Modelling of rheological behaviour of macaíba pulp at different temperatures

ABSTRACT Fruit pulps undergo temperature variations during processing, leading to viscosity changes. This study aimed to analyse the rheological behaviour of macaíba pulp at different temperatures (10 to 50 ºC, with 5 ºC increments) and speeds (2.5 to 200 rpm, totalling 17 speeds). Experimental measurements were performed in a Brookfield viscometer, fitting the Ostwald-de-Waele, Mizrahi-Berk, Herschel-Bulkley, and Casson models to the experimental data of shear stress as a function of shear rate. Among the models used, the Mizrahi-Berk model (R² > 0.9656 and average percentage deviation - P ≤ 4.1%) was found to best fit the rheogram data. Macaíba pulp exhibited a non-newtonian behaviour and was characterised as pseudoplastic. It showed fluid behaviour indexes below unity under the studied conditions, with decreases in apparent viscosity as temperature and shear rate increased. Such behaviour could be described by the Arrhenius equation. The Mizrahi-Berk and Falguera-Ibarz models (R² > 0.99 and P ≤ 10%) best fitted the data and were used to represent the viscosity behaviour of macaíba pulp. The activation energy values of macaíba pulp ranged between 17.53 and 25.37 kJ mol-1, showing a rheological behaviour like other fruit pulps.

Fluid Behaviour Analysis on Liquefaction Using Korinofaction Device

Earthquakes can be followed by liquefaction, which is a response of saturated soil when it is subjected to shock or stress that cause loss of soil strength or bearing capacity as an impact of the increasing of soil pore water and the loss of the soil stress’s effectiveness. This research using Korinofaction that work to cause cyclic loads or vibrations that come from DC servo motor with an adjustable speed and force. The earthquake’s strength is measured by the number of rpm measured on the digital tachometer. Korinofaction is equipped with plumbing system to observe fluid behaviour during liquefaction. The results of research showed that silty sand and silt was liquefied in VIII Modified Mercalli Intensity earthquake and cause the occurrence of water flow on the surface due to increase soil pore stress. The flow rate that triggers liquefaction in the silty sand is 6,769 × 10-5 m 3/ second ’ and silt is 5,0 × 10-5 m 3/ second . The water flow that flows in the silty sand had permeability of 4,76 × 10-4 Cm/second while on the silt is 6,09 × 10-4 Cm/second . After liquefaction, gradient hydraulic of silty sand is 4,76 mm and silt is 6,09 mm. Based on this research liquefaction caused mobilized debris flow and muddy debris flow.

ON THE ROLL DAMPING OF AN FPSO WITH RISER BALCONY AND BILGE KEELS

Although the topic of roll damping of vessels at sea is already brought to the attention of naval architects by Froude more than 100 years ago, the physics of it remain intriguing, even today. An accurate prediction of the motions of offshore structures in harsh environments, designed for 25 years continuous operation, is the topic of this paper. Model test experiments for two FPSO’s developed by SBM for Petrobras are discussed. It is shown that the FPSO submerged riser balcony on one side of the vessel contributes to the roll damping through similar physics as the bilge keel does. Flow memory effects are discussed in detail since these are shown to have a noticeable effect on the roll damping coefficients. The paper further employs 3D CFD simulations to enhance the understanding of the fluid behaviour around the FPSO appendages, necessary to construct a rational and accurate roll damping model in the future.

Flow Assurance and Thermodynamic Challenges of operating CO2 Pipelines for variations in terrains and environments

The requirement for capturing and storing Carbon Dioxide will continue to grow in the next decade and a fundamental part of this is being able to transport the fluid over large geographical distances in numerous terrains and environments. The evolving nature of the fluid supply and the storage characteristics ensure the operation of the pipeline remains a challenge throughout its operational life. This paper will examine the impact of changes in the fluid composition, storage locations, ambient conditions and the various operating modes the pipeline will see throughout the lifecycle, highlight the technical design and operational challenges and finally give guidance on future developments. The thermodynamic behaviour of CO2 with and without impurities will be demonstrated utilising the fluid characterisation software, MultiflashTM. The fluid behaviour and hydraulic performance will be calculated over the expected operational envelope of the pipeline throughout field life, highlighting the benefits and constraints of using the single component module in OLGATM whilst comparing against a compositional approach when dealing with impurities. The paper will demonstrate through two case studies of varying nature including geographical environment, storage location (aquifer vs. abandoned hydrocarbon reservoir) and ambient conditions, the following issues: The impact of the storage type on the pipeline operations and how this will evolve with time; The environmental conditions and the impact these have on selection of process equipment and operational procedures (i.e. shutdown); and The impact the CO2 composition has on the design of the CO2 pipeline, and The paper will conclude with a set of guidelines for undertaking design analysis of CO2 pipelines for variations in fluid composition, storage locations and ambient conditions as well as some key operational strategies. This paper utilises the current state of the art tools and how these evolving tools are making this technically challenging area more mainstream.

Preventing Wax Deposition in Crude Oil Using Polyethylene Butene and Nano Zinc Oxide

This research examines the use of 75nm Zinc Oxide nanoparticles (Nano ZnO) and Polyethylene Butene (PEB) in reducing the viscosity of Nigerian waxy crude oil. The rheology of the crude oil was studied by measuring the viscosity and shear stress of crude samples contaminated with varying concentration of PEB (500ppm, 1000ppm, 2000ppm, 3000ppm, 4000ppm and 5000ppm), varying concentrations of Nano ZnO (1wt%, 2wt%, 3wt% and 4wt%) and different blends of PEB and Nano ZnO at temperatures of between 10°C to 35°C and shear rates from 1.7 to 1020s-1. From Rheological Modelling analysis conducted, the Power law pseudoplastic model was the best fit for the experimental data with a regression coefficient of 0.99. Analysis of crude sample before addition of inhibitor showed evidence of non-Newtonian fluid behaviour as the shear stress-shear rate relationship curves were nonlinear due to wax precipitation at low temperatures (10°C to 15°C). The waxy crude demonstrated shear thinning behaviour with increasing shear rates (increasing turbulence) and the viscosity reduced with increasing temperature. The addition of inhibitors (PEB, Nano ZnO and their blends) effected Newtonian fluid behaviour in the crude samples as the shear stress-shear rate relationship curves were linear at all temperatures under study. The optimum concentration of the inhibitors in this study is 2000ppm PEB (causing 33% viscosity reduction) and 1wt% Nano ZnO (effecting 26% viscosity reduction). The best concentration of the blend was 2000ppm PEB blended with 1wt% Nano ZnO which effected a viscosity reduction of 41%. The research demonstrates the novel application of the blend of Nano ZnO and PEB in improving flowability of Nigerian waxy crude oil especially in offshore conditions with prevailing cold temperatures.

CFD Modelling of Wake-Induced Vibration At Low Reynolds Number

Flow-induced vibration is an enthralling phenomenon in the field of engineering. Numerous studies have been conducted on converting flow kinetic energy to electrical energy using the fundamental. Wake-induced vibration is one of the configurations used to optimise the generation of electricity. The results of the study on the effect of the gap between the multiple bluff bodies will provide insight into optimising the energy harvesting process. This study focuses on fluid behaviour and response behind two circular cylinders arranged in tandem when interacting with a fluid flow at low Reynolds numbers ranging from 200 to 1000. The study has been done on several gap lengths between the two cylinders, between 2D and 5D. The study was carried out numerically by using OpenFOAM. At Re = 1000, it is found that the gap length of 2.5D is optimal in terms of producing the highest lift force coefficient on the downstream circular cylinder.

Structural and Rheological Properties of Nonedible Vegetable Oil-Based Resin

Jatropha oil-based polyol (JOL) was prepared from crude Jatropha oil via an epoxidation and hydroxylation reaction. During the isocyanation step, two different types of diisocyanates; 2,4-toluene diisocyanate (2,4-TDI) and isophorone diisocyanate (IPDI), were introduced to produce Jatropha oil-based polyurethane acrylates (JPUA). The products were named JPUA-TDI and JPUA-IPDI, respectively. The success of the stepwise reactions of the resins was confirmed using 1H nuclear magnetic resonance (NMR) spectroscopy to support the Fourier-transform infrared (FTIR) spectroscopy analysis that was reported in the previous study. For JPUA-TDI, the presence of a signal at 7.94 ppm evidenced the possible side reactions between urethane linkages with secondary amine that resulted in an aryl-urea group (Ar-NH-COO-). Meanwhile, the peak of 2.89 ppm was assigned to the α-position of methylene to the carbamate (-CH2NHCOO) group in the JPUA-IPDI. From the rheological study, JO and JPUA-IPDI in pure form were classified as Newtonian fluids, while JPUA-TDI showed non-Newtonian behaviour with pseudoplastic or shear thinning behaviour at room temperature. At elevated temperatures, the JO, JPUA-IPDI mixture and JPUA-TDI mixture exhibited reductions in viscosity and shear stress as the shear rate increased. The JO and JPUA-IPDI mixture maintained Newtonian fluid behaviour at all temperature ranges. Meanwhile, the JPUA-TDI mixture showed shear thickening at 25 °C and shear thinning at 40 °C, 60 °C and 80 °C. The master curve graph based on the shear rate for the JO, JPUA-TDI mixture and JPUA-IPDI mixture at 25 °C, 40 °C, 60 °C and 80 °C was developed as a fluid behaviour reference for future storage and processing conditions during the encapsulation process. The encapsulation process can be conducted to fabricate a self-healing coating based on a microcapsule triggered either by air or ultra-violet (UV) radiation.

CASSON FLUID OF A STAGNATION-POINT FLOW (SPF) TOWARDS A VERTICAL SHRINKING/STRETCHING SHEET

This study presents a convectively heated hydromagnetic Stagnation-Point Flow (SPF) of an electrically conducting Casson fluid towards a vertically stretching/shrinking sheet. The Casson fluid model is used to characterize the non-Newtonian fluid behaviour and using similarity variables, the governing partial differential equations are transformed into coupled nonlinear ordinary differential equations. The dimensionless nonlinear equations are solved numerically by Runge-Kutta Fehlberg integration scheme with shooting technique. The effects of the thermophysical parameters on velocity and temperature profiles are presented graphically and discussed quantitatively. The result shows that the flow field velocity decreases with increase in magnetic field parameter and Casson fluid parameter .

Evaluation of different methodologies for the design of the wellfield in shallow geothermal systems

Low enthalpy geothermal resources play an essential role in climate change mitigation. When ensuring the correct future operation of ground-source heat pump systems, an accurate design is mandatory. In this sense, different methodologies can be implemented. Although using sophisticated software constitutes the most optimal solution, its implementation is sometimes inviable in certain projects (the increase of the initial investment required is not justified in small plants). This work is focused on evaluating and comparing procedures used in the design of shallow geothermal systems. Thus, the research includes a simple method based on manual calculations, the Climasoft free application, Earth Energy Designer (EED) software, and the new geothermal tool GES-CAL developed by researchers from the TIDOP Research Group (University of Salamanca). The objective is to evaluate this new software and compare the results of all the detailed methodologies. This comparison derives from applying these tools in the calculation of the same case study (a single-family house placed in Ávila, Spain). Results show that the easiest methods involve oversized well-field schemas that also mean higher initial investments. Regarding GES-CAL, it is considered an accurate and valid alternative for the design of all heat exchanger configurations, especially for those installations placed in the region of Ávila. However, EED is recommended to calculate high-power geothermal systems that require an exhaustive analysis of the ground and the heat carrier fluid behaviour.

Magnetoviscosity of a Magnetic Fluid Based on Barium Hexaferrite Nanoplates

This paper presents the results of an experimental study of the influence of an external magnetic field on the shear flow behaviour of a magnetic fluid based on barium hexaferrite nanoplates. With the use of rheometry, the magnetoviscosity and field-dependent yield-stress in the fluid are evaluated. The observed fluid behaviour is compared to that of ferrofluids with magnetic nanoparticles having high dipole interaction. The results obtained supplement the so-far poorly studied topic of the influence of magnetic nanoparticles’ shape on magnetoviscous effects. It is concluded that the parameter determining the observed magnetoviscous effects in the fluid under study is the ratio V2/l3, where V is the volume of the nanoparticle and l is the size of the nanoparticle in the direction corresponding to its orientation in the externally applied magnetic field.