Heat and Mass Transfer at the Wall of a Square Mechanically Stirred Gas-Liquid-Solid Catalytic Reactor

Wall mass and heat transfer rates in a square gas-sparged, mechanically stirred reactor were measured by the electrochemical technique under the effect of various geometrical and hydrodynamic variables. For the 45° impeller, the mass transfer data fit the equation Sh = 0.7Sc^0.33Re^0.2Re_g^0.5 with an average deviation of ±6.9 %. For the 90° impeller, the data fit the equation Sh = 0.95Sc^0.33Re^0.14Re_g^0.53 with an average deviation of ±7.5 %. Gas sparging enhanced the wall mass transfer rates by factors of up to 2.61 and 3 for the 90° and 45° impellers, respectively, with a significant decrease in the total power consumption. The contribution of the present results to the operation of multiphase mechanically agitated vessels in different aspects is outlined.     

Surface roughness and dispersion parameters of indium doped amorphous As2Se3 thin films

Both a binary amorphous system of composition As₂Se₃ and a ternary amorphous system of composition amorphous (As₂Se₃)_0.99In_0.01 with thickness in the range 150–250 nm have been prepared by thermal evaporation technique. Indium doping and thickness effects on the features of As₂Se₃ thin films have investigated. The optical transmission spectra of these films have been measured in the range 200–1200 nm where the absorption coefficient and the optical energy gap Eg are evaluated. The refractive index and surface roughness of the prepared films are found to be highly dependent on film thickness and indium doping, using Swanepoel method.The single oscillator energy (E_o) and the energy dispersion parameter (E_d) have been calculated and discussed in terms of the Wemple and DiDomenico model. The results reveal that, they are thickness dependent—both E_o and E_d being higher for the undoped samples than that for the doped films.     

Calculation of dpa rate in graphite box of Tehran Research Reactor(TRR)

Radiation damage is an important factor that must be considered while designing nuclear facilities and nuclear materials. In this study, radiation damage is investigated in graphite, which is used as a neutron reflector in the Tehran Research Reactor(TRR) core.Radiation damage is shown by displacement per atom(dpa) unit. A cross section of the material was created by using the SPECOMP code. The concentration of impurities present in the non-irradiated graphite was measured by using the ICP-AES method. In the present study the MCNPX code had identified the most sensitive location for radiation damage inside the reactor core. Subsequently, the radiation damage(spectral-averaged dpa values) in the aforementioned location was calculated by using the SPECTER, SRIM Monte Carlo codes, and Norgett,Robinson and Torrens(NRT) model. The results of ‘‘Ion Distribution and Quick Calculation of Damage'(QD)method groups had a minor difference with the results of the SPECTER code and NRT model. The maximum radiation damage rate calculated for the graphite present in the TRR core was 1.567 × 10~(-8) dpa/s. Finally, hydrogen retention was calculated as a function of the irradiation time.     

A novel method for the management of sulfone-rich waste produced in the oxidative desulfurization (ODS) process

The oxidative desulfurization (ODS) process is one of the new desulfurization processes for the production of clean fuels. Despite the benefits of the ODS process, this process faces several important challenges. One of the most important challenges of this process is the management of a waste which is rich of sulfone compounds. In the present study, a new strategy which is the addition of waste to the bitumen with other solid waste such as high density polyethylene (HDPE) waste has been investigated. The experimental design method was applied to investigate the effect of addition of the sulfone and HDPE wastes to the properties of the bitumen blends including degree of penetration, softening point, and mass loss. It was found that the sulfone waste can be added to the bitumen as a softener. The results showed that several grades of bitumen including 50/60, 60/70, 85/100 can be produced through the addition of sulfone waste along with the HDPE waste to the base 60/70 bitumen. In general, the application of simple processes such as mixing the wastes with the bitumen can reduce the cost of waste management, considerably.     

Effects of post-drying methods on pomelo fruit peels

Process conditions of alkali refining, bleaching, and deodorization of crude chufa oil extracted from chufa (Cyperus esculentus L.) tubers grown in Korea were optimized to obtain an edible grade vegetable oil. The overall scope of refining conditions was similar to other vegetable oils. The degumming process, however, could be omitted since phospholipids were removed during alkalirefining and bleaching processes. RBD (alkali-refined, bleached, and deodorized) chufa oil fully satisfied Korean quality standards for edible vegetable oil. Chufa oil contained a high level of oleic acid, along with palmitic acid and linoleic acid. Physicochemical properties of chufa oil were similar to olive oil. The order of oxidative stability of chufa oil was crude>deodorized>degummed>refined>bleached oil. RBD chufa oil was virtually colorless and bland tasting, and was considered suitable for edible purposes.     

A review on operating parameters for optimum liquid oil yield in biomass pyrolysis

Pyrolysis is one of the potential routes to harness energy and useful chemicals from biomass. The major objective of biomass pyrolysis is to produce liquid fuel, which is easier to transport, store and can be an alternative to energy source. The yield and composition of pyrolysis oil depend upon biomass feedstock and operating parameters. It is often necessary to explore about the effect of variables on response yield and instinct about their optimization. This study reviews operating variables from existing literature on biomass pyrolysis. The major operating variables include final pyrolysis temperature, inert gas sweeping, residence times, rate of biomass heating, mineral matter, size of biomass particle and moisture contents of biomass. The scope of this paper is to review the influence of operating parameters on production of pyrolysis oil.     

Simulation of natural gas transmission pipeline network system performance

Simulation has proven to be an effective tool for analyzing pipeline network systems （PNS） in order to determine the design and operational variables which are essential for evaluating the performance of the system. This paper discusses the use of simulation for performance analysis of transmission PNS. A simulation model was developed for determining flow and pressure variables for different configuration of PNS. The mathematical formulation for the simulation model was derived based on the principles of energy conservation, mass balance, and compressor characteristics. For the determination of the pressure and flow variables, solution procedure was developed based on iterative Newton Raphson scheme and implemented using visual C＋＋6. Evaluations of the simulation model with the existing pipeline network system showed that the model enabled to determine the operational variables with less than ten iterations. The performances of the compressor working in the pipeline network system xvhich includes energy consumption, compression ratio and discharge pressure were evaluated to meet pressure requirements ranging from 4000-5000 kPa at various speed. Results of the analyses from the simulation indicated that the model could be used for performance analysis to assist decisions regarding the design and optimal operations of transmission PNS.     

Numerical Investigation on the Impact of DBD Plasma Actuators on Temperature Enhancement in the Channel Flow

The present study indicates the impact of different arrangements of dielectric barrier discharge (DBD) plasma actuators on temperature field in a channel flow. The modified lumped circuit element electro‐static model was used to calculate induced Lorentz body force and plasma dissipation of the actuators. Different distributions of temperature in the modeled channel flow for each arrangement of actuators (one, two, and three attached actuators) are discussed. According to the numerical simulation, DBD plasma actuators are beneficial devices for increasing temperature in the channel flow, especially near the location of the actuators that can be considered for related applications. The actuators are modeled under an incompressible flow regime with low Reynolds number of 335, and the configurations of the actuators are set to be 3 KV for the peak voltage amplitude, 10,000 Hz for the voltage frequency, and Kapton as the dielectric.     

Numerical investigation of nonuniform transverse magnetic field effects on the flow and heat transfer of magnetic nanofluid in a sintered porous channel

In this paper, fluid flow and convective heat transfer of a ferrofluid (water and 4 vol% Fe₃O₄) in sintered Aluminum porous channel, which is subjected to a nonuniform transverse magnetic field have been studied. The numerical simulations supposed an ordinary cubic and staggered arrangement organized by uniformly sized particles with a small contact area for the porous media and constant heat flux at the surface of the microchannel. A wire, in which the electric current passes creates a nonuniform magnetic field, which is perpendicular to the flow direction. To do this simulation, the control volume technique and the two‐phase mixture model have been employed. The results show that the obtained local heat transfer coefficient on the channel surface increased with increasing mass flow rate and decreased slightly along the axial direction. Moreover, exerting the above‐mentioned magnetic field increases the Nusselt number that enhances the heat transfer rate while it has no effect on the pressure drop along the channel.