Minimum Pressure Drop Research Articles

Investigation of effects on turbulent heat transfer of twisted wavy tape elements in the tube

In this study, the turbulence effects created by the twisted wavy tape elements placed inside a plain tube were investigated with experimental results. Changes in heat transfer and pressure drop due to turbulence generation by the tape elements were examined experimentally. The results obtained for a plain tube were compared to the literature and the experimental system was validated. The Re range of the experiments was between 5000 and 20,000. Geometrical parameters were two different amplitudes of twisted wavy tape elements with a single width value and a single twist ratio. In addition, by changing the number of waves, a total of 6 twisted wavy tape elements were used. According to the results, the highest performance factor is obtained around Re = 5000 for the lowest twisted wavy tape element amplitude and highest wavenumber. On the other hand, the minimum pressure drop is calculated for the minimum wavenumber. In addition, it is observed that there is an increase in pressure drop and heat transfer depending on the increase in the number of waves. Compared to the twisted tape element, a performance enhancement of around 42% was found in the case of the twisted wavy tape element.

Modeling and Optimization of a Micro-Channel Gas Cooler for a Transcritical CO2 Mobile Air-Conditioning System

This study focuses on developing and optimizing of a microchannel gas cooler model for evaluating the performance of a transcritical CO2 mobile air-conditioning system. A simulation model is developed with the aid of MATLAB R2022a. A segment-by-segment modeling approach is utilized by applying the effectiveness-NTU method. State-of-the-art heat transfer and pressure drop correlations are used to obtain air and refrigerant side heat transfer coefficients and friction factors. The developed model is validated through a wide range of available experimental data and is able to predict a gas cooler capacity and pressure drop within an acceptable range of accuracy. The average errors for a gas cooler capacity and pressure drop are 3.79% and 10.24%, respectively. Furthermore, a parametric optimization method is applied to obtain optimal microchannel heat exchanger dimensions, including the number of tubes, microchannel ports, and passes. Different combinations were selected within the practical range to obtain optimal dimensions while keeping the total core volume constant. The simultaneous effect of the number of tubes, the number of ports in each tube, and the number of passes is determined. The objective of the current optimization technique is to minimize the pressure drop for the specific design capacity under different operating conditions without changing the overall volume of the gas cooler. The average pressure drop reduction for the optimal geometry as compared with the baseline geometry under all operating conditions is about 15%. The results from this study can be used to select an optimal geometric design for the required design capacity with a minimal pressure drop without the need for expensive prototype development and testing.

Optimization of U-shaped flow channel by RBFNN and NSGA-II

Mobile machinery is in desperate need of weight reduction. To achieve this goal, their hydraulic reservoirs are developing in the direction of miniaturization and lightweight. However, this development of the hydraulic reservoir can lead to excessive air content in the hydraulic system and hard pump suction. At present, how to solve this conflict has not been studied and how the hydraulic reservoir structure influences the deaeration and inside pressure drop is not clear. In this paper, a U-shaped flow channel in a minimized hydraulic reservoir was numerically optimized and analysed for efficient deaeration of hydraulic systems and minimal inside pressure drop. Based on the multiphase flow simulation database, radial basis function neural networks and an NSGA-II were combined for the flow channel optimization. Results showed that two optimized structures raised the degassing rate by 8.8% and 18.1% and reduced the pressure drop rate by 23.7% and 13.5%, respectively. The flow field analysis and bubble motions were investigated among the initial and optimized flow channel structures. On the baffle's left side, bubbles were degassed by the buoyance force. On the baffle's right side, the wall confinement bubbly jet transformed bubbles to the free surface and degassed, but this jet formed by the deep baffle would increase the pressure drop, which agrees with the parameter sensitivity result. Additionally, vortex structures caused by the jet flow entrained bubbles and impeded deaeration. Consequently, the strong vortex was suppressed in optimum models to increase degassing capacity.

Numerical Simulation of Subcooled Boiling in Swing Rectangular Channel based on Non-Equilibrium Thermal Model

Theoretical analysis on the fluid flow in a vertical rectangular channel under swing motion is performed to establish the mathematical model which is based on Eulerian two-fluid framework and non-equilibrium subcooled boiling model. It is analyzed that the flow and heat transfer characteristics and the force of the fluid under the condition of forced flow and swing motion condition. The results show that, for the existence of Coriolis force, the period of acceleration of the fluid is 1/2 of the period of swing angle, and the phase differ. In the rectangular channel, the angle of pressure isoline and horizontal line is sinusoidal likely, which is behind the swing angle phase; Due to the influence of the periodic force field, with the increase of the swing angle, the bubbles in the rectangular channel move to one side, and the wall temperature also increases, which leads to the deterioration of heat transfer; In a swing period, the vapor volume fraction at the outlet and the pressure drop between the inlet and outlet of the rectangular channel fluctuate, and the vapor volume fraction is located at the minimum pressure drop, and the vapor volume fraction at the outlet fluctuates in a trough type.

Optimization of silver/water-based porous wavy direct absorption solar collector

Direct Absorption Solar Collectors (DASCs) are a widely utilized technology in residential applications. However, having known the limitation in DASC size, the efficiency must be enhanced by applying effective modifications and optimizing design parameters. In this study, the performance of a wavy bottom-shaped collector filled with an aluminum porous medium was investigated and the most influential characteristic parameters are specified. Then a design for DASC using Polyvinylpyrrolidone-coated silver nanofluid is proposed and characteristic parameters are optimized based on the full factorial design of the experiment methodology. The model consists of four primary factors, including nanofluid volume concentration (C=0.025%,0.05%,0.1%), porosity (ε=0.8,0.88,0.95), bottom wave amplitude (A=2.5,5,7.5mm), and bottom wavenumber (λ=15,30,60m−1). The results indicated that lowering porosity and increasing nanofluid concentrations improves collector efficiency, whereas rising the wave amplitude and wavenumber causes a higher pressure drop. Additionally, by employing the full factorial design, the main and interaction effects of factors on the efficiency and pressure drop of DASC as the response variables are evaluated. Thus, an optimum value is observed for wave amplitude to reach maximum efficiency and minimize pressure drop. By integrating a porous medium and a wavy bottom with nanofluid, the efficiency of DASC is enhanced from 52 to 93.7%, paving the way for their use in residential applications.

Design Optimization, Thermohydraulic, and Enviro-Economic Analysis of Twisted Perforated Tape Insert-Based Heat Exchanger With Nanofluid Using Computational Fluid Dynamics and Taguchi Grey Method

Abstract In this paper, the effect of perforated twisted tape insert (PTTI)-based heat exchanger (HX) utilizing nanofluid as working fluid undercooling, turbulent flow model has been investigated numerically. Parameters, i.e., nanofluid mass flow rates (0.018–0.038 kg/s), perforated pitches (20 mm–40 mm), and perforated diameters (2 mm–4 mm) variation effects on fluid outlet temperature, Nusselt ratio, Friction ratio, pressure drop, overall thermal performance, CO2 discharge, and heat exchanger operating cost (HXOC) have been investigated. This work also focuses on design optimization with three different factors and three levels for higher heat transfer coefficient (HTC) and minimum pressure drop based on the Taguchi–Grey method. Computational fluid dynamics (CFD) output is used as an input value for statistical analysis. Results revealed that the PTTI in HX successfully achieved overall heat transfer enhancement in the range of 19.2% to 28.5%, but at the cost of pressure penalty of 126% to 163% higher than the plain tube. Critical Reynolds number 7927, above which PTTI in HX is least suitable for heat transfer enhancement as fluid velocity dominates over heat transfer and 1.7–2.5 times higher carbon discharge to the environment and HXOC. Preference sets of geometrical and fluid parameters are obtained using Grey analysis. Based on statistical analysis, in the considered levels, a group of parameters to attain higher HTC and minimum pressure drop are mass flow rate of 0.018 kg/s, a perforated pitch of 20 mm, and a perforated diameter of 4 mm.

Study on performance of heat collecting evaporator of direct expansion solar heat pump

The heat collection evaporator was modeled based on equilibrium homogeneous theory, and the Runge-Kutta calculation method was used to analyze and solve the flow in the heat collection evaporator. The influence of environmental factors such as solar irradiance, ambient temperature and wind speed on the variation of refrigerant pressure in two kinds of heat collecting evaporator was analyzed under the set working conditions. The results show that the solar energy irradiance has a great influence on the pressure drop in the tube of serpentine heat collecting evaporator, and the maximum pressure drop of the refrigerant in the tube is 16.3%, minimum pressure drop is 7.8%. However, it has little influence on the pressure drop of the tube sheet evaporator. The maximum pressure drop in the refrigerant tube of the tube sheet evaporator is 4.8%, minimum pressure drop is 1.8%. When the irradiance reaches 800 W/m2, the refrigerant in the serpentine-tube evaporator has been completely vaporized at 6 m, it’s completely vaporized at 3 m.

Particle Dynamic Characteristics of the Vertical Tubes in a Horizontal-Vertical Pneumatic Conveying System with Different Curvature Radius Bends

To examine the flow characteristics of particles in the vertical tube corresponding to different curvature radius bends, the particle velocity is measured at the Minimum Pressure Drop (MPD) using a high-speed Particle Image Velocimeter (PIV). This experiment explores the effects of particle flow characteristics at different curvature radius bends and their corresponding vertical tubes with pressure drop, power consumption, the intensity of particle fluctuation velocity, power spectrum and time-frequency characteristics. It is observed that the pressure drop and power consumption can be reduced with the help of a large curvature radius bend. Besides, the reduction of particle velocity in the large curvature radius bend and its corresponding vertical tube is less, and the particle possesses a larger intensity of fluctuation velocity in its corresponding vertical tube. The particles in the vertical tube corresponding to the large curvature radius bend lead to large peaks of the power spectrum in the low-frequency region, which is closely linked to the pressure drop. Eventually, the dynamics of particles in a vertical tube are revealed from the perspective of time-frequency analysis by using a continuous wavelet transform.

Experimental and numerical study of installing a dune model in a 90° bend in the horizontal-vertical pneumatic conveying system

In the pneumatic conveying process, particles move to the bend under the influence of inertia to form a particle rope, which will cause serious wear between the particles and the pipe wall, and then the dune model is designed and installed in the 90° bend to reduce energy consumption and wear in this study. Firstly, the minimum pressure drop velocity of particles transported by different size dune models was obtained through experimental study. Then the energy saving mechanism of the dune model is studied by CFD-DEM coupling. The experimental results show that the installation of the dune model reduces the minimum pressure drop velocity. The numerical simulation results show that the number of collisions between the particles and the tube wall in the vertical tube decreases after the installation of the dune model, which reduces the energy loss. Moreover, the increasing of tail size of the dune model is beneficial to the diffusion and acceleration of the particles in the vertical tube.

Parametric investigation on the thermo-hydraulic performance of a novel solar air heater design with conical protruded nozzle jet impingement

A numerical investigation is carried out on heat transfer behaviour of a novel solar air heater (SAH) design with impinging jets through conical protruded nozzles using CFD simulations. The impact of non-dimensional parameters is analyzed by varying the nozzle length ratio (Ln/Dh) from 0.0434 to 0.434, nozzle throat diameter ratio (Dnt/Dh) from 0.0217 to 0.1086 and nozzle base diameter ratio (Dnb/Dh) from 0.0434 to 0.1086 for Reynolds number (Re) variations from 2900 to 14300. The present results with jet impingement design have been compared with a conventional parallel flow SAH under similar conditions and also with some existing designs. Results show that for a combination of Ln/Dh = 0.2608, Dnt/Dh = 0.0217, and Dnb/Dh = 0.0652, the highest thermal efficiency of 91.25 % and exergy efficiency of 3.55 % are obtained at Re value of 14,300 and 2900, respectively. Also, the highest Nusselt number (Nu) of 223.18 is observed for the same combinations at Re = 14300, whereas the highest thermo-hydraulic performance parameter (THPP) of 3.65 is observed for Re = 5740 owing to minimum pressure drop across the collector. With much improved thermal efficiency and THPP, the proposed design and the developed CFD model can be used for further development of impinging jet SAH design.

‘Brine Management through brine mining of trace metals’ for developing Secondary sources of nuclear fuel

The brine and seawater are important and largely untapped sources of critical trace metals and elements. The coupling of selective recovery of trace metals from seawater/brine with desalination plants gives an added advantage of energy credits to desalination plants and as well as reduce the cost of desalinated water. In this paper, status review on recovery of important trace metals and other alkali metals from seawater is presented. The potential of Indian desalination plants for recovery of trace metals, based on recovery ratio of 0.35 is also highlighted. Studies carried out by the process based on adsorption using Radiation Induced Grafted (RIG) polymeric adsorbents and then fractional elutions are presented. The fouling factors due to bio fouling and dirt fouling have been estimated for various locations of interest through field trails. The pay loader in the form of compact Contactor Assembly with minimum pressure drop, for loading specially designed radiation grafted sorbent in leaflet form has been briefed, as required for plant scale facility. The typical conceptual process design details of farm assembly of project CRUDE are described.

Numerical investigation of heat transfer enhancement in microchannel heat sink with fan cavities using secondary channels and ribs

A computational three-dimensional modeling of microchannel heat sink (MCHS) with fan cavity and four different rib configurations along with secondary channels (SCs) has been performed in detail to identify the influence of geometrical parameters on characteristics of heat transfer and provide insight into optimum configuration. The adverse effect of high processing speed and heat flux demands lower operational temperature at the expense of high pumping power in order to increase the lifespan of electronic equipment. Single phase, laminar flow of fluid is considered in the Reynolds number range from 136 to 588. The novel design of the SC benefits heat transfer enhancement by the increase in flow area, originates secondary flows subsequently transforms into symmetric counter-rotating vortices on the basis of rib, however, the influence of the rib blocking effect also depletes, resulting in minimal pressure drop. The comparison between various rib structures confirms that the FC-FTR-SC configuration acquired superior heat transfer performance with a TP of 2.07, at Re = 261. The FC-FTR-SC configuration has a great deal of evidence that pumping power decreases by 10.1% and TP increases by 11.7% as β increases from 0.5 to 1.25. The influence of four geometric parameters: relative width of rib ( α), relative width of the SC ( β), relative length of cavity ( γ), and relative angle of the SC ( ϕ) on heat transfer enhancement and pressure drop have been performed using parametric optimization, response surface methodology.

Experimental Studies of PowerCore Filters and Pleated Filter Baffles.

The material most commonly used to filter and clean the intake air of vehicle internal combustion engines is pleated filter paper, which in most cases is shaped in the form of a cylinder or panel. The production technology has a low cost and is not complicated. In addition to high separation efficiency and filtration performance, pleated filter media are required to have low initial pressure drop, which depends on the geometry of the bed. Much research has been conducted in this area. Dust accumulated in the filter bed causes an increase in pressure drop, which is the cause of deformation and sticking of pleats. The lack of stability of the pleats, the need to strengthen them, and the need to obtain small sizes while achieving high efficiency and accuracy of filtration of engine intake air was the reason for the development of a different design and a new technology for making filter cartridges called PowerCore. The distinctive feature of these filters is axial flow in one direction of the air stream, which avoids turbulence and thus minimizes pressure drop. This paper presents a comparative analysis of a standard PowerCore and PowerCore G2 filter bed and two cylindrical filters with a pleated filter bed made of cellulose and polyester. The conditions and methodology of experimental testing of filters with test dust are presented. During the tests, the characteristics of separation efficiency and filtration performance, as well as pressure drop as a function of the mass of dust retained on the filter of two PowerCore filters and two cylindrical filters were performed. Three specimens of test filters with the same filtration area were made from each sample of filter bed. The results showed that in each test of the filter bed, there is an initial filtration period characterized by low (96–98%) initial separation efficiency and the presence of large (dpmax) dust grains. As the dust loading of the bed increases, the separation efficiency and filtration performance obtain higher and higher values. The initial period of filtration ends when the conventional value (99.9%) of separation efficiency is reached. The duration of this period depends on the type of filter bed and for the PowerCore G2 filter ends for a dust loading of km = 33.1 g/m2, and for the cellulose filter for km = 117.3 g/m2. During the initial period, the air behind the PowerCore G2 filter contains grains with sizes in the range of dpmax = 9–16 µm. Behind the cellulose filter, dust grains are much larger, dpmax = 17–35 µm. The total operating time of the PowerCore G2 filter, limited by the achievement of the permittivity resistance Δpwdop = 3 kPa, is twice that of the other filter compositions tested.

Solar energy assisted thermal treatment model to decontaminate airborne viruses in hospital

• Thermal treatment model based on porous heating to decontaminate the airborne viruses in hospitals. • Solar parabolic collector and electric heaters are used to heat the infected air to abolish the virus. • An insulated chamber ascertains the requisite exposure period for complete decontamination. • The heat exchanger, storage tanks, and air-cooling system are anticipated for optimal cooling of the high-temperature decontaminated air. The evolution of airborne viruses across the globe has caused many deaths in recent decades. Currently, the world is witnessing the terrible behavior of SARS-CoV-2. The airborne viruses attached to the suspended air particles for a long time and spread rapidly. The dispersal of airborne viruses in the indoor air increases the risk of diseases. The present study endorses a solar-assisted heat treatment model to decontaminate airborne viruses and provide hospitals with disinfected air. A simplified model comprises the heating and cooling sections to abolish airborne viruses and cool the treated air. The heating section includes a solar parabolic trough collector (PTC)/electrical heater, porous domain, and decontamination chamber, while the cooling unit comprises storage tanks and an air cooler. A heat exchanger exchanges energy between hot and cold air streams. A solar PTC offers air heating during day time; however, the porous domain with the electrical heaters acts during the night and intermediate time. The airborne viruses can be abolished by passing through a porous domain and decontaminating chamber at 105 °C upholding an exposure period of 5 mins. The cooling section cools the disinfected air to comfortable conditions. A numerical analysis finds the optimal porosity of 0.9, owing to an exit temperature of 105 °C and a minimal pressure drop of 5.16 kPa. The high-temperature disinfected air leaving the storage tank (ST-2) further cools in an air cooler. Besides, the system’s energy efficiency is noted at 37.4 % and 91.1 % during daytime and nighttime operations, respectively.

Ammonia decomposition in a porous catalytic reactor to enable hydrogen storage: Numerical simulation, machine learning, and response surface methodology

Ammonia decomposition is a promising technique for storing and producing hydrogen without carbon emissions. Herein, the potential of hydrogen production via ammonia decomposition in a porous catalytic shell and tube reactor is studied for the first time. The underlying relationship between eight process variables, including reactor structural and operational ones, and the system performance is developed by the aids of computational fluid dynamics (CFD), artificial neural network (ANN), and response surface methodology (RSM). It is found that the reactor (shell-side) inlet velocity, tube inlet temperature, reactor inlet temperature, and porosity are the most influential parameters in ammonia conversion, system efficiency, hydrogen flow rate, and pressure drop, respectively. Moreover, three optimal designs with minimal pressure drop are proposed, considering different optimization objectives. The suggested designs, that are suitable for constructing experimental prototypes, have a porosity of around 0.8 and pore diameters >1.5 mm.

Wavelet multi-scale analysis on particle dynamic characteristics of the vertical tubes in a horizontal-vertical pneumatic conveying system

To study the flow characteristics of particles in the vertical tube, the velocity is measured at the minimum pressure drop (MPD) by using a high-speed particle image velocimeter (PIV). Firstly, the pneumatic conveying system’s pressure drop and the particle velocity characteristics in the vertical tube were investigated. Then, for the axial fluctuation velocity of the particles, the continuous wavelet transform, and one-dimensional discrete orthogonal wavelet decomposition are used to reveal the dynamic characteristics of the particles based on the time-frequency characteristics, the contribution of wavelet levels to the energy of particle fluctuations, the auto-correlation of each wavelet level and the probability distribution of wavelet levels. The results demonstrate that large-scale movement dominates particle movement in the vertical tube, whereas small-scale movement increases as conveying height rises. The energy contribution of the low-frequency wavelet level is larger, and this contribution decreases with the acceleration of the particles along the tube. The high-frequency wavelet level’s auto-correlation coefficients decay more slowly and have a longer duration. At increasing wavelet levels, the skewness and kurtosis coefficients grow, and the departure of the Gaussian probability distribution becomes more obvious.

Numerical analysis of permeate flux in reverse osmosis by varying strand geometry

In regions with limited potable water availability, membrane desalination is being employed to filter water using a pressure-driven approach. Because of the high energy consumption required to produce the pressure differential needed for this method, researchers have been trying different geometric designs of spacer filaments to enhance the amount of permeate flux in terms of energy utilization. The purpose of spacer filaments is to support membranes structurally and induce turbulent mixing in spiral wound membrane desalination. In this paper, the improvement of mass transfer in desalination driven by reverse osmosis has been studied using Computational Fluid Dynamics (CFD) with the introduction of spiral wound membranes that are lined with spacer filaments in a zig-zag formation having alternating diameters for strands. The fluid flow characteristics for a 2-dimensional geometric model were resolved using the open-source program OpenFOAM by changing the Reynolds number to just before the inception of instabilities. Ratios of alternate strand diameters were also varied between one and two. Based on a detailed analysis of velocity contours, pressure distribution, wall shear stresses, and steady-state vortex systems, the research findings offer guidance for employing alternating strand design in zig-zag formation for optimum mass transfer and minimal pressure drop when accounting for concentration polarization.

Optimized pleat geometry at specific pleat height in pleated filters for air purification.

The performance of an air purifier is determined by its clean air delivery rate (CADR), expressed as the product of the air flowrate and filter collection efficiency. A high CADR in a commercial air purifier is achieved using a pleated air filter with high filtration performance at a given air flowrate. However, obtaining this high filtration performance depends on the knowledge of the manufacturer, including the optimal pleating design, which remains uncertain to date. In this study, test pleated filters were prepared by folding a flat electrostatically-charged E12 filter medium to obtain different pleating geometries. The proper pleat geometry of the pleated filter, which has a minimum pressure drop at a fixed air flowrate, was dependent on the pleat length (PL ) and pleating ratio (α=pleat height/pleat width), wherein as the PL increases, the α range required to achieve a minimum pressure drop similarly increases. Based on the filter quality factor (qF ), the optimal pleat geometry of a pleated filter was between α values of 6-8, irrespective of the PL . Although both PL and α have certain influences on the qF , α has a greater influence on the pleated filter with no dead zone.

Numerical simulation on structure optimization of escape-pipe of cyclone separator with downward outlet

In this paper we report on the development of a downward outlet cyclone separator suitable for use as a primary device for pyrolysis gas-coke separation in pulverized coal pyrolysis processes. The downward outlet cyclone separator consists of cylindrical shell that is joined by a cone, to which a downward exhaust pipe is connected. The characteristics of the pyrolysis coke separator were numerically investigated using the concept of a downward outlet cyclone. The motion of the coke particles in a flow field was simulated using discrete phase model (DPM), where a new set of geometrical designs was optimized to achieve the minimum pressure drop and maximum separation efficiency. A comparison of numerical simulations of new designs confirmed the superior performance of the new design compared to the conventional upward outlet used in the pyrolysis of pulverized coal. It was shown that this downward outlet cyclone separator was capable of achieving a separation efficiency of around 77.77% in handing fine particles with sizes of 1 to 10 μm at a pressure drop of around 700 Pa. • The coefficient of determination of experimental and simulation is 0.83 to 0.96. • Different parameters of exhaust pipe produce different degrees of influence. • The optimization by orthogonal test of downward outlet cyclone is A5B4C1. • This design simplifies the multistage separation of pulverized coal pyrolysis.

Genetic algorithm for the design and optimization of a shell and tube heat exchanger from a performance point of view

A new approach to optimize the design of a shell and tube heat exchanger (STHX) is developed via a genetic algorithm (GA) to get the optimal configuration from a performance point of view. The objective is to develop and test a model for optimizing the early design stage of the STHX and solve the design problem quickly. GA is implemented to maximize heat transfer rate while minimizing pressure drop. GA is applied to oil cooler type OKG 33/244, and the results are compared with the original data of the STHX. The simulation outcomes reveal that the STHX's operating performance has been improved, indicating that GA can be successfully employed for the design optimization of STHX from a performance standpoint. A maximum increase in the effectiveness achieves 57% using GA, while the achieved minimum increase is 47%. Furthermore, the average effectiveness of the heat exchanger is 55%, and the number of transfer units (NTU) has improved from 0.475319 to 1.825664 by using GA.