Gearboxes are always subject of study in order to increase their efficiency. Energy losses in gear contacts are transformed into heat which is distributed among the gearbox components increasing their temperature. A thermal model of the gearbox brings the opportunity of a deeper understanding of the heat dissipated related to the power losses in the gear contact. A MATLAB program based on ordinary differential equations was developed in order to make a thermal model of an FZG test gearbox. The model is based on a thermal network where each node represents a machine element. The thermal network is composed by thermal resistances due to deformation in the gear contact, conduction, convection and radiation. With thermal resistances, power losses and thermal inertia of each element, the temperature evolution was obtained by applying the First Principle of Thermodynamics. Due to the temperature evolution, heat transfer between different elements was estimated. Additionally, experimental results from an FZG test rig were implemented in the model and also used to verify its accuracy. Furthermore, additional features to the model such as a cooling system and spray lubrication were also studied. Results show a wide capability and handling of the program in terms of thermal analysis: heat flux direction and magnitude, visual tools such as thermal network of the test gearbox, as well as the analysis of different operating conditions. With these tools, an approach to the minimum amount of lubricant necessary and other ways to quench overheating could then be reached. Keywords: Thermal network, FZG gear test rig, heat flow, temperature, MATLAB, ODE. / Växellådor är ständigt ett forskningsområde för att förbättra deras verkningsgrad. Energiförluster i kuggkontakter omvandlas till värme som sprids i växellådan som sedan värmer upp komponenterna. En termisk modell av växellådan gör det möjligt för djupare förståelse hur värmen sprids i förhållande till energiförlusterna i kuggkontakten. Ett MATLAB-program baserat på ordinära differential-ekvationer utvecklades för att göra en termisk modell av en växellåda i en kuggrigg från FZG. Modellen är baserad på ett termiskt nätverk där varje nod representerar en maskinkomponent. Det termiska nätverket består av resistanser som uppstår på grund av deformation i kuggkontakten, ledning, konvektion och strålning. Med termiska resistanser, energiförluster, termisk tröghet från komponenterna och genom att applicera termodynamikens första grundsats kunde temperatur-genereringen bestämmas. Från temperatur-genereringen kunde värme-ledningen mellan komponenter uppskattas. Testresultat från en FZG-kuggrigg användes för att verifiera modellens noggrannhet. Andra egenskaper till modellen, som ett annat kylsystem och spraysmörjning studerades för att undersöka möjligheteten att adderas till modellen. Resultat visar på en bred användning av modellen i avseende på termisk analys: värmeflödets storlek och riktning, ett visuellt redskap för växellådans temperatur och hur växellådans temperatur varierar under olika driftförhållanden. Med de här redskapen kan den minsta oljemängden som behövs för att smörja kuggkontakten undersökas och hur kylning av kugghjulen kan förbättras. Nyckelord: Termiskt nätverk, FZG kugghjuls-rigg, värmeflöde, temperatur, MATLAB, ODE

Phase change of the water in the soil skeleton under cold climate conditions (also known as frost action in soils) affects soil properties and can be responsible for serious alterations in a soil body; causing damages (due to the volumetric expansion known as frost heave) to structures on or below the ground surface such as foundations, roads, railways, retaining walls and pipelines, etc. In order to improve the current design methods for roads against frost action, the Swedish Transport Administration (Trafikverket) has initiated a research program. The main goals of the program are to revise the existing frost heave estimation methods and improve the frost susceptibility classification system for subgrade soils. Literature was reviewed to gather the details of different freezing test equipment around the world and to identify common trends and practices for laboratory freezing tests. Based on the literature review and the collaboration with the University of Oulu, Finland an experimental apparatus was assembled for studying frost action in the laboratory. A detailed description of the experimental apparatus is given. Top to down freezing of specimens (of 10cm height and diameter) can be monitored while keeping track of water intake, vertical displacements (heave) and the temperature profile within the sample. Loads can be applied at the top of the sample to study the effects of overburden. Moreover, the test setup was modified with a camera system to have the option of recording the experiments. Disturbed samples of two different soil types were tested. Experiments with fixed and varying temperature boundary conditions were conducted to assess the validity of the assumptions for the frost heave estimation methods currently in use in Sweden. To this end, a qualitative relationship between frost heave and heat extraction rates based on theoretical equations was established. It was shown that there is a significant difference between the preliminary findings of the experimental work and the current system being used in Sweden to quantify heave. Image analysis techniques were used on two experiments that were recorded by the camera system. Image recording and correlation analyses provided detailed information about frost front penetration and ice lens formation(s) under varying temperature boundary conditions. Thawing has also been regarded in further studies. Results of the image analyses were compared to readings from conventional displacement measurements during the same test. Significant agreement between the results of image analyses and displacement measurements has been found. Image analysis was shown to be a viable method in further understanding of frost heave mechanisms. Shortcomings and disadvantages of utilizing the theoretical equations as well as the image analysis techniques were discussed. Potential remedies for overcoming the drawbacks associated with each approach are suggested. The work is concluded by discussing the potential improvements, planned upgrades (addition of pore pressure transducers) and the future experiments to be conducted. / Modellering av tjällossningsförlopp vid vägdimensionering

No description available.

För att verifiera att komponenter håller under en förväntad livslängd kan en Accelererad Livstids Testning (ALT) användas. En av huvudaspekterna som kan förstöra ett ALT-test av plastkomponenter är om kontakttemperaturen överstiger glasövergångstemperaturen. Detta eftersom det förändrar testkomponentens materialegenskaper. För att förhindra att detta inträffar i en ALT byggdes en testrigg medtemperatursensorer för att övervaka kontakttemperaturen. Om kontaktpunkten modifieras med en temperatursensor förändrar det uppbyggnaden av ytan och gör testet ogiltigt. Metoden som används är istället att mäta temperaturen på ytan på testdelen och simulera kontakttemperaturen med en modell baserad på den Finita Elementmetoden. Denna avhandling jämför de två teknikerna Tunn Film RTD och Tunn Termoelement Tråd Typ T i samband med uppbyggnaden av en värmeöverföring FEM-modell. Det undersöktes också vilken teknologi av IR-enpunkts sensor och Tunn Film RTD som har högst prestanda med avseende på fyra kvalitetsparametrar under användning tillsammans med testriggen. Slutsatserna är att Tunn Film RTD och Tunn Termoelement Tråd av Typ T sensorerna båda ger en liknande precision i mätningar för att bygga en användbar FEM-modell. När de används på testriggen presterar Film RTD:n är bättre än IR-sensorn i tre av fyra områden med avseende på de fyra definierade kvalitetsparametrarna. Tunn Film RTD är den rekommenderade teknologin för denna typ av mätning. / To verify that components last for an expected lifetime an Accelerated Life Testing (ALT) can be used. One of the main aspects that can ruin an ALT of plastic components is if the contact temperature rises above the glass transition temperature, since this changes the material properties of the tested component. To prevent this from occurring in a ALT, a test rig was built with temperature sensors to monitor this contact temperature. If the contact point is modified with a temperature sensor, this will change the surface and make the test invalid. The method is instead to couple surface temperature measurements with a Finite Element Model (FEM) to estimate the contact temperature. This thesis compares the two techniques Thin Film RTD and Thin Thermocouple Wire Type T in conjunction with the building of a heat transfer Finite Element Method (FEM)-model. It also investigates which technology of Non Contact IR Single Point sensor or Thin Film RTD have the highest performance in use with the test rig with regard to four quality parameters. The conclusions are that RTD and the Thermocouple Type T sensors both provide equal precision in measurement to build a useful FEM model. In application on the test rig, the Thin Film RTD is better than the Infrared (IR)-sensor in three out of four areas when compared in the four defined quality parameters. Thin Film RTD is the recommended technology in this application.

Controlling the temperature of the exhaust valves is paramount for proper functioning of engines and for the long lifespan of valve train components. The majority of the heat outflow from the valve takes place along the valve-seat-cylinder head-coolant thermal path which is significantly influenced by the thermal contact resistance (TCR) present at the valve/seat and seat/head interfaces. A test rig facility and experimental procedure were successfully developed to assess the effect of the valve/seat and seat/head interfaces on heat outflow from the valve, in particular the effects of the valve/seat interface geometry, seat insert assembly method, i.e. press or shrink fit, and seat insert metallic coating on the operating temperature of the valve. The results of tests have shown that the degree of the valve-seat geometric conformity is more significant than the thermal conductivity of the insert: for low conforming assemblies, the mean valve head temperature recorded during tests on copper-infiltrated insert seats was higher than that recorded during tests on noninfiltrated seats of higher conformance. The effect of the insert-cylinder head assembly method, i.e. shrink-fitted versus press-fitted inserts, has proved negligible: results have shown insignificant valve head temperature variations, for both tin-coated and uncoated inserts. On the other hand, coating the seat inserts with a layer of tin (20-22¿m) reduced the mean valve head temperature by approximately 15°C as measured during tests on uncoated seats. The analysis of the valve/seat and seat/head interfaces has indicated that the surface asperities of the softer metal in contact would undergo plastic deformation. Suitable thermal contact conductance (TCC) models, available in the public domain, were used to evaluate the conductance for the valve/seat and seat/cylinder head interfaces. Finally, a FE thermal model of the test rig has been developed with a view to assess the quality of the calculated TCC values for the valve/seat and seat/head interfaces. The results of the thermal analysis have shown that predicted temperatures at chosen control points agree with those measured during tests on thermometric seats with an acceptable level of accuracy, proving the effectiveness of the used TCC models.

Salar de Atacama (SdA) located in Northern Chile is home to one of the planet’s largest salar systems and lithium resources. Managing groundwater resources in salars is not obvious due to the lack of scientific understanding on the connectivity between the freshwater and brine systems. Using heat as a tracer in SdA provides a cost-effective method to further investigate groundwater flow in salars. This study employs 372 temperature-depth profiles from 90 boreholes between 2013-18 to understand the distinct thermal zones and flow between them in SdA. Three thermal zones exist within the southern margin of SdA’s thermal regime, at higher elevations alluvial fans containing freshwater have a temperature range between 23-28 °C. Down-gradient 2.5 km into the salar transition zone, characterized by freshwater lagoons and newly formed carbonates, the temperature range decreases to 12-17 °C. The transition zone, adjacent to the mature halite crust which hosts a lithium bearing brine and ranges in temperature from 18-22 °C. A 2D numerical groundwater and heat flow model was created to test three hydrologic scenarios to determine how the currently observed thermal regime exists and what the role of groundwater flow is between the different thermal zones. Results demonstrate that a focused flow concept matches current thermal observations with warm inflowing water discharging into the transition zone, cooling due to evaporation, reinfiltrating and preferentially flowing near the surface and discharging again at lagoons near the halite nucleus. Initial focused flow models had the halite nucleus and transition zone hydraulically connected, but results displayed advective flow between the two zones and the halite nucleus carried too much heat from current observations. Indicating the halite nucleus and transition zone has minimal connection, otherwise advective flow would result in thermal equilibrium and a lack of distinct zones as observed. Proper interpretation of temperature-depth profiles along with 2D models place critical constraints on the connectivity between the brine and freshwater systems, providing insight into salar surface energy budgets and a more comprehensive understanding of groundwater flow in the southern margin of SdA. This work gives a new perspective on the groundwater system in SdA while also contributing a novel case study to using heat as a tracer in salar systems.

No description available.

Two-thirds of submarine volcanism in the Earth's ocean basins is manifested along mid-ocean ridges and the remaining one-third is revealed along intraoceanic arcs and seamounts. Hydrothermal systems and the circulation patterns associated with these volcanic settings remove heat from the solid Earth into the deep ocean. Hydrothermal circulation continues to remove and redistribute heat in the crust as it ages. The heat and mass fluxes added to the deep ocean influence mixing in the abyssal ocean thereby affecting global thermohaline circulation. In addition to removing heat, hydrothermal processes extract chemical components from the oceanic and carry it to the surface of the ocean floor, while also removing certain elements from seawater. The resulting geochemical cycling has ramifications on the localized mineral deposits and also the biota that utilize these chemical fluxes as nutrients. In this dissertation, I analyze observed conductive heat flow measurements in the Panama Basin and borehole thermal measurements in Brothers Volcano and use mathematical models to estimate advective heat and mass fluxes, and crustal permeability. In the first manuscript, I use a well-mixed aquifer model to explain the heat transport in a sediment pond in the inactive part of the Ecuador Fracture Zone. This model yields mass fluxes and permeabilities similar to estimates at young upper oceanic crust suggesting vigorous convection beneath the sediment layer. In the second manuscript, I analyze the conductive heat flow measurements made in oceanic between 1.5 and 5.7 Ma on the southern flank of the Costa Rica Rift. These data show a mean conductive heat deficit of 70%, and this deficit is explained by various hydrothermal advective transport mechanisms, including outcrop to outcrop circulation, transport through faults, and redistribution of heat by flow of hydrothermal fluids in the basement. In the third manuscript, I analyze the borehole temperature logs for two sites representative of recharge and discharge areas of hydrothermal systems in the Brothers Volcano. I develop upflow and downflow models for fluids in the borehole and formation resulting in estimated of flow rates and permeabilities. All three independent research works are connected by the common thread of utilizing relatively simple mathematical concepts to get new insights into hydrothermal processes in oceanic crust. / PHD / Two-thirds of underwater volcanic activity in the Earth’s ocean basins is exhibited in areas where new material for Earth’s outer shell is created and the remaining one-third is displayed along areas where the outer shell is destroyed. In these areas, hot springs that are under water and their water movement patterns remove heat from the solid outer shell and puts it into the deepest parts of the ocean. Hot water circulation continues to remove and redistribute heat and various chemical elements in the shell as it grows old. This heat and chemical elements, which get added to the deep ocean water, influences the way water mixes and forms layers in the world oceans. This also affects the movement of ocean currents. The chemical elements removed from the shell by hot water gets deposited as minerals on the ocean floor in places where hot springs arise. This variety of minerals provides nutrients for different marine organisms. In this work done during my PhD studies, I examine the heat and temperature that was measured in the Panama Basin and Brothers Volcano. I utilize these examinations to build simple math models to find out how much heat and chemical components are being added to the deep ocean water. I also find out the methods in which the hot water springs appear on the ocean floor and the patterns in which the hot water circulates in the Earth’s outer shell. All of these estimates will help the scientists who are studying the patterns and changes in ocean currents by giving them a number on how much heat is released from the inside of the Earth.

The thesis is composed of three parts - theoretical, computational and a project part. The theoretical part deals with heat sharing through conduction, flow and radiation. The computational part is focused on the overall calculation of the heating system to operate smoothly and reliably. Three gas condensing boilers are designed as a source of heat. The heating of the water is solved as a reservoir. It's source of heat is one gas condensation boiler. The project part contains a technical report and the project documentation on the stage of the implementation dossier.

Thermoelectric generators (TEG) are re-emerging technology that can be used to recover heat waste from commercial and industrial processes to generate electricity, enhancing fuel utilization and lowering greenhouse gas emissions. TEG modules are solid-state heat engines that produce no noise or vibration during operation. Notably, TEG modules are also able to operate at low-temperature differences, which makes them ideal for a wide range of heat waste recovery applications. Annular thermoelectric generator (ATEG) modules are optimal in applications where either the heat source or sink are round in shape. Bi2Te3 solution-based compounds are of significant interest in the application of thermoelectric materials (TE) used in low-temperature cooling and power generation applications. The main objective of the current work is to design a mechanically reliable ring-shaped ATEG module with a predictable performance using spark plasma sintered Bi2Te3 TE material for low temperature waste heat recovery applications. In terms of structure, this work is divided into two parts. The first part investigates how the use of a powder pre-treatment technique affects the mechanical and thermoelectric properties of P- and N-type Bi2Te3. In addition, part one also presents the measurements of these materials’ mechanical and thermoelectric properties, which serve as inputs for the finite element models used to design thermoelectric modules with parallel and perpendicular configurations vis-a-vis the sintering pressing direction. The second part evaluates the thermoelectric performance and thermal stresses of a ring-shaped ATEG couple that has been integrated between hot-side and cold-side heat exchangers. To this end, two configurations are compared with respect to their heat/electrical current flow paths: one that allows for radial flow (radial configuration), and one that allows for axial flow (axial configuration). The P- and N-type Bi2Te3 powder was treated using a mechanically agitated fluidized powder reduction facility that was built in-house. The characteristic uniaxial tensile strength of the P-type Bi0.4Sb1.6Te3 increased from 13.9 MPa to 26.3 MPa parallel to the sintering pressure, and from 16.3 MPa to 30.6 MPa perpendicular to the sintering pressure following oxide reduction using 5% H2 ˗ 95% Ar at 380 ℃ for 24 h. The figure of merit, ZT, increased from 0.35 to 0.80 and from 0.42 to 1.13 at room temperature (25 ℃) in the parallel and the perpendicular directions, respectively, after the surface oxide reduction treatment. On the other hand, the annealing effects of the oxide reduction pr-treatment of the N-type (Bi0.95 Sb0.05)2(Se0.05 Te0.95)3 using 5% H2 ˗ 95% Ar at 380 ℃ for 24 h were found to be responsible for the majority of the mechanical properties and ZT enhancement. Additionally, the characteristic uniaxial tensile strengths for this material increased from 30.4 to 34.1 MPa and from 30.8 to 38 MPa in the parallel and the perpendicular directions, respectively. The ZTmax (150 ℃) increased from 0.54 to 0.63 in both the parallel and perpendicular directions due to oxide reduction, while annealing led to an increase to 0.58 and 0.62 in the parallel and the perpendicular directions, respectively. An analytical model was constructed to compare the thermoelectric performance of the two configurations under three different hot-side thermal resistances, and a 3D coupled finite element ANSYS model was constructed to study and compare the thermal stresses of the two configurations at different dimensions. The two models were then used to create 2D maps in order to investigate the effects of ATEG couple configuration and dimensions, as well as the hot-side thermal resistance, with the goal of identifying the optimum design. The optimization of module geometry requires a trade-off between performance and mechanical reliability. The results of these investigations showed that increases in the temperature difference across the ATEG couple (ΔT) led to increases in both power and thermal stresses in both configurations. When both configurations were generating the same power at ΔT = 105 ℃, the thermal stresses in the radial configuration were as much as 67 MPa higher than those in the axial configuration due to the formation of additional tensile hoop stresses. The lowest thermal stress obtained for the axial couple configuration was 67.8 MPa, which was achieved when the couple had an outer diameter of 16 mm, an axial thickness of 1 mm, a ΔT of 14.8 ℃, and power generation of 10.4 mW per couple. The maximum thermal stress values were located at the corners of the interface between the solder and the TE rings due to the mismatched coefficient of thermal expansion. This thesis makes a novel contribution to the state-of-the-art literature in ring-shaped ATEG modules, as it details a well-characterised spark plasma sintered Bi2Te3 TE material and a methodology for designing a ring-shaped ATEG module with reliable, robust, and predictable thermoelectric and mechanical performance. The details of the contribution made by this work have been disseminated in the form of three journal publications, which have been integrated into this sandwich Ph.D. thesis. / Thesis / Doctor of Science (PhD)