, the computational cost), without compromising the accuracy. Moreover, the Reynolds-Stress-Transport turbulence model is accurately selected among the most diffused ones, in order to properly match the test bench data.The proposed methodology allows to reduce of nearly one order of magnitude the total number of cells required for the simulation of the heat exchanger performance. The heat transfer is predicted with high accuracy, i.e. error is always lower than 4%. As for the pressure loss, the deviation compared to the experiments increases up to nearly 15% (for one of the simulated conditions) but it is considered still acceptable.

Unveiling impacts of heat flux distribution on forced convection in horizontal evacuated tubes

Integration of evacuated tubes with solar thermal desalination can significantly enhance thermal efficiency and water production. To provide optimization strategies for such desalination systems, 3D numerical simulations were performed to analyze the influence of the heat flux distribution on forced convection in horizontal evacuated tubes in terms of pressure drop, secondary flow, temperature distribution, and Nu. The improved method considered multi-layer wall heat transfer, fluid–solid coupling heat transfer, and temperature dependent fluid properties. Non-uniform heat fluxes significantly affected the friction pressure drop in the laminar regime, but were less pronounced in the transition and turbulent regimes. At low Re, the backward non-uniform heat flux strengthened the secondary flow while the forward non-uniform heat flux suppressed it. The rapid warming of the wall temperature occurred over a short distance due to the difference in thermal conductivity between the fluid and solid domains. The non-uniformity of heat flux distribution moderately affected average fluid temperature. The influence of heat flux distribution on secondary flow and average temperature weakened as Re increased. Furthermore, a correction factor was introduced to quantify the impact of heat flux distribution on Nu. For forward and backward non-uniform heat fluxes, it assumes values of 0.94 and 0.86 respectively.

Flow and mass transfer for the adsorption separation of para-xylene in a packed bed by particle-resolved CFD simulations

As the leading polyester product chain, para-xylene (PX) is the most important xylene isomer. In industry, high purity paraxylene is mainly produced by adsorption separation technology. In this study, the PX adsorption process has been investigated by a 3D particle-resolved CFD model. For spherical particle packed beds, the channeling effect, flow stagnation and backflow regions are the main factors leading to non-ideal flow. According to the residence time distribution (RTD) and adsorbent efficiency, the more uniform the flow in the packed bed, the higher the adsorption separation efficiency. Therefore, low feed flow rate and large bed-to-particle diameter ratio (N) are beneficial to the adsorption process. In addition, the effect of particle geometries (trilobe, five-lobe, Raschig ring, four-spoke ring, and six-hole cylindrical) on the flow and adsorption characteristics of the packed bed has been investigated in terms of pressure drop, adsorbed amount and adsorbent efficiency. Internal void particles perpendicular to the flow direction are unfavorable for the adsorption process. The four-spoke ring adsorbent with more surface areas has the largest bed adsorbed amount and exhibits the best adsorption performance. The trilobe adsorbent has the largest adsorbed amount per unit bed pressure drop and is the optimally shaped adsorbent for industrial PX adsorption separation.

Performance Evaluation of Geometrically Different Pediatric Arterial Cannulae in a Pediatric Cardiopulmonary Bypass Model.

To define a reference chart comparing pressure drop vs. flow generated by a set of arterial cannulae currently utilized in cardiopulmonary bypass conditions in pediatric surgery. Cannulae from two manufacturers were selected considering their design and outer and inner diameters. Cannula performance was evaluated in terms of pressure drop vs. flow during simulated cardiopulmonary bypass conditions. The experimental circuits consisted of a Jostra HL-20 roller pump, a Quadrox-i pediatric oxygenator (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set. The circuit was primed with lactated Ringer's solution only (first condition) and with human packed red blood cells added (second condition) to achieve a hematocrit of 30%. Cannula sizes 8 to 16 Fr were inserted into the cardiopulmonary bypass circuit with a "Y" connector. The flow was adjusted in 100 ml/min increments within typical flow ranges for each cannula. Pre-cannula and post-cannula pressures were measured to calculate the pressure drop. Utilizing a pressure drop limit of 100 mmHg, our results suggest a recommended flow limit of 500, 900, 1400, 2600, and 3100 mL/min for Braile arterial cannulae sizes 8, 10, 12, 14, and 16 Fr, respectively. For Medtronic DLP arterial cannulae sizes 8, 10, 12, 14, and 16 Fr, the recommended flow limit is 600, 1100, 1700, 2700, and 3300 mL/min, respectively. This study reinforces discrepancies in pressure drop between cannulae of the same diameter supplied by different manufacturers and the importance of independent translational research to evaluate components' performance.

Influence of distributor plate design on mixing characteristics of rice husk biomass in a bubbling fluidized bed gasifier: An experimental and CFD study

This study investigates the mixing characteristics of rice husk biomass in a bubbling fluidized bed gasifier (BFBG) using different distributor plates: perforated, 45° slotted, and hybrid plates. The study explores the fluidization characteristics of a biomass/sand mixture using three distributor plates, observing the maximum difference in initial minimum fluidization velocity (Umf,i) and final minimum fluidization velocity (Umf,f) for perforated plate, indicating axial mixing and segregation, while the 45° slotted plate represents uniform bed expansion and fluidization, and the hybrid plate exhibits an intermediate behavior. Axial and lateral biomass distribution is also studied, and it is found that with the 45° slotted plate the highest axial distribution of rice husk is observed at the lower portion due to lateral and swirling flow whereas perforated plate causes the highest deviation at the lower portion but approaches ideal mixing at the mid and upper sections due to axial dominant flow. The hybrid plate exhibits a blend of axial and lateral flows, resulting in intermediate axial distribution at lower and upper section of gasifier. Radially, the perforated plate has the highest concentration of biomass at maximum height whereas the 45° slotted plate has concentration near the walls, and the hybrid plate has optimal mixing throughout. The hybrid plate also achieves the highest mixing index at all air velocities. Overall, the study provides insights into biomass mixing in BFBGs and highlights the superior performance of the hybrid distributor plate.The CFD study also carried out to complement the experimental results in terms of pressure drop and mixing behavior by employing different distributor plats. Multiphase two fluid model (TFM) with kinetic theory of granular flow has been employed for CFD simulations with the engagement of k-epsilon turbulence model. The simulation results are in good agreement with experimental results in terms of bed pressure drop quantitatively and mixing characteristics of rice husk biomass qualitatively.

A Semi-Empirical Correlation for the Onset of Density Wave Oscillations in a Helical Coil Steam Generator

NuScale Power has completed a series of full-length helical coil steam generator tests at SIET Laboratories in Piacenza, Italy. The test program included an investigation of the onset and evolution of density wave oscillations (DWOs). This paper describes the mechanisms leading to the onset of DWOs. A semi-empirical DWO stability correlation was developed from first principles using data from tests performed in the full-height (2015) TF-2 counterflow test facility. This research supports the concept that the onset of DWOs is caused by liquid bridging inside the boiling length of the tubes. A DWO onset correlation is obtained by performing a steady-state momentum balance on the liquid slug created by liquid bridging in annular flow. This yields a momentum balance equation in terms of a set of dimensionless superficial velocities, a corresponding dimensionless pressure drop term, and an average void fraction. Envelope theory is then used to obtain a critical void fraction, which is substituted into the dimensionless momentum balance to obtain a DWO onset correlation similar to the Wallis countercurrent flooding correlation. Predictions using the DWO stability correlation have been compared to DWO experiments from the (2022) TF-2, TF-1, and Polimi. The predictions for the onset and termination of DWOs show excellent agreement with the data.

Heat Transfer Improvement of Prismatic Lithium-Ion Batteries via a Mini-Channel Liquid-Cooling Plate With Vortex Generators

Abstract Temperature is a critical factor affecting the performance and safety of battery packs of electric vehicles (EVs). The design of liquid cooling plates based on mini-channels has always been the research hotspots of battery thermal management systems (BTMS). This paper investigates the effect of adding vortex generators (VGs) to the liquid cooling channel on the heat dissipation capacity and temperature uniformity of the battery. The shape of the vortex generators (triangle, trapezoid, and semicircle), placement position (middle, inlet, and outlet of the channel), different flowrates, and different numbers of channels on the heat dissipation of the battery are systematically analyzed. The research results indicate that (1) compared to the triangular and trapezoidal vortex generators, the semicircular vortex generators have a lower cost in terms of pressure drop while maintaining the same heat dissipation efficiency. The pressure drop of the semicircular vortex generators is 15.89% less than that of the trapezoidal vortex generators and 20.49% less than that of the triangular vortex generators. (2) The effect of adding vortex generators is more obvious when the flowrate is small in the cooling channels. When the flow velocity is 0.025 m/s, the heat dissipation performance can be increased by 7.4%. (3) When the cross-sectional area of the inlet is fixed, the heat dissipation effect of more channels is better. The average temperature of three and seven cooling channels decreases from 311.23 K to 310.07 K, with a decrease of 8.87%. (4) The temperature difference can be effectively reduced when the vortex generators are concentrated near the outlet of the flow outlet. Its temperature difference is 1.8 K lower than that when the vortex generators are placed near the inlet, with a decrease of 10.5%.

Review and comparison of turbulent convective heat transfer in state-of-the-art 3D truss periodic cellular structures

To promote the development and application of periodic cellular structures (PCSs), this paper reviews and systematically compares the heat transfer and pressure drop of state-of-the-art 3D truss PCSs. Relative merits among these PCSs in the turbulent regime are clarified which have been fuzzy in the open literature. The topological and orientation effects on the thermo-fluids of the PCSs are also investigated. Twelve PCSs with the same height and porosity, separately in two different orientations, are evaluated by numerical simulations. These PCSs include the cubic lattice (CL), the body-centered cubic lattice (BCCL), the face-centered cubic lattice (FCCL), octet lattice (OL), circular pyramid lattice (CPL), rectangular pyramidal lattice (RPL), tetrakaidecahedron lattice (TL), X-lattice (XL), shifted X-lattice (SXL), circular tetrahedral lattice (CTL), rectangular tetrahedral lattice (RTL), and Kagome lattice (KL). It is found that the entry and exit effects on heat transfer and pressure drop are limited within the first four unit cells and the last unit cell, respectively. For a given Reynolds number within the range of 2692–11087, the SXL in orientation A (SXL-OA in abbreviation) exhibits the best overall heat transfer; and the SXL-OA also has the best endwall heat transfer. In addition, the OL-OA, XL-OA and SXL-OA show the best heat transfer on the PCS core. In terms of pressure drop for a given Reynolds number, the RTL-OA and RTL-OB exhibits the highest and the lowest pressure drop, respectively. For a given pumping power, the OL exhibits the best overall heat transfer. Thermo-fluidic mechanisms are also explored with representative PCSs. For the given porosity and range of Reynolds number, correlations for overall heat transfer, local heat transfer and pressure drop are presented, which are beneficial for engineers to quickly evaluate and compare the PCSs made of different materials. The systematic comparison in the turbulent regime extends the comparison in the laminar regime in the open literature, which is expected to promote reasonable development and application of PCSs in heat exchangers and thermal management systems. Applications of PCSs in different scenarios and future work are also commented.

Electrospun nylon‐66 nanofiber coated filter media for engine air filtration applications

AbstractAir filtration plays a vital role in the performance and operations of engines, especially for heavy‐duty combat vehicles operating in the desert environment. Conventional cellulose media comprises micro‐fibers exhibiting low filtration efficiency for particles within the range of 0.1 to 0.5 μm (most penetrating particle size, MPPS). Nanofiber coating on cellulose media can increase the filtration efficiency, however, with the penalty of an increase in pressure drop. The features of nylon‐66 nanofibers, such as high mechanical strength, greater thermal stability, and high surface‐to‐volume ratio, will be beneficial for developing nano‐coated filter media. In this study, electrospun nylon‐66 nanofibers were coated over two cellulose‐based filter media and tested on an air filtration test rig that employs a suction‐type blower replicating the realistic condition of a heavy‐duty engine intake. The test rig was fabricated to evaluate the performance of the nano‐coated filter media in terms of pressure drop, filtration efficiency, and quality factor (Q‐factor). The experimental results demonstrated that the nylon‐66 nano‐coated media have higher Q‐factor (in the MPPS range) than the cellulose media due to the increased filtration efficiency compared to the rise in pressure drop. Therefore, such electrospun nylon‐66 nanofiber‐coated air filters can be an alternative to conventional cellulose media.

Comparison Between Numerical and an Experimental Results of Pressure Drop in a Perforated Horizontal Wellbore with a 90° Perforations Phasing

Comparison Between Numerical and an Experimental Results of Pressure Drop in a Perforated Horizontal Wellbore with a 90° Perforations Phasing

Thermal boundary layer depletion in minichannels by electrohydrodynamic conduction pumping

The article presents a numerical analysis of two-dimensional laminar flow and heat transfer in a minichannel with flat plate electrode pairs periodically flushed to the bottom wall. The two-way coupled governing equations of flow, heat transfer, electric potential and charge conservation are solved using the opensource finite-volume framework of OpenFOAM. Two cases of the minichannel at completely horizontal (case A) and 90° bent (case B) configurations are considered. The inlet laminar flow with Reynolds number varying from 10 to 1000 has been taken into account. The applied electric potential is varied in three steps 0, 0.5 and 1 kV. Electrohydrodynamic (EHD) conduction pumping due to the residual conductivity of the working fluid and the electric-field enhanced dissociation of free charges generate vortices in the proximity of electrodes. The flow and thermal performance of the minichannel in the presence of EHD conduction induced vortices are quantified in terms of pressure drop, Nusselt number and a performance factor (which is a combined function of pressure drop and Nusselt number). The vortices generated by EHD conduction pumping phenomenon deplete the thermal boundary layer, aid mixing and enhance the heat transfer. The mean and local Nusselt numbers are notably increased with only a minimal raise in pressure drop. In both the configurations of the minichannel, the performance factor is greater than 1 for the entire parameter space considered in this study. However, the thermal boundary layer depletion and heat transfer enhancement is prominent at low Reynolds number flows. The maximum drop in performance factor from case A to case B is only 18.5%. Results of this study indicate that EHD conduction pumping is a potential technique to enhance heat transfer in minichannels with minimum additional power consumption.

Coupling cellular substrates and radial flow reactors for enhanced exhaust abatement in automotive DeNOx-SCR

Cellular materials, such as open-cell foams and POCS, are envisioned as alternative structured substrates to the standard honeycomb monoliths for improving automotive DeNOx-SCR abatement efficiency thanks to their superior gas-to-solid mass transfer properties. The innovative substrates are numerically assessed through Computational Fluid Dynamics simulations to parametrically investigate their performances in terms of pressure drop and abatement efficiency in full-scale geometries as a function of cell size and operating conditions. Cellular substrates (open-cell foams and 3D printed POCS) are tested first as a direct replacement of the monolith preserving the catalyst loading and the standard device geometry. An increment in NO conversion is observed due to the enhanced gas–solid transfer. However, a concomitant unacceptable increase in the pressure drop across the device is apparent in all the conditions for both commercial foams and POCS. To avoid this issue, a radial flow configuration of the reactor is hereby proposed for the first time for mobile ATS systems to reduce the pressure drop. Such a configuration is only possible for cellular substrates, since they are characterized by isotropic permeability. The simulations revealed that the new reactor loaded with cellular materials is a compelling solution granting comparable or lower pressure drops than honeycomb monoliths with a concomitant improvement of the abatement efficiency. The best reactor configuration offered up to a 5% conversion increase and up to a 5-fold pressure drops reduction compared to the state-of-the-art. Even so, better performances than the honeycomb were found for other reactor configurations, allowing for a flexible choice of the final design.

Impact of vapour bubble movement on the process of two-phase heat transfer phenomena over hybrid elliptical tubes

The use of modified surface to improve the performance of two-phase heat exchanger in terms of pressure drop and heat transfer rate is one of the current need of industries. In light of this, the current analysis compares the diabatic two-phase heat transfer performance of hybrid elliptical tubes with that of traditional circular tubes at atmospheric pressure using distilled water as a quiescent test fluid. For the purpose of this investigation, a circular tube made of AISI 304 with a diameter of 25 mm and a heating length of 130 mm is used. In order to maintain the same surface area and heating length as a circular tube, the hybrid elliptical tubes are fabricated with varying aspect ratios of 1.17, 1.31, and 1.47. The heat flux varies between 14.87 and 94.82 kW/m2. For two orientation angles, i.e. 0ᵒ and 90ᵒ, the heat transfer performance of hybrid elliptical tubes are investigated. The analysis of results confirmed that both the tubes exhibit boiling characteristics. However, hybrid elliptical tubes outperform circular tubes in terms of heat transfer rate. It is also found that the hybrid elliptical tube with 0ᵒ orientation resulted in higher heat transfer coefficient about 20.61%, 36.74% and 20.69% than that of 90ᵒ orientation for aspect ratio of 1.17, 1.31 and 1.47 respectively. Regardless of orientation angle, the hybrid elliptical tube with aspect ratio of 1.31 demonstrated the highest heat transfer coefficient of all aspect ratios. Also, a non-dimensional correlation is developed which is found to predict the heat transfer coefficient of circular as we as hybrid elliptical tubes within an error band of ±12%.

Performance evaluation criteria and entropy generation of hybrid nanofluid in a shell-and-tube heat exchanger with two different types of cross-sectional baffles

Improving the thermo-hydraulic performance of shell-and-tube heat exchangers is of interest to researchers due to their broad applications in the industry. Thermo-hydraulic behavior and entropy generation of hybrid nanofluid in a shell-and-tube heat exchanger with two different types of cross-sectional baffles are numerically examined using the two-phase Eulerian-Eulerian Model (EEM). The volume fraction of nanoparticles (φ) changes from 0 to 2% and the Reynolds number (ReNumber) varies from 25000 to 45000. EEM, Realizable k-ε turbulence model, finite volume method (FVM), and SIMPLE algorithm are used for modeling. According to the numerical results obtained in terms of pressure drop, total entropy generation, and performance evaluation criteria (PEC), baffle 1 is more appropriate. In terms of heat transfer rate and average Nusselt number values, baffle 2 is more suitable. The PEC maximum change was 5.13% at Re = 45000 and φ = 0% by changing the type of baffle from the second type to the first type. The maximum rise in the total entropy generation was 73.68% for φ = 0% for the first type of baffles.

Design characteristics and validation of the turbine model — Case of development of turbine effect in sloped collector solar chimney plant

Blade design for a solar chimney power plant turbine is modeled geometrically. NACA 4412 blade is selected for its favorable lift to drag characteristics in the considered diameter range. The constructed model is integrated into a solar chimney plant and validated against existing examples in literature. A similar process is applied using a reverse fan model. Margins of discrepancies obtained from the turbine and reverse fan models are used as indicators for the total deviation expected from using the reverse fan model with a sloped collector plant. Here, the effect of turbine pressure change on the temperature rise and air flow are examined to set the upper limit of pressure drop and check the capacity of the system for power generation. The maximum air flow velocity at the center of the sloped collector reached 9.8 m/s. The highest achievable temperature difference was 37 °C. The favorable working zone for turbine operation inside the tower of a sloped collector solar chimney in terms of pressure drop and air flow rate is marked based on a constant efficiency.

The Development of Empirical Correlations to Understand the Frictional Behavior of Aqueous Biomass Slurry Flows in Vertical Pipes

Highlights The frictional pressure drop correlation of agricultural residue-water slurry flows in vertical pipes is developed. Multiple linear regression with the backward elimination method was used in RStudio to obtain the optimal model. Some regression coefficients differ for different types of biomass feedstocks. The predicted pressure drops agree well with the experimental data within a 95% CI. Empirical models for the onset velocity of drag reduction of different particle sizes of biomass are proposed. Abstract. Large-scale biofuel production at levels equivalent to conventional oil refineries using long-distance pipeline hydro-transport of biomass can be a cleaner alternative to fossil fuels when it comes to economics and traffic congestion associated with the overland transportation of biomass. The transport of aqueous slurries of several saturated mass concentrations (5%-40%) and four particle sizes (from <3.2-19.2 mm) of two types of agricultural residue biomass (ARB) feedstock (corn stover and wheat straw) was studied through a vertical test section of a 29 m long, 50 mm diameter closed circuit pipeline facility, and frictional pressure drops were recorded at different flow rates (0.5-4.3 m s-1). A framework was developed in RStudio (4.0.5) to analyze the experimentally obtained frictional pressure drops of biomass slurries through a multiple linear regression approach using a backward elimination method and Akaike information criterion. An empirical model was proposed to predict slurry frictional pressure drop in terms of slurry velocity, slurry solid mass concentration, particle aspect ratio, and feedstock type. The model satisfactorily predicted the frictional pressure drops of both feedstocks of biomass-water slurry flows through pipes within a 95% confidence interval. The correlations introduced for onset velocities of drag reduction in terms of slurry solid mass concentrations seemed helpful to interpret the transition points of the corresponding slurries in vertical upward flows through pipes. The empirical correlation developed in this research could help select biomass slurry pumps and pipe dimensions when designing a typical long distance pipeline network for biofuel production at the commercial level. Keywords: Agricultural biomass wastes, Frictional loss prediction, Numerical model, Onset velocity correlation, Regression coefficients, Upward pipe flow.

Coreflood investigation of HPAM/GO-SiO2 composite through wettability alteration

In this study a novel polymeric nanocomposites HPAM/GO-SiO2 for enhanced oil recovery is investigated experimentally. An investigation of the composite's structural integrity, morphological interactions, and possible bonding effects was conducted. Response surface method was used to replicate contact angle measurements. Because of the complicated nature of nanopolymeric solutions, there are several metrics of wettability that are more sensitive than others. The model's insufficiency was not supported by any evidence. Fluid flow in hybrid polymeric nanofluids was studied using the central composite design with an R2 of 93.48%. Nanoparticle concentrations were optimised using CCD models (0.05 wt%). Hence, the wettability alteration plays a dominant role in the oil displacement mechanism. Core flood testing was used to develop a new chemical composition that outperformed the common polymer. Experiments comparing floods showed that the GO-SiO2/HPAM composite was superior in terms of pressure drop, water cut, and ultimate oil recovery. Using HPAM and GO-SiO2/HPAM at concentrations of 0.05 wt% results in 15.47 and 30.82% increase in the oil recovery.

Two-phase simulation of entropy generation and thermo-hydraulic behavior of a therminol/CuO-diamond nanofluid in a heat exchanger

Many researchers have optimized the thermo-hydraulic performance of heat exchangers (HE) used in industries. Using passive methods, such as nanofluid, turbulator, and fins can be beneficial in the field. In this paper, two-phase entropy generation and thermo-hydraulic behavior of hybrid nanofluid CuO-diamond/Therminol hybrid nanofluid in a HE equipped with high fins, micro fins, and turbulator are numerically examined. The volume fraction of nanoparticles changes from 0 to 4% and the flow Reynolds numbers (Re) are 14,000, 18,000, 22,000, and 26,000. Two-phase Eulerian-mixture method, k-ω turbulence model, finite volume method, and SIMPLEC algorithm are employed for the simulations. It is concluded that in terms of pressure drop, the use of tubes with micro fins is more favorable. The maximum values of the average Nusselt number (Nu) correspond to the heat exchanger equipped with high fins. The largest change in the average Nusselt number at all Reynolds numbers and volume fractions investigated is 32.67%, which occurs at a Reynolds number of 22,000 and a volume fraction of 4%. From the point of view of the total entropy generation in the presence of a hybrid nanofluid, it is more desirable to use a heat exchanger with micro fins.

Thermal-hydraulic analysis of Syltherm 800 thermal oil / γ-AlOOH nanofluid in a baffled shell and tube heat exchanger equipped with corrugated helical tube with two-phase approach

Present investigation studies two phase Syltherm 800 thermal oil / γ-AlOOH nanofluid flow and heat transfer in a baffled shell and tube heat exchanger equipped with corrugated helical tube numerically. Effects of using helical tube, corrugations, baffles and also their geometrical parameters are analyzed in thermal-hydraulic viewpoint. The governing equations are solved using finite volume method. The Eulerian-Eulerian single fluid two phase approach is used due to simulate the nanofluid flow. The code validation is done using valuable experimental and numerical references in literature and based on results there is a remarkable coincidence among the numerical results obtained from this work and the attained data of references in Nusselt number and pressure drop terms. According to obtained results, the configuration with 200 mm coil pitch, 70 mm coil diameter, Four-Obstacle arrangement, 20 mm obstacle diameter and novel baffle arrangement filled with nanofluid at 4% nanoparticle volume fraction (ϕ) and 30 nm nanoparticles diameter is suggested as the most efficient model among all configurations with performance evaluation criterion, (PEC)= 9.32, at Reynolds number of 54,000.

Analysis at cell scale of porosity effect on forced convection with nanofluids in porous structures with Kelvin cells

• The study is provided with Kelvin cell structure for different porosity values. • Pressure and temperature have periodic trends inside the structures. • Highest velocities are recorded at lower porosities between two cells. • Highest temperature differences are detected between outlet and inlet sections. In this paper a numerical investigation in metal porous structures with Kelvin cell model is carried out on water/Al 2 O 3 nanofluids using the single-phase model. The employed foams are characterized by a fixed value of cells per inch (CPI) equal to 10 for porosity ɛ equal to 0.85, 0.90, 0.92, 0.95, 0.97. For porosity of 0.95 structures at 5, 20 and 40 CPI are also analyzed. Three different values of Al 2 O 3 nanoparticle volume concentrations ϕ , equal to 0, 2 and 4% are used. Results are showed and discussed in terms of pressure drop and temperature profiles, velocity and temperature fields. Correlations for the evaluation of permeability K and drag coefficient C F and their values are also shown. Furthermore, dimensionless entropy generation as function of Reynolds number has been evaluated. The results reveal that both the pressure and the temperature have a periodic trend with oscillations that vary both for the geometric aspects and for the properties of the fluids used. The velocity and temperature fields then serve to understand the dynamic and thermal characteristics: the highest velocities are recorded at lower porosities and at the contact zones from between two cells, as well as the highest temperature differences between outlet and inlet sections. The correlations with which permeability and drag coefficient are obtained reveal that they depend only on the foam used and not on the fluid considered. Finally, the trend of the dimensionless entropy generation as a function of the Reynolds number is decreasing and reducing with increasing porosity.