Reaction Engineering, Kinetics and Catalysts,
S. M. S. Hosseini; H. Hashemipour rafsanjani; A.R. Talebizadeh
Volume 14, Issue 4 , December 2017, , Pages 3-16
Abstract
An alumina-supported nickel catalyst was prepared by impregnation of Ni2+ solution onto mesoporous alumina under microwave irradiation (denoted as M-Ni/Al2O3). For comparison, a catalyst with the same nickel content was prepared by conventional impregnation method (denoted as UM-Ni/Al2O3). Both M-Ni/Al2O3 ...
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An alumina-supported nickel catalyst was prepared by impregnation of Ni2+ solution onto mesoporous alumina under microwave irradiation (denoted as M-Ni/Al2O3). For comparison, a catalyst with the same nickel content was prepared by conventional impregnation method (denoted as UM-Ni/Al2O3). Both M-Ni/Al2O3 and UM-Ni/Al2O3 catalysts were applied to the syngas (H2 + CO) production by methane oxy-steam reforming in order to investigate the effect of preparation method on the catalytic performance. The reaction experiments were performed in a fixed-bed continuous flow reactor under atmospheric pressure. M-Ni/Al2O3 catalyst exhibited higher methane conversion (XCH4: 0.94) than UM-Ni/Al2O3 (XCH4: 0.58) in the oxy-steam reforming reaction. In addition, the value of syngas yield in M-Ni/Al2O3 (3.21 mole per mole of methane) was almost twice of one for UM-Ni/Al2O3 catalyst (1.59 mole per mole of methane). Various operating conditions such as the influences of the O2/CH4 and H2O/CH4 feed ratios, temperature, and GHSV on the methane conversion and yield of products were investigated. According to the structural characterization (FTIR, XRD, N2 adsorption/desorption, H2-TPR and TEM), the excellent catalytic performance of M-Ni/Al2O3 catalyst was reasonably attributed to the nano size and uniform distributed nickel species (<6 nm) which interacted to the alumina support strongly.
Separation Technology,
N. Kakoui; M. Nikzad; A. A. Ghoreyshi; M. mohammadi
Volume 15, Issue 2 , May 2018, , Pages 3-21
Abstract
The present study investigates the potential applicability of the extracted pectin from sour orange pomace as adsorbent for Ni (II) removal from aqueous solution. Pectin extraction from the pomace was carried out using HCl and the highest pectin extraction yield of 26.75% was obtained. The Fourier transform ...
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The present study investigates the potential applicability of the extracted pectin from sour orange pomace as adsorbent for Ni (II) removal from aqueous solution. Pectin extraction from the pomace was carried out using HCl and the highest pectin extraction yield of 26.75% was obtained. The Fourier transform infrared (FTIR) spectroscopy analysis confirmed that the structure of the extracted pectin was similar to the commercial one. The morphology and chemical characteristics of pectin beads were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) techniques. The influence of several parameters including pH, initial metal concentration, adsorption temperature and time was studied to optimize nickel removal. The maximum Ni (II) removal of 85.1% was obtained at initial concentration of 20 mg/L and the highest adsorption capacity of 19.76 mg/g was achieved at nickel concentration of 100 mg/L. Kinetic and equilibrium studies were done to evaluate Ni (II) sorption from aqueous solution by the synthesized beads. Results showed that the sorption process follows a pseudo- second- order kinetic model. The equilibrium data were well correlated with Langmuir and Redlich-Peterson models by high regression coefficients.
Modeling and Simulation
M.R zeynali; M. Nazari; S. Karimi; S. M. Seyedmohaghegh; S. Soltani
Volume 14, Issue 2 , 2017, , Pages 3-16
Abstract
In this research samples of PVOH were synthesized at various reaction conditions (temperature, time, and amount of catalyst). First at 25˚C and 45˚C and constant catalyst weight samples of PVOH were prepared with different degree of hydrolysis at various times. For investigation of the effects of temperature, ...
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In this research samples of PVOH were synthesized at various reaction conditions (temperature, time, and amount of catalyst). First at 25˚C and 45˚C and constant catalyst weight samples of PVOH were prepared with different degree of hydrolysis at various times. For investigation of the effects of temperature, at times 20 and 40 min and constant weight of catalyst PVOH was prepared at various temperatures. Increasing the time and temperature of the hydrolysis reaction caused increasing degree of hydrolysis and reducing the molecular weight of the samples. Considering the variation of reaction condition, the effects of each parameter on molecular weight, degree of hydrolysis and conversion were investigated individually and also collective. Also, by an artificial neural network method, using experimental results (temperature, time and catalyst amount as input and conversion, degree of hydrolysis and molecular weight as output) a network by Levenberg-Marquardt (LM) back propagation with tan-sigmoid transfer function was established. Finally, the established model presented a good prediction capability and enabled us to predict the output in terms of arbitrary in puts. PVOH is an important polymer and prediction its properties during production significantly improves the quality of the products. Neural network technique is used to model the chemical processes to predict the behavior of the process. In this research we investigated the effects of various processing parameters on the properties of PVOH.
Reaction Engineering, Kinetics and Catalysts,
A. Payan; M. Fattahi; B. Roozbehani; S. Jorfi
Volume 15, Issue 3 , September 2018, , Pages 3-14
Abstract
The nitrogen doped TiO2 as heterogeneous photocatalyst via sol-gel method were successfully synthesized. The physicochemical, morphological and textural characteristics of the obtained TiO2 samples were characterized by advanced analysis techniques. The photocatalytic activity of the samples were evaluated ...
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The nitrogen doped TiO2 as heterogeneous photocatalyst via sol-gel method were successfully synthesized. The physicochemical, morphological and textural characteristics of the obtained TiO2 samples were characterized by advanced analysis techniques. The photocatalytic activity of the samples were evaluated for degradation of 4-CP under solar irradiation. The as-synthesized photocatalysts were characterized with X-ray diffraction (XRD), surface area measurements (BET and BJH), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and energy dispersive X-ray spectrum (EDX). The activities of as-prepared TiO2 photocatalysts were examined for the degradation of 4-Chlorophenol aqueous solution under solar irradiation in a photoreactor and photocatalytic degradation mechanism and pathway have been investigated. The results show that the 3% wt. N-doped TiO2 nanoparticles under conditions (solution pH of 4.0, catalyst loading of 2 g/L, initial 4-CP concentration of 10 mg/L, Time of 8 h) exhibits much higher photocatalytic degradation efficiency (91%) as compared with that of 5% wt. N-doped (83%), 1% wt. N-doped (71%), and pure TiO2 (35%).
A. Mohammadi; J. Moghaddas
Volume 16, Issue 3 , September 2019, , Pages 3-22
Abstract
Although not listed on the United States Pharmacopeia (USP), like standard USP 2, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on ...
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Although not listed on the United States Pharmacopeia (USP), like standard USP 2, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on a tablet containing trace amounts of the active pharmaceutical ingredient. In this work, firstly, small volume USP 2 apparatus was designed and manufactured using downscaling rules and considering standard USP 2 as a reference. Then, velocity profile, flow patterns, and shear rate were obtained by PIV and COMSOL simulation software at paddle speeds of 66 and 133 rpm, corresponding to agitation speed of 50 and 100 rpm, respectively, in the standard USP 2. Comparison between experimental and computational results showed acceptable adaptation. Instantaneous velocity data showed eddies and secondary flows in different zones of the vessel, which is desirable for micro-mixing but undesirable in terms of system consistency and reproducibility, as sampling from these zones are known to lead to inconsistent data. Furthermore, increased agitation rate led to the disappearance of rotational zones around the paddle. The magnitude of velocity and shear rate increased by 35% with an increment of paddle stirring from 66 to 133 rpm.
A. Bahrami; Y. Ghorbani; E. Gulcan; F. Kazemi; H. Kakaei; S. Farajzadeh
Abstract
Particle size distribution is an important parameter in flotation process, which affects the floatability and therefore the flotation kinetics. This study aims to investigate the effects of particle size distribution on flotation kinetics of bituminous coal. For this purpose, a series of batch flotation ...
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Particle size distribution is an important parameter in flotation process, which affects the floatability and therefore the flotation kinetics. This study aims to investigate the effects of particle size distribution on flotation kinetics of bituminous coal. For this purpose, a series of batch flotation experiments were conducted in rougher stage, and concentrates were collected in different time periods. Then particle size distribution for each concentrate was determined. Five flotation kinetic models were applied for the modeling of data obtained from the flotation tests using MATLAB (Matrix Laboratory) software. The relationship between flotation rate constant, maximum combustible recovery and particle size were studied. The results show that the maximum flotation combustible recovery and flotation rate are obtained with an intermediate particle size (-250 +106 μm). Results of flotation tests fitted well to all five kinetic models. It is found that the first - order model with rectangular distribution of floatability, provides the best fit to the experimental data obtained from the flotation processes among the tested models.
Modeling and Simulation
Hajar seyfi; Sirous shafiei; Reza Dehghanzadeh; Parya Amirabedi
Abstract
The removal of Acrylonitrile (AN) from waste gas streams using biological methods, due to their better performance, has recently gained more attraction. The purpose of this research is modeling the AN removal by a bio-filter. The validation of the model is done by using the experimental data of a bench-scale ...
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The removal of Acrylonitrile (AN) from waste gas streams using biological methods, due to their better performance, has recently gained more attraction. The purpose of this research is modeling the AN removal by a bio-filter. The validation of the model is done by using the experimental data of a bench-scale bio-filter bed column including yard waste compost and shredded hard plastics and thickened municipal activated sludge. In this work the kinetics of the biodegradation of Acrylonitrile is first investigated. Then equations of the biofilm and air are obtained at a steady state and constant temperature. The unknown parameters of the model are determined by the least square optimization method along with solving the model equations using MATLAB. For inlet concentrations less than 1 g/m3 the model results show reasonable similarities to the experimental data. The effect of various parameters on the bio-filter performance is evaluated. The Peclet number, biofilm thickness and biomass concentration are the most important parameters. The proposed model can be useful for design purposes.
Separation Technology,
S. Ghasemi; A. Behnamfard; R. Arjmand
Abstract
The thickening of the iron ore tailings allows process water to be partially recovered and recirculated, also it reduces the fresh water consumption, which results in lower operating costs and less environmental impacts. The settling characteristics of the mineral components of an iron ore tailing in ...
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The thickening of the iron ore tailings allows process water to be partially recovered and recirculated, also it reduces the fresh water consumption, which results in lower operating costs and less environmental impacts. The settling characteristics of the mineral components of an iron ore tailing in the thickening process may be different under various pulp conditions. Hence, the study of the characteristics of the mineral components of the iron ore tailings separately can provide very useful information about the thickening of an iron ore tailing. In this research, the settling behavior of the main mineral components of iron ore tailings including quartz and magnetite have been investigated under various operational conditions. The quartz and magnetite showed different settling behaviors, so as the maximum settling rate of quartz was achieved under different pulp conditions than that of magnetite was. There was a big difference between the maximum settling rates of quartz and magnetite, as the maximum settling rates of quartz and magnetite were 197 and 873 m/h respectively. In the thickening of an iron ore tailing, the pulp conditions must be set based on the settling behavior of the mineral component with the lowest settling rate.
Thermodynamics,
M. Rahmanzadeh Derisi; N. Esfandiari
Abstract
One of the methods to reduce the particle size is the GAS method. In this method, the solute and antisolvent should be dissolved well in a solvent. But the solute is not dissolved in a solvent. The aim of studying this model is to determine the phase equilibrium and thermodynamic conditions of (CO2, ...
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One of the methods to reduce the particle size is the GAS method. In this method, the solute and antisolvent should be dissolved well in a solvent. But the solute is not dissolved in a solvent. The aim of studying this model is to determine the phase equilibrium and thermodynamic conditions of (CO2, solvent, 5-Fluorouracil) in the GAS process. The solvents include methanol, ethanol, acetone, 1-propanol, and 1-butanol. The Peng-Robinson equation of state with a linear combination of Vidal and Michelsen mixing rules (PR-LCVM) was used for the thermodynamic modeling. The volume expansion of the binary system (CO2, solvent) and ternary system (CO2, solvent,5-Fluorouracil) at the temperature range of 313.15-319.15 K was investigated. The Pmin values for the binary system were 66.7, 69.6, 60, 73.7, and 76.8 bar respectively for methanol, ethanol, acetone, 1-propanol, and 1-butanol at 313.15 K,. The Pmin for the ternary system was also calculated. The comparison between the Pmin values of binary and ternary systems showed that for a constant temperature and a certain solvent, the calculated minimum pressure in the ternary system was greater than the same in the binary system
Modeling and Simulation
A. H. Oudi; A. Irankhah
Abstract
The optimization of the ammonia synthesis plant to increase the production of ammonia is studied in this line of research. In this paper, the steady-state ammonia synthesis is simulated using the Aspen HysysV.11 software. By comparing the simulation results with the industrial information, a mean relative ...
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The optimization of the ammonia synthesis plant to increase the production of ammonia is studied in this line of research. In this paper, the steady-state ammonia synthesis is simulated using the Aspen HysysV.11 software. By comparing the simulation results with the industrial information, a mean relative error of 7.71 % was obtained, which indicated the high accuracy of the simulation. Then, four effective variables were selected from among 11 independent variables by the Plackett-Burman method. The effects of the Hydrogen flow in the feed stream, Recycle stream pressure, Feed stream temperature, and input temperature of the third reactor were investigated, and the response surface design method of the central composite design was performed to plant optimize. It is obtained that the Hydrogen flow in the feed stream is equal to 6255 , the feed stream pressure is equal to 205 bar, the temperature of the excess stream inlet in the first reactor is equal to 663 K, and the temperature of the stream inlet of the second reactor is 677.5 K which increased the ammonia production by 7.5 %.
Reaction Engineering, Kinetics and Catalysts,
Sh. Masoumi; J. Towfighi
Volume 12, Issue 4 , October 2015, , Pages 4-14
Abstract
"> The effects of templating on the catalytic performance of SAPO-34 catalyst have been investigated in conversion of methanol to olefins. SAPO-34 catalysts were synthesized using a different combination of morphine, tetraethyl ammonium hydroxide (TEAOH) and triethylamine (TEA) as structure-directing ...
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"> The effects of templating on the catalytic performance of SAPO-34 catalyst have been investigated in conversion of methanol to olefins. SAPO-34 catalysts were synthesized using a different combination of morphine, tetraethyl ammonium hydroxide (TEAOH) and triethylamine (TEA) as structure-directing agents during synthesis of gel with nominal composition as 1Al2O3:1P2O5:0.4SiO2:2yTEAOH:2xTEA:2(1-(x+y))morpholine:70H2O. The different SAPO-34 samples were characterized by XRD, SEM, FTIR, BET, EDX and TPD techniques. Increasing TEAOH in synthesis gel led to decreasing mean crystal size. The catalytic performance of the synthesized catalysts was tested in MTO reaction at 410C and a feed WHSV of 6.5 1/h. The catalyst synthesized by combination of tri-templates exhibited highest light olefins yield in 100% methanol conversion. The optimum values (X=0.17, Y=0.34) were obtained by central composite design and response surface contour plots.
Transport Phenomena,
S. M. Mirfendereski
Volume 16, Issue 1 , March 2019, , Pages 22-38
Abstract
Abstract In this work hydrothermal synthesis of zeolite NaA crystals with a composition of Al2O3:aSiO2:bNa2O:cH2O was investigated. Effects of SiO2/Al2O3, Na2O/Al2O3 and H2O/Al2O3 ratios and crystallization temperature and time were studied on crystallinity and crystal size of zeolite NaA crystals. It ...
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Abstract In this work hydrothermal synthesis of zeolite NaA crystals with a composition of Al2O3:aSiO2:bNa2O:cH2O was investigated. Effects of SiO2/Al2O3, Na2O/Al2O3 and H2O/Al2O3 ratios and crystallization temperature and time were studied on crystallinity and crystal size of zeolite NaA crystals. It was tried to understand the interactions between these parameters. The crystal species of zeolite NaA were characterized by XRD and SEM. Considering the interactions between these parameters showed that effects of increasing SiO2/Al2O3 and Na2O/Al2O3 ratios simultaneously neutralize each other so that their overall effect is not significant. On the other hand, the effects of increasing SiO2/Al2O3 and H2O/Al2O3 ratios reinforce each other and significantly affect crystallinity and crystal size. Increasing alkalinity increases crystallization rate and reduces synthesis time. Also, effects of increasing crystallization temperature and time simultaneously reinforce the effects of each other. The effect of decreasing alkalinity is moderated with that of increasing Na+ content in the synthesis gel.
Reaction Engineering, Kinetics and Catalysts,
Volume 11, Issue 4 , October 2014, , Pages 10-20
Separation Technology,
Volume 2, Issue 1 , January 2005, , Pages 10-23
Abstract
The effects and influences of various operational parameters on the efficiency of mixer-settlers are thoroughly studied in this paper. One of the most important factors in designing a mixer-settler is to obtain an optimum operational extraction and overall efficiency. These two factors are dependent ...
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The effects and influences of various operational parameters on the efficiency of mixer-settlers are thoroughly studied in this paper. One of the most important factors in designing a mixer-settler is to obtain an optimum operational extraction and overall efficiency. These two factors are dependent on various parameters such as impeller shape, size and speed of impeller, baffle size, residence time, volumetric flow rates and the ratio of heavy to light phases. In this paper, the effect of impeller speed and volumetric flowrates of two phases on efficiency are studied. Also, the effect of hold-up of each stage upon stage efficiency is studied. According to the above experiments and achieved results, it can be concluded that in general, an increase in impeller speed and solvent amount results in an increase in extraction efficiency. Also, when hold-up of the dispersed phase decreases, the stage efficiency usually increases up to a certain point.
Separation Technology,
Volume 8, Issue 4 , October 2011, , Pages 11-23
Modeling and Simulation
Volume 1, Issue 1 , April 2004, , Pages 11-21
Reaction Engineering, Kinetics and Catalysts,
Volume 1, Issue 2 , July 2004, , Pages 11-18
Abstract
Copper-manganese oxide catalysts are prepared with an atomic ratio of Cu/Mn=2/1 using a coprecipitation procedure under air atmosphere. The time of aging, i.e., the time that precipitate remains in contact with the precipitating medium, has been varied from 0 (for unaged precursor) to 300 minutes and ...
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Copper-manganese oxide catalysts are prepared with an atomic ratio of Cu/Mn=2/1 using a coprecipitation procedure under air atmosphere. The time of aging, i.e., the time that precipitate remains in contact with the precipitating medium, has been varied from 0 (for unaged precursor) to 300 minutes and the effect of precipitate aging time in each atmosphere upon the structure and morphology of different catalysts and their precursors is investigated. The precursors and catalysts were characterized by powder X-ray diffraction (XRD), temperature programmed reduction (TPR) and transmission electron microscopy (TEM). X-ray diffraction and electron microscopy showed that aging of the initial precursor altered the structure of the precursor. The TPR reduction profiles of the copper — manganese mixed oxide catalysts showed a dramatic change of shape on aging. In all catalysts, CuO was completely reduced to metal while the MnO did not reduce under the experimental conditions.
Modeling and Simulation
Volume 9, Issue 1 , January 2012, , Pages 12-22
Thermodynamics,
Volume 7, Issue 4 , October 2010, , Pages 12-21
Reaction Engineering, Kinetics and Catalysts,
Volume 6, Issue 1 , January 2009, , Pages 12-22
Modeling and Simulation
Volume 5, Issue 4 , October 2008, , Pages 12-22
Abstract
The turbulent flow field generated in a baffled stirred tank was computed by large eddy simulation (LED) and the flow field was developed using the Sliding Mesh (SM) approach. In this CFD study, mixing times and power number have been determined for a vessel agitated by a 6-blade Rushton turbine. The ...
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The turbulent flow field generated in a baffled stirred tank was computed by large eddy simulation (LED) and the flow field was developed using the Sliding Mesh (SM) approach. In this CFD study, mixing times and power number have been determined for a vessel agitated by a 6-blade Rushton turbine. The predicted results were compared with the published experimental data. The satisfactory results of comparisons indicate the potential usefulness of this approach as a computational tool for designing stirred reactors.
Modeling and Simulation
Volume 7, Issue 1 , January 2010, , Pages 13-27
Separation Technology,
S. Shirazian; S. N. Ashrafizadeh
Volume 12, Issue 1 , January 2015, , Pages 13-21
Abstract
ine"> Chabazite zeolite membranes were synthesized for their potential application in dehydration of natural gas. The membranes were prepared using secondary growth method on porous ·-alumina substrates. Hydrothermal treatment was applied for the synthesis of chabazite seeds. The membranes ...
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ine"> Chabazite zeolite membranes were synthesized for their potential application in dehydration of natural gas. The membranes were prepared using secondary growth method on porous ·-alumina substrates. Hydrothermal treatment was applied for the synthesis of chabazite seeds. The membranes were synthesized at four temperatures of 100, 120, 140, and 160°C; and duration of 20 h. Separation performance of assynthesized membranes was evaluated through permeation ofwater vapor and methane as single gas. Moreover, the structure and morphology ofas-synthesized chabazite zeolite membranes as well as seeds were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS). The results revealed that the optimum temperature for the synthesis ofchabazite membranes is 140°C while at lower and higher temperatures, lower separation performances were observed. At the optimum synthesis temperature, an ideal selectivity of 23 was obtained for water vapor/methane, while a thin and integrated chabazite zeolite layer of about 5 m in thickness was synthesized over the surface ofalumina substrate.
Transport Phenomena,
R. Beigzadeh; A. Parvareh; M. Rahimi
Volume 12, Issue 2 , April 2015, , Pages 13-25
Abstract
"> Despite numerous studies of shell and helically coiled tube heat exchangers, a few investigations on the heat transfer and flow characteristic consider the geometrical effects like coil pitch. Moreover, this scarcity is highlighted for the shell side of this type of heat exchangers. This study ...
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"> Despite numerous studies of shell and helically coiled tube heat exchangers, a few investigations on the heat transfer and flow characteristic consider the geometrical effects like coil pitch. Moreover, this scarcity is highlighted for the shell side of this type of heat exchangers. This study reports experimental and Computational Fluid Dynamics (CFD) investigations on heat transfer and flow characteristics of a shell and helically coiled tube heat exchanger. The experiments were carried out using a helically coiled tube, which was placed in a cylindrical shell. Hot and cold water were used as the process fluids on the tube and shell side, respectively. The CFD modeling technique was employed to describe the experimental results, fluid flow pattern, and temperature profiles as well as dead zones in the heat exchanger. Quantitative predicted results of CFD modeling show a good agreement with the experimental data for temperature. The effect of the coil pitch on heat transfer rate was numerically studied and it was found that the heat transfer coefficient intensifies with an increase in coil pitch. The average turbulent kinetic energy (k) for the old coil tube and twice coil pitch heat exchanger was computed as 2.9×10-3 and 3.3×10-3 m 2 /s2, respectively. This indicates an increase of about 14% in flow turbulent kinetic energy. Nusselt numbers were compared with those estimated using published correlation and a mean relative error (MRE) of 14.5% was found between the experimental and predicted data. However, a good agreement was obtained in lower shell Reynolds numbers (lower than Re=200).
Transport Phenomena,
Volume 5, Issue 1 , January 2008, , Pages 13-21
Abstract
Common methods to design heat exchanger networks (HENs) by pinch technology usually need an evolutionary step to reduce the number of heat transfer units. This step is called loop breaking and is based on the removal of exchangers that impose minimum increase on utility consumption. Loops identification ...
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Common methods to design heat exchanger networks (HENs) by pinch technology usually need an evolutionary step to reduce the number of heat transfer units. This step is called loop breaking and is based on the removal of exchangers that impose minimum increase on utility consumption. Loops identification and breaking is a tedious task and becomes more complicated in large networks. This paper presents a rapid nonlinear programming (NLP) formulation for the evolution of HENs in which loop identification is not required. The objective of the NLP is the minimization of HENs annual cost, which is not considered in current methods. In this method a search is done to find the best units elimination of which improves HENs annual cost. The search continues until the minimum number of units (MNU) is achieved and the exchangers that must be removed from the network are specified. The method was applied to some networks reported in the literature and better results were obtained. Also, the convergence of the presented method is very fast and it can be applied to different networks designed by pinch technology.