Simulation of Liquid-Liquid Dispersed Flow in Horizontal Pipe Using Computational Fluid Dynamics

Liquid-liquid dispersed flows are commonly encountered in many of the industrial applications such as polymerization, emulsification, batch and continuous stirred reactors and pipeline flows such as in petroleum industries. Liquid-liquid two phase flows are very complex due to the existence of several flow patterns and mechanisms. Numerical approaches offer the flexibility to construct computational models which can adapt large variety of physical conditions without constructing large scale prototypes. The present work focuses on predicting the phase hold-up across a pipe cross-section and ambivalence range for phase inversion phenomena at different mixture velocity and range of input water fraction. The Computational Fluid Dynamics (CFD) computations were carried using FLUENT 6.2.16 while the geometry was created in pre-processor, GAMBIT 2.2.3. Dispersed phase dynamics and the turbulent continuous phase are modeled using an Eulerian-Eulerian approach and standard ε−k turbulence model. To check the reliability of the CFD code, the predicted results were validated with experimental results of previous work at different mixture velocities and phase fractions. CFD predicted the flow phenomenon such as phase transition from water-in-oil dispersion to oil-in-water dispersion and flow development along the length of the pipe. CFD code also predicted the phase hold-up distributions at pipe cross section. The pressure gradient trends similar to those observed in previous experimental results were obtained using CFD code. The phase inversion point obtained was within the ambivalence range suggested in literature. The numerical CFD simulations also confirmed that interphase drag, lift and turbulent dispersion forces has significant influence on spatial phase distribution. CFD simulations so obtained were subsequently compared with experimental results from previous researchers and correlation featuring range of mixture velocities and phase inputs. The predicted hold-up profiles were in good agreement with the previous experimental results for high mixture velocities and were in reasonable agreement with those of lower mixture velocity. Overall good qualitative agreement was achieved between physical model and simulated results

Waste tire rubber in polymer blends: a review on the evolution, properties and future

This review addresses the progress in waste tire recycling with a particular attention to incorporation of waste tire rubber (WTR) into polymeric matrices. Methods of waste tire downsizing, importance of WTR characterization and current practice of WTR modification has been emphasized. Detailed discussion on influence of WTR size, loading, modification, compatibilization and crosslinking on the rheological, mechanical and thermal properties of rubber, thermoplastic and thermoplastic elastomer blends utilizing WTR has been reported. By far, thermoplastic elastomer blends; though still in its infancy; has shown the most promising properties balance which is capable of commercialization. Rubber/WTR blends also show ease of processing and acceptable properties. Thermoplastic/WTR blends suffers in term of toughness and elongation at break. However, the waste thermoplastic/WTR is a viable solution to address polymeric waste problem. Review also highlights the lack of studies concentrating on dynamic mechanical, aging, thermal and swelling properties of WTR polymeric blends

Devulcanization of waste tire rubber using Amine Based Solvents and Ultrasonic Energy

This research project focuses on an alternative pathway of devulcanizing waste tire rubber by using amine based chemicals. Waste tire rubbers are known to be as toxic, non-degradable material due to their vulcanized crosslink carbon structure, and disposing of such waste could impose hazardous impacts on the environment. The current rubber recycling methods that are practiced today are rather uneconomical, nonenvironmentally friendly, and also producing recycled rubber with low quality due to the alteration in the main polymeric chains of waste rubber. This project aims to answer the question of whether the usage of amine can produce high quality rubber, where the properties of recycled rubber is almost the same as new/virgin rubber. With known potential of amine, it is a challenge for the chemical to selectively cleave the sulfur bonds without affecting the main carbon backbone chain in the rubber structure and diminishing much of the rubber properties. To study this research, aminetreated rubber must undergo devulcanisation process by applying heat and sonication energy. Then, the properties of the amine-treated rubber were determined through a set of characterization tests and analysis which are: gel content test to determine the weight of rubber before and after devulcanization, the thermogravimetric analysis (TGA) to determine the thermal degradation and stability of rubber, and Fourier Transform Infrared Spectroscopy (FTIR) to determine any structural change of the rubber. In this research so far, the first two preliminary analysis tests have been performed. The gel content test has shown that tertiary amine samples possessed a lower gel content (%) of (77 – 63 %), compared to primary amine samples (falls within the range of 80%), as well as the TGA test in which tertiary amine samples degrade faster than primary amine samples (suggesting a higher degree of rubber structure breakdown). For each type of amine, the concertation of amine did not play a major role in affecting the degree of devulcanization (as the concentration increased, the degree of devulcanization decreased for some samples). FTIR analysis showed that only sulphur-sulphur bonds were cleaved during the devulcanization process, leaving the carbon-sulphur bonds unaffected

Choline Chloride: Urea-based deep eutectic solvent as additive to proton conducting chitosan films

Chitosan (CS) film has been regarded as one of the bioresources that shows its ability to conduct proton upon modification. Nonetheless, CS film in nature is brittle and shows extremely high swelling degree towards water, leading to the impractical applications for fuel cell membranes and batteries. Formation of natural polymeric film requires plasticiser to crosslink natural polymers in improving the mechanical strength. Here, we investigate the potential of choline chloride (ChCl) and urea based deep eutectic solvent (DES) as additive in CS film with the aim to improve the mechanical property of the film. In this study, ChCl:urea- based DES was mixed with pure CS solution at different volume ratio and casted into a film. The film will be investigated on the functional groups, water uptake, ionic conductivity, proton exchange capacity and its morphology. Based on the SEM morphology result, it was found that addition of DES improves the homogeneity of the membrane film mainly attributed to the presence of strong bonds between the CS monosaccharides. Besides that, it also contributed towards better plasticising effect of the film that improves the flexibility of the membrane. The addition of DES has further improved the ionic conductivity of CS film from 2.98×10-3 to 1.23×10-2 S/cm; while drastically reduced the water uptake from 698.89 % to 180.67 %

Parametric study for devulcanization of waste tire rubber utilizing Deep Eutectic Solvent (DES)

Waste rubber is a polymeric material containing 50% of rubber and is generally referred to as waste tyre rubber. The main purpose of this research is to study ultrasonic devulcanisation of waste rubber utilising deep eutectic solvent (DES) of ZnCl2:Urea by improving process parameters such as sonication time, reaction temperature and rubber: DES mass ratio by effectively cleaving cross-link sulphur bonds. DES was created and prepared by mixing ZnCl2 with urea at 2:7 and 1:4 molar ratios respectively. Physicochemical properties of the prepared DES was measured using DSC, KFT and TGA analysis to find the freezing point, moisture content and degradation temperature, whereby their freezing point below 60°C, moisture content lower than 3.0 wt.% and 200°C degradation temperature average. Rubber to DES mass ratio was varied at 1:20, 1:30 and 1:40 and sonicated for 15 minutes inside ultrasonic water-bath. Samples were placed onto hot plate whereby heating temperature was varied at room temperature, 130°C, 150°C, and 180°C for 15 minutes. Samples were filtered, washed with distilled water and dried in oven for 24 hours. Once dried, samples were taken for analysis using TGA, EDX, FESEM, FTIR and Gel content. Under TGA analysis, most samples have an average degradation temperature of 200°C, hence justifying a successful devulcanisation. EDX analysis shows two occurrences during devulcanisation process which is bond reformation and cleavage. Furthermore, it is determined that heating temperature of 130°C is an important parameter as it is the optimum temperature for ZnCl2:Urea. Under FTIR analysis, it shows that disulphide bond, S-S is the only bond that is being broken while the rest still remains the same. Gel content analysis showed that samples have a lower soluble fraction after devulcanisation process. Finally, FESEM proves that at 130°C and 15 minutes is the optimum temperature and time which is illustrated by the smooth surface at that particular point

Electron beam crosslinked natural rubber/multiwalled carbon nanotube nanocomposite

The physical properties of the rubber blends are influenced by vulcanization and filler distribution. Normally, rubbers are vulcanized by systems based on sulfur or peroxide with the most common filler carbon black. Radiation can also produce crosslink densities like those obtained by sulphur curing, but the net effects, are similar, though not identical. The type of crosslink formed in this method (–C–C–) give rise to better mechanical properties at higher temperature. This work reports on the investigations carried out on natural rubber (SMR) filled with the multiwall carbon nanotubes (MWCNTs). This system of SMR/MWCNTs was subjected to different radiation dosages and compared with nonradiated samples in order to determine the improvement in mechanical properties of the rubber system in the presence of MWCNTs and irradiation dosages. The amount of MWCNTs in this study was varied from 1 to 7 Phr and the irradiation doses were varied from 50 to 200 KGy. Mechanical properties, especially, tensile strength (TS), elongation at break had been studied as a function of irradiation dose and degree of loading with MWCNTs. Gel fraction indicated an increase in the degree of crosslink with the increase in the MWCT and radiation dosage. XRD was carried out to check the increase in the crytallinty of the nanocomposite system. The overall results obtained indicate significant improvement in the mechanical and thermal properties by radiation crosslinking in presence of MWCNTs. These results were further supported by TEM micrograph and nanoindentation

Pretreatment studies and characterization of bio-degradable and 3D-printable filaments from coconut waste

Natural fiber based filaments are economic, environmental friendly and sustainable which enable them to be applied in the production of novel composite materials. This research aims to produce 3D printed filaments composed of Poly lactic acid (PLA) reinforced with 5 wt%, 10 wt% and 15wt% of coconut fiber (CF) and coconut shell powder (CSP). These fillers were alkaline and silane treated in order to enhance the thermal properties. These fillers were characterized by FTIR, SEM and TGA analysis. The SEM images show that there are structural changes in the fillers after successive treatments. TGA results shows enhancement of thermal stability for CF by 10 °C whereas decreased by 10 °C for CSP. These fillers are melt blended with PLA as a polymer matrix and extruded as filaments. The filament which is reinforced with CSP holds good for 3D printing whereas, the filaments reinforced with CF clogged during the process of 3D printing due to the large diameter of the filaments

Stability and characterization of CNT nanofluids using polyvinyl alcohol dispersant

In this research, CNT-water nanofluids are synthesized using polyvinyl alcohol (PVA) dispersant where each of the CNT concentration ranging from 0.01 to 0.1 wt% is tested with 0.25 to 3.00 wt% of PVA to optimize the dispersion and stability of nanofluids. The nanofluids are sonicated for 4 hours using ultrasonic water bath and the stability is analyzed using UV-Vis spectrophotometer. The dispersion state of the CNT-water nanofluid is further examined using optical microscope. The stable nanofluids of each CNT concentration identified were then tested for their thermo-physical properties such as thermal conductivity and viscosity with respect to temperature ranging from 25 to 70 °C. The results revealed that 0.5 to 1.5 wt% of PVA dispersant give the optimum stability to the entire range of CNT concentration studied. It was found that the thermal conductivity enhancement of CNT-water nanofluid stabilized by PVA increased non-linearly with temperature. Although PVA suppressed the thermal conductivity of water, the addition of CNT is able to surpass its effect and the results showed that there is approximately 1 to 44 % enhancement for the range of CNT concentration and temperature studied. It was also observed that the viscosity for 1.5 wt% of PVA aqueous solution at 25 °C is approximately 7.5 mPa.s, which is significantly greater than water. However, the presence of CNT nanoparticles is able to reduce the viscosity of its respective optimum PVA solution by 2 to 6% for the entire range of CNT concentrations investigated, showcasing self-lubrication effect of CNT. Moreover, the viscosity of the nanofluids decreases significantly with increasing temperature

Effect of interphase forces on two-phase liquid: liquid flow in horizontal pipe

A two-fluid model (Eulerian-Elurian model) is used to simulate dispersed two-phase immiscible liquids (oil-water) in a horizontal pipe. Effect of interphase forces (drag, lift and turbulent dispersion) is discussed. In the present study water is considered as dispersed and oil as continuous phase. The exchange between the phases is represented using source terms in conservation equations. Standard k-e turbulence model is used to induce turbulence in continuous phase. Comparison between mathematical simulation using CFD code FLUENT 6.2 and experimental data indicates that the interphase forces are important and has a strong effect on flow behaviour. Different drag, lift and turbulent dispersion expressions are evaluated. The CFD simulations are in good agreement with published experimental data