فهرست مطالب

Chemistry and Chemical Engineering - Volume:38 Issue:1, 2019
  • Volume:38 Issue:1, 2019
  • تاریخ انتشار: 1397/11/12
  • تعداد عناوین: 23
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  • Ramin Ghahremanzadeh, Maryam Yousefi *, Fatemeh Yazdi Pages 1-10
    The aim of this work is a green synthesis of gold nanoparticles using the aqueous extract of Anthriscus sylvestris, Ferula gummosa, and Achillea eriohora leaf and stems as the reducing agents. The effects of reducing agent concentration in the reaction mixture and temperature on the size of the gold nanotriangles were studied. The nanoparticles were characterized using UV–Vis spectroscopy, XRD, and SEM. XRD studies show that the particles are crystalline in the cubic phase. However, the reduction of gold ions by plant extracts resulted in the formation of spherical gold nanoparticles with diameters from 18 to 56 nm.
    Keywords: Anthriscus sylvestris, Ferula gummosa, Achillea eriohora, Biosynthesis, Gold nanoparticles
  • Yadolah Ganjkhanlou, Abdolmajid Bayandori * Pages 11-16
    The particle size distribution of the resultant cobalt ferrite samples was determined from Scanning Electron Microscopy (SEM) images using the granulometry image analysis method. Results showed the nanosized particles of the samples. The X-Ray Diffraction (XRD) patterns of samples were also analyzed by Rietveld refinement method. The results indicated that the precipitated sample at 95 oC had cubic cobalt ferrite structure with F3dm:3 space group and high crystallinity. The lattice parameters, microstrain and crystallite size of samples were also calculated from the XRD pattern. With increasing the precipitation temperature, the crystallite and particle sizes were increased while the lattice parameter and microstrain were decreased. Regarding the results, it can be concluded that the lattice parameter of cobalt ferrite has a diverse relationship with crystallite size.
    Keywords: Local thresholding algorithm, X-ray diffraction, image processing, Particle size distribution
  • Sana Kachbouri, Elimame Elaloui, Younes Moussaoui * Pages 17-26
    Mesoporous amorphous and nanocrystalline titanium dioxide were prepared by simple and environmental friendly modified Sol-Gel method using cationic (C14TAB, C16TAB, C18TAB) and nonionic (Plantacare UP K55) surfactant as pore forming agent. The obtained particles were characterized by BET, TEM, FT-IR and XRD techniques. The effect of cationic surfactant chain length and type of template on the photocatalytic activity of as prepared TiO2 nanoparticles were investigated by the degradation of rhodamine B in water solution under UV irradiation. The results indicated that this process was well described by pseudo-first order kinetic model. All the prepared titanium dioxide particles with cationic and nonionic surfactant exhibited higher performance for rhodamine B photo-degradation. The sample with large pore size and small particle size which obtained by using C18TAB surfactant showed high photocatalytic activity compared with the others samples and commercial P25. The mechanism of photocatalytic degradation of rhodamine B was proposed based on the degradation products determined by GC/MS and LC/MS. The performance of the recycled TiO2 as photocatalyst was investigated.
    Keywords: : Sol-gel processes, Mesoporous materials, Reaction mechanisms, Photochemistry, Nanostructures
  • Mehdi Kalhor *, Zahra Seyedzade Pages 27-41
    In this research, by a simple and modified method, nanoporous of Ni(II) ion loaded Y-type zeolite (NNZ) was designed and applied as a novel highly efficient catalyst for the synthesis of quinoxalines, pyrido[2,3-b]pyrazines, and indolo[2,3-b]quinoxalines 3a-s. These heterocycles were obtained through a one-pot condensation reaction of aryl-1,2-diamines with 1,2-diketones or the isatin in the presence of catalytic amount of Ni@zeolite-Y in ethanol or acetic acid at room temperature giving good to excellent yield. The structure of entitled catalyst was identified with FT-IR spectroscopy, Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. This method has some advantages such as the use of inexpensive, safety, stable and recyclable catalyst, high yields, short reaction times, and easy isolation of the product. It can be claimed that this approach in simplicity covers the goals of green chemistry.
    Keywords: Synthesis, Ni@zeolite-Y, nano-catalyst, o-arylenediamines, isatin, Quinoxaline, Pyridopyrazine, indoloquinoxaline
  • Sahar Mohajeri *, Mina Kamani, Ali Akbar Salari, Maziar Noei, Maryam Ebrahimikia, Nastaran Ahmadaghaei, Nazanin Molaei Pages 43-48
    Electrical sensitivity of a beryllium oxide nanotube (BeONT) was examined toward aniline (C6H5 NH2) molecule by using Density Functional Theory (DFT) calculations at the B3LYP/6-31G (d) level, and it was found that the adsorption energy (Ead) of aniline on the pristine nanotubes is about -19.06kcal/mol. However, when nanotube has been doped by P and S atoms, the adsorption energy of aniline molecule was decreased. The calculation showed that when the nanotube is doped by S, The adsorption energy is about -8.61kcal/mol and also the amount of HOMO/LUMO energy gap (Eg) will reduce significantly. As a conclusion, Beryllium oxide nanotube is a suitable adsorbent for aniline and can be used in different processes of aniline. It seems that nanotube (BeONT) is an appropriate semiconductor after being doped. The doped BeONT in the presence of aniline generates an electrical signal directly and therefore can be potentially used for aniline sensors.
    Keywords: sensor, Nanotube, DFT, Aniline
  • Alireza Aliabadi *, Rezvan Fereidooni, Amir Kiani Pages 49-55
    Cancer is a big global problem and is one of the top and main causes of mortality in developed countries. Many of the current treatments and anticancer therapeutics have problems with severe side effects and on the other hand, the drug resistance is also another obstacle in the cancer chemotherapy. Hence, there is a strong demand for the discovery and development of effective new antineoplastic therapies. According to the in vitro effectiveness of 1,3,4-thiadiazole based compounds as anticancer agents, new 1,3,4-thiadiazole based derivatives with various electron withdrawing and electron donating moieties were synthesized and tested by MTT assay against three cancerous cell lines. PC3 (Prostate cancer), U87-C-531 (Glioblastoma) and MDA-MB-231 (Breast cancer) cell lines were applied for MTT assay and obtained results were compared to imatinib. Study of the structure activity relationship of prepared compounds showed electron withdrawing substituents such as Cl, F and NO2 enhanced the anticancer properties compared to compound without any substituent (compound 3l) or compounds with electron donating (methoxy) substituent (compounds 3j and 3k). Totally, compound 3a (IC50 = 10.6 µM) showed superior activity against PC3 cell line and compounds 3d  (IC50 = 10.3 µM), 3h (IC50 = 12.5 µM) and 3j (IC50 = 11.3 µM) exhibited higher activity against MDA-MB-231 cell line compared to imatinib as reference drug.
    Keywords: Synthesis, 1, 3, 4-Thiadiazole, MTT, Anticancer
  • Sadia Naureen *, Faryal Chaudhry, Nadia Asif, Munawar Ali Munawar, Misbahul Ain Khan Pages 57-64
    A series of new tetrasubstituted imidazoles 2-phenyl-3-(1, 4, 5-triphenyl-1H-imidazol-2-yl)-1H-indole derivatives substituted with –F, Cl, Br, I,-OCH3 and -NHCOCH3 were synthesized using a multicomponent reaction. The compounds were obtained in good yields by easy workup and with high purity
    Keywords: Indoles, Imidazoles, Multicomponent, NMR
  • Yufeng Ma, Puyou Jia *, Lihon Hu, Guodong Feng, Meng Zhang, Yonghong Zhou Pages 65-71
    A bio-based plasticizer, epoxidized acetylation cardanol, was synthesized from cardanol, which experienced acetylation reaction and epoxidation reaction. Chemical structure of epoxidized acetylation cardanol was characterized by FT-IR and 1H NMR. Plasticized PVC films (PVC-P) were prepared by casting method with 40%wt of epoxidized acetylation cardanol as a plasticizer. Thermal stability and plasticizing effect of PVC and PVC-P were investigated. The results presented that epoxidized acetylation cardanol enhanced the thermal stability of PVC-P and decreased glass transition temperature (Tg) from 81.9°C to 1.6°C. The tensile strength decreased from 26.60 MPa to 8.06 MPa, the elongation at break increased from 167.21 % to 905.44%. All of the results indicated that epoxidized acetylation cardanol could be used as the main plasticizer for preparing flexible PVC materials.
    Keywords: plasticizer, PVC, Cardanol, Synthesis, DSC
  • Kunal Roy * Pages 73-82
    The reaction of [Ru(L)2(H2biim)](ClO4)2 [L1 = 2,2¢-bipyridine (bpy) or L2 =  2-(phenylazo)pyridine (pap) and H2biim = 2,2¢-biimidazole] with Au(tht)Cl (tht = tetrahydrothiophene) in presence of base in methanol produced a terametallic cationic complex [{Ru(L)2(biim)}2Au2]2+, [1]2+ which was isolated as its perchlorate salt. The compounds were characterized by various spectroscopic techniques. ESIMS data of these fully corroborate with their formulation. Spectral data of all the polymetallic systems are reported and compared. The redox properties of the complexes are interesting. The complex [{Ru(bpy)2(biim)}2Au2](ClO4)2 showed one irreversible metal based oxidation at 1.43 V whereas the compound [{Ru(pap)2(biim)}2Au2](ClO4)2 showed one irreversible ligand based oxidation at 1.34 V. This type of binding mode of the biimidazolate anion containing Ru2Au2 core is rare in the literature. ‘Metal complex as ligand’ strategy provides a platform for the synthesis novel polymetallic complexes of gold(I).
    Keywords: Biimidazole ligand, Gold(I) complexes, Hetero-polymetallic Complex, Self-assembly
  • Xiaojun Guo *, Dai Li Pages 83-91
    Spherical-like hydroxyapatite (HA, Ca10(PO4)6(OH)2) particles were prepared by the co-precipitation method in a simulated physiological environment. The effect of calcining temperature, calcining time and the Ca/P ratio of the initial feeding on the morphology and crystallinity of HA were investigated in detail. Interestingly, while the Ca/P ratio of the initial feeding is 1.80, the obtained HA powders calcined at 800 °C for 2 h contain trace amounts of Na and Mg ions, and the (Ca+Na+Mg)/P ratio is equal to 1.66, which is close to the stoichiometric ratio 1.67 of HA. And a better route with shorter reaction time for the synthesis of HA containing trace amounts of Na and Mg elements was acquired.
    Keywords: Hydroxyapatite, co-precipitation, Simulated body fluids, Calcining temperature
  • Farah Sadat Halek, Sayed Mohsen Hosseini *, Sayed Siavash Madaeni, Samaneh Koudzari Pages 93-99
    Poly (phenylene-ether-ether) sulfone membrane was fabricated and characterized by efficient glycerol/biodiesel separation produced from waste cooking oils trans-esterification. The membrane preparation was processed by phase inversion technique. The morphology, Physico-chemical properties and separation behavior of membranes were studied at various PPEES concentration. A uniform surface was observed for the prepared membranes by scanning electron microscopy. AFM images exhibited that surface roughness was decreased from 9.24 to 7.26 nm by the increase of PPEES concentration from 12 to 15 %wt. Similar trend was found for the membrane Flux, water content, and porosity by the increase of PPEES content ratio up to 15 %wt. The efficiency of glycerol removal and mechanical strength was also improved by the increase of polymeric matrix concentration.
    Keywords: Poly (1, 4-phenylene ether-ether-sulfone), Polymeric membrane, Glycerol, biodiesel separation, Physico-chemical characterization
  • Thabo Matthews, Stephen Majoni, Bothwell Nyoni, Bobby Naidoo, Halenden Chiririwa * Pages 101-109
    The efficiency of using a composite of carbon black and sodium bentonite in treating drinking water contaminated with lead and copper ions was analysed. The effects of pH, contact time, concentration and adsorbent dosage using an adsorbent composite of 20 % sodium bentonite and 80 % carbon black were studied. The adsorption data was tested with respect to Langmuir, Freundlich and Temkin isotherms. The data fit well with the Langmuir isotherm model with high coefficients of determination for both metal ions adsorption. The adsorption kinetics follows a pseudo second-order model for both metal ions. The maximum metal ion uptake (qmax) of the composite adsorbent is 7.69 and 0.80 mg/g for lead and copper respectively.
    Keywords: Adsorption, carbon black, Sodium bentonite, Isotherms, Kinetics
  • Mallappa A. Devani *, Basudeb Munshi, Bipin Bihari Lal, Sandip Mandal, John U. Kennedy Pages 111-125
    This work aims at the modeling of bio-sorption of cadmium(II) onto physically and chemically activated Cajanus cajan (Pigeon pea) husks. Experimental data obtained were fitted to a number of isotherm and kinetic models, and the results interpreted. The monolayer Cd(II) bio-sorption capacities of the husk were found to considerably increase by 2.82 times due to chemical activation, for bio-sorption from a solution containing an initial Cd(II) concentration of 100 mg/L and by about 1.78 times for a solution containing an initial Cd(II) concentration of 150 mg/L. Further, the BackPropagation Artificial Neural Network (BP-ANN) was applied to understand the accuracy and prediction of isotherm and kinetic data. The tangent sigmoid transfer function was used at the input to hidden layer whereas a linear function was used at output layer. The isotherm and kinetic data were distributed into training (65%) and testing (35%) phase. The training, testing, and prediction by BP-ANN were found to be adequate, with an absolute relative percentage error of 2.1827 and correlation coefficient R2of 0.9967 and 0.9863 at prediction for isotherm and kinetic studies, respectively. Comparison of BP-ANN and experimental results indicated that the prediction model is capable of predicting the bio-sorption effectiveness with good accuracy.
    Keywords: ANN Modeling, Biosorption, Cajanus cajan, Isotherms, Kinetics
  • Newsha Javadnia, Abdolhadi Farrokhnia * Pages 127-139
    Cadmium is an extremely toxic metal, which even in low levels is harmful to the human body, animals and also plants. Human manufactures such as cadmium-nickel batteries and pesticides, plastic, make the earth polluted with cadmium; therefore removal of the cadmium Water is vital for human and animal. Scientists use different methods for cadmium removal including adsorption, precipitation, ion exchange, and solvent extraction. In this study the removal of cadmium ion from aqueous solution by nanoparticles of cobalt oxide were investigated. The sol-gel method was used to synthesize cobalt oxide nanoparticles. The characterization of synthesized cobalt oxide was investigated by Fourier Transfer Infrared Spectrometry (FT-IR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), and a Transmission Electron Microscope (TEM). The important parameters influencing on the adsorption process were studied, including pH, buffer volume, amount of adsorption, contact time, in-time differentiate temperature and Taguchi designed experiment. The kinetic of removal process was investigated and found that it is followed pseudo-second-order kinetics. In this study, four famous isotherms were considered to investigate and the results indicated that the Langmuir model gave a better fit to the experimental data.
    Keywords: Cadmium, Removal, Isotherm model, Cobalt oxide
  • Tahereh Navaei, Karim Zare, Farshad Taleshi *, Mohammad Yousefi Pages 141-154
    The present work investigates the efficiency of the nickel oxide/carbon nanotube (NiO/CNT) nanocomposite for the removal of Cd2+ metal ions from an aqueous. The NiO/CNT nanocomposite was synthesized by the direct co-precipitation method in an aqueous media in the presence of CNTs. The resulting materials were characterized by FT-IR, XRD, SEM, N2 adsorption-desorption analysis. In order to optimize the adsorption of Cd2+ ions on NiO/CNT nanocomposite, the effects of the different parameters—namely pH, contact time, initial concentration of Cd2+, and adsorbent dosage—were also studied. Experimental data revealed that the Cd2+ ions adsorption of the NiO/CNT nanocomposite was through Langmuir and Temkin isotherm models rather than the Freundlich model. The kinetic data of adsorption of Cd2+ ions on the adsorbent was best described by a pseudo-second-order equation, indicating their chemical adsorption. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. The obtained values showed that the adsorption was spontaneous and exothermic in nature. The reusability test showed that the Cd2+ could be easily removed from the surface site of NiO/CNT nanocomposite by a 0.1 M nitric acid solution as the adsorption capacity was maintained after 5 cycles of the adsorption/desorption process. This suggests that NiO/CNT nanocomposite can be reused through many cycles of water treatment and regeneration.
    Keywords: Adsorption, Carbon nanotubes, Composite, heavy metals, Removal
  • Ali Naderi, Batool Naderi * Pages 155-161
    The deficiency of calcium, magnesium, potassium, and iron leads to severe disorders in human body organs. This study introduces Dooshab as a food source of these useful elements. The Dooshab which translates to grape syrup is widely used in Iran. In the traditional method of the Dooshab production, the white soil is added to the grape juice and the mixture is boiled. After cooling, it is filtered. To get the syrup, the filtered juice is boiled again and concentrated. In this research, grape juice was divided into two equal parts. A known amount of white soil was added to one of the samples. Then, both samples were boiled and left to cool down. After paper filtering, the pH of each sample was measured. Heating was continued until liquids were concentrated and converted to syrup. Both samples which are produced from using mud-boiled up the stage and skipping this step were diluted to fixed volumes. Similar amounts of two samples were ashed and dissolved in distilled water and tested. The atomic absorption spectroscopy, spectrophotometry, and flame atomic emission spectroscopy techniques were used for quantitative analyses. The calcium, magnesium, iron and potassium quantity are 12 mg, 6.82 mg, 2.32 mg, and 250 mg in 25 mL of the Dooshab and 1.75 mg, 0.65 mg, 1.28 mg, and 65 mg in 25 mL of grape sauce, respectively. This study demonstrates that boiling of grape juice with the white soil decreases the acidity and increases the amounts of useful elements in grape syrup.
    Keywords: Dooshab, grape syrup, Grape sauce, spectroscopy, Quantitative analysis
  • Saber Barkhori, Saeid Khanzadi *, Mohammad Hashemi, Mohammad Azizzade Pages 163-172
    The present study is aimed at evaluating the effect of functional alginate coating incorporated with Lactoperoxidase (LPOS) and Zataria multiflora Essential Oil (ZEO) or both as natural additives on microbial and chemical characteristics of rainbow trout fillets. Firstly, Different treatments of trout fillets were prepared using ZEO (0.5 and 1%) and LPOS (5%) individually and in combination. Then stored in the refrigerator for 16 days and were analyzed for chemical (pH and Total Volatiles Base-Nitrogen (TVB-N)) and microbial (Total mesophilic viable count, psychotropic count, Shewanella putrefaciens count, and Pseudomonas spp. count) characteristics at 4-day intervals. Results indicated that the combination of ZEO and LPOS had the strongest effect on chemical spoilage parameters (TVN, pH) and spoilage microbial flora of trout fillets during storage; however, samples with the individual use of ZEO or LPOS also had statistically significant(P<0.05) effects on preserving the chemical and microbial quality of trout fillets. According to the results, the application of sodium alginate coating impregnated with LPOS and ZEO especially in combination can control undesirable chemical and microbial changes of fish and extend its shelf life during refrigeration.
    Keywords: Rainbow trout, Sodium alginate coating, Lactoperoxidase system, zataria multiflora essential oil, Shelf life
  • Sayyed Hossein Hashemi *, Zahra Monfaredzadeh Pages 173-183
    A novel molecularly imprinted polymer-coated stir bar has been used to selectively extract diclofenac (DFC) directly from real samples. DFC was used as template molecule for preparation of MIP coating. The effect of different parameters on the extraction efficiency were studied and the optimum conditions were established as: the absorption and desorption times were fixed at 10 min, stirring speed was 600 rpm, pH was adjusted to 5.1, the amount of NaCl was 0.35 mol/L and extraction process was performed at a temperature of 45 °C. Under the optimum conditions, the linear range of method was 0.5- 500.0 µg/L for DFC and the detection limit was calculated to be 0.15 µg/L with an enrichment factor of 242 folds. The technique was successfully applied for the analysis of trace amounts of DFC in seawater and commercial tablet samples. The mean recoveries of spiking real samples with DFC at 10.0 µg/L level were between 94.2-100.0 % with a mean RSD of 0.7-4.6%.
    Keywords: Diclofenac, Molecularly imprinted polymer-coated stir bar, Seawater analysis, Sample preparation, Pharmaceutical analysis
  • Shirin Elmi, Maryam Dehdab, Mehdi Shahidi, Mohammad Mehdi Foroughi Pages 185-200
    Molecular Dynamics (MD) simulation and Density Functional Theory (DFT) methods have been used to evaluate the efficiency of four quinoline derivatives on corrosion inhibition in the aqueous phase. Some quantum chemical parameters such as hardness (η), electrophilicity (w), polarizability (a), energy of the highest occupied molecular orbital (EHOMO), energy of the lowest unoccupied molecular orbital (ELUMO), electronegativity (c), total amount of electronic charge transferred (ΔN), Total Negative Charges (TNC) on the whole of the molecule, Molecular Volume (MV), surface area and Fukui index were calculated. Molecular dynamics simulation showed a view of the dynamic evolution of the interaction energy between surface of metal and inhibitors. Results of two methods showed QUIN4 inhibitor has higher negative interactions and efficiency as compared to the other inhibitors, which was consistent with the experimental report.
    Keywords: Corrosion, Quinoline Derivatives, DFT, Molecular Dynamics Simulation, Carbon Steel
  • Mohammadreza Shahnazari *, Hamidreza Lari, Masoud Ziabasharhagh Pages 201-212
    The enactment of strict laws on reducing pollution and controlling combustion has given rise to the necessity of considering a new approach to energy supply in the future. One such approach is the use of hydrogen as an alternative to fossil fuels. Hydrogen and synthesis gas are typically produced through the partial oxidation of methane in porous media. This process was theoretically simulated in this study through the modeling of a tubular reactor filled with a porous medium. With a view to achieving increased hydrogen production, the investigation focused on the following tasks: The best equivalence ratio of fuel to air was determined, and the effects of reactor diameter and length were examined to identify the most favorable reactor size for hydrogen production. The effects of fuel flow rate and porous media properties, such as grain size and porosity, on hydrogen production, were also investigated.
    Keywords: partial Oxidation, Porous media, combustion, methane reforming, Hydrogen
  • Mohammad Reza Habibi, Meysam Amini *, Ali Arefmanesh, Esmaeil Ghasemikafrudi Pages 213-232
    The buoyancy-driven boundary-layer flow from a heated horizontal circular cylinder immersed in a water-based alumina (Al2O3) nanofluid is investigated using variable properties for nanofluid viscosity. Two different viscosity models are utilized to evaluate heat transfer enhancement from a cylinder. Exact analytic solutions of the problem are attained employing a novel powerful technique is known as the Optimal Homotopy Analysis Method (OHAM). The accuracy and reliability of the results are verified by comparing them with experimental results in the literature. It is found that the characteristics of flow and temperature distributions are significantly influenced by the volume fraction of alumina nanoparticles, as well as nanofluid viscosity models. Enhancing the volume fraction of nanoparticles, the surface shear stress and the local Nusselt number both increase in the middle regions of the cylinder. The results also indicated that with increasing the nanoparticles volume fraction, isotherms become less dense and the absolute values of the stream-function decrease within the domain. Based on the results of the parametric study, two correlations (based on two different effective viscosity models) are proposed for the average Nusselt number of the alumina-water nanofluid in terms of volume fraction of the nanoparticles and the Rayleigh number which can be used as benchmarks for future investigations. However, uncertainties of viscosity models showed different manners on heat transfer coefficient versus nanoparticles volume fraction.
    Keywords: Natural convection, nanofluid, Horizontal cylinder, analytical solution, Viscosity models
  • Zahoor Hussain, Muhammad Zaman, Muhammad Nadeem, Atta Ullah * Pages 233-242
    Granular flow simulation using CFD has received a lot of attention in recent years. In such cases, CFD is either, coupled with Discrete Element Method (DEM) techniques for appropriate incorporation of inter-particle collisions, or the Eulerian CFD approach is used in which granular particles are treated as they were fluid. In the present study, a CFD analysis was performed for granular flow in an industrial screw feeder to study the choking phenomena. Eulerian multiphase flow model, also known as two-fluid model in the case of two phases, was used along with the solids closures based on Kinetic Theory of Granular Flow (KTGF). The rotating effect of the half pitch screw was incorporated by using the immersed boundary method (IMB). Variation of mass flow through change in revolution per minute (RPM) and moisture content was studied in this work. A jump condition in the axial profiles of both the solid phase volume fraction and pressure was observed near the inlet. It was found that the jump condition in solid phase volume fraction and pressure profiles reduces by increase in the RPM of the screw.
    Keywords: Computational Fluid Dynamics (CFD), Kinetic Theory of Granular Flow (KTGF), Immersed Boundary Method (IBM), Screw Feeder
  • Ali Saberimoghaddam *, Mohammad Mahdi Bahri Pages 243-253
    Heat exchangers are the most important equipment in refrigeration processes. Design and modeling of heat exchangers operating at low temperatures are different from other regular heat exchangers. This study includes two sections. In the first section, design and modeling considerations needed for evaluating the real thermal behavior of heat exchangers at low temperatures were discussed. These considerations are usually neglected by researchers who have modeled the heat exchanger at low temperatures.  In the second section, a counter current helically coiled tube in tube heat exchanger operating in hydrogen liquefier was modeled and simulated considering notes discussed in the first section. The model was validated compared with the data presented by literature. The results showed the small positive effect of longitudinal heat conduction on hydrogen liquefaction. The heat in-leak into cold fluid resulted in higher cold fluid outlet temperature and higher hot fluid outlet temperature. Simulations showed that the heat in-leak into cold fluid leads to limit the overdesign for cryogenic heat exchangers. A comparison between models with considering different assumptions was presented and showed that the result may vary significantly based on the regarded assumptions.
    Keywords: heat exchanger, longitudinal heat conduction, heat in-leak, Low temperature', refrigeration