فهرست مطالب mohammadreza omidkhah

In this study, polyaniline nanocomposite with aluminum oxide (PANI/Al2O3) was synthesized in situ polymerization method and the anti-corrosion ability of nanocomposite was investigated. Products were identified by chemical analysis of Fourier Transform InfraRed (FT-IR) spectroscopy, X-ray crystallography (XRD), and thermal weighing calorimetric analysis (TGA). Also, anti-corrosion properties were analyzed by Open Circuit Potential (OCP)analysis, Electrochemical Impedance Spectroscopy (EIS), and potentiodynamic polarization curves. To investigate anti-corrosion performance, different percentages of nanocomposites (3, 6, 9, and 12 %) were added to industrial paint and applied to steel sheets as a coating. The results of corrosion performance illustrated that the steel sheets coated with PANI/Al2O3 nanocomposites along with the paint, have less corrosion compared to the samples of pure steel sheets and the cases coated with PANI/Al2O3 nanocomposites. Also, the 6 % coating containing PANI/Al2O3 nanocomposite along with paint on steel sheets showed the best anti-corrosion properties. The open-circuit potential analysis results make it clear that the coatings containing PANI/Al2O3 nanocomposite with paint have a higher performance compared to pure paint coatings in 3 wt% NaCl solution. EIS analysis revealed resistance of the coating containing 6 % PANI/Al2O3 along with the paint is more than other samples in 3 % NaCl solution.

Naphtha cracking processes call for low aromatic feedstocks to satisfy the operational considerations regarding the quality of their feedstocks. Therefore, the issue of the aromatics removal from petroleum fractions has become more serious. In this study, the experimental investigation and thermodynamic modeling of the liquid-liquid equilibria of the quinary system naphtha cut (including paraffinic, naphthenic, and aromatic species), sulfolane, and water, over the temperature range of 303.2 to 333.2 K, have been studied. The molecular representatives of paraffinic, naphthenic, and aromatic species of naphtha cut have been determined based on different objective functions. Physical properties estimation and modeling of equilibrium data reveal higher accuracy of vapor pressure- and viscosity-based objective functions in the structural modeling of naphtha cut. The root-mean-square deviations for the mentioned functions were determined to be about 1.47 and 1.48%, respectively. Thermodynamic modeling with the predictive UNIFAC model showed a good agreement with the experimental measurements. Also, the interaction coefficients extracted from the 75 ºC equilibrium data led to minimum deviation in the equilibrium modeling. Finally, the phase diagrams show the noticeable effect of water content and the small effect of temperature on the system equilibria.

Process industries are often exposed to hazardous chemicals and operating units are subject to different temperatures and pressures. Depending on different operating and environmental conditions, Accident assessment and modeling in the field of process industry safety will be of great help in understanding and dealing with the accident. Of all the process equipment, tanks have the most potential risks due to the accumulation of large volumes of chemicals. The purpose of this study is to model and assess the risk of LPG pressure vessels in different scenarios such as explosion and ignition with different weather conditions. Therefore, appropriate control strategies and safety measures can be suggested with it. Three spherical LPG tanks related to Isfahan Oil Refinery were modeled, For comprehensive modeling of scenarios, reservoir rupture in different weather conditions was investigated And its intensity was obtained. Based on the available data from previous incidents and the availability of its recurrence rate, the degree of risk was estimated. Individual and collective risk curves of rupture of these reservoirs were placed in the warning area. Finally, suggestions were made to reduce this risk.

The present research has studied the performance of a mixed solvent of sulfolane and 3-methyl-N-butylpyridinium dicyanimide to dearomatize the naphtha fraction of the Tehran oil refinery. Analysis of variance and artificial neural network analysis (as a standard multi-layer perceptron network) reveals that regarding the solvent selectivity, degree of product paraffinicity, and the production yield of dearomatized product, ionic liquid content in the mixed solvent has the highest degree of importance among design variables, whereas, the solvent-to-feed ratio is the most effective one in the solvent capacity response. The findings show the negligible effect of the extraction temperature and the absence of positive and negative synergistic effects between sulfolane and 3-methyl-N-butylpyridinium dicyanimide. Considering the penalty function approach and different single-objective and multi-objective functions, the optimum values of the solvent-to-feed ratio and the ionic liquid content were found as 2.03:1 and 99.47%. As a rough estimate, the mixed solvent leads to a 47% decrease in the required amount of solvent compared to the sulfolane solvent.

This study has examined the extractive dearomatization of naphtha cracker feedstock. By considering the solvent-to-feed ratio (2:1-4:1), solvent water content (0-10 wt.%), and extraction temperature (30-60 ºC) as major operating variables and the solvent capacity, solvent selectivity, and the yield and the degree of paraffinicity of the dearomatized fraction as the response of experiments, the priority of variables in the prediction models was determined. The analysis of variance and a standard multilayer perceptron artificial neural network showed that in extractive dearomatization of the blended naphtha cut with sulfolane solvent, the priority of variables follows the trend of solvent water content, solvent-to-feed ratio, and temperature. Also, by optimizing the operation, using the penalty function approach, and defining six different single- and multi-objective functions, the optimum values of the solvent water content, solvent-to-feed ratio, and extraction temperature were found as 9.98%, 3.86:1, and 32.6 oC, respectively. Finally, the maximum values for the degree of paraffinicity and the yield of the dearomatized fraction were obtained as 94.36 and 95.95%, respectively.

Thermophysical properties of base ionic liquid (C10H19F6N2P) (IL) and Io Nanofluids (INF) containing different contents of (0.05, 0.1, and 0.5 wt%) MultiWalled Carbon NanoTubes (MWCNTs) and Graphene (Gr) were measured experimentally. INF exhibited augmentation in thermal conductivity, viscosity, and heat capacity with respect to the base fluid. Maximum thermal conductivity breakthrough was detected at 39%, 48% of MWCNT-IL, and 0.5wt% of Gr-IL, respectively. Eventually, the experimental viscosity and thermal conductivity data were fitted with the existing theoretical models. The findings highlighted that the viscosity of MWCNTs-IL and Gr-IL was in unison with the particle aggregation effect (Krieger-Dougherty model) and both INF effective thermal conductivity are prognosticated by the interfacial layer approach with sufficient accuracy.

Previous studies have used molecular dynamics simulation to assess the feasibility of applying vertically aligned carbon nanotube membranes (VA-CNT) for salt water desalination. The presented report experimentally determined the potential of salt water desalination by employing VA-CNT membranes. The VA-CNT membranes were synthesized through the template-assisted pyrolysis of polybenzimidazole-Kapton inside the pores of anodized aluminum oxide (AAO) and characterized by several techniques. The permeability, salt rejection, and biofouling tendency of VA-CNT membranes were measured in various operating conditions; the results were compared with the performance of a commercial reverse osmosis (RO) membrane (BW30). The VA-CNT membrane permeability was about twofold higher than the permeability of the RO membrane. Furthermore, the VA-CNT membranes had higher stability against biofouling phenomena; they also showed antibacterial activity so that about 70% of the adsorbed cells on the VA-CNT membranes were killed by CNTs tips that were vertically aligned on the membrane surface. The rejection efficiency of the VA-CNT membrane was comparable to that of the commercial RO membrane. Finally, the chlorine stability studies showed that high hypochlorite exposure (48000 ppm.h) did not significantly fail the flux and rejection of the VA-CNT membranes, confirming their chemical stability. This study shows the high capability of the VA-CNT membrane in the water treatment process.

 In recent years, researchers have proposed various methods for gas separation because of rising greenhouse gases in the atmosphere and causing enormous environmental problems. One of the newest and emerging methods is membrane gas separation. In the last decade, mixed matrix membranes (MMMs) have received much attention due to their ability to successful separation of polar gases from mixtures.

In this study, a novel two-component mixed matrix membrane was prepared by incorporating the nickel zinc iron oxide nanoparticles into the Pebox polymer matrix. This is owing to combination the unique features of Pebax copolymer such as high mechanical strength and gas permeability, with nanoparticle properties as considerable permeability and selectivity, and appropriate mechanical and thermal stability. The gas permeability test was performed for pristine membrane and MMMs at 35 °C and pressure range from 2 to 10 bar. Fabricated membranes were also evaluated by FESEM, FTIR-ATR, DSC and XRD tests

Results demonstrated that in the case of the optimum membrane with 1 wt.% of filler loading and at 10 bar, the CO2 permeability was increased about 128% and reached to 278 Barrer, compared to pristine membrane. However, the CO2/CH4 and CO2/N2 selectivities were improved by 175 and 183 percent, respectively. This superior results was due to the presence of iron, nickel, and zinc atoms in the filler structure, which resulted in a better interaction with CO2. On the other hand, the presence of CO2-friendly segments in the Pebax structure caused much higher CO2 permeability in comparison with other light gases.

The purpose of this paper is to find the optimal geometry of Venturi for the production of biodiesel by hydrodynamic cavitation. Intensive methods such as hydrodynamic cavitation eliminate the limitation of mass transfer in the transesterification reaction. In this paper, a venturi design was developed to create cavitation in biodiesel production. The most important property of venturi in creating cavitation and retrieving the pressure is the convergence and divergence angles. The four convergence angles of 22°, 20°, 17°, and 15° and four divergence angles of 12°, 10°, 7° and 5° in Gambit 2.4 software were designed and evaluated with Fluent 6.3 software and their CFD was analyzed. The maximum pressure recovery (85% of input pressure) and cavitation generation was for venturi 17-10 (Convergence angle 17° and divergence angle 10°), which was used in the experimental setup of biodiesel production. The biodiesel production efficiency with this venturi was 95.6%. The FTIR spectrum of the biodiesel was taken to confirm its purity.

Considering the importance of deep desulfurization of commercial diesels in accordance with the global standards, in this study, the oxidative desulfurization of a commercial diesel of Tehran Oil Refinery using MoO3/γ-Al2O3 catalyst has been fully investigated. The synthesized catalyst has been characterized using FT-IR, SEM, EDS, BET and XRD analyses. The effect of Mo loading and main process variables (temperature, O/S molar ratio, catalyst amount, reaction time and type of extraction solvent) have been investigated. Acetonitrile has been suggested as the most effective solvent. The stability of the catalyst has been evaluated. The evaluation has shown the main effect of other hydrocarbons of the commercial diesel on the catalyst stability in addition to the effect of ODS products and water impurity adsorption on the catalyst surface. The results have indicated a very good catalytic role of MoO3/γ-Al2O3 in ODS of the diesel. Finally, at the optimal process variables, about 90% of sulfur compounds which have been present in the diesel with initial sulfur concentration of 590 ppmw have been removed using one step extraction of sulfones by acetonitrile.

A new method is developed to enhance the gas separation properties of mixed matrix membranes (MMMs) by interior modification of an inorganic nano-porous particle. Ship-in-a-bottle (SIB), as a novel synthesis strategy, is considered to encapsulate a polyaza macrocyclic Ag-ligand complex into the zeolite Y, which is resulted in a new host-guest nano-composite. It is consequently incorporated into a glassy polymer matrix to fabricate a novel MMM for CO2 separation. Accordingly, cellulose acetate (CA) with relatively low gas permeability is selected as the membrane polymeric matrix to provide an appropriate opportunity for better tracking the effect of incorporating the new synthesized nano-porous hybrids. The results showed a promising increase in both the CO2 permeability (45.71%) and CO2/N2 selectivity (40.28%) of the prepared MMM over its pristine CA membrane. It can be concluded that the proposed method makes it possible to fabricate novel MMMs with significant intensification in performance of the current MMMs.

Among the various types of Poly (ether block amides), Pebax1657 shows excellent separation properties for polar or condensable gases such as carbon dioxide in comparison with other light gases. In this research, Pebax1657 as an organic phase and silver nanoparticles as an inorganic phase were considered for preparation of mixed matrix membranes. Moreover, in one side, silver nanoparticles as fillers could enter the polymer chains and enhance the gas permeability by increasing the fractional free volume of membranes. On the other side, partially positively polarized silver nanoparticles beside electron rich parts of PEO segment of the copolymer could increase the CO2 affinity of membranes, which results in increasing the permselectivity of the MMMs for CO2 over CH4 and N2. Also, permeability and selectivity of membranes were studied at different operating temperature and pressures. Moreover, (fabricated) membranes were characterized by FTIR, SEM, and XRD analyses. Obtained results revealed that Ag nanoparticles have decreased the membrane crystallinity and interacted with soft segment of the copolymer, which could enhance transport properties of the polar gases. In addition, the results of gas permeation have shown excellent improvement in permeability and selectivity at temperature of 35 °C and pressure of 10 bar. For the optimum membrane in comparison with the neat one, CO2/CH4 and CO2/N2 selectivities have increased about 112 about 76 % respectively. On the other hand, an increase in the fractional free volume of the neat polymeric matrix has caused to enhance the CO2 permeability up to 141 %.

Asymmetrically mixed matrix Matrimid-MIL-53 membranes with silicone cover layer were fabricated. For better understanding of membrane fabrication process, three main parameters of fabrication, Matrimid concentration, silicone concentration and weight percentage of metal organic framework (MIL-53) particles, were optimized by an experimental design method. Cross-section SEM images were used to study the membrane structure and polymer-particles interface. Moreover, thermal resistance of the membranes and the existence of various bonds in them were investigated by FTIR and TGA analyses. The results showed that membranes had porous structure with finger-like morphology. At low and moderate percentages of particles, there were no non-selective voids observed at polymer-particles interface. The thermal resistance of membranes increased with the increase of MIL-53 weight percentage and the destruction temperature of polymer increased from 410°C to 450°C. The permeability tests results showed that the Matrimid (20% wt)-MIL-53(15% wt)/PMHS (10%wt) membrane exhibited the highest level of CO2/CH4 selectivity (23.6). However, in the membrane with 30 wt% particles loading, selectivity decreased due to particles agglomeration and void formation. The experimental design results showed that the concentration of silicone in covering solution had significant effect. CO2 and CH4 permeability decreased and ideal selectivity of CO2/CH4 increased with silicone concentration enhancement. Although the Matrimid concentration had a little effect on CO2/CH4 ideal selectivity, its enhancement increased the selectivity of the gases. The optimization results showed the membrane with 17.8% of Matrimd polymer, 13.2% of silicone polymer and 15.5 wt% of MIL-53 particle displayed the highest selectivity and CO2 permeability.

According to the benefits of oxidative desulfurization (ODS) and ultrasound assisted oxidative desulfurization (UAOD) processes and in order to industrialize these processes, it is necessary that the kinetics of these processes be studied and modeled, so as to be able to design and simulate them in semi industrial and industrial scale. Therefore, kinetics modeling of oxidative desulfurization reaction of 4,6-DMDBT over molybdenum catalyst supported on alumina has been investigated. For expression of reaction kinetics equations, Langmuir Hinshelwood and Eley Rideal mechanisms have been used. Genetic algorithm was used for optimization. Based on, Langmuir-Hinshelwood and Eley Rideal models results, Langmuir-Hinshelwood mechanism can describe the kinetic behavior of UAOD and ODS processes. Micro kinetics equations and rate determining step are identified according to the results of the models.

The performance of poly (4-metyl-1-pentyne) as mixed matrix membrane (MMM) mixed with MIL 53 particles was studied to separate mixtures of carbon dioxide and nitrogen. MIL 53 particles was added to the polymer matrix with 10, 20 and 30 weight percentages. The adsorption of CO2 and N2 gases by MIL 53 was evaluated and the adsorption data was analyzed by Langmuir equation. Structure and thermal/mechanical properties of prepared membranes were characterized by means of FTIR, SEM, TGA and elongation test. Moreover, the gas permeation properties of membranes were studied by measuring the permeation of pure CO2 and N2. Furthermore, for accurate understanding of the gas permeation properties of the membranes, diffusion and solution coefficient of gases in neat membrane and MMMs were calculated using modified time-lag method. The results from TGA analysis showed that the degradation temperature of MMMs was enhanced and increased to 348ºC for membrane containing 30 wt% of MIL 53. The SEM images also illustrated a relatively uniform dispersion of particles with proper polymer/filler interfaces in the polymer matrix. The gas permeation results revealed that the permeability of both gases (especially CO2) increased with increasing MIL 53 loading, in which the permeability of CO2 increased from 98.74 Barrer in neat membrane to 217.65 Barrer in MMM containing 30 wt% filler. Moreover, calculation of CO2/N2 selectivity depicted that the selectivity enhanced from 16.66 to 22.70. Finally, the performance of MMMs was compared with Robeson’s upper bound in CO2/N2 separation and results showed that the MMM having 30 wt% of MIL 53 took over the Robeson bound.

The catalytic dehydrogenation of propane as an initial material in propylene production is very important. The application of Pt-Sn/γ-Al2O3 as a industrial catalyst in dehydrogenation process of propane has shown to be very active and selective. Using membrane reactors is the suitable method for solving the thermodynamic limitation of this process. In this study, the dehydrogenation of propane has been investigated by using a membrane reactor. This study is based on two parts; first the manufacturing of membrane and its structure are investigated and, in the other section, the application of membrane to dehydrogenation is studied. The investigation of membrane surface morphology and XRD show the existence of a Pd-Ag homogeneous phase. The effects of different parameters such as temperature, He/propane ratio, and propane flow on conversion and propene selectivity have been investigated. This reaction has been performed with and without a membrane. The results show that the application of membrane increases the conversion from a range of 19.78-43.24 to 21-47.13 and raises the selectivity from 41.36-79.86 to 50.71-89.44.

In this study, the effect of MIL-53 particles on CO2/CH4 separation of Matrimid was investigated. MIL-53 used as an additive due to its especial pore structure and considerable selectivity respect to CO2. For the purpose of mixed matrix membrane structure with different weight percent of MIL-53 on CO2/CH4 separation, membranes fabricated with symmetric and asymmetric structure. Morphology of membranes studied with cross sectional SEM images and a performance of membranes in gas separation evaluated through permeability measurement. SEM images showed that a proper compatibility between particles and polymer along with proper dispersion of particles within polymer matrix were achieved. Results from gas permeation test demonstrated that increasing in weight percent of MIL-53 in membranes led to the permeability and selectivity enhancement. Moreover, permeability results showed that the CO2 permeability was increased from 0.056 GPU in neat symmetric membrane up to 0.113 GPU in mixed matrix membrane that containing 15 wt. % of MIL-53 particles. CO2/CH4 selectivity also increased 85% compared to neat membrane and reached to 51.8. In addition, permeability results illustrated that the gases permeability in asymmetric membranes was 100 times higher than those in symmetric membranes.

The effect of NH2-MIL 53 metal organic framework (MOF) on gas transport properties of poly (4-methyl-1-pentyne) (PMP) was investigated. Various characterization methods such as FTIR، DSC، SEM and gas adsorption test as well as a series of CO2/CH4 gas separation tests (i. e.، pure and mixed gas test) were conducted in order to determine the effect of ligand functionalization (–NH2) on the properties of the prepared mixed matrix membranes and their gas transport characteristics. The results of DSC showed that glass transition temperature (Tg) increased by increasing NH2-MIL 53 loading. The SEM images also demonstrated that the NH2-MIL 53 particles were dispersed well in the PMP matrix with no noticeable agglomeration. The gas adsorption test of NH2-MIL 53 particles revealed there was a selective adsorption behavior with respect to CO2. It was also found that، incorporation of NH2-MIL 53 into the PMP resulted in an increase in gas permeability (especially towards CO2) and a higher CO2/CH4 selectivity. Adding 30 wt% NH2-MIL 53 into the polymer matrix increased CO2 permeability and CO2/CH4 selectivity of the mixed gas from 83. 35 to 210. 21 barrer and 7. 61 to 19. 88، respectively. Rising the temperature from 30 to 60°C led to the permeability increment of both CO2 and CH4 in the mixed gas test، while the CO2/CH4 selectivity decreased. Moreover، the results showed that amino groups required no regeneration and their performance did not decline during 120 h of permeation test. A comparison between the permeation data and those calculated from permeation models revealed that the Bruggeman model could fit the CO2 permeability data better than the Maxwell and Lewis models.

The effect of Materials Institute Lavoisier-53 (MIL-53) particles on gas transport properties of polymethylpentyne (PMP) was investigated. MIL-53 was added to the polymer matrix with different loadings of 10، 20 and 30 wt%. The properties of MIL-53 and prepared membranes were analyzed through FTIR، SEM and TGA methods. The adsorption of CO2 and CH4 was conducted and analyzed accurately through Langmuir equation to investigate the gas transport properties of membranes. The results from TGA showed that degradation temperature (Td) increases significantly with increasing MIL-53 loading. SEM images demonstrated that MIL-53 particles dispersed well in polymer matrix with no considerable agglomeration and no non-selective void formation at polymer/filler interface. In addition، CO2 and CH4 permeability measurement along with calculation of CO2/CH4 selectivity were performed. The results showed that the permeability of gases (especially for CO2) increased significantly by increasing the MIL-53 loading. Additionally، CO2/CH4 selectivity showed an increasing trend with increasing the MIL-53 weight percent. Unlike CH4، the CO2 solubility coefficient increased with increasing the MIL-53 loading because of high free volume of membrane and selective adsorption of CO2 with MIL-53. Despite CO2 solubility enhancement its diffusivity coefficient remained more or less unchanged. The enhancement in CH4 permeability has been mainly attributed to its slight incremental diffusivity due to the membrane''s increasingly higher free volume. Finally، a comparison between membranes performance and CO2/CH4 Robeson upper bound showed that، the performance of membranes improved due to the presence of MIL-53 which was very close to the Robeson bound.

Developing new methods and technologies for CO2 removal with a variety of applications, such as purification of synthesis gas, natural gas sweetening, and greenhouse gas sequestration are nowadays carried out in research works involving polymeric membranes. By employing suitable reactive carriers into the membrane matrix, the solubility and absorption rate of the reactive gas (i.e., CO2) are enhanced. In facilitated transport membrane, the selective transport through the membrane occurs owing to a reversible reaction between the reactive carriers and the target gas, while in contrast the solution-diffusion is the dominant mechanism for permeation of inert gases such as CH4, N2 and H2. In this work, the cross-linking of diethanolamine (DEA)-impregnated polyvinyl alcohol (PVA) by glutaraldehyde (GA) with different blend compositions (GA/PVA: 0.5, 1, 3, 5, 7 ratio%) were performed in the absence of an acid catalyst and organic solvents in order to avoid any interference in CO2 facilitation reaction with DEA. The fabricated membranes were characterized by differential scanning calorimetry, Fourier transform infrared (FTIR) and scanning electron microscopy. Furthermore, the effects of cross-linking agent content and feed pressure on CO2/CH4 transport properties were investigated in pure gas experiments. Finally, the cross-linked membranes showed reasonable CO2/CH4 permselectivity indexes in comparison to uncross-linked membranes. The best-yield in CO2-selective membranes (DEA-PVA/GA (1 wt%)/PTFE) represented the best CO2/CH4 selectivity of 91.13 for pure gas experiments.

The validity of a newly derived equation which is thoroughly theoretical is investigated in this article. This new equation is mainly used for equilibrium-constant calculation of multicomponent mixtures of hydrocarbons in nonideal two phase systems (liquid/vapor). It is based on taking ideas from a new theory of a contemporary scientist who believed that activity is equal to minimum thermodynamic volume. An equation for calculation of this minimum volume which has been developed before is the basis of this article methodology. The new equilibrium-constant equation has been used for a flash evaporation process as an example. The results from a typical calculation have been compared with a semi-empirical graph and that of Aspen Plus software in order to evaluate the validity and applicability of this new equation.

In this paper after an introduction about the necessity of innovation in an increasingly competitive global economy, part of the existing government-level technological innovation programs managed by Ministry of Industry and Mine is briefly described with special attention given to the technology and industry. Some of he challenges facing the program is also highlighted.

This paper presents a simple methodology for cost estimation of a near optimal heat exchanger network, which comprises mixed materials of construction. In traditional pinch technology and mathematical programming it is usually assumed that all heat exchangers in a network obey a single cost model. This implies that all heat exchangers in a network are of the same type and use the same materials of construction (an assumption that is unwarranted). The method introduced in this article enables the designer to decomposes the total cost of a heat exchanger into two elements, namely cost of the tubes and cost of the shell, thereby predict a more reliable cost for the network. By subsequent use of the binary variables and evaluation of the physical conditions of the streams, one can assign the streams to pass either through shell or tubes. Whereby, shell and tubes can be of different materials and therefore different cost models can be applied. Another advantage of the approach is that the pressure drop in each side of the exchanger (shell or tubes) can be assessed leading to more accurate evaluation of corresponding heat transfer coefficient for each individual stream. Finally an objective function (total cost) can be defined based on mixed materials of construction and different values of heat transfer coefficients. The proposed model has been utilized in three different case studies and the results are compared with those of a commercially available software (SUPERTARGET). The comparison shows reductions of more than 17% and 14% in total annual costs in the two cases, and 2.5% reduction in third, confirming the fact that more accurate evaluation of heat transfer coefficient for each individual stream can lead to better network design.