The combustion dynamics and stability are dependent on the quality of mixing and vaporization of the liquid fuel in the pre-mixer. The vaporization characteristics of different blends of biofuel droplets injected into the air stream in the pre-mixer are modeled in this current study. The focus of this work is on the blended alternate fuels which are lately being considered for commercial use. Two major alternate fuels analyzed are ethanol and Rapeseed Methyl Esters (RME). Ethanol is being used as a substitute for gasoline, while RME is an alternative for diesel. In the current work, the vaporization characteristics of a single droplet in a simple pre-mixer has been studied for pure ethanol and RME in a hot air jet at a temperature of 800 K. In addition, the behavior of the fuels when they are mixed with conventional fuels like gasoline and diesel is also studied. Temperature gradients and vaporization efficiency for different blends of bio-conventional fuel mixture are compared with one another. The model was validated using an experiment involving convection heating of acoustically levitated fuel droplets and IR-thermography to visualize and quantify the vaporization characteristics of different biofuel blends downstream of the pre-mixer. Results show that the 20 µm droplets of ethanol-gasoline 50-50 blend is completely evaporated in 1.1 msec, while 400 µm droplets vaporized only 65% in 80 msec. In gasoline-ethanol blends, pure gasoline is more volatile than pure ethanol. In spite of having higher vapor pressure, ethanol vaporizes slowly compared to gasoline, due to the fact that latent heat of vaporization is higher for ethanol. For gasoline-ethanol blended fuels, ethanol component vaporizes faster. This is because in blended fuels gasoline and ethanol attain the same temperature and ethanol vapor pressure is higher than that for gasoline. In the case of RME-diesel blends, initially diesel vaporizes faster up to 550K, and above this temperature, vapor pressure of RME becomes dominant resulting in faster vaporization of RME. Current work also looks into the effect of non-volatile impurities present in biofuels. Depending on source and extraction process, fuels carry impurities which impact vaporization process. In this work these effects on ethanol blended fuel have been studied for different concentration of impurities. The presence of non-volatile impurities reduces the vaporization rate by reducing the mass fraction of the volatile component at the surface. However, impurities also increase the surface temperature of the droplet. Finally, the effects of hot and cold spots in the prevaporizer have been investigated. Due to inefficient design, prevaporizer may have local zones where the temperature of air increases or decreases very sharply. Droplets going through these abnormal temperature zones would vaporize at a different rate than others. Current study looks into these droplets to understand the vaporization pattern.

Abstract Since ancient times, warm or cold skin on the human body has been used as a parameter in evaluating health. Changes in body temperature are attributed to diseases or disorders. The assessment of body temperature is often performed to measure fever by detecting an elevated core temperature. With techniques such as infrared thermography, it is possible to perform a non-contact temperature measurement on a large surface area. The overall aim of this thesis was to contribute to a better understanding of the hand skin temperature variability in healthy persons and in persons experiencing whitening fingers (WF). The enclosed four papers discuss issues such as thermal variability response to cold stress test (CST) in repeated investigations; the specific rewarming pattern after CST; the difference between the hand’s palmar and dorsal temperatures; and evaluating skin temperatures and response to CST in participants with WF and healthy participants. All four papers used an experimental approach involving healthy males (I-III) and females (III) as well as individuals with (IV) and without WF (I-IV). Data were generated using dynamic infrared imaging before and after a CST. The radiometric images were analyzed using image analysis and statistics. The study showed that: (I) there is variability in hand skin temperature; (II) there are cold and warm hand skin temperature response patterns; (III) the skin temperatures on the palmar and dorsal sides of the hand are closely related; and (IV) a baseline hand skin temperature measurement can distinguish between whitening fingers and controls. The conclusion of this thesis is that it is necessary to engage in thorough planning before an investigation in order to choose the most adequate method for evaluating peripheral skin temperature response depending on the question asked.

The leading edge of a turbine vane is subject to some of the highest temperature loading within an engine, and an accurate understanding of leading edge film coolant behavior is essential to efficient engine design. Although there have been many investigations of the adiabatic effectiveness for showerhead film cooling within the leading edge region, there have been no previous studies in which individual rows of the showerhead were tested with the explicit intent of validating superposition models. For the current investigation, a series of adiabatic effectiveness experiments were performed with a five-row showerhead, wherein each row of holes was operated in isolation. This allowed evaluation of superposition on both the suction side of the vane, which was moderately convex, and the pressure side of the vane, which was mildly concave. Superposition was found to accurately predict performance on the suction side of the vane at lower momentum flux ratios, but not for higher momentum flux ratios. On the pressure side of the vane, the superposition predictions were consistently lower than measured values, with significant under-prediction of adiabatic effectiveness occurring at the higher mass flow rates. Possible reasons for the under-prediction of effectiveness by the superposition model are presented. / text

Les normes européennes EURO 5 / EURO 6 de réduction des émissions polluantes des véhicules automobile sont de plus en plus sévères. La boucle de recirculation des gaz d’échappement, dite boucle EGR (Exhaust Gas Recirculation), est une solution de dépollution à la source car elle réduit les quantités émises d’oxydes d’azote et de particules de suie. Ce contexte entraîne une utilisation plus intensive de la boucle EGR, d’où une augmentation de son encrassement. Assurer la fiabilité de cette boucle est un enjeu important pour les constructeurs automobiles. Un montage expérimental dont on contrôle les conditions opératoires a été conçu pour recréer les dépôts observés dans l'échangeur EGR d'un moteur Diesel. Il permet de déterminer les paramètres pilotant la formation et l’évolution du dépôt d'encrassement, via une mesure de sa masse, une analyse de sa composition chimique et un suivi des transferts thermiques (thermocouples, caméra infra rouge) dans l’échangeur au cours du temps. / The EURO 5 and EURO 6 European norms on the vehicle pollutant emission reduction are stricter than the previous. The Exhaust Gas Recirculation system, also called as EGR system, is a solution for the remediation at source, because it reduces the quantity of emitted nitrogen oxides and soot particles. The resulting intensive use of the EGR system increases the fouling in the involved heat exchanger. Ensuring the reliability of the EGR system is an important challenge for car manufacturers. An experimental set-up, with controlled operating conditions, has been built to recreate the deposit observed in the EGR heat-exchanger of Diesel engines. It enables to determine the parameters driving the fouling deposit formation and evolution, via a weight measurement, a chemical composition analysis and a follow-up of the thermal transfer (thermocouples, IR camera) in the heat-exchanger over the time.

abstract: Granular material can be found in many industries and undergo process steps like drying, transportation, coating, chemical, and physical conversions. Understanding and optimizing such processes can save energy as well as material costs, leading to improved products. Silica beads are one such granular material encountered in many industries as a catalyst support material. The present research aims to obtain a fundamental understanding of the hydrodynamics and heat transfer mechanisms in silica beads. Studies are carried out using a hopper discharge bin and a rotary drum, which are some of the most common process equipment found in various industries. Two types of micro-glass beads with distinct size distributions are used to fill the hopper in two possible packing arrangements with varying mass ratios. For the well-mixed configuration, the fine particles clustered at the hopper bottom towards the end of the discharge. For the layered configuration, the coarse particles packed at the hopper bottom discharge first, opening a channel for the fine particles on the top. Also, parameters such as wall roughness (WR) and particle roughness (PR) are studied by etching the particles. The discharge rate is found to increase with WR, and found to be proportional to (Root mean square of PR)^(-0.58). Furthermore, the drum is used to study the conduction and convection heat transfer behavior of the particle bed with varying process conditions. A new non-invasive temperature measurement technique is developed using infrared thermography, which replaced the traditional thermocouples, to record the temperatures of the particles and the drum wall. This setup is used to understand the flow regimes of the particle bed inside the drum and the heat transfer mechanisms with varying process conditions. The conduction heat transfer rate is found to increase with decreasing particle size, decreasing fill level, and increasing rotation speed. The convection heat transfer rate increased with increasing fill level and decreasing particle size, and rotation speed had no significant effect. Due to the complexities in these systems, it is not always possible to conduct experiments, therefore, heat transfer models in Discrete Element Method codes (MFIX-DEM: open-source code, and EDEM: commercial code) are adopted, validated, and the effects of model parameters are studied using these codes. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2020

Infrared transition location estimates can be fast and useful measurements in wind tunnel and flight tests. Because turbulent boundary layers have a much higher rate of convective heat transfer than laminar boundary layers, a difference in surface temperature can be observed between turbulent and laminar regions of an airfoil at a different temperature than the free stream air temperature. Various implementations of this technique are examined in a wind tunnel. These include using a heat lamp as an external source and circulating fluid inside of the airfoil. Furthermore, ABS plastic and aluminum airfoils are tested with and without coatings such as black paint and surface wraps. The results show that thermal conduction within the model and surface reflections are the driving issues in designing an IR system for detecting transition. Aluminum has a high thermal diffusivity so is a poor choice for this method. However, its performance can be improved using an insulating layer. Internal fluid circulation was far more successful than the heat lamp because it eliminates the reflected IR due to the heat lamp. However, using smooth surface wraps can mitigate reflection issues caused by the heat lamps by reducing the scatter within the reflection, producing an IR image with fewer contaminating reflections.

The ability to resolve reactions within a monolith spatially and temporally is key in developing reliable kinetic models, as well as in validating proposed reaction mechanisms. In this work, two techniques, IR-thermography and spatially-resolved capillary inlet mass spectrometry (SpaciMS), were used to measure temperature and gas-phase concentrations. Specifically, they were applied to monitor the axial distribution of temperature and concentration profiles during propylene oxidation over a Pt/Al2O3 monolith-supported catalyst. Also, the effect of thermally aging the catalyst on the temperature and concentration patterns observed was investigated. During temperature programmed oxidation experiments, the data show that conversion of propylene began at the outlet, and a reaction front generated at the rear of the monolith traveled upstream, as a moving reaction zone, thereby creating a temperature wave pattern since the reaction is exothermic. The conversion was always complete downstream of this reaction zone at any point along the catalyst. When the reactor was cooled, the conversion of propylene started to drop, accompanied by a similar temperature wave pattern that traveled in the opposite direction (from upstream to downstream) and was attributed to a phenomenon known as wrong-way behavior. Finally, thermally aging the catalyst led to a slower and more localized moving hot zone.

The ability to resolve reactions within a monolith spatially and temporally is key in developing reliable kinetic models, as well as in validating proposed reaction mechanisms. In this work, two techniques, IR-thermography and spatially-resolved capillary inlet mass spectrometry (SpaciMS), were used to measure temperature and gas-phase concentrations. Specifically, they were applied to monitor the axial distribution of temperature and concentration profiles during propylene oxidation over a Pt/Al2O3 monolith-supported catalyst. Also, the effect of thermally aging the catalyst on the temperature and concentration patterns observed was investigated. During temperature programmed oxidation experiments, the data show that conversion of propylene began at the outlet, and a reaction front generated at the rear of the monolith traveled upstream, as a moving reaction zone, thereby creating a temperature wave pattern since the reaction is exothermic. The conversion was always complete downstream of this reaction zone at any point along the catalyst. When the reactor was cooled, the conversion of propylene started to drop, accompanied by a similar temperature wave pattern that traveled in the opposite direction (from upstream to downstream) and was attributed to a phenomenon known as wrong-way behavior. Finally, thermally aging the catalyst led to a slower and more localized moving hot zone.

For a PV plant it is of fundamental importance that the operation of the PV modules is free from faults or at least that the faults can be detected early, to ensure efficient electricity production. Some defects such as cracks can be seen in visible light while microcracks and damage to the silicon material can only be seen through special lighting. This study focuses on the most common defects in photovoltaic (PV) systems. Compare the infrared (IR) technology with the new ultraviolet (UV) fluorescence image technique for PV characterization, based on their accuracy and uncertainty factors under an experimental field investigation. In this study, first a literature study was conducted to the most common defects in PV system and their impact on electricity generation. Then a simulation model of a PV system was created in PVsyst and exported to Microsoft Excel which was used to evaluate how different defects at different stages of the PV cell's life cycle impact electricity generation, performance parameters and economic exchange. Furthermore, experiments with UV and IR was implemented at a PV system located in Dalarna and some PV modules at MDH. It was conducted that occurrence of snail tracks, delamination and hot spots in combination with bypass failures and non-functioning cell will affect the economic profitability in the long run and the payback time will increase since their impacts on electricity generation and performance parameters are huge. The worst case is when PV modules are affected by the fault in bypass diode and non-functioning cell which result to a payback time longer than the module's lifetime and huge amount electricity losses in different bypass diodes configurations. Since UV and IR are two different methods that are performed in two different ways, different errors occurred during the measurements. The biggest external factor was the weather that determined if the experiment could be implemented. The IR method gave decent results and was quicker to use, but the UV method highlighted some defect which could not be seen with the IR technology.

Characterization of local boiling trends, in addition to the typically reported area-averaged trends, is essential for the robust design and implementation of phase change technologies to sensitive heat transfer applications such as electronics cooling. Obtaining the values of heat fluxes corresponding to locally varying surface temperatures has been a challenge limiting most investigations to area-averaged results. This thesis illustrates the importance of a spatially local heat transfer analysis during boiling. Pool and submerged jet impingement boiling scenarios on a silicon surface are considered at the macroscale (27.5 mm heater with multiple nucleation sites) and microscale (1000 ��m heater for isolated bubble generation), by the use of two thin film serpentine heater geometries. The macroscale heater highlights the effect of spatial variations in imposed heat flux on boiling heat transfer with a circumferentially uniform but radially non-uniform heat flux distribution. The microscale heater simulates a local hot-spot for spot cooling on an electronic device. Spatial variation in boiling heat transfer and bubble dynamics with and without a jet flow are documented using thin film voltage sensors along with qualitative and quantitative high speed imaging and infra-red thermography. Unique to this study is the documentation of local boiling curves for different radial locations on the heat transfer surface and their comparison with the corresponding area-averaged representations. It is shown here that sectionally averaged representations of boiling curves over regions of like-imposed heat flux can substantially simplify the interpretation of data while retaining important information of the local variations in heat transfer. The radial influence of the convective jet flow on the bubble dynamics and boiling heat transfer is assessed for a single circular submerged jet configuration. Varied parameters include jet exit Reynolds numbers, nozzle geometry, test fluid (deionized water and FC-72), fluid subcooling and the supplied heat flux. Distinct modifications of the surface temperature distribution imposed by the impinging jet flow are highlighted by comparing radial temperature profiles during pool and jet impingement boiling. It is demonstrated that in contrast with pool boiling, thermal overshoots during jet impingement boiling for a highly wetting fluid like FC-72 are highest in regions farthest from the impingement point. The effect of jet inertia on bubble departure characteristics are compared with pool boiling under subcooled conditions for FC-72. Qualitative high speed visualization indicates the presence of two modes of bubble generation during jet impingement boiling (a) bubble departure from the surface and (b) bubble separation from the source resulting in sliding bubbles over the surface. The effect of jet flow on bubble entrainment is depicted. Quantitative results indicate that in general departure diameters for pool and jet impingement boiling increase and plateau at a maximum value with increasing power input while no notable trends were observed in the corresponding departure frequencies. The largest departure diameters for jet impingement boiling at fixed fluid subcoolings of 10��C and 20��C were found to be smaller than that for the corresponding pool boiling test by a factor of 1.6 and 2.3, respectively. / Graduation date: 2013