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In many technical applications chemical reactions are used. One of these is a so called decolorization, in which an ion exchange resin is used to remove a dye from water. To apply this decolorization technique a Rotating Bed Reactor, or RBR for short, can be used. It is filled with the ion exchange resin and spun inside the water. Whilst spinning, the reactor percolates the water, letting it interact with the ion exchange resin and thus removing the dye. This project aims to use Computational Fluid Dynamics (CFD) as a tool to create a model for the decolorization process when a RBR is used. The goal is to achieve a reaction model for the process that can be applied to various RBR models, i.e. scaled, to aid for example product development and research. A decolorization process in which methylene blue is removed from deionized water using a SpinChem S2 RBR inside a V2 vessel, using a NRW 1160 ion exchange resin, is investigated. Experiments are conducted where the concentration of methylene blue in deionized water is measured during the decolorization process using a transmittance probe. From the experimental results a linear regression model is fitted to achieve a model for the reaction's rate constant, determining its reaction rate, depending on the fluid velocity inside the RBR and the temperature of the fluid. CFD is used to find the flow field for different rotational speeds of the RBR inside the vessel. Using the steady-state flow field species transport simulations are done using the created reaction model. This is done to compare numerical simulations to experimental results. The results show that the created reaction model can predict the time taken to absorb the methylene blue onto the ion exchange resin. Deviations from the exact decay rate of methylene blue concentration is seen, and are concluded to come from conversion of global reaction rate in the vessel to local reaction rate inside the RBR. The reaction model has not been tested explicitly on other types of RBR, thus nothing can be said about its performance. However, care has been taken to not include any RBR geometry dependent parameters in the model.

This thesis evaluates two variants of Volumeof fluid method, namely Piecewise Linear Interface Construction (PLIC) and Multidimensional Tangent of Hyperbola for Interface Capturing (MTHINC) used in two-fluid simulations for interface tracking.Simulations of a single rising bubble in different conditions are performed aimed to assess the accuracy of the methods, and to check their convergence with grid size. The results show that both methods demonstrate convergence with mesh refinement, while PLIC captures the transient part of rising process of bubble more accurately than MTHINC in 2D case. Denna avhandling utvärderar två varianter av metoden Volume of fluid för flerfas strömningar, nämligen Piecewise Linear Interface Construction (PLIC) och Multidimensional Tangent of Hyperbola for Interface Capturing (MTHINC) som används i tvåvätskesimuleringar för gränssnittsspårning.Simuleringar av en enda stigande bubbla under olika förhållanden utförs för att bedöma metodernas noggrannhet och för att kontrollera deras konvergens med gridsstorlek. Resultaten visar att båda metoderna visar konvergens med grid förfining, medan PLIC fångar den övergående delen av stigande bubbelprocess mer exakt än MTHINC i 2D-fall.

Throughout recent years, computer based programs has been applied to solve and analyze industrial problems. One of these developed programs is the Computational Fluid Dynamics (CFD) program. The purpose of implementing CFD analysis is to solve complex flow behavior which is not possible with ordinary calculus. The extensive application of CFD in the industry is a result of improved commercial CFD codes in terms of more advance partial differential equations (PDE) describing various physical phenomena, CAD and mesh-grid generating tools and improved graphical user interfaces (GUI). Today, CFD usage has extended to fields such as aerodynamic, chemical process engineering, biomedical engineering and drying technology. As there is an on-going expansion of CFD usages in the industry, certain issues need to be addressed as they are frequently encountered. The general demand for simulation of larger control volumes and more advanced flow processes result in extensive requirement of computer resources. Numerous complex flow topics today require computer cluster networks which are not accessible for every company. The second issue is the implementation of commercial CFD codes in minor industrial companies is utilized as a black box based on the knowledge on fluid mechanic theory. A vital part of the simulation process is the evaluation of data through visual analysis of flow patterns, analysis on the sensitivity of the mesh grid, investigation of quantitative parameters such as pressure loss, velocity, turbulence intensity etc. Moreover, increased partnerships between industry and the academic world involving various CFD based design processes generally yields to a verbal communication interface which is a crucial step in the process given the fact of the level of dependency between both sides. The aim of this thesis is to present methods of CFD analysis based on these issues. In paper I, a heuristically determined design process of the geometry near the front trap door of an internal duct system was achieved by implementing the CFD code COMSOL MultiPhysics as a communication tool. The design process was established by two counterparts in the project in which CFD calculations and geometry modifications were conducted separately. Two design criteria presenting the pressure drop in duct and the outflow uniformity was used to assess geometry modifications conducted by a CAD-engineer. The geometry modifications were based on visual results of the flow patterns. The geometry modifications confirmed an improvement in the geometry as the pressure drop was reduced with 23% and the uniformity was increased with 3%. In paper II, volume-averaged equations were implemented in a tube-fin heat exchanger in order to simulate airflow. Focus was on achieving a correct volume flow rate and pressure drop (V-p) correlation. The volume averaged model (VAM) is regarded as a porous medium in which the arrangement of fins and tube bundles are replaced with volume-averaged equations. Hence, the computational time was reduced significantly for the VAM model. Moreover, experimental results of the (V-p) correlation showed good agreement with the VAM model.

Today’s mobile machines most often contain hydraulic valve controlled drives in an open loop-circuit. For the purpose of saving energy the constant pressure pumps have, in the past, often been replaced by load-sensing pumps and load-sensing valves. In mobile applications these load-sensing solutions have significantly reduced the energy consumption. However, in applications with unequal drive pressure levels the load sensing systems still result in energy losses, referred to as metering losses. Throttling losses associated to load lowering have also been paid more attention to in the energy debates. By instead adopting direct pump displacement control, with the capability of energy recuperation in lowering motions, many of these losses can be avoided. In this article the author has studied a hydraulic system configuration where each actuator/supply system comprises an electrically controlled variable displacement pump/motor working in an open-circuit together with four separate electrically controlled valves. The four valves render a solution versatile in control, as the cylinder chambers can be connected to pump and/or tank as well as be closed at any time. Depending on how the valves are controlled different modes of operation are achieved, which in turn yields different total energy efficiency depending on the present working point. In this study the performance, operability and energy consumption is evaluated in a wheel loader that is first looked upon with its original load sensing hydraulic system and then modified with a completely new pump controlled hydraulic system. Measurements published in this article demonstrate the advantages and drawbacks of pump control in an open circuit compared to a load sensing system. Performance is evaluated by looking at productivity, loading capacity and duty cycle time of a typical loading cycle. Operability is evaluated by looking at response times, load oscillations and driver comfort. Theoretical calculations of energy efficiency including metering and throttling losses over the valves as well as pump efficiency, line losses and losses in the recuperation phase are evaluated and validated. The fuel consumption of the pump-controlled wheel loader is measured and put side by side to measurements of the same machine equipped with a load-sensing hydraulic system.

This is a Master Thesis done at the Swedish Defence Research Agency with the purpose to design and investigate how different geometries of a compression surface integrated with an intake affects the performance such as distortion, boundary layer diversion, pressure recovery and deceleration of speed. The work was divided in two parts. In the first part, CFD calculations using the FOI developed Edge 4.1 code were made for the compression surfaces alone. In the second part the most promising design was integrated with an intake. Two more bumps with the intake were modelled and the three geometries were compared to the intake without bump. Surface flow, deceleration of Mach number, pressure recovery, mass flow, boundary layer diversion, lift and drag were the factors chosen to be examined, boundary layer diversion and pressure recovery being the two most vital.

Today´s mobile machines most often contain hydraulic valve controlled drives in an open loop circuit. For the purpose of saving energy, the constant pressure pumps have in the past frequently been replaced by load-sensing pumps and load-sensing valves. However, considering applications where the load is helped by the gravitational force, even these hydraulic systems often suffer from poor efficiency. In this article, a novel pump-controlled hydraulic system is studied where energy recuperation from lowering motions is posssible. The pumps are fully displaceable in both directions, working as motors when lowering loads. The amount of recuperated energy is highly dependent of the chosen control strategy, the hydromechanical properties as well as the target application. Furthermore, the article describes how valve design becomes an important feature in an attempt to reach high efficiency and machine operability.