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The development of microchannel manufacturing technology has led to a growing interest in using them as heat exchangers. Microchannels are used to control the temperature of equipment and components that generate a high amount of heat flux. Heat transfer can be further increased by dispersing particles (nano-sized particles) with a low volume fraction into the base fluid (nanofluid). A nanofluid can change the thermophysical properties of a base fluid and improve its thermal performance. The purpose of this study was to examine the heat transfer characteristics of oil-based nanofluid within wavy microchannels in series and parallel arrangements of microchannels. In order to examine the performance of each microchannel separately and to make it easier to draw their diagrams, they are named 1 and 2. Experiments were performed on TiO2 and SiO2 oil-based nanofluids in volume fractions of 0.05 and 0.1, flow rates of 0.5, 1.0, and 1.5 lit/min, and inlet temperatures of 40°C, 45°C, 50°C, 55°C. The results show an increase in the Nusselt number of the base fluid up to 41.8% in the series arrangement and also a decrease in the surface temperature in the series arrangement compared to the parallel arrangement. Also, TiO2 and SiO2 nanofluids with a volume fraction of 0.1 caused the highest increase in heat transfer, up to 56% and 52.7% in parallel arrangement and up to 45.8% and 42% in series arrangement compared to the base fluid, respectively. The pressure drop of the test section in series arrangement was up to 82.1% higher than parallel.

The Darkhovein Water System was commissioned in 1969 for supplying water to the port of Bandar-e Imam Knomeini and the Mahshahr Petrochemical Complex via the Kut-e Amir Pumping Station in Ahvaz. In addition, it has been the sole source of drinking water for Shadegan County, including villages. In this research, using the Water Gems software, the flow pattern in the Darkhoin water transition line was modeled and the change in the diameter of the pipes and pumping and its effect on the pressure, velocity and losses were investigated. Based on the results, a 33.3% decrease in the pipe diameter resulted in pressure losses of less than 3 m throughout the pipeline. This low pressure drop was due to the normal flow velocity. Furthermore, a reduction in the pump propeller diameter from 500 mm to 460 mm in addition to the mentioned decrease in the pipe diameter led to a significant reduction in pressure. Moreover, the average pressure in Scenario 1 was found to be 75 m, while those in Scenarios 2-6 were 72 m, 65 m, 60 m, 55 m, and 40 m, respectively, indicating pressure drops of 3.3 m, 12.4 m, 19.7 m, 25.7 m, and 46.2 m, respectively, across the pipeline.

The Darkhovein Water System was commissioned in 1969 for supplying water to the port of Bandar-e Imam Knomeini and the Mahshahr Petrochemical Complex via the Kut-e Amir Pumping Station in Ahvaz. In addition, it has been the sole source of drinking water for Shadegan County, including villages. In this research, using the Water Gems software, the flow pattern in the Darkhoin water transition line was modeled and the change in the diameter of the pipes and pumping and its effect on the pressure, velocity and losses were investigated. Based on the results, a 33.3% decrease in the pipe diameter resulted in pressure losses of less than 3 m throughout the pipeline. This low pressure drop was due to the normal flow velocity. Furthermore, a reduction in the pump propeller diameter from 500 mm to 460 mm in addition to the mentioned decrease in the pipe diameter led to a significant reduction in pressure. Moreover, the average pressure in Scenario 1 was found to be 75 m, while those in Scenarios 2-6 were 72 m, 65 m, 60 m, 55 m, and 40 m, respectively, indicating pressure drops of 3.3 m, 12.4 m, 19.7 m, 25.7 m, and 46.2 m, respectively, across the pipeline. [ABSTRACT FROM AUTHOR]

Having been developed in accordance with the Montreal Protocol, R134a has been proposed as a potential replacement for R12. In accordance with the Kyoto Protocol, the use of R134a, which has a significant global warming potential, must be restricted. It has been stated that there is no one refrigerant or combination available that can address both the ozone depletion potential (ODP) and the global warming potential (GWP) concerns at the same time. According to the research, the goal of this effort was to produce an environmentally friendly refrigerant combination with minimal ODP and GWP values that perform virtually identically to R12 in terms of performance. With extremely low ODP and GWP values, R406a has the potential to be a useful refrigerant. Experimental investigations conducted on R406a refrigerant have shown that it may be a viable replacement for R12. In this research, the pressure drop created by the torsion in the steam condensation of R-406a inside the horizontal tubes and also changes in the heat transfer coefficient are investigated experimentally. In each experiment, parameters such as mass flow, refrigerant temperature and pressure, and water at the inlet and outlet of the condensers were measured. Examination of the results for annular and torsional fins pipes, it was determined that heat transfer and pressure drop increase with the reduction of the pitch. The use of spirals increases the average heat transfer coefficient and pressure drop by about 47% and 220%, respectively, compared to the pipe without fins. Finally, using the results from the twisted tubes and based on the relationships that best match the experimental results related to the pressure drop, a new relationship for the pressure drop in the twisted tubes was obtained. The values calculated by it are in the range of approximately 15% of the experimental values.

IntroductionCyclone separators use the centrifugal force generated by the gas flow stream to separate the particles from their carrier gas. Simple design, low capital, and easy maintenance make them ideal for use as a valuable pre-refining or sedimentation device. The cause of the particles moving towards the wall and separating from the fluid phase is the centrifugal force created by the rotational flow in a cyclone.Computational fluid dynamics (CFD) is one of the most well-known and widely used advanced modeling methods used for a variety of applications, including separation processes, thermal processes such as dryers, as well as a wide range of engineering and agricultural applications. The numerical solution of Navier-Stokes equations is the basis of all CFD techniques, which is the result of the rapid progress of computers and a deep understanding of the numerical solution of turbulence phenomena.Materials and MethodsThe measurement system of experimental data includes a cyclone separator, feeder, piping, and fan. Measurements of velocity and pressure were carried out using a hot wire air flow rate, (Model 8465-TSI with a resolution of 0.07 m.s-1 and a working range of 0.125 to 150 m.s-1), as well as a differential pressure gauge (CPE310s- KIMO, with an accuracy of 0.1 Pa), respectively. To investigate the effect of the output flow regulator plate on the cyclone performance, five different positions in addition to the base position (zero degree angle or fully open) including angles of 15, 30, 45, 60, and 75 degrees were evaluated.The conservation laws governing the various flows and geometries in the CFD include the conservation law of mass, conservation law of momentum, and conservation law of energy.According to the Mach number value, the pressure base solver was selected. Also, the Reynolds stress model (RSM) was applied to model the flow turbulence. In the discrete phase model (DPM), the fluid phase is solved continuously by solving averaged time equations, while the dispersed phase is calculated by tracing a large number of particles through the flow field.The boundary conditions used in this study include the inlet velocity boundary condition at the inlet of the cyclone, the outlet pressure boundary condition in the upper and lower outlet sections, and the non-slip wall boundary condition for other surfaces. The particle collision to the wall was also defined as reflective. In the mesh section of the cyclone simulation, five mesh levels were used to check the mesh independence test. The numbers of mesh cells in the five levels were 196810, 283120, 427890, 634940, and 1045290. The selected mesh was 427890 level regarding time consideration.Results and DiscussionIn the first section, the validation of simulation results with experimental results is discussed. The value of the velocity magnitude decreased with increasing the angle of the plate, which is probably due to the reduction of the inlet level as well as the reduction of the exhaust airflow in the cyclone air outlet.The maximum value of velocity magnitude occurred according to the direction of the air inlet in the cyclone inlet, which is gradually reduced due to the rotational motion inside the cyclone.The collection efficiency in the cyclone at different levels of regulating plate has values of 85.1% to 95.3%, with maximum collection efficiency at 30° which was 95.3%. The turbulent intensity contours show that turbulence intensity decreases to an angle of 30 °, and then reaches an almost constant value for the 30, 45, and 60 ° angles.ConclusionAs the angle of the output current regulator plate increased, the magnitude of velocity decreased significantly.The separation efficiency showed an increasing-decreasing trend for different values of the regulator plate such that up to a 30° angle of the plate had a positive effect on the separation efficiency.In general, considering the compromise between separation efficiency and pressure drop as two key parameters affecting the performance of the cyclone, an angle of 30 degrees was selected as the best angle among the studied angles for application.

In this research, utilization of typical moisture separation process in conventional steam cycle power plants, for NPPs are recommended; and by applying CFD, two-phase flow of this process is simulated. Results show that with increasing of loading, the pressure drop across the separator increases, and a linear relationship between pressure drop and inlet flow kinetic energy density is established. Also, with increasing inlet width, pressure drop decreases and the efficiency increases. However, excessive increasing of input width leads to a decrease in mass flow at lateral outputs. Study on the variation of lateral outlet diameter show that variation of mentioned parameter does not affect pressure drop and efficiency significantly, but reducing of that lead to increasing lateral out let steam mass fraction. Based on the performed assessment, horizontal steam separator as a component with desirable efficiency and pressure drop, can be recognized as a suitable option for utilization in small and low power NPPs as well as propulsion systems. For validation, an analysis of two phase flow in a vertical cylinder cyclone is performed and results show good agreement with experimental data.

Introduction: Generally, geometrical parameters of the cyclone have a profound effect on determining its performance. The air outlet (Vortex Finder) as one of the cyclone’s components has a significant impact on the cyclone’s internal flow pattern, pressure drop and even dust removal efficiency. Material and Methods: Two different air outlets were designed in order to be easily installed and removed. The ribs (both in the opposite and the same swirl direction with the air flow) were inserted at the inner wall of the vortex finder. The step length of the blades was calculated to be 1.5. The dust feeder was injected the silica particles with a concentration about of 2.1 gr/m3 into the inlet air. The results of dust removal efficiency of the cyclone were calculated and compared for three groups of total dust, PM10 and PM2.5 in different experimental conditions. Results: Installation of spiral blades in same swirl direction as the air flow inside the cyclone increased 7.75, 7.73 and 6.75 percent in total efficiency, PM10 and PM2.5, respectively. The dust removal efficiencies for total dust, PM10 and PM2.5 increased by 2.6%, 2.33% and 1.5%, respectively, when the swirl direction of ribs and air flow was the opposite. The effect of helical blades on pressure drop for the first experimental setup (same direction) decreased by (- 2.5%) and in the second one (opposite direction) increased by (+ 2.03%). The best quality factor was also calculated for the cyclone with the blade aligned with the air flow direction. Conclusion: Use of ribs in the inner wall of the cyclone vortex finder, especially when the rotation direction of the ribs and airflow are the same, leads to a decrease in pressure drop and increase in dust collection efficiency which finally leads to improvement of cyclone performance.

Background and Objective: Air pollution in industrial work environments has adverse effects on worker health. Among these effects, one can refer to chronic obstructive pulmonary disease and asthma, which impose direct and indirect costs on society. Local exhaust ventilation is considered an appropriate approach to remove pollutants released in indoor work environments. This study aimed to develop a smart application for designing and selecting local exhaust ventilation systems. Materials and Methods: This study was designed and performed at two stages. At the first stage, a smart application that could select and design the best local exhaust ventilation system was developed using Visual Basic 6.0. Subsequently, for the validation of this application, the results obtained by the application were compared with the benchmarks. Statistical analysis was performed in SPSS software (version 22), and the Bland-Altman plot was utilized to examine the consistency among the results. Results: Among the parameters, the maximum difference was related to the static pressure drop of the channel with a 5% difference, and the lowest difference was related to the size of the calculated diameters, in which no difference was observed. Bland-Altman plot showed that the standard deviation of the results of the designed software in the calculations of 28 branches of the ventilation systems designed for static pressure, velocity pressure, and total pressure was in the range of ±2SD. Conclusion: Since the software presented in this study has an error of less than 5%, it can be used as a suitable and reliable tool for designing local suction ventilation systems.

IntroductionCyclones are widely used to separate solid particles from the fluid phase. Due to the ease of construction, low running costs, and hard-working conditions at high temperatures, people's interest in using cyclones is increasing day by day. Engineers are generally interested in two parameters to perform a complete evaluation of the design and operation of a cyclone. These parameters are the particle collecting efficiency and the pressure drop inside the cyclone. The precise prediction of the pressure drop in cyclone is very important which it is directly related to operating costs.Computational Fluid Dynamics (CFD) is a diversified tool for predicting flow behavior in a wide range of design and operational conditions. Numerical solution of Navier-Stokes equations is the basis of all CFD techniques, which is the result of fast computer upgrades and a better understanding of the numerical resolution of turbulence.Materials and MethodsRegarding preliminary experimental tests and understanding the fluid flow, the flow rate of 0.08 kg s-1 was selected as the flow rate. Six levels of inlet velocities 10, 12, 14, 16, 18, and 20 m s-1 were selected for understanding the effect of inlet velocity on the cyclone performance. The measurements were carried out using a hot-air anemometer (TSI-8484model with a resolution of 0.07 m s-1 and an operating range of 0.125 to 50 m s-1), and a pressure differential meter instrument (CPE310s-KIMO model) with an accuracy of 0.1 Pa.The region is discretized as a finite volume in a set, called the region grid or mesh after discretization. For incompressible fluids, pressure-based and density-based solvers are used, respectively. Regarding the velocity of the material entering the cyclone and low Mach number, a pressure-based solver could be used in this study.The shear stress transport model (SST) is a modified version of the k-ω 2-equation model. This model combines the two turbulence k-ω and k-ε models. The Lagrangian discrete phase model in Ansys Fluent follows to the Euler-Lagrangian model.Defining the best type of boundary condition is important for solving the problem and extracting solving fields. The boundary conditions used in this study include the inlet velocity in the entrance of cyclone and output pressure in both the upper and lower output sections.Results and DiscussionIn the results section, the results are initially validated by experimental results. Then, the parameters relating to separation efficiency and pressure drop are discussed. Finally, the tangential and axial velocities are considered as important parameters in the cyclone performance.One of the important issues in the cyclones is the static pressure because it completely affects the phenomenon of separation in the cyclone. The velocities of 16 m s-1 and 18 m s-1 have a good potential for use as the base velocity of the inlet fluid to the cyclone. The velocity of 20 m s-1 is not suitable for separation due to high-pressure drop related to high static pressure.The separation efficiency in the cyclone was 92 to 99% at all levels, the highest separation efficiency of 99% occurred at the velocity of 16 m s-1 and the lowest separation efficiency of 9% happened at the velocity of 20 m s-1.An increasing trend in axial and radial velocities occurred and the highest tangential velocity occurring in the input section. Considering the working conditions, the inlet velocities of 10 m s-1 to 16 m s-1 are appropriate for the turbulence intensity viewpoint.Conclusions(1): The speeds 16 m s-1 and 18 m s-1 showed a good potential for use as a base velocity of the fluid to the cyclone.(2): The highest separation efficiency for the velocity of 16 m s-1 (99%) and lower isolation efficiency was obtained at velocity of 20 m s-1 (92%).(3): The velocities of 10 m s-1 to 16 m s-1 are suitable input rates from the point of view of turbulence intensity.(4): It is concluded that from the point of view of wear to the velocity of 10 to 16 m s-1, practical use is possible, and the velocity of 18 m s-1 and 20 m s-1 require the reinforcement of the relevant sections.

Background and Objective: Pulse jet baghouse systems are of interest due to their high filtration velocity. They are used as inlets from the top and bottom. The purpose of this study was to compare the pressure drop and collection efficiency at different inlet positions in a baghouse. Materials and Methods: In this experimental study, a pilot baghouse system was designed at 12ft/min permeability for MDF particles. For each inlet, after several filtration-cleaning periods, the pressure drop was measured by a manometer. Isokinetic sampling was carried out by Grimm monitor model 1.108 for the determination of the efficiency. To observe the behavior and Tyndall effect of the particles, a light and safety glass were used in one dimension of the baghouse. Results: The mean of pressure drop during the filtration-cleaning was reported as 3 cmWG in the bottom inlet. In addition, the means of the top-expansion inlet and top-flanged inlet were observed to be 2.42 and 2.57 cmWG, respectively; however, the particles were settled on the bottom in the expansion. The efficiency means of the top-expansion and top-flanged inlets were 99.995% and 99.994%, respectively, which were significantly higher than that reported for the bottom inlet (99.974%). Nevertheless, after several filtration-cleaning periods, the efficiency values of the bottom, top-expansion, and flanged inlets were obtained as 99.99%, 99.97%, and 99.96%, respectively. There was no significant difference in the means of total efficiency among different inlets. Conclusion: The collection efficiency values were similar for baghouse with the inlet from the top and bottom. The pressure drop for baghouses with top inlets was lower than that reported for the baghouses with bottom inlets. It is recommended to use top inlets in case of predominantly fine particles with low density or in the presence of a pre-separator, and bottom inlets are suggested in case of large particles. However, due to the slight difference of pressure drop and more functional limitation of the top inlet, the bottom inlet is preferred in practice.

Rotating Packed Beds (RPBs) are used in many processes of chemical engineering, such as distillation, absorption, production of nanoparticles, natural gas sweetening, and etc. The fluid flow analysis in this equipment is necessary to obtain the hydrodynamic information and investigation of transport phenomena. In this paper, 3D simulation of single phase and two phase flows are carried out using Computational Fluid Dynamics (CFD). The effect of some parameters such as rotational speed, gas and liquid flow rates, number of rotor holes, fixed and moving baffle are investigated on the pressure drop. The single phase flow analysis showed that the tangential velocity has the most effect on the velocity magnitude comparison with the radial and axial velocities. The simulation results showed that dry and wet pressure drop increase with increasing gas flow rate as the average errors between experimental data and simulation results with and without baffle are 5.3% and 3.6%, respectively. It was also known that increasing liquid flow rate has negligible effect on the pressure drop. It was seen that wet pressure drop increases with increasing both rotational speed and rotor holes. The moving baffle insertion into the bed was caused that wet pressure drop decreases 14%.

Introduction Cyclones are vilely used to separate solid particles from the fluid phase. Due to the ease of construction, low running costs, and hard-working conditions at high temperatures, people's interest in using cyclones is increasing day by day. Engineers are generally interested in two parameters to perform a complete evaluation of the design and operation of a cyclone. These parameters are the particle collecting efficiency and the pressure drop inside the cyclone. The precise prediction of the pressure drop in cyclone is very important which it is directly related to operating costs. Computational Fluid Dynamics (CFD) is a diversified tool for predicting flow behvior in a wide range of design and operational conditions. Numerical solution of Navier-Stokes equations is the basis of all CFD techniques, which is the result of fast computer upgrades and a better understanding of the numerical resolution of turbulence. Materials and Methods Regarding preliminary experimental tests and understanding the fluid flow, the flow rate of 0.08 kg S٠1 was selected as the flow rate, six levels of inlet velocities 10, 12, 14, 16, 18, and 20 m s-1 were selected for understanding the effect of inlet velocity on the cyclone performance. The measurements were carried out using a hot-air anemometer (TSI-8484model with a resolution of 0.07 m s-1 and an operating range of 0.125 to 50 m s-1), and a pressure differential meter instrument (CPE310S-KIMO model) with an accuracy of 0.1 Pa. The region is discretized as a finite volume in a set, called the region grid or mesh after discretization. For incompressible fluids, pressure-based and density-based solvers are used, respectively. Regarding the velocity of the material entering the cyclone and low Mach number, a pressure-based solver could be used in this study. The shear stress transport model (SST) is a modified version of the k-® 2-equation model. This model combines the two turbulence k-® and k-s models. The Lagrangian discrete phase model in Ansys Fluent follows to the Euler-Lagrangian model. Defining the best type of boundary condition is important for solving the problem and extracting solving fields. The boundary conditions used in this study include the inlet velocity in the entrance of cyclone and output pressure in both the upper and lower output sections. Results and Discussion In the results section, the results are initially validated by experimental results. Then, the parameters relating to separation efficiency and pressure drop are discussed. Finally, the tangential and axial velocities are considered as important parameters in the cyclone performance. One of the important issues in the cyclones is the static pressure because it completely affects the phenomenon of separation in the cyclone. The velocities of 16 m s-1 and 18 ms have a good potential for use as the base velocity of the inlet Euid to the cyclone. The velocity of 20 m s-1 is not suitable for separation due to highpressure drop related to high static pressure. The separation efficiency in the cyclone was 92 to 99٥/٠ at all levels, the highest separation efficiency of 99٥0 occurred at the velocity of 16 m s-1 and the lowest separation efficiency of 9٥/o happened at the velocity of 20 m s-1. An increasing trend in axial and radial velocities occurred and the highest tangential velocity occurring in the input section. Considering the working conditions, the inlet velocities of 10 m s-1 to 16 m s-1 are appropriate for the turbulence intensity viewpoint. Conclusions: (1) The speeds 16 m s-l and 18 m s-l showed a good potential for use as a base velocity of the fluid to the cyclone.(2): The highest separation efficiency for the velocity of 16 m s'1 (99%) and lower isolation efficiency was obtained at velocity of 20 m s-1 (92%). (3): The velocities of 10 m s-1 to 16 m s-1 are suitable input rates from the point of view of turbulence intensity. (4): It is concluded that from the point of view of wear to the velocity of 10 to 16 m s-1, practical use is possible, and the velocity of 18 m s-1 and 20 m s-1 require the reinforcement of the relevant sections. [ABSTRACT FROM AUTHOR]

The purpose of this article is the numerical study of flow and heat transfer characteristics of Nanofluids inside a cylindrical microchannel with rectangular, triangular, and circular cross-sections. The size and shape of these sections have a significant impact on the thermal and hydraulic performance of the microchannel heat exchanger. The Nanofluids used in this work include water and De-Ethylene Glycol (DEG) as the base fluids and Al2O3, Cu, SiO2 and CuO as the nanoparticles. To solve the problem and extract the required data, a 3-D simulation was performed for the microchannel using ANSYS FLUENT 15.0 software and the effect of the cross-sectional shape of the fluid flow and the type of nanoparticles on the thermal transfer and fluid flow parameters was studied. From the obtained results, it can be observed that the addition of nanoparticles to the base fluid increases the heat transfer and pressure drop. The results also show that rectangular channels have the best performance among the three geometries examined as its heat transfer coefficient was 19.26% higher than the triangular cross section which had the worst performance.

Introduction: Air pollution is now recognized as an important environmental and health concern. Biological control processes, due to their durable, cost-effective and eco-friendly, have become a good alternative to physic-chemical methods. Biotechnology is based on the activity of microorganisms. The aim of this study was to compare the capability of Pseudomonas Putida PTCC 1694 (bacteria) and Polarotus Stratus IRAN 1781C (mushroom) in the removal of toluene from the air stream and its biodegradation under same operating conditions. Material and Methods: To this purpose, a bio filter containing two parallel columns was designed and constructed on a laboratory scale and the experiments were carried out based on measuring the removal efficiency (RE), elimination capacity (EC) and pressure drop in these two columns. Thus, the bacteria were inoculated in one of the columns and in the other the fungus was inoculated. Results: The bacterial testing lasted for 20 days and the fungal testing lasted for 16 days. The contaminant loading rates (LR) for bacterial and fungal bio filters were 11.65±2.26 and 11.94±2.56 g/m3.h, respectively. The results showed that the fungal bio filter was more capable of eliminating of toluene vapor than bacterial bio filter (9.65±3.53 vs 9.18±2.6 g/m3.h). However, the pressure drop in the bacterial bio filter was lower than the fungal bio filter (1±0.28 vs 1.1±0.32 cm water). Conclusion: According to the results, fungal bio filtration appeared to be more successful than bacterial bio filtration in the removal of toluene.

In this paper, the exergy analysis of a direct-expansion solar-assisted heat pump system (DX-SAHP) has been presented considering the effects of the pressure drop associated with the ï‌ow of R134a refrigerant through the condenser, collector/ evaporator and connection pipes. In order to calculate the two phase refrigerant pressure drop through the evaporator and condenser, the homogeneous model of pressure drop inside horizontal pipes has been used. The DX-SAHP system mainly employs a bare ï‌at-plate solar collector with a surface area of 4 m2, a hot water tank with the volume of 150L, a rotary-type hermetic compressor and a thermostatic expansion valve. Furthermore, the effect of various parameters including ambient temperature, solar radiation, collector area and compressor speed have been analyzed on the exergy efficiency and exergy loss of the system. The results of the simulation have good agreement with the experimental results and show that the increase in solar collector/evaporator pressure drop adversely affects the system COP and the solar collector efficiency. During the operation of the DX-SAHP system within a year, it is concluded that the largest value of the exergy efficiency of the system is 22.7 percent and the lowest value of the exergy loss is 12.6 kW. The obtained values are particularly due to the minimum amount of solar radiation in December. Results indicate that the solar collector has the minimum value exergy efficiency amounted to 12.6 percent and the maximum value of exergy loss amounted to 2.19 kW, among all of the system components.

In the current study, experimental and numerical methods have been used to investigate the pressure drop and the separation efficiency of wire mesh demisters in an air-water system. Using the designed and manufactured experimental model, various parameters such as air velocity, packing density, and wire diameter in plastic and metallic demisters have been studied. Numerical simulation was carried out in two-dimensional and transient form using K-epsilon (k-ε) turbulence model in commercial software ANSYS Fluent and validated against experimental results. The Eulerian-Lagrangian discrete phase model was also used to simulate the water droplet trajectory at diameters of 0.2 and 0.05mm. The numerical simulation results are sufficiently accurate compared to the experimental data. The numerical solver predicts separation efficiency with error of about 20% and pressure drop with error of less than 20% compared to experimental data. The numerical simulation results show that increasing the diameter of water droplets at higher air velocities and higher packing densities is more effective and increases the separation efficiency up to 36%. Also, increasing the packing density increases the separation efficiency for droplets with a diameter of 0.2mm and decreases the separation efficiency for droplets with a diameter of 0.05mm. The results show that the separation efficiency of plastic demister is more than the separation efficiency of metallic demister and in lower packing densities, the use of plastic demister is advisable. [ABSTRACT FROM AUTHOR]

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This research has been investigated water pressure drop through the multistage industrial orifices that are installed into a pipe in 1300 MW Arak-Shazand Thermal Power Plant. Whereas having turbulence flow done simulating model was standard . In order to reach a specific water pressure drop with a specific water flow rate, the optimum design is implemented based on the composition of orifice stageâs number along with changing the diameter of the holes and numberâs. Finally to verification of simulationâs results, it will be compared with results of experimental test that is done with multistage orifices installed into a pipe. That could be illustrated good adjustment with together. Also this pressure drop lead to increase the percentageâs opening spray control valves that has extreme influence to decrease corrosion and better work of control valves.

One of the most common systems to collect the suspended particles from the air is fibrous filters. An important parameter to evaluate the filters performance is pressure drop. In this work the influence of the arrangement of the fibers at the fibrous media on the pressure drop is studied. Three different parallel, staggered and random arrangements are considered to model the fibrous media. The effects of these arrangements are investigated at different solid volume fractions. The results are compared and discussed with existing empirical and semi analytical relations. It is observed that using regular arrangement results in larger pressure drop than random one or which is predicted by empirical tests.

In this paper, black powder of the separation from air flow by a helical one-channel dust concentrator have been experimentally studied and the efficiency and pressure drop have been investigated by Computational fluid dynamics (CFD) simulations in different operating conditions. Experimental set-up is a helical one-channel including 29 branches for exporting diluted stream out. It also has two suction devices at the ends of channels in order to provide testing in high inlet flow. Black powder particles with certain particle size distribution have been tested, whose average particle size has been determined 0.327 μm by DLS and SEM images processing. CFD simulation of helical one-channel dust concentrator for air-black powder separation has been done with FLUENT software. The Realizable k-ε turbulent model, as an optimal turbulence model in terms of accuracy and speed in simulation, has been used. According to evaluation of the results, the experimental results have been compared and it showed 5.2% error. To investigate the effect of operating condition, the various air flow rate and solids mass fractions were investigated and the results showed that the simulation efficiency has increased more than 4.1% by increasing 58% of the inlet volumetric flow rate. The separation efficiency had no change by increasing the solid mass fraction from 7% up to 20%. [ABSTRACT FROM AUTHOR]

In this research, taking into account the pressure drop of the streams, a simple and useful method is presented for finding the proper path of hot and cold streams inside shell-tube heat exchangers in the synthesis of heat exchangers networks (HENs). Generally, the HENs synthesis by mathematical programming leads to the problems which are answered by Mixed Integer Non Linear Programming (MINLP) methods. Optimization of such formulations results convergence difficulties due to the existence of both continuous and integer variables. In this study, instead of solving simultaneously integer and continuous variables, the genetic algorithm was used to find optimal HEN structure (integer variables). To find optimal values for continuous variables of the network, by categorizing this type of variables into two groups and using Quasi Linear Programming (QLP) instead of the nonlinear programming model (NLP), the complexity of the NLP model solution is also greatly reduced. The optimal values of continuous and integer variables are obtained with respect to a common objective function that reaches the minimum annual cost of the HEN. The comparison of the proposed method with the references shows that this method has the ability to reduce the cost of pumping flows to about 0.76%. [ABSTRACT FROM AUTHOR]

Background and Objectives: The goal of the present study was to develop nanofibrous media filters containing MgO nanoparticles for future application in removing particles from gas stream. Materials and Methods: Electrospun nanofibers were fabricated using experimental design prepared by Response Surface Methodology. Optimization of electrospinning parameters was conducted for achieving the desired filter properties including fiber diameter, porosity, and bead number. After taking SEM images, the determination of fiber diameter and number of beads were performed through Image Analysis and the calculation of porosity percent was performed by MATLAB. A filter media was produced based on the optimized conditions of electrospinning and it was certified by the HEPA filter performance test. Results: In terms of morphological quality of fibers including fiber uniformity, absence of branching and lower numbers of beads, experiment standard No. 2 (STD 2: concentration 16 wt%, voltage 10 kV, and distance 15 cm) had the best combination. Maximum fiber diameter was also observed in STD 2. Among the electrospinning, the highest correlation coefficient was observed between solution concentration and response variables and the relationship between concentration and both fiber diameter and porosity percent was statistically significant (p 0.05) and a weak negative relationship was seen between fiber diameter and bead number (r=-0.2, p>0.05). Conclusion: Solution concentration was found as the most affecting factor on the filter properties, so that the higher concentration leaded to the lower bead number and greater fiber diameter. Increase in fiber diameter resulted in larger pore size and higher porosity. Quadratic models were known for understudy variables. Efficiency of the optimized filter was comparable with the HEPA filter and it had the lower pressure drop.

In this paper, the separation black powder from air flow experimentally have been studied by spiral-channels dust separator and the efficiency and pressure drop of spiral-channels dust separator has been investigated by CFD simulations in different operating conditions. Powder particles have been tested from a sample of powders of Saveh Strengthening Station, whose average particle size has been determined by DLS and SEM images processing, 0.327 micrometers. CFD simulation of spiral-channels dust separator has been done with FLUENT software. The RNG k-ε turbulent model as an optimal turbulence model has been used. The difference between the experimental and the simulation results was revealed around 16% and 7.15% for efficiency and pressure drop parameters respectively. To illustrating the effect of operating condition, the various flow rate and solids mass fraction were investigated and results showed that maximum efficiency is the highest input volumetric flow rate. Also, the results showed that this system has the efficiency of more than 80% for separating Black Powder particles and with increasing 40% of the volumetric flow rate, the separation efficiency increased up to 10%. If, by increasing the mass fraction of solids by 5 times, the efficiency increased only by 3%. The pressure drop of the separator increased up to about 50% with increasing the volumetric flow rate from 80 to 140 m3/hr. [ABSTRACT FROM AUTHOR]

An experimental study for the convection heat transfer coefficient in a region of nanofluid containing Al2O3 oxide nanoparticles of 20 nanometer diameter in water as a base fluid through circular annular tube in the cosine thermal flux boundary condition was carried out. The primary purpose of this investigation was accomplished on the surface temperature of the heat source (inner pipe) determined at the maximum upper than the middle of pipe for the whole entry temperatures and surface temperature for nanofluid which was less than that of the base fluid. However, the nanofluid did not have any effect on the location point on the maximum temperature surface. Then, the convection heat transfer coefficient and Nusselt number were scrutinized showing that both of them increase by increasing of the volume fraction and Reynolds number. The maximum value of the heat transfer coefficient of nanofluid belongs to the volume fraction of 1.5% and the Reynolds number near 2100 which is 19%, compared to that of the base-fluid. The effect of entrance temperature and pressure of nanofluid on the heat transfer coefficient was also studied. The experimental data have shown that by increasing the entrance temperature, the heat transfer coefficient improves but the pressure has a negligible effect on heat transfer. The results demonstrated that the relative pressure drop of nanofluid increased remarkably by increasing the volume fraction. Furtheremore, we observed that by decreasing the Reynolds number the pressure drop increased because of more sediment of nanoparticle at lower velocities.

The main objective of this study is to design and construct the new, spouted bed dryer, for food drying sensitive foods specially. For this purpose, firstly a new design of dryer was planned to achieve the maximum efficiency and flexibility for liquids and solids drying. After constructing and initial setup of spouted bed, basic experiments such as investigation of an inert particles motion, pressure drop, energy consumption were conducted and optimal system requirements for two particle size (5.8 & 7.8 mm) were determined. The results indicated that changes in pressure drop in the dryer chamber containing inert particles are followed from the Ergun equation. Energy consumption in this system is variable in the range of 3-8 kW per hour. Also results reveals that the energy consumption of the new design of spouted bed dryer is less than the spray dryer for liquid foods drying.

In contrast with two stream heat exchangers, the three stream ones owns much more complexity in design and rating and a comprehensive rating method has not been proposed, yet. In this paper, a new rating method is presented in order to be used in three stream plate -fin heat exchangers. Rating, in heat exchangers, means finding out the heat load of the heat exchanger or in other words calculating the outlet temperature of each stream and furthermore, determining the pressure drops of each stream. In this paper, the differential equations of energy conservation and heat balance of each steam is extracted and a set of differential equations in terms of outlet temperatures is constructed. The general solution of this set of equations is then extracted. In order to expand the general solution to plate -fin heat exchangers, the geometric, thermal and hydraulic modeling are applied based on fin geometric specification which used rectangular type in this paper without losing generality. Based on all of the extracted equations, a comprehensive algorithm of rating of the three stream plate -fin heat exchangers is presented. In order to evaluate the presented algorithm, a case study is used and the results will be shown. Furthermore, a parametric study is applied to the case study to evaluate the effects of the geometric parameters of the fins such as height and frequency on heat load and pressure drop of the heat exchanger. [ABSTRACT FROM AUTHOR]

Background and purpose: The emission of hydrogen sulfide (a malodorous and toxic pollutant) into the atmosphere is considered a public health concern due to its potential hazardous effects on human health. Therefore, the removal of hydrogen sulfide from polluted air streams is of paramount importance. This study aimed to evaluate the role of a polyurethane foam/palm fiber-based biofilter in the removal of hydrogen sulfide. Materials and methods: Air stream containing H2S was introduced into the biofilter at a flowrate of 7 L/min and an empty bed retention time (EBRT) of 47 seconds. The inlet and outlet concentrations of H2S were measured. Moreover, the amount of sulfate and pH in bed, leachate from the biofilter and pressure drop along the biofilter height were monitored. Results: In this study, the biofilter provided 100% removal efficiency for inlet H2S concentration of 288.0 mg/m3 at EBRT of 47 seconds. The maximum elimination capacity (ECmax) of the biofilter was 24.1 g/m3 .h at a loading rate of 28.0 g/m3 .h, corresponding to a removal efficiency of 86.1%. As the elimination capacity of H2S increased the sulfate content of packing bed increased to 10.8 mg/g bed and the pH reduced to <2.1. The pressure drop along the biofilter column remained <5 mm throughout the operational period. Conclusion: The polyurethane foam/palm fiber mixture could be considered as a potential biofilter carrier, with low-pressure drop, to treat air streams containing H2S. [ABSTRACT FROM AUTHOR]

Background and Objectives: The goal of the present study was to develop nanofibrous media filters containing MgO nanoparticles for future application in removing particles from gas stream. Materials and Methods: Electrospun nanofibers were fabricated using experimental design prepared by Response Surface Methodology. Optimization of electrospinning parameters was conducted for achieving the desired filter properties including fiber diameter, porosity, and bead number. After taking SEM images, the determination of fiber diameter and number of beads were performed through Image Analysis and the calculation of porosity percent was performed by MATLAB. A filter media was produced based on the optimized conditions of electrospinning and it was certified by the HEPA filter performance test. Results: In terms of morphological quality of fibers including fiber uniformity, absence of branching and lower numbers of beads, experiment standard No. 2 (STD 2: concentration 16 wt%, voltage 10 kV, and distance 15 cm) had the best combination. Maximum fiber diameter was also observed in STD 2. Among the electrospinning, the highest correlation coefficient was observed between solution concentration and response variables and the relationship between concentration and both fiber diameter and porosity percent was statistically significant (p <0.05 and p <0.01, respectively). A weak positive correlation was found between fiber diameter and porosity percent (r=0.29, p>0.05) and a weak negative relationship was seen between fiber diameter and bead number (r=-0.2, p>0.05). Conclusion: Solution concentration was found as the most affecting factor on the filter properties, so that the higher concentration leaded to the lower bead number and greater fiber diameter. Increase in fiber diameter resulted in larger pore size and higher porosity. Quadratic models were known for understudy variables. Efficiency of the optimized filter was comparable with the HEPA filter and it had the lower pressure drop. [ABSTRACT FROM AUTHOR]

The modeling and optimization of a rectangular finned multi stream plate-fin heat exchangers is presented in this paper. The proposed method for thermal modeling of this type of heat exchangers is based on uniform heat distribution along the plates. So, the heat streams are distributed along the multi stream heat exchanger based on two principles: equal quantity of stream channel distribution and uniform heat distribution in each of the channels. The geometric, thermal and hydraulic modeling and design of the multi stream heat exchanger is carried out based on rectangular fin specifications. The total annual cost (TAC), the summation of capital investment and operating and maintenance costs are regarded as objective function to be minimized. The main variables are heat exchanger core dimension such as length, width, height and the fin geometric parameters such as fin pitch and height. The genetic algorithm is utilized as optimization tool to minimize the total annual cost of the multi stream plate fin heat exchanger. The proposed method is applied to a case study. The results of the current method is compared with the literatures. [ABSTRACT FROM AUTHOR]

Simulation and analysis of two phase flow that crosses over tube bundles is crucial in safety analysis and design of kettle reboilers and steam generators. The geometry complexity of the tube bundle flow field increases the difficulty of the conventional numerical analysis. One of the methods to reduce the numerical calculations cost is to use the porous media theory instead of the complete tube bundle modeling. Drag and tube bundle resistance force equations have been used in the porous media analysis. Based on available experimental results, two tube bundle arrangements have been considered. Due to existence of symmetric geometry and uniform energy source over the tube bundle, the two dimensional symmetric models have been used as well. It was observed that the predicted pressure drop in this research has acceptable adaptation with the experimental results. Meanwhile, by considering different outlet boundary conditions, calculated void fraction is compared to the experimental results and showed better accuracy than similar CFD research. It was observed that the enhancement of the tube bundle thermal power increases the void fraction in the heating area of the reboiler. [ABSTRACT FROM AUTHOR]

Variation of the cross-sectional area of a channel affects the flow field and, therefore, convective heat transfer between the fluid and channel walls. In this paper, a geometrical model is proposed for a wavy channel carrying steady laminar flow of an incompressible fluid. The two-dimensional channel is modeled as a combination of a number of subsonic diffusers and nozzles. Effects of the geometrical characteristics such as length, boundary shape and symmetry of the channel, which describe the shape of these nozzles and diffusers, are investigated. Numerical studies at Re=200 show that the shape of the wall does not dramatically affect the convection heat transfer rate in the steady laminar regime. However, optimization studies can be carried out to change the shape of the channel and improve the average Nusselt number to some extent. It is shown that the average Nusselt number increases with the increase of the length of the diffuser part, but the asymmetry of the channel might increase or decrease the average Nusselt number. Finally, a genetic algorithm is introduced and used to optimize the geometrical parameters which describe the aforementioned nozzles and diffusers and, hence, the shape of the channel. [ABSTRACT FROM AUTHOR]