Iron ore pellets are a highly refined product supplied to the steel making industry for use in blast furnaces or direct reduction processes. The use of pellets offers many advantages such as customer adopted products, transportability and mechanical strength yet the production is time and energy consuming. Being such, there is a natural driving force to enhance the pelletization in order to optimize production and improve quality. The aim with this thesis is to develop numerical models with which the drying zone of an induration furnace can be examined and optimized. To start with, a continuous model of velocity and temperature distribution in the up-draught drying zone, without regard to moisture transport, is developed with aid of Computational Fluid Dynamics (CFD). The results show a rapid cooling of air due to the high specific surface area in the porous material. With the global model an overall understanding of heat transfer is gained, but the heat and moisture transport should also be investigated on a smaller scale in order to account for small scale phenomena such as turbulence and dispersion. Drying of a bed of iron ore pellets is therefore considered by modeling a two-dimensional discrete system of round pellets. The system is divided by modified Voronoi diagrams and the convective heat transfer of hot fluid flow through the system including dispersion due to random configuration of the pellets is modeled. The results show that the temperature front advances much faster in the gaps between pellets than in the interior of the pellets even if all the heat energy of the air goes in heating of the pellets initially. Decrease of temperature is possible for low dew points of the input air due to evaporation. If the dew point temperature is higher than the temperature of the pellets on the other hand, there is slight condensation of the steam at the beginning of the process and the temperature increases faster than it would for pure thermal heating. An uneven distribution in temperature and moisture content between pellets is furthermore displayed in the discrete system. This phenomenon is related to the natural dispersion occurring in random system of pellets.To further investigate drying of individual pellets, forced convective heating of a cylindrical porous pellet with surrounding flow field taken into account is first examined. A model with properties similar to that of an iron ore pellet is numerically investigated and with interface heat transfer condition provided by CFD, the simulations show an increased heating rate for the porous cylinder when compared to a solid. The most plausible explanation to this is that there is less solid to heat up for the porous medium since the porous cylinder behaves as if it was impermeable from a fluid flow point of view. With diffusive liquid transport inside the two-dimensional pellet and corresponding evaporation at the surface, simulations of drying show an initial warm up phase with a succeeding constant rate drying phase. Constant drying rate will only be achieved if the surface temperature is constant, i.e. if it has reached the wet bulb temperature. The falling rate period will subsequently start at the forward stagnation point when the local moisture content approaches zero, while other parts of the surface still provide enough moisture to allow surface evaporation. The phases will thus coexist for a period of time. Experiments are carried out in order to examine the drying behavior of a single iron ore pellet with main goal to retrieve data for validation of the computational drying models. The experiments are performed with two inlet temperatures and one pellet from the experiments is scanned by an optical scanning equipment. In order to investigate the influence of surface irregularities and overall geometry on drying, simulations of the first drying period are compared for: 1) a scanned pellet 2) an oval pellet resembling the experimental one with equivalent volume 3) a spherical pellet with equivalent volume. The results show that the local moisture content at the surface is influenced by both surface irregularities and overall geometry. A smooth surface will decrease the local variation of moisture while a spherical geometry will, compared to an oval, increase the difference. A diffusive model taking into account capillary flow of liquid moisture and internal evaporation is developed to account for the whole drying process and simulations of the scanned pellet are validated with good agreement. The result clearly shows four stages of drying; i) evaporation of liquid moisture at the pellet surface, ii) surface evaporation coexisting with internal drying as the surface is locally dry, iii) internal evaporation with completely dry surface and iv) internal evaporation at boiling temperatures. A moisture front moving towards the core of the pellet will start to develop at the second drying stage and the results show that the front will have a non-symmetrical form arising from the surrounding fluid flow. With the developed drying model, simulations are then carried out on a spherical pellet with aim to investigate how the inlet air humidity affects drying. The results indicates that the effect of air dew point arise from the start of the first drying period, i.e the surface evaporation period, while the difference is reduced at the end of the period due to a prolonged stage of constant rate drying attained at high dew points. The wet-bulb temperature is increased with humidity and condensation will occur if the pellet surface temperature is below the dew point. Furthermore it is found that the moisture gradients at the surface and inside the pellet are increased with drying rate. / Godkänd; 2010; 20101103 (annlju); DISPUTATION Ämnesområde: Strömningslära/Fluid Mechanics Opponent: Professor Graham Nathan, The University of Adelaide, Australia Ordförande: Professor Staffan Lundström, Luleå tekniska universitet Tid: Onsdag den 8 december 2010, kl 09.00 Plats: F431, Luleå tekniska universitet

Iron ore pellets are a highly refined product and for companies such as LKAB it is important to constantly improve the pelletization in order to enhance production and improve product quality. A long term goal has been established to develop and considerably refine tools and techniques with which the drying zone of a pelletizing plant can be optimized. The aim with this research project is to numerically investigate how material and processing parameters influence the drying. This will be applied to several scales: i) The constituents of the pellets and their properties and geometry. ii) The geometry of the pellet, their permeability and size distribution. iii) The geometry of the bed and the processing conditions including the state of the air (ex. humidity, temperature and velocity). To start with, a pellet bed model of velocity and temperature distribution in the up-draught drying zone without regard to moisture transport is developed with aid of Computational Fluid Dynamics (CFD). Results from simulations show a rapid cooling of air due to the high specific surface area in the porous material. Following this work, heat and mass transport within a single pellet during drying is modeled. Heat transfer and convective transport of water and air through the capillaries of the porous media is computed and vaporization by boiling is taken into account. A sensitivity analysis shows that it is important to use a realistic value of the convective heat transfer coefficient when the vaporization of water is a dominating drying mechanism while the temperature of the solid and capillary movement of water is not influenced to the same extent. The derived model is applicable to a number of numerical set up such as a single pellet placed in infinite space. To further develop a single pellet model, forced convective heating of a porous media with surrounding flow field taken into account must first be examined. Therefore, a two dimensional model with properties similar to that of an iron ore pellet is numerically investigated. With interface heat transfer condition provided by CFD, the heat transfer and fluid flow around and within a porous cylinder is examined. The results lay foundation of future development of a single pellet drying model where heat and mass transfer models are combined and coupled to the surrounding flow field. / Godkänd; 2008; 20080428 (ysko)

Black liquor (BL), a by-product of the chemical pulping process, is an important liquid fuel in the pulp and paper industry. It contains almost all of the inorganic cooking chemicals along with the lignin and other organic matter separated from the wood during pulping in the digester. To recover the organic combustion heat and cooking chemicals (sodium and sulphur) from the produced black liquor in kraft pulping, Tomlinson kraft recovery boilers are traditionally used. However, the kraft recovery boiler is not thermodynamically efficient and suffers from problems with explosion phenomena, fouling, and emissions. A potential technology for improving the recovery cycle is pressurised gasification of black liquor. However, uncertainties about the reliability and robustness of the technology are preventing a large-scale market introduction. One important step towards a greater trust in the process reliability is the development of simulation tools that can provide a better understanding of the process and improve performance through optimisation. This licentiate thesis is concerned with the modelling and simulation of an entrained flow gasifier for pressurised gasification of black liquor at high temperature. The thesis comprises three papers presenting the simulation results obtained from different models using CFD (Computational Fluid Dynamics). In paper A a simplified gasification model, considering just the gas phase, is used to make a qualitative study of the effect of burner spray angle on the gas flow in the gasifier. In paper B the simulation results from a more advanced model with gas/droplet interaction, are compared to the results presented in paper A. Finally, in paper C a complex model for pressurised gasification of black liquor droplets is presented and used to study the influence of uncertainties in model parameters. / Godkänd; 2003; 20070122 (ysko)

This project aims to design and develop hydro jet which is integrated to Electric motor, whichis limited to run at 70% PWM. Which limits the efficiency of the system, to make an efficientsystem, hydro jet parameters are not defined which are desired to be defined by design fourimpellors for basic Radinn G2x Jet Pack design. The impellors will be four expected points inHydro Jet and final impellor is assumed to lie between these design points, to find the finalspecifications of the hydro jet, the hydro jet will be designed, using computational fluiddynamics they will be analysed. After analysis, they will be manufactured and tested in poolfacility where MGM controller will be used to measure the numerical data from electric circuitwhich powers the system to analyse the performance parameters to finalize the validity of 100% PWM. Microsoft Excel is used to calculate the Hydro Jet Geometric parameters, which areused in Solid Works, where parametric modelling is used to design impellors based ongeometric parameters calculated in Excel. Using Computational fluid dynamics hydro jetperformance is simulated and analysed. To validate the design further, prototypes aremanufactured and tested using workshop pool testing facility using MGM software. As a result,four hydro jet points are calculated, analysed and tested, four pumps are designed for specificflow rate, velocity and torque is calculated for four hydro jets. They are calculated and verifiedusing computational fluid dynamics, as a result flow rate, velocity and torques are calculatedfor all four hydro jets. Four impellors are manufactured and then tested in Radinn work shopand as a result current, power and rpm of the hydro jets are measured using MGM software.From power, rpm and current the torque can be calculated, while rpm is compared againstpredicted computational fluid dynamics results. The results from this project is limited toRadinn G2x jet pack, motor and other parts of the hydro jet’s Jet pack are standard parts

This Licentiate is about Whole Body Vibrations and focuses on transient vibrations with human's discomfort and motion assessment. Whole Body Vibrations occurs when a body is in contact with a vibrating surface. Whole Body Vibrations is a major problem in terrain vehicle, which affects both the physiological and psychological health and discomfort. The first study, Paper A, focus on the prediction of vibration discomfort based on r.m.s.-values in z-direction of seat. In the case of individual results, the correlation coefficient was 0.54. Based on averages for each test condition, the correlation coefficient was 0.93. Study in Paper B focus on the prediction of vibration discomfort and perceived motions. By analysis of vibration values in one-third octave bands of x-direction in the top of the seat backrest, pitch motion and vertical motions in seat, pitch alone with variable length was found to give best correlation with the vector sum of perceived motions (r=0.677). Surprisingly, one-third-octave band higher than 50Hz give a high contribution to the prediction of perceived motions. One of the background variables, "Length of driver", was found to have a statistically significant effect on perceived motions. Tall driver perceived less motion than short drivers. In Paper C, focus on evaluating the effect of two seat design (sliding and fixed) in minimizing the discomfort from transient vibrations. Results showed that sliding seat is superior in attenuating vibration that contains transient vibration in horizontal direction. Sliding seat was perceived to give less overall and low back discomfort compared to fixed seat. / Godkänd; 2002; 20070224 (ysko)

Godkänd; 1998; 20070404 (ysko)

The goal of the Turbine 99 Draft Tube experiments is to provide extensive experimental data on a well-defined sharp-heel draft-tube flow. The data bank has served as calibration data for the simulation challenge presented by the Turbine 99 workshop in Porjus in June 1999. This thesis gives some background on draft-tube flows in general and discusses in some detail the parameters and flow conditions relevant to the Turbine 99 draft tube. Some comments on the research and development conducted so far in the project and future plans are given at the end. In the three accompanying papers, details of the developments and the scientific results are presented: Paper 1. Presents the scope of the work and some initial results from the measurements Paper 2. Discusses the quality of the measurements Paper 3. Presents some of the results from the measurements / Godkänd; 2000; 20070318 (ysko)

Impact sound insulation is one of the most important aspects when assessing sound insulation of floor constructions in buildings. For assessing the impact sound insulation of aconstruction, a standard tapping machine is used as a sound source. However, the use of the current standard tapping machine has been criticised, especially with regard to measurement of wooden joist floors since the noise spectrum generated by a tapping machine differs from the spectrum generated by actual footfall. There are insufficient low frequency components in the noise spectrum produced by the tapping machine and it does not, therefore, accurately reflect low frequency noise from the construction.Reduce impact sound level from wooden joist floors are the main object of our study. It is important to be able to predict the sound insulation properties of wooden joist constructions at the design stage. To reduce the noise level in the receiving room, the input power transmitted through the construction must be estimated where the appropriate sound- and vibration-insulation can be designed.This study has investigated the waveform and frequency spectra of human footfall (walking, rum- ingand jumping); of the dropping of sand balls, sand bags and tires; and of the standard tapping machine. The impact sound power radiation from a wooden joist construction while applying different impact sources, such as actual footfall and the standard tapping machine, have also been studied.Research was also carried out regarding the development of a practical impact sound insulation calculation method for wooden joist floor constructions. The characteristics with regard to mechanical properties of floor construction was calculated using the impedance method. The impact sound level inside the sound receiving room was determined. The method developed can predict the basic performance of the wooden floor structure when excited by impact sounds. / Godkänd; 1995; 20070108 (biem)

Godkänd; 1996; 20080328 (ysko)

The technology for solar cars participating in the Bridgestone World Solar Challenge is constantly evolving. Teams from other universities are implementing innovative solutions in order to be a top contender in the event. JU Solar Team, the representatives for Jönköping University, are looking into applying wheel enclosures inside the body of the solar car, to improve the aerodynamics even further. Thus, the study will investigate how to integrate this component by using methods of design, fluid simulations and concept generation. In this case we are evaluating the effects of using enclosed wheels with the model from the 2019 solar car by JU Solar Team. The purpose of this is to generate empirical value for upcoming generations that will compete in the challenge. The study is built around the 2019 solar car with its dimensions and modules, this include; the wheel suspension, the car body, steering angle, wheel and rim. Simulations are performed with and without enclosed wheels, and stationary wheels and rotating wheels. Wheel rotation and fluid speed are inherited from the driving speed of 72 km/h. Models were simplified during simulations to save computational time.  The results show that wheel enclosures improve the aerodynamics of a solar car. With this simulation configuration and the fourth developed concept, an improvement of 8.22% was achieved.  The study is limited to models being simplified and basic simulations. The research found facilitates possible further investigation for wheel enclosures: manufacturing method, materials and strength evaluation.