Heat transfer in a twin-screw multiphase pump: Thermal modeling and one application in the petroleum industry

This paper presents a model of the heat transfer processes in the casing and rotors of a twin-screw multiphase pump. The model was developed to study the influence of temperature rise in the subsea multiphase pumping system-500 (SMPS), being developed by Petrobras, that operates with a twin-screw multiphase pump. The model is divided in three parts: heat transfer in the casing, in the rotor and energy balance of fluid. For the rotor, a helicoidal coordinate system is used to calculate the heat transfer. Axial symmetry is considered so it is possible to construct a two-dimensional model. The casing is modeled using an eccentric cylindrical coordinate system. In this case, the temperature gradient in axial direction is neglected and a two-dimensional calculation is carried out. The finite volume method is used to solve the transformed partial differential equations. With the two heat transfer models implemented, the fluid temperature is calculated using a simple energy balance that takes into account electric power, transferred heat and fluid internal energy. The implemented model was used to simulate thermal behavior of casing and rotors during loss of prime events faced by SMPS-500. Experimental data collected in pump trials are used as initial input parameters and the model calculates temperature evolution during the loss of prime events.     

Magnetic multicore nanoparticles for hyperthermia--influence of particle immobilization in tumour tissue on magnetic properties

When using magnetic nanoparticles as a heating source for magnetic particle hyperthermia it is of particular interest to know if the particles are free to move in the interstitial fluid or are fixed to the tumour tissue. The immobilization state determines the relaxation behaviour of the administered particles and thus their specific heating power. To investigate this behaviour, magnetic multicore nanoparticles were injected into experimentally grown tumours in mice and magnetic heating treatment was carried out in an alternating magnetic field (H = 25 kA m(-1), f = 400 kHz). The tested particles were well suited for magnetic heating treatment as they heated a tumour of about 100 mg by about 22 K within the first 60 s. Upon sacrifice, histological tumour examination showed that the particles form spots in the tissue with a mainly homogeneous particle distribution in these spots. The magnetic ex vivo characterization of the removed tumour tissue gave clear evidence for the immobilization of the particles in the tumour tissue because the particles in the tumour showed the same magnetic behaviour as immobilized particles. Therefore, the particles are not able to rotate and a temperature increase due to Brown relaxation can be neglected. To accurately estimate the heating potential of magnetic materials, the respective environments influencing the nanoparticle mobility status have to be taken into account.     

Comparison of toxic product yields of burning cables in bench and large-scale experiments

Toxic product yields from five commercial cables obtained from a steady state tube furnace (SSTF) method (IEC 60695-7-50, Purser furnace) are compared with results from a large-scale test, which uses the physical fire model in the proposed prEN50399-2-2 test, with the addition of effluent gas analysis, using Fourier transform infrared (FTIR), and for further comparison, a static tube furnace method (NF X 70-100). This work represents one of the first attempts to establish a relationship between bench- and large-scale toxic product yields for burning cables. This is difficult because the cables have been formulated for low flammability, and therefore do not burn consistently. The tube furnace burns the cable completely, whereas the large-scale test effluent is the result of a combination of flame spread and toxic product yields, both of which are fire scenario dependant. There is significant differentiation between cable types based on composition, and arising because only a portion of the cables burn in the large-scale test, accompanied by possible decomposition of hydrate sheaths. The fire stage of the large-scale test appears to have been replicated in an appropriate manner, given the correspondence of the CO₂/CO ratios. The yields of CO₂, CO, HCl and smoke show reasonable agreement, given the differences in the extent of burning, and the accuracy of the mass-loss data available for the large-scale test. The yields and extent of burning have been combined to demonstrate the estimation of toxic hazard for a particular fire scenario based around the large-scale test, which shows only marginal sensitivity to the differences in toxic product yield between the SSTF and the large-scale test.     

Sugarcane Bagasse Ash as a Potential Quartz Replacement in Red Ceramic

Sugarcane bagasse ash (SCBA) is an industrial waste that contains silicon and aluminum oxides as the major components and iron, calcium, magnesium, and potassium oxides as the main minor components. In this paper, SCBA from one Brazilian factory was characterized and tested for its influence on the ceramic properties of clay/ash ceramic probes. Prismatic probes were pressed (18 MPa) using a ceramic mass mixed with 0%, 5%, 8%, and 10% ash. The probes were fired at temperatures between 800° and 1200°C. X-ray diffraction, X-ray fluorescence, thermal analysis (differential thermal analysis, thermogravimetric analysis/differential thermogravimetric analysis), and tests for texture (particle-size analysis), flexural strength, and linear shrinkage were carried out to characterize the samples. The results showed that the amount of ash to be incorporated will depend on mainly the composition of clay but also ash, and indicated that the clay used in this work can incorporate up to 10% weight of ash to produce solid bricks. The results also showed an improvement in ceramic/ash properties up to sintering temperatures higher than 1000°C.     

Relationships Between Sex and Stress Hormone Levels in Feces and Marking Behavior in a Wild Population of Iberian Wolves (Canis lupus signatus)

Feces deposited by the breeding alpha pair on exposed substrates and/or zones may act as visual and olfactory marks associated with social dominance in wolves. The aim of this study was to determine if there was a correlation between marking behavior, sex hormone levels, and physiological stress in a wild population of Iberian wolves in Northwest Spain. The glucocorticoid and sex hormone levels were measured in feces collected as a function of exposure (conspicuous/inconspicuous), height (above ground level/at ground level), and strategic location in the habitat (at crossroads/off crossroads), as well as the frequency of re-marking. The feces, believed to serve as marking cues, had higher glucocorticoid levels (cortisol) and sex hormones (testosterone, progesterone, and estradiol). The results suggest that in Iberian wolves, the alpha pair is subject to higher social stress than subordinate individuals, and that the reproductive suppression of subordinates is not mediated by chronic glucocorticoid elevation.     

Fusarium avenaceum -- the North European situation

The Fusarium species complex found on small-grain cereals in Northern Europe is largely dominated by F. avenaceum, while other important species include F. tricinctum, F. poae, F. culmorum and F. graminearum. The dominance of F. avenaceum has in recent years initiated extensive analytical activity in Norway and Finland in order to gain insight into the contamination of grain with secondary metabolites related to the fungus. Of these, moniliformin is the most studied compound with regard to toxicity. However, the data from analytical surveys indicate that field conditions in Northern Europe do not favour production of the metabolite. Instead, enniatins are regularly found in ppm-concentrations in grain, especially wheat and barley, while the bio-production of a range of other F. avenaceum related metabolites has so far barely been investigated. This paper summarises the results from mycological and chemical analyses of grain samples from Norway and Finland for major Fusarium species and F. avenaceum-related secondary metabolites.     

Photoirradiation of dissolved humic acid induces arsenic(III) oxidation

The fate of arsenic in aquatic systems is influenced by dissolved natural organic matter (DOM). Using UV-A and visible light from a medium-pressure mercury lamp, the photosensitized oxidation of As(III) to As(V) in the presence of Suwannee River humic acid was investigated. Pseudo-first-order kinetics was observed. For 5 mg L(-1) of dissolved organic carbon (DOC) and 1.85 mEinstein m(-2) s(-1) UV-A fluence rate, the rate coefficient k degrees exp was 21.2 +/- 3.2 10(-5) s(-1), corresponding to a half-life <1 h. Rates increased linearly with DOC and they increased by a factor of 10 from pH 4 to 8. Based on experiments with radical scavengers, heavy water, and surrogates for DOM, excited triplet states and/or phenoxyl radicals seem to be important photooxidants in this system (rather than singlet oxygen, hydrogen peroxide, hydroxyl radicals, and superoxide). Photoirradiation of natural samples from freshwater lakes, rivers, and rice field water (Bangladesh) showed similar photoinduced oxidation rates based on DOC. Fe(III) (as polynuclear Fe(III)-(hydr)oxo complexes or Fe(III)-DOC complexes) accelerates the rate of photoinduced As(III) oxidation in the presence of DOC by a factor of 1.5-2.     

Mechanical properties of pea starch films associated with xanthan gum and glycerol

The aim of this study was to evaluate the effect of the addition of xanthan gum and glycerol to the starch of green pea with high content of AM (cv. Utrillo) in the preparation of films and their physical characteristics. Filmogenic solution (FS) with different levels of pea starch (3, 4, and 5%), xanthan gum (0, 0.05, and 0.1%), and glycerol (glycerol–starch ratio of 1:5 w/w) were studied. The FS was obtained by boiling (5 min), followed by autoclaving for 1 h at 120°C. The films were prepared by casting. Films prepared only with pea starch were mechanically resistant when compared to other films, prepared with corn, cassava, rice, and even other pea cultivars (yellow, commercial). The tensile strength of these films is comparable to synthetic films prepared with high‐density polyethylene and linear low‐density polyethylene. However, they are films of low elasticity when compared to other films, such as rice starch films, and especially when compared to polyethylene films. The increased concentration of starch in the solution increased the puncture force. The increased concentration of glycerol slightly decreased the film crystallinity and interfered in the mechanical properties of the films, causing reduction of the maximum values of tensile strength, strain at break, and puncture force. The plasticizer also caused an increase of elongation at break. Xanthan gum was important to formation of films; however, it did not affect their mechanical properties.