ABSTRACT. The industry is currently seeing a rapid development of cyber-physical system products containing integrated software, hardware, and communication components. The increasing system complexity in the automotive and aerospace industries are some examples. The systems that are developed have increasing demands of dependability and usability. Moreover,  lead time and cost efficiency continue to be essential for industry competitiveness. Extensive use of modeling and simulation - Model-Based Systems Engineering  tools - throughout the value chain and system life-cycle is one of the most important ways to effectively target these challenges. Simultaneously there is an increased interest in open source tools that allow more control of tool features and support, and increased cooperation and shared access to knowledge and innovations between organizations.

Modelica is a modern, strongly typed, declarative, equation-based, and object-oriented (EOO) language for model-based systems engineering including modeling and simulation of complex cyber-physical systems  Major features are: ease of use, visual design of models with combination of lego-like predefined model building blocks, ability to define model libraries with reusable components, support for modeling and simulation of complex applications involving parts from several application domains, and many more useful facilities. This talk gives an overview of some aspects of the Modelica language  and the OpenModelica environment including the ModelicaML UML/Modelica profile for systems engineering – the most complete Modelica open-source tool for modeling, engineering, simulation, and development of systems applications (www.openmodelica.org).

Special features are MetaModeling for efficient model transformations, debugging support for equation-based models,  the ModelicaML profile for UML-Modelica cyber-physical hardware-software modeling,  the Functional Mockup Interface for general tool integration  and model export/import between tools, model-based optimization, as well as generation of parallel code for multi-core architectures.

ABSTRACT. Continuously increasing price of oil and gas, energy crisis and increased environmental consciousness towards the greenhouse gas emission have opened a new opportunity to the biomass, the oldest source of energy known to mankind. The energy source neutral to CO2 needs to be utilized efficiently. One of the options to do so is gasification of biomass for transport biofuel production. In this work, the emphasis is on the composition of syngas production which can be further processed for conversion of biomass to transport biofuels. Biomasses such as wood chips are heated in a gasification reactor to produce a mixture of gases, mainly CO and H2. Process flow sheets for steam gasification of woody biomass have been simulated in the process simulation program ASPEN PLUS to study the process and to optimize the process parameters, materials, catalysts and reaction condition for syngas production.The Peng-Robinson equation of state with Boston-Mathias is selected for the considered model. The model describes the hydrodynamic parameter and reaction kinetics modeling. The required kinetic expressions and hydrodynamic equations are extracted from the literature. Gasification temperature, biomass moisture, steam to biomass ratio (STBR), air-fuel ratio, air and steam temperature are the most important operating parameters that is considered and studied to examine the gasifier performance. The impact of these process parameters on gasification is determined by sensitivity woody analysis. The results regarding composition of the syngas and the heating value for the considered biomass is compared with experimental data from the literature. The suggested model can be used as the guideline for more complex gasifier design and selection of the process equipment.

ABSTRACT. Temperature effects on kinetic coefficients for the biochemical processes particle disintegration, hydrolysis and substrate uptake reactions were included in the anaerobic digestion model 1 (ADM1). It was evaluated on data from a pilot experiments in a 220 liter AD sludge bed reactor treating diary manure for 4 months of varying loads and temperatures; 25, 30 and 35 °C. Implementing individual temperature effects for each biochemical reaction gave the best fit for both biogas production and intermediate products. Simulated overall soluble and particulate organic carbon removal, pH and acetate are close to measured values while propionate is underestimated. Temperature has a moderate influence on steady state biogas production in sludge bed AD (1.6 % per degree at 30 – 35 °C and 3.4 % per degree at 25 – 30 °C), implying the net energy gain can peak at T < 35 °C in some cases.

ABSTRACT. Gasification is a flexible technology where all types of organic waste including biomass from manure can be used as feed to the reactor. The recovery of energy from solid waste offers several benefits including substantial reduction in the total quantity of waste and reduction in environmental pollution. In the gasification process carbonaceous feedstock is fluidized with steam, air or oxygen to at temperature about 800-900°C. The most suitable application of the product gas from the reactor is dependent on the quality and composition of the gas. The producer gas can be used in gas engines or turbines to produce electricity or it can be used in production of liquid fuel for transport. In this study, livestock manure is analyzed regarding moisture and ash content and heating values. Bomb Calorimeter is used to measure heating values, moister dryer to measure the water content and muffle furnace for determination of ash content. Different types of manure have been tested and a few are considered as possible feedstock to a gasification reactor. Gasification of manure is simulated using the data obtained from the analysis. The simulations are performed using the process simulation software Aspen Plus. Reaction equations and kinetics found in literature are included in the Aspen Plus simulations. The focus has been to study the heating values and fractions of the different components in the product gas. The results are discussed and different modifications of the process parameters in the simulations are considered.

ABSTRACT. Personal care products (PCPs) such as soaps, perfumes, toothpastes, lotions, etc. contain various chemicals. Triclosan (TCS) is widely used as an antibacterial additive in PCPs. Traces of TCS are found in human plasma and milk indicating absorption through the skin and/or after oral ingestion.

In this paper, a Physiologically Based Pharmacokinetic or Toxicokinetic (PBPK/TK) model is developed to assess the behavior of TCS in human body after exposure to PCPs orally or through the skin. The model will describe metabolism, kinetics and distribution in human organs.

The developed model is based on available literature data on biotransformation in rodents and humans, and is simulated using MATLAB and/or Modelica. The intention of the work is to further develop the model and fit model parameters to experimental data, and to develop a PBPK model useful for human risk assessment of TCS.

ABSTRACT. Heavy oil reservoirs cover up two third of the world’s hydrocarbon reservoirs. Even though it is vast energy resource, heavy oil recovery is not considered economical due to its high viscous properties. Generally horizontal wells are more suitable for heavy oil recovery. When the heavy oil is produced with water drive, a water breakthrough is expected in the higher permeable zones of the reservoir or in the heel of the well. Once water has reached the well, heavy oil reservoirs tend to produce more water than oil. In order to overcome this issue, inflow control devices are being used. Conventional inflow control devices (ICDs) are only capable in in delaying a water breakthrough. The disadvantage of ICDs is that, it cannot control the water inflow, once the water breakthrough has occurred. Autonomous inflow control valve (AICV) is designed to choke or stop the inflow as soon as the water breakthrough takes place. In order to evaluate the performance of AICVs for different reservoir conditions, OLGA-Rocx simulations were carried out. Simulations with fractured, heterogeneous and homogeneous reservoirs were performed. By comparing the obtained results with conventional ICDs it was found that the AICVs have a superior potential in limiting the water inflow to the base pipe (86% reduction in water accumulation compared to normal ICDs in fractured reservoirs). It was also observed that, AICVs are more effective in heterogeneous and fractured reservoirs as it can restrict the early water breakthrough. Even in homogeneous reservoirs, AICVs have the capability in controlling the water inflow. As a result, oil production rate would also be reduced compared to the ICD system, however, the lifetime of the well will be increased by using AICV.

ABSTRACT. At Telemark University College, Faculty of Technology, on-going work deals with energy efficiency of heating residential buildings. The work ranges from modeling to control of such buildings. Of particular interest in this study is the possibility to “harvest” solar energy via a solar collector, and use this energy to heat the building. Such heating must be combined with auxiliary heating, e.g. electric heating. Lie et al. (2014) discuss basic models for the complete system, with model parameters and operating conditions.

For control, the following question is of interest: if it is possible to predict solar irradiation, can this be used to improve the efficiency of energy use in the building? In other words: if we know that tomorrow will by sunny, can we then reduce electric heating during the night based on the knowledge that tomorrow’s sun will re-heat the stored water? Or vice versa: if we know that tomorrow will be cloudy, can we use this fact to heat the stored water in the night when the electricity is cheap? This problem is studied in Beyer et al. (2014).

In the discussion of Lie et al. (2014), the model is too simplistic and needs some refinement. The following improvements are needed, in order of importance:

1. Heat integration during ventilation should be included. Currently, the major heat loss is via ventilation. 2. The water storage model should be improved to include the effect of stratification in the tank (the tank is not well mixed) – either by some plug flow model or by dividing the storage tank into 2-3 compartments. 3. The Under Floor Heating (UFH) model is too simple. 4. Heat transfer should be computed from correlation models instead of using fixed numbers. 5. The solar collector model can be improved.

In this first improvement of the model, the two first points will be addressed. Thus, the model will be modified to include heat integration. Next, an improved water storage model will be developed to better capture the observed fact that hot water in water storage tanks have a temperature typically at 90C. The resulting improved model will be compared to the model of Lie et al. (2014).

References

Lie, B., Pfeiffer, C., Skeie, N.-O., Beyer, H.-G. (2014). “Models for Solar Heating of Buildings”. Proceedings, 55th International Conference of Scandinavian Simulation Society (SIMS 2014), October 21-22 2014, Aalborg University, Denmark. Beyer, H.-G., Lie, B., Pfeiffer, C., Arachchige, D.D. (2014). “Using history based probabilistic irradiance forecasts for supporting the predictive control of solar thermal systems”. Proceedings, EuroSun 2014, September 16– 9, Aix-les-Bains, France.

ABSTRACT. A major challenge in oil industry is the declining oil production and the relatively low recovery rate. Estimates show that although the oil is localized and mobile, more than half of the oil is remaining in the reservoir after shut down. There are therefore strong incentives for using CO2 injection for Enhanced Oil Recovery (EOR) for mature oil reservoirs with significant volume of residual oil. Injection of CO2 to reservoirs can also solve the demand for CO2 storage and contribute to reduce the emission of greenhouse gases. In general CO2 is injected to the reservoir as a supercritical fluid which has mobility similar to a gas but density similar to a liquid. Therefore supercritical CO2 behaves as an effective solvent for many oils. Miscible CO2 flooding can be performed for oil having lower viscosities which is capable of increasing the oil mobility. Generally CO2 is not miscible with crude oil on first contact. But at sufficiently high pressures and temperatures, it achieves miscibility with oil. The minimum pressure at which CO2 and oil are completely mixed with each other at any proportion is called as the minimum miscibility pressure (MMP). When reservoir oil contacts the injected CO2, the oil begins to dissolve into the dense CO2 phase and the dense CO2 begins to dissolve into the oil phase. Eventually the oil and the injected CO2 become a single phase due to repeated contacts with time. Dissolving CO2 in oil leads to interfacial tension reduction and promotes more oil recovery. CO2 also causes oil swelling and due to that trapped oil droplets move out of the rock pores and move towards the production wells. Oil viscosity reduction is another advantage of CO2 flooding and the amount of reduction is more significant in high viscous oils. Due to the acid effect on the rock formation as a result of CO2 flooding, reservoir properties such as porosity and permeability can be altered. In this work near well simulations have been performed using the software Rocx in combination with OLGA. The relative permeability is essential in simulations of oil reservoirs. When CO2 is injected to the reservoir, the relative permeability and the residual oil saturation change. The relative permeability is given as input to Rocx. A better understanding of reservoir conditions when CO2 is injected to the reservoir is needed. Near well simulations have been performed with CO2 injection and without CO2 injection to study the increase in oil recovery. Different permeability curves and residual oil saturations have been included for the two cases, and the results show clearly that additional oil can be produced by performing CO2-EOR.

ABSTRACT. Bitumen is used as anticorrosion to protect steel armor wires in subsea cables and umbilicals. Bitumen's viscoelastic behavior influences the mechanical properties of the cables, in particular the bending stiffness. UFLEX2D is a software tool for mechanical analyses of cables and similar structures, which can include the viscoelastic effect of bitumen using a Kelvin-Voigt model. This paper evaluates how well the Kelvin-Voigt model is able to resemble bitumen's viscoelastic properties. It is concluded that the Kelvin-Voigt model's lack of temperature dependence can be managed, while the model's handling of strain amplitude is too simple to fully explain bitumen's behavior. It is also concluded that the Kelvin-Voigt model has limited abilities to resemble the frequency response of bitumen.

ABSTRACT. The properties of the flow from fire water nozzles, like droplet size and velocity distribution within the spray, are known to influence the fire suppression efficiency. To analyze the flow properties, the water spray is recorded with the use of a high-speed camera and laser light. Typically, each image of the water spray may contain tens of droplets, yielding a huge number of possible droplets paths between adjacent frames, i.e. with n droplets in two subsequent frames generates n^2 possible droplets paths with n! possible configurations using brute-force approach. In this paper, we propose an optimization method based on the Hungarian algorithm to calculate the droplet paths. Using this framework, each droplet path is optimized with respect to droplet position, droplet size and droplet velocity.

ABSTRACT. The depletion of oil production and the low recovery rate are the major challenges faced in oil production. Several studies have shown that considerable amount of oil still remains in the reservoir after the well shutdown. Heavy oil reservoirs occupy more than two third of globally oil reserves. The recovery factor and the lifetime of a well in heavy oil reservoirs is strongly affected by reservoir properties as permeability and porosity, residual oil saturation and the time of water breakthrough. Different enhanced oil recovery (EOR) methods are used to change the relative permeability and the residual oil saturation. In this study, modelling and simulations are carried out to observe the influence of the relative permeability on oil recovery. The relative permeability in a reservoir changes with time due to the change in water saturation during oil production. Simulations are performed on reservoirs with an underlying aquifer using different relative permeability curves and various residual oil saturations. The study has mainly focused on the impact on the total flow rates, the water breakthrough time and the oil recovery. The reservoir simulator, Rocx in combination with OLGA is used in this research work. The results show that the total oil production and the time of water breakthrough are strongly affected by the relative permeability. These outcomes can be utilized when considering EOR methods to increase the oil recovery factor and delaying water breakthrough in future.

ABSTRACT. Deep geologic injections and storage of Carbon dioxide (CO2) for enhanced oil recovery (EOR) are an upcoming combination due to the potential for increased oil production from depleted oilfields at the same time reducing the carbon footprint from industrial sources. CO2-EOR refers to a technique for injection of supercritical-dense CO2 into an oil reservoir. Remaining oil, not producible by primary and secondary techniques, has been successfully produced using EOR with CO2 since early 1970’s. CO2 mixes with oil and changes the oil properties making the immobile oil mobile and producible. Coupled CO2-EOR and storage is an attractive storage option because of its potential to increase the oil production from mature oilfields. The reservoir physical properties (porosity, permeability) together with fluid properties significantly affect the CO2 storage and CO2-EOR performance. This study focus on CO2 storage and CO2-EOR in carbonate reservoirs including simulations of CO2-distribution in the rock. Carbonate reservoirs are characterized by low permeability and high heterogeneity causing significant amount of CO2 to be recycled. The simulations are carried out using a commercial reservoir simulation software. Criteria for the performed simulations are a highly heterogeneous carbonate reservoir with fractures. The results are discussed.

ABSTRACT. Elements of subsea cables and umbilicals can be classified as helical and non-helical. These two element types behave very differently at cable bending. This paper focuses on helical cable elements during cable bending. The arc length of helical elements at cable bending is derived, which leads to an integral that can not be solved analytically. When establishing strains and stresses of helical elements, it is essential that this integral is calculated with very high accuracy. An integration error of 0.01% is unacceptable in many applications. Maclaurin series expansion is used to convert this integral into an integral that can be solved analytically. It is proved that arbitrary integration accuracy can be achieved by increasing the order of the Maclaurin polynomial. Expressions for upper and lower boundaries of the integration error are also provided. The main advantage of the integration approach derived in this paper is that it provides an analytical expression for the integral, which can be used in mechanical analyses of cables and umbilicals.

ABSTRACT. In hydraulic engineering, transcritical flows are often required in some applications. One example is in a Venturi channel where the occurrence of critical depth is used to estimate flow rate in the channel. In this paper, a simple numerical scheme that predicts transcritical flows in hydraulic structures is developed based on the Saint Venant Equations (SVE). The solution of this scheme is aimed to be used in real time to calibrate the model that uses a measured liquid level to estimate flow rate of the fluid in a Venturi channel. The proposed algorithm consists of a set of ordinary differential equations derived from discretizing SVE in space along the channel axis. The results based on this scheme show that the algorithm is capable of predicting flows involving transcritical conditions. Errors associated with the scheme are relatively small in locating shocks in flows with imposed downstream boundary level, and in predicting the transition within the throat of Venturi channels.

ABSTRACT. Problem of optimal train control with the aim of minimizing energy consumption is one of the old optimal control problems. During last decades different solutions have been suggested based on different optimization techniques, each including a certain number of constraints or different train configurations, one being the control on the tractive effort available from traction motor. The problem is previously solved using dynamic programming for trains with continuous tractive effort, in which velocity was assumed to be the control variable. The paper at hand presents a solution based on dynamic programming for solving the problem for trains with discrete tractive effort. In this approach, tractive effort is assumed to be the control variable. Moreover a short comparison is made between two approaches regarding accuracy and ease of application in a driver advisory system.

ABSTRACT. In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM). For the purposes here, only gas flowing over the fin side is simulated assuming constant inner tube wall temperature. The study couples conjugate heat transfer mechanism with turbulent flow in order to describe the temperature and velocity profile. In addition, performance characteristics of the heat exchanger design in terms of heat transfer and pressure loss are determined by parameters such as overall heat transfer coefficient, Colburn j-factor, flow resistance factor, and efficiency index. The model provides useful insights necessary for optimization of heat exchanger design.

ABSTRACT. A numerical study is carried out to investigate heat transfer and friction argumentation in spirally corrugated tubes. 28 geometrically different tubes are investigated to cover a large set of different corrugation characteristics. The pipes investigated have pitch lengths l/D in the range 0.5 to 2.0 and pitch heights h/D in the range 0 to 0.16. Furthermore, the flow conditions defined by the Reynolds number are investigated for Re = 5000 and Re = 10000, resulting in a total of 56 Computational Fluid Dynamics (CFD) simulations. The performance of the heat exchangers are evaluated based on the Nusselt number, friction factor, and performance evaluation criterion coefficient combining the two into a single unique dimensionless parameter. The results suggest corrugation to be an effective way to increase the performance of tube heat exchangers. If only heat transfer is considered without paying attention to pressure loss, the optimal tubes have high corrugation heights, where the Nusselt number can be increased by a factor of 2 compared to the non-corrugated tube. If the performance evaluation criterion is used, the optimal geometry has a moderate corrugation height h=D between 0.05 and 0.10 and a low corrugation length l/D around 1.0, which can be explained by a high increase in pressure loss due to severe corrugation.