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.
Transport Phenomena,
Volume 6, Issue 3 , July 2009, , Pages 13-25
Abstract
"> Waste heat recovery is very important, because it not only reduces the expenditure of heat generation, but also it is of high priority in environmental consideration, such as reduction in greenhouse gases. One of the devices used in waste heat recovery is heat pipe heat exchanger. An experimental ...
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"> Waste heat recovery is very important, because it not only reduces the expenditure of heat generation, but also it is of high priority in environmental consideration, such as reduction in greenhouse gases. One of the devices used in waste heat recovery is heat pipe heat exchanger. An experimental and theoretical research is carried out to investigate heat performance of an air to water thermosyphon heat pipe heat exchanger according to ε-NTU method. The experiments were done according to the following procedure: cold water with 0.1kg/s flows through the condensation section and hot air in a closed cycle is blown into the evaporation section. A blower with varying frequency of current turns in the mass flow rate between 0.14-0.6 kg/s and a temperature range of 125-225°C. The results of the experiments show that as the ratio of C Ch c rises, the rate of heat transfer goes up. The efficiency of the heat pipe heat exchanger remains constant as the temperature of the hot stream goes up, but the amount of heat transferred increases.
Modeling and Simulation
Volume 3, Issue 1 , January 2006, , Pages 13-28
Transport Phenomena,
Volume 3, Issue 2 , April 2006, , Pages 13-19
Abstract
An experimental study was carried out to obtain the mean convective heat transfer coefficient of aqueous carboximethyl cellulose (CMC) solutions in double-pipe heat exchangers. Co-current and counter- flows were considered in the investigation. From the experimental data a Nusselt number was calculated ...
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An experimental study was carried out to obtain the mean convective heat transfer coefficient of aqueous carboximethyl cellulose (CMC) solutions in double-pipe heat exchangers. Co-current and counter- flows were considered in the investigation. From the experimental data a Nusselt number was calculated for a wide range of Graetz number, Reynolds number, and CMC concentrations. Increasing the Graetz and Reynolds numbers promote the heat transfer and variation of CMC concentration has a noticeable effect on the Nusselt number.
Modeling and Simulation
Volume 10, Issue 3 , July 2013, , Pages 14-26
Biomedical and Biotechnology,
Volume 10, Issue 2 , April 2013, , Pages 14-21
Separation Technology,
Volume 9, Issue 2 , April 2012, , Pages 14-21
Modeling and Simulation
Volume 9, Issue 3 , July 2012, , Pages 14-21
Process Control and Engineering, Process Safety, HSE
Volume 8, Issue 1 , January 2011, , Pages 14-19
Transport Phenomena,
Volume 6, Issue 2 , April 2009, , Pages 14-28
Separation Technology,
Volume 5, Issue 3 , July 2008, , Pages 14-28
Abstract
Corn stalk can be used as an alternative non-wood raw material to produce cellulosic dissolving grade pulp. In this work, the potential of corn stalk in the production of dissolving pulp (alpha-cellulose) was investigated. It was collect ed from a corn stalk farm of Kermanshah, Iran. The sequences of ...
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Corn stalk can be used as an alternative non-wood raw material to produce cellulosic dissolving grade pulp. In this work, the potential of corn stalk in the production of dissolving pulp (alpha-cellulose) was investigated. It was collect ed from a corn stalk farm of Kermanshah, Iran. The sequences of experimental work were: water and acid prehydrolysis at 160˚C for 30min, followed by Kraft pulping at 170˚C for 90min, and bleached by HEH & HEHP sequences. The influence of active alkali (14-20%), and sulphidity (10-25%) on the pulp properties such as yield, kappa number, and degree of polymerization was investigated. In optimum conditions (water prehydrolysis; pulping with active alkali of 20%, sulphidity of 25%; and HEH bleaching sequence), the alpha-cellulose content, degree of polymerization, and ash content of the produced dissolving pulp were acceptable: 94.7%, 269 and 1% respectively. The properties of the produced pulp were comparable with the pulp obtained by other sources. Active alkali was the most important influent parameter, with respect to delignification, whereas the sulphidity had a minor effect.
Energy
Volume 4, Issue 1 , January 2007, , Pages 14-20
Abstract
Heterogeneous photocatalytic degradation of Polynuclear Aromatic Hydrocarbons (PAHs) contaminated soil in the Pars Economic and Energy Zone was carried out under laboratory conditions to evaluate the potential use of this technology for in situ remediation. Analysis of soil samples show that contaminated ...
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Heterogeneous photocatalytic degradation of Polynuclear Aromatic Hydrocarbons (PAHs) contaminated soil in the Pars Economic and Energy Zone was carried out under laboratory conditions to evaluate the potential use of this technology for in situ remediation. Analysis of soil samples show that contaminated soil is primarily related to the concentration of phenanthrene. Hence phenanthrene is used for photocatalytic degradation under laboratory conditions. Soil samples were spiked with two phenanthrene concentrations (50 and 100 mg kg-1), loaded with catalyst TiO2 and exposed to uv light with 125 W power. Different catalyst loads (1, 2, 3 and 4 % w/w) were tested in phenanthrene contaminated soil (50 mg kg-1) for up to 16h exposure. Both the catalyst and phenanthrene concentration show no influence on the kinetics of the phenanthrene degradation. The results indicated that the optimum removal condition was at 2% w/w catalyst and 100% w/w water with 85% degradation efficiency. The degradation efficiency of other PAHs was also assessed with the optimum condition. This paper shows that photocatalytic is a particularly important methodology, in which a major process is being made in the oxidative methods for the degradation of organics such as PAHs in contaminated soil
Modeling and Simulation
mohsen pirdashti; kamyar movagharnejad; silvia Curteanu; Florin Leon; Farshad Rahimpour
Volume 13, Issue 4 , November 2016, , Pages 14-32
Abstract
Guanidine hydrochloride has been widely used in the initial recovery steps of active protein from the inclusion bodies in aqueous two-phase system (ATPS). The knowledge of the guanidine hydrochloride effects on the liquid-liquid equilibrium (LLE) phase diagram behavior is still inadequate and no comprehensive ...
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Guanidine hydrochloride has been widely used in the initial recovery steps of active protein from the inclusion bodies in aqueous two-phase system (ATPS). The knowledge of the guanidine hydrochloride effects on the liquid-liquid equilibrium (LLE) phase diagram behavior is still inadequate and no comprehensive theory exists for the prediction of the experimental trends. Therefore the effect the guanidine hydrochloride on the phase behavior of PEG4000+ potassium phosphate+ water system at different guanidine hydrochloride concentrations and pH was investigated in this study. To fill the theoretical gaps, the typical of support vector machines was applied to the k-nearest neighbor method in order to develop a regression model to predict the LLE equilibrium of guanidine hydrochloride in the above mentioned system. Its advantage is its simplicity and good performance, with the disadvantage of an increase the execution time. The results of our method are quite promising: they were clearly better than those obtained by well-established methods such as Support Vector Machines, k-Nearest Neighbour and Random Forest. It is shown that the obtained results are more adequate than those provided by other common machine learning algorithms.
Modeling and Simulation
M. Etebarian; k. movagharnejad
Volume 16, Issue 2 , June 2019, , Pages 14-40
Abstract
Two main objectives have been considered in this paper: providing a good model to predict the critical temperature and pressure of binary hydrocarbon mixtures, and comparing the efficiency of the artificial neural network algorithms and the support vector regression as two commonly used soft computing ...
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Two main objectives have been considered in this paper: providing a good model to predict the critical temperature and pressure of binary hydrocarbon mixtures, and comparing the efficiency of the artificial neural network algorithms and the support vector regression as two commonly used soft computing methods. In order to have a fair comparison and to achieve the highest efficiency, a comprehensive search method is used in neural network modeling, and a particle swram optimization algorithm for SVM modeling. To compare the accuracy of the models, various criteria such as ARD, MAE, MSE, RAE and R2 are used. The simulation results show that the ARD for the prediction of the true critical temperature and pressure of the binary hydrocarbon mixtures for the final optimized ANN-based model is equal to 0.0161 and 0.0387, respectively. The corressponding ARD value for the SVM-based model is equal to 0.0086 and 0.0091 for critical temperature and pressure, respectively. Simulation results show that although both models have a very high predictive accuracy, the SVM has higher learning speed and accuracy than ANN.
N. Yavari; M. Poorabdollah; L. Rajabi
Abstract
In this study, unmodified graphite and graphite modified with a silane agent were used to ameliorate the thermal conductivity coefficient and dynamical properties of unsaturated polyester resin. The effect of unmodified graphite and modified graphite addition on thermal conductivity coefficient and dynamical ...
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In this study, unmodified graphite and graphite modified with a silane agent were used to ameliorate the thermal conductivity coefficient and dynamical properties of unsaturated polyester resin. The effect of unmodified graphite and modified graphite addition on thermal conductivity coefficient and dynamical properties of unsaturated polyester resin in the graphite amounts of 0.02% and 0.3% by weight were studied using solid thermal conductivity measuring device and DMA test. The results showed that the silane modifier can help to create strong covalent bonds between graphite particles and unsaturated polyester resin network and cause changes in thermal and dynamic properties compared to unmodified graphite particles. Adding 0.3% of the weight of the unmodified graphite to the unsaturated polyester resin resulted in a 7% raise in the storage modulus in the glassy region. However, adding the same amount of graphite modified using the silane agent increased the storage module by 33% in the glassy region. Silane modifier caused better dispersion of graphite particles in the resin structure. Superior dispersion of graphite particles caused more interaction between graphite particles and resin network, which significantly increased the modulus of unsaturated polyester resin. In contrast, better dispersion of graphite particles because of the presence of silane agent increased the thermal resistance at the surface of graphite particles, which reduced the thermal conductivity coefficient compared to unmodified graphite.
Transport Phenomena,
F. Shafiee Langari; K. Movagharnejad*
Volume 12, Issue 3 , July 2015, , Pages 15-32
Abstract
ne"> The osmotic dehydration of three agricultural products including carrot, zucchini and turnip has been studied in this research. The effect of several factors including temperature, sample to osmotic solution weight ratio and the concentration of the osmotic solutes on the osmotic dehydration ...
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ne"> The osmotic dehydration of three agricultural products including carrot, zucchini and turnip has been studied in this research. The effect of several factors including temperature, sample to osmotic solution weight ratio and the concentration of the osmotic solutes on the osmotic dehydration of these agricultural products were investigated experimentally. The experimental studies consist of two different concentrations (10%, and 20 W/W% for carrots, 30%, and 50 W/W% for zucchini and 40%, and 50 W/W% for turnips), two different vegetable/solution weight to weight ratios (1:10 and 1:15 for all materials) and two different temperatures (30°C and 50°C for carrots and zucchini and 40°C and 50°C for turnips). Three dietary coatings including pectin, carboxymethyl cellulose and corn starch have been selected to control the solids uptake during the osmotic process. The Azuara model proved to be the most accurate correlation to describe the kinetics of the osmotic dehydration of these three agricultural products. The root mean square error of the Azuara model for solid gain in different conditions was between 0.014 and 0.065 for carrots, 0.011 and 0.030 for zucchini and 0.008 and 0.014 for turnips. The root mean square error of the Azuara model for water loss in different conditions was between 0.008 and 0.016 for carrots, 0.003 and 0.008 for zucchini and 0.009 and 0.017 for turnips.
Modeling and Simulation
P. Darvishi; S. M. Salehi
Volume 12, Issue 4 , October 2015, , Pages 15-27
Abstract
Current drug-eluting stent (DES) technology is not optimized with regard to the pharmacokinetics of drug release, more research on the drug-eluting stent design and flux of drug release to the arterial wall is necessary. Considering a three-dimensional (3D) cylindrical mathematical model, a novel free ...
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Current drug-eluting stent (DES) technology is not optimized with regard to the pharmacokinetics of drug release, more research on the drug-eluting stent design and flux of drug release to the arterial wall is necessary. Considering a three-dimensional (3D) cylindrical mathematical model, a novel free drug mass transfer release has been formulated and applied for better estimation of the drug concentration in the tissue. The transport equations involved both convection and diffusion equations. Besides, a reversible reaction in the arterial wall was considered. The present model was solved by an appropriate numerical simulation method and the predicted results were compared with in vivo data. To find out the rate-limiting step, the time scale analysis was also applied. The obtained results showed that the binding process is more limited by convection and diffusion, where convection is the rate-controlling step. It is also demonstrated that the presented approach has advantages over the prior free drug mass transfer models, including better data prediction and satisfying mass transfer consistency.
Transport Phenomena,
Volume 6, Issue 4 , October 2009, , Pages 15-26
Abstract
This paper reports a study on the effect of the heat flux, cooling water flow rate, fill ratio and extra volume on the overall performance of a partially vacuumed thermosyphon. A rig was made from a 1 m copper tube with an inner and outer diameter of 17.5 and 19 mm. The heights of the evaporator, the ...
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This paper reports a study on the effect of the heat flux, cooling water flow rate, fill ratio and extra volume on the overall performance of a partially vacuumed thermosyphon. A rig was made from a 1 m copper tube with an inner and outer diameter of 17.5 and 19 mm. The heights of the evaporator, the adiabatic section and the condenser are 40, 20 and 40 cm, respectively. The temperatures at different places on the thermosyphon and on the inlet/outlet ofthe cooling water were measured. It was observed that change in heat flux, fill ratio and employing different extra volumes, has a significant effect on its performance. On the other hand, with changes in the cooling water flow rate the performance ofthe thermosyphon was altered regarding the trapped air movement. In order to illustrate the effect ofthe existence ofair in deactivating the thermosyphon, the pipe was cooled down by disconnecting the evaporator power input. It was seen that the thermosyphon loses its performance as the trapped gas occupies the whole condenser. The whole study shows that due to the existence ofthe trapped air, the heat loads can have significant effects on the thermosyphon performance.
Biomedical and Biotechnology,
Volume 2, Issue 2 , April 2005, , Pages 15-21
Abstract
From an engineering point of view, the effect of light intensity distribution on the stability of growth rate should be taken into account in designing effective photobioreactors and sustaining stable growth rates. In the experiments described here, in order to keep operational parameters at an almost ...
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From an engineering point of view, the effect of light intensity distribution on the stability of growth rate should be taken into account in designing effective photobioreactors and sustaining stable growth rates. In the experiments described here, in order to keep operational parameters at an almost constant level, a semi-continuous culture method was developed for cultivation of photosynthetic cells under defined light intensity distributions. In the semi-continuous culture, a portion of culture broth containing grown cells was repeatedly replaced with the fresh medium at a predetermined time interval to maintain the cell concentration and the volume of the broth constant at their initial values. Under illumination from one and both sides, photosynthetic cells were cultivated in a flat plate photobioreactor with various light path lengths. The results obtained showed that stability of the growth rate strongly depended on the distribution of light intensity and the ratio of light intensity in the illuminated to that in the dark zone inside a photobioreactor. These parameters should be taken into consideration for stable cultivation of photosynthetic cells.
Modeling and Simulation
A. Saberimoghaddam; M. M Bahri Rasht Abadi
Volume 14, Issue 1 , March 2017, , Pages 15-25
Abstract
Longitudinal heat conduction is an important parameter in the cryogenic field, especially in cryogenic heat exchangers. In the present work, the parasitic effect of tube wall longitudinal heat conduction on temperature measurement has been studied in cryogenic laminar hydrogen flow. The effects of various ...
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Longitudinal heat conduction is an important parameter in the cryogenic field, especially in cryogenic heat exchangers. In the present work, the parasitic effect of tube wall longitudinal heat conduction on temperature measurement has been studied in cryogenic laminar hydrogen flow. The effects of various parameters such as wall cold end temperature, wall thermal conductivity, gas volumetric flow, and tube wall thickness have been investigated by finite element method. The model was also validated versus the data obtained from experiments. The simulations showed that the temperature decrease in gas flow occurs in the end section of tube length. This section is independent of tube cold end temperature and causes for large temperature measurement error in laminar flows. Results showed that a few millimeters change in temperature sensor position results in measurement errors up to 80 %. The higher tube wall thermal conductivity and tube wall thickness result in higher parasitic effects of longitudinal heat conduction.
Separation Technology,
M. Yasemi; M. Rahimi; A. Heydarinasab; M. Ardjmand
Volume 15, Issue 3 , September 2018, , Pages 15-33
Abstract
In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence ...
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In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence angles and diameters were examined. Microchannels with different confluence angles and diameters were examined. The effects of pH, temperature, and volumetric flow ratio and contact time of the two phases were investigated. The response surface methodology was used to optimize extraction yield of tannin from Quercus leaves in the employed microchannels. Based on this optimization, maximum yield was achieved at pH=2, temperature=33.1℃, volumetric flow ratio =1.2 and contact time of 25.35s. Results show that extraction-using microchannel has many advantages over traditional methods, including shorter time and higher economic efficiency. Moreover, microchannel provides smaller volume of fluids resulting in lower solvent consumption, lower waste production, shorter analytical times, smaller space requirements, and lower energy consumption.
Energy
A. Mohammadi; B. Ghobadian
Abstract
A batch process was developed for the production of biodiesel from high free fatty acid feedstocks. The mixed-integer nonlinear programming (MINLP) problem, caused due to applying the hierarchical procedure together with Malone’s algorithm for the conceptual design, was solved. Meanwhile, the optimum ...
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A batch process was developed for the production of biodiesel from high free fatty acid feedstocks. The mixed-integer nonlinear programming (MINLP) problem, caused due to applying the hierarchical procedure together with Malone’s algorithm for the conceptual design, was solved. Meanwhile, the optimum states of major process parameters such as the utilization of the process equipment, paralleling, splitting, and the merging of unit operations, the process cycle time (CT), and the combination of batch and continuous units were determined. Based on the present optimization study, the optimum value of the process cycle time and the optimum number of the esterification reactors in series were obtained as 3.257 h/batch and 3 stages respectively. The batch process was found to be suitable for a capacity of less than 260 tons/yr, while the continuous process was suitable for a capacity of greater production rates. The results showed that the production rate had a direct effect on the economic potential of the process and that it should be set at its maximum possible practical value. Also, the break-even point for the optimum state occurred at the production rate of 130 tons/yr.
Reaction Engineering, Kinetics and Catalysts,
Volume 11, Issue 3 , July 2014, , Pages 16-25
Reaction Engineering, Kinetics and Catalysts,
Volume 10, Issue 4 , October 2013, , Pages 16-27
Polymer Engineering and Technology,
Volume 10, Issue 1 , January 2013, , Pages 16-29