Physical-mechanical Properties of Aged Knitted Fabric for Swimsuits

The physical and mechanical properties of knitted fabrics for sports swimsuits are analysed in this paper. The knitted fabrics were experimentally aged in seawater and exposed to the sun continuously for 100 hours. Data were processed for nine knitted fabrics with the same raw material composition, polyamide and elastane in different proportions. The physical-mechanical properties of all nine samples before and after aging, as well as the drying rate and water absorption capacity, were examined. The results show that the properties of the knitted fabric changed in all samples. The sample with a higher elastane content (59% PA and 41% EL) is less sensitive to changes in mass per unit area and thickness after aging (−0.89% and 0.40%). The results of maximum wetted radius absorption water on the top and bottom of the knitted fabric, spreading speed absorption and drying time are shown. The results show that the values of the maximum wetted radius of absorbed water and the spreading speed increase for all samples, while the drying time for the knitted fabrics show different results

Thermal protection properties of aerogel-coated Kevlar woven fabrics

This paper investigated the thermal properties of aerogel-coated Kevlar fabrics under both the ambient temperature and high temperature with laser radiation. It is found that the aerogels combined with a Kevlar fabric contribute to a higher thermal insulation value. Under laser radiation with high temperature, the aerogel content plays a vital role on the surface temperature of the fabrics. At laser radiations with pixel time 330 μs, the surface temperatures of the aerogel coated Kevlar fabrics are 400-440°C lower than that of the uncoated fabric. Results also show that the fabric temperature is directly proportional to pixel time. It can be concluded that the Kevlar fabrics coated with silica aerogel provides better thermal protection under high temperature

Amélioration des performances d'un moteur thermique à fluide auto-oscillant par la caractérisation du cycle thermodynamique et du changement de phase

L'objectif de cette thèse est de mieux comprendre les principes de fonctionnement d'un moteur thermique fluidique auto-oscillant (SOFHE) récemment découvert, en caractérisant le cycle thermodynamique (diagramme P-V) et le changement de phase (évaporation-condensation). Le SOFHE est proposé pour la récolte d'énergie thermique, couplé à un transducteur électromécanique, pour alimenter des capteurs sans fil utilisés dans l'Internet des objets (IoT). Le SOFHE est une bulle de vapeur piégée par un bouchon liquide (agissant comme un piston) dans un tube de petit diamètre. Cette bulle de vapeur-bouchon liquide est mise en oscillation par une évaporation-condensation cyclique d'une film liquide mince formée par une fibre de mèche. La première démonstration expérimentale du SOFHE a montré une faible puissance électrique de 1 µW. Cependant, on ne savait toujours pas comment le cycle thermodynamique inconnu de la SOFHE se comporte sous une charge et quelle densité de puissance mécanique la SOFHE peut générer. Pour répondre à cette question, le cycle thermodynamique et la densité de puissance de la SOFHE sont caractérisés expérimentalement pour la première fois sous une charge mécanique variable. La principale contribution de cette caractérisation est de fournir une base de référence pour l'adaptation de l'impédance qui est cruciale pour la conception d'une charge compatible pour la SOFHE. Il est également démontré que la densité de puissance mécanique de la SOFHE est de l'ordre de 0.5 milliwatts/cm3, ce qui en fait une solution prometteuse pour l'alimentation d'une gamme de capteurs sans fil dont la puissance requise est de l'ordre de 10s microwatt. Nous avons également étudié l'effet de la température de fonctionnement de la source de chaleur et de deux paramètres de conception, notamment la longueur de la fibre de mèche et la longueur du bouchon liquide, sur la puissance de la SOFHE. L'augmentation significative de la puissance en augmentant la longueur de la fibre a été la force motrice de la deuxième phase de notre étude dans laquelle nous avons caractérisé le profil de changement de phase complexe et inconnu (évaporation-condensation) de la SOFHE. Un nouveau dispositif a été conçu pour visualiser la variation du film mince autour de la fibre lorsque nous avons joué sur sa longueur à l'intérieur de la zone de vapeur. Les observations ont prouvé notre hypothèse de la formation de coins capillaires entre la fibre et la paroi interne du tube qui pompent le liquide du liquide vers la zone de vapeur. Cela conduit à la formation d'un film mince avec une très faible résistance thermique qui alimente l'évaporation. Le taux de variation de la masse de vapeur, appelé taux de changement de phase, est également mesuré. Il est démontré que pour maximiser l'amplitude de l'oscillation et, par conséquent, la puissance du SOFHE, l'amplitude du taux de changement de phase doit augmenter et être complètement déphasée par rapport à la position. Un nombre sans dimension est également proposé pour évaluer l'efficacité du profil du taux de changement de phase. Enfin, pour mieux contrôler le changement de phase, une nouvelle conception de la SOFHE est proposée et démontrée dans laquelle nous pouvons intégrer des structures de mèche sur mesure pour imiter l'effet de la fibre insérée. Le dispositif est un microcanal à section carrée avec des angles aigus et un chemin capillaire gravé sur la paroi inférieure qui est fabriqué par un procédé standard de microfabrication. Il est démontré que l'amplitude et, par conséquent, la puissance de la SOFHE augmente (multiplication par cinq de 30 à 150 µw/ cm3) avec l'ajout d'un chemin capillaire. Cela ouvre une nouvelle voie vers l'ingénierie du changement de phase de la SOFHE en concevant différentes structures de mèche pour améliorer les performances de la SOFHE.Abstract: The aim of this thesis is to better understand the working principles of a recently discovered self-oscillating fluidic heat engine (SOFHE) by characterizing the thermodynamic cycle (P-V diagram) and phase change (evaporation-condensation). The SOFHE is proposed for thermal energy harvesting, coupled with an electromechanical transducer, for powering wireless sensors used in the Internet of Things (IoT). The SOFHE is a vapor bubble trapped by a liquid plug (acting as a piston) in a small diameter tube. This vapor bubble-liquid plug is set in oscillations by a cyclic evaporation-condensation of a thin liquid film formed by a wicking fiber. The first experimental demonstration of the SOFHE showed a low electrical power of 1 μW. However, it is still unclear how the unknown thermodynamic cycle of the SOFHE behaves under a load and how much mechanical power density the SOFHE can generate. To address this question, the thermodynamic cycle and power density of the SOFHE are experimentally characterized for the first time under a varying mechanical load. The main contribution of this characterization is to provide a baseline for impedance matching that is crucial for designing a compatible load for the SOFHE. It is also shown that the mechanical power density of the SOFHE is in the range of milliwatts/cm3 (maximum 0.5 mW/cm3) which makes it a promising solution to power a range of wireless sensors with a power requirement of tens of microwatt. We also studied the effect of the operating heat source temperature and two design parameters, including the length of the wicking fiber and the length of the liquid plug on the power of SOFHE. The significant increase of the power by increasing the fiber length was the driving force behind the second phase of our study in which we characterized the complex and unknown phase change profile (evaporation-condensation) of the SOFHE. A new setup was designed to visualize the variation of the thin film around the fiber as we played with its length inside the vapor zone. The observations proved our hypothesis of forming capillary corners between the fiber and the inner wall of the tube that pumps liquid from the liquid plug toward the vapor zone. This leads to the formation of a thin film with a very small thermal resistance that feeds evaporation. The rate of change of mass of vapor, the so-called phase change rate, is also measured. It is shown that to maximize the amplitude of the oscillation and consequently the power of the SOFHE, the amplitude of the phase change rate should increase and be completely out of phase with the position. A dimensionless number is also proposed to evaluate the effectiveness of the phase change rate profile. Finally, to better control the phase change, a new design of the SOFHE is proposed in which we can integrate tailored wicking structures to mimic the effect of the inserted fiber. The device is a square cross-section microchannel with sharp corners as well as an etched capillary path on the bottom wall that is fabricated by a standard microfabrication process. It is shown that the amplitude and consequently the power of SOFHE increase (a fivefold increase from 30 to 150 μw/ cm3) as we add a capillary path. This opens a new path towards engineering the phase change of the SOFHE by designing different wicking structures to improve its performance

Tracing back the source of contamination

From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer

Analyzing And Modelling Of Comfort And Protection Properties Of Fire Fighters Protective Clothings

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2015Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2015İtfaiyeci kıyafetlerinin konfor özellikleri koruyuculuk özellikleriile birlikte önemli bir performans göstergesidir. Yangın söndürme oldukça tehlikeli bir iş olup, günümüzde itfaiyeciler çok tehlikeli çalışma koşullarında bulunduklarından kendilerini koruyabilmek için kişisel koruyucu kıyafetler giymektedirler. Ayrıca  itfaiyeciler işlerini çok kısıtlı birsüre de gerçekleştirmek zorunda olduklarından hareket kabiliyetleri veçalışma performansları yüksek oran da giysi konforuna bağlıdır. Koruyucu giysinin yangın  ortamında gereken termal korumayı sağlaması ve aynı zamanda vücut tarafından gerçekleştirilen metabolic aktiviteler sonucu üretilen ısıyı dengelemesi yangın koşullarında çok önemlidir. Koruyucu giysi yapısıterin buharlaşmasını, havalanmayı ve aynı zamanda yangından korunmayı sağlamalıdır. Bu çalışmada ilk aşama olarak termal konfor özellikleri, itfaiyeci kıyafetlerinin yangın koruması, termo-fizyolojik konfor özelliklerinin geliştirilmesine katkı sağlayan faktörler, giysi denemeleri analizleri ve araştırmacı yorumları ile ilgili çalışmalar hakkında literatür araştırması yapılmıştır. Bu tezde, itfaiyeci giysisi üretiminde kullanılan kumaş katmanlarının belirlenmesinde genel ve özel olarak uygulanan objektif ölçüm metodlarını kullanarak, koruyucu itfaiyeci giysisi için konfor ve koruyuculuk özelliklerinin çalışılması üzerine odaklanılmıştır.   Alambeta ve Permetest gibi kumaşların konfor özelliklerinin incelenmesinde kullanılan objektif ölçüm cihazları hızlı ölçüm kabiliyeti ve giysiye zarar vermeden ölçüm yapması bakımından çalışmada kullanılması uygun görülmüştür. Hava geçirgenliği, termal kamera, yanma testi cihazları gibi çalışmada kullanılan diğer konfor ve yanmaya dayanıklılık ölçüm cihazları tezin malzeme ve metot kısmında detaylı bir şekilde açıklanmıştır. Sonuçların analizi,  tezin ikinci bölümünde detaylı bir şekilde verilen konfor, termal konfor, giysi konforu özellikleri, giysi katmanlarından ısı ve nem transfer mekanizmaları gibi temel bilgilerle desteklenmiştir. Ayrıca, yangından korunma, itfaiyeci termal ortamları ve standartlara göre uygun test cihazları detaylı bir şekilde incelenerek çalışmada kullanılmıştır. Su buharı direnci, termal direnç, termal iletkenlik, termal absorplama, termal difüzyon, hava geçirgenliği ölçülmüş ve analiz edilmiştir. Çok katmanlı kumaşların konfor seviyelerini belirlemek için rölatif termal konfor indeksi hesaplanmıştır. Bu termal konfor indeksi yanma test sonuçları ile karşılaştırılarak kumaş katmanlarının objectif olarak değerlendirilmesi ve sıralanması sağlanmıştır. Sonuçlar ve tartışma bölümünde uygulanan tüm test yöntemi sonuçları ve değerlendirilmesi sunulmuştur.  Bu çalışmalara ek olarak giysi denemeleri gerçekleştirilerek objektif test yöntemleri kullanılarak elde edilen konfor deneyi sonuçlarının gerçek giysi giyimi esnasında oluşan durumla uygunluğu karşılaştırılmıştır.Testo 885 termal kamera ölçümler esnasında kullanılmıştır. İstatistiksel analizler rölatif termal konfor indeksi kullanılarak elde edilen kumaş değerlendirmesinin termal kamera kullanılarak gerçekleştirilen giyim denemeleri ile uyumlu olduğunu göstermiştir. Son olarak, gelecek çalışmalar için  sonuçlar ve tavsiyeler  verilmiştir. Genellikle bu tez geçerli yöntemlerle birçok potansiyel sorunları ele adı ve nesnel ölçümlere dayalı konfor ve koruma seviyesine kendi isteğine göre montajında kullanılan her katmanlı kumaş tarama yapilabıldi. Su buharı geçirgenliği, ısıl direnç, termal ekstensiyonu termal difüzyon ve kumaş koruma performansları kullanılan 64 katmanlı toplamı olarak özelliklerinin analize yapıldı. Çok katmanlı itfaiyeciler tüm koruyucu giysiler için hava iletimini engelleyen termal engellerin nedeniyle hava geçirgen değildir. Bu sonuca en iyi beklentilerini karşılamak amacıyla, giysiler kullanan tek mikroklima parametrelerini aynı zamanda kullanıcı ve fiziksel aktivite türü ve yoğunluğu kişisel özellikleri ile ilgili koşullarını belirlemek gereklidir.Protection together with comfort is very important subject for the performance of protective equipment. Firefighting is very dangerous work and today firefighters wear personal protective equipment to protect themselves during their highly dangerous work. Also they have to perform their jobs under very restrict time intervals so their motion and working performances are highly dependent on clothing comfort. The balance of thermal protection from fire and metabolic heat stress generated by the human body due to metabolic activities is very important during fire situations. The structure of the garments must allow evaporation of perspiration, ventilation and also thermal protection from fire. In this study, first of all the technical literatures were reviewed concerning the studies  related to thermal comfort properties, fire protection  performance of fire fighters clothings, factors contributing to improvement of thermo-physiological comfort, wear trials  comfort analysis and also the reviews including researchers recomendations. The thesis aimed  to focus on studying both comfort and protection  performance of fire fighters protective clothings by using objective measurements applied generally and specifically in screening the most comfortable/ protective fabric layers used to produce fire fighters protective clothing.  The objective measurement equipments such as Alambeta device and Permetest were found to be appropriate and useful  instruments to measure comfort parameters, and also both being fast and non-destructive. Beside these there are others test apparatus used such as air-permeability tester, thermal camera, burning tests equipment sets, all described well in materials and methods sections of this thesis work. The analysis of results is supported by basic knowledges of various aspects of comfort, thermal comfort, clothing comfort properties, mechanisms  of heat and moisture transfer through the coveralls all which provided in chapter two of the thesis. Additionally, understanding about fire protection, fire fighters thermal environments, and appropriate test apparatus based on standards were  used. Water vapour resistance, thermal resistance, thermal conductivity, thermal absorption, thermal diffusion, air permeability were measured and analysed. The relative thermal comfort index of multi-layered fabrics was calculated to see their comfort levels. This thermal comfort index was used to compared against the burning test results to attain an objective of screening and listing the layers of fabrics. The results and discussions section of the thesis represents all steps and values based on the analysis of the several test results. Additionaly the wear trials have been conducted to compare the objective measurements conformity with the analysis done by measuring human worn fire fighters protective clothings. The Testo 885 thermal imaging camera was used to measure. Statistical analysis showed that the conformity of fabric evaluation using RTCI with those carried out by wear trials measurements by using thermal camera. The thesis addressed several potential problems with the current  methods for screening  each single layered fabrics used in assembly according to their demand to comfort and protection level based on objective measurements. In analysis of properties such as water vapour permeability, thermal resistance, thermal absorptivity, thermal diffusion and protection performances total of sixty four layered fabrics used.  All of the multilayered firefighters protective clothings are not air permeable because of the thermal barriers which hinder air transmission. From several tests done for all samples its possible to conclude that, the thermal resistance measured by Alambeta device results greater than that measured by Permetest device for the same sample. The relative thermal comfort index calculated for fabric layers evaluate and provide well screened status weather a particular type of fabrics when made garments and investigated wear trially would definitely ensure thermal comfort. The more burning tests resistance time in seconds to convective and radiant heat source, the more protective the assemblies and its used to rank the performances of samples. In order to meet the best expectations to this conclusion, it is necessary to precisely specify the conditions of using the garments, not only concerning microclimate parameters but also personal features of the user and the type and intensity of physical activity.Yüksek LisansM.Sc

Human reproduction in space. Late results

Objectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version

Developing thermal infrared imaging systems for monitoring spatial crop temperatures for precision agriculture applications

Master of ScienceDepartment of Biological & Agricultural EngineeringAjay ShardaPrecise water application conserves resources, reduces costs, and optimizes plant performance and quality. Existing irrigation scheduling utilizes single, localized measurements that do not account for spatial crop water need; but, quick, single-point sensors are impractical for measuring discrete variations across large coverage areas. Thermography is an alternate approach for measuring spatial temperatures to quantify crop health. However, agricultural studies using thermography are limited due to previous camera expense, unfamiliar use and calibration, software for image acquisition and high-throughput processing specifically designed for thermal imagery mapping and monitoring spatial crop water need. Recent advancements in thermal detectors and sensing platforms have allowed uncooled thermal infrared (TIR) cameras to become suited for crop sensing. Therefore, a small, lightweight thermal infrared imaging system (TIRIS) was developed capable of radiometric temperature measurements. One-time (OT) and real-time (RT) radiometric calibrations methods were developed and validated for repeatable, temperature measurements while compensating for strict environmental conditions within a climate chamber. The Tamarisk® 320 and 640 analog output yielded a measurement accuracy of ±0.82°C or 0.62ºC with OT and RT radiometric calibration, respectively. The Tamarisk® 320 digital output yielded a measurement accuracy of ±0.43 or 0.29ºC with OT and RT radiometric calibration, respectively. Similarly, the FLIR® Tau 2 analog output yielded a measurement accuracy of ±0.87 or 0.63ºC with OT and RT radiometric calibration, respectively. A TIRIS was then built for high-throughput image capture, correction, and processing and RT environmental compensation for monitoring crop water stress within a greenhouse and temperature mapping aboard a small unmanned aerial systems (sUAS). The greenhouse TIRIS was evaluated by extracting plant temperatures for monitoring full-season crop water stress index (CWSI) measurements. Canopy temperatures demonstrated that CWSI explained 82% of the soil moisture variation. Similarly, validation aboard a sUAS provided radiometric thermal maps with a ±1.38°C (α=0.05) measurement accuracy. Due to the TIR cameras’ performance aboard sUAS and greenhouse platforms, a TIRIS provides unparalleled spatial coverage and measurement accuracy capable of monitoring subtle crop stress indicators. Further studies need to be conducted to produce spatial crop water stress maps at scales necessary for variable rate irrigation systems

Investigation of the pool boiling heat transfer enhancement of nano-engineered fluids by means of high-speed infrared thermography

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 445-466).A high-speed video and infrared thermography based technique has been used to obtain detailed and fundamental time- and space-resolved information on pool boiling heat transfer. The work is enabled by recent advances in heat transfer diagnostics and motivated by increased interest in the enhancement of heat transfer for applications such as micro-electronics, space heat-transfer systems, and advanced nuclear reactors. This study critically examined the fundamental processes occurring during nucleate boiling, critical heat flux, and rewetting on thin-film heating elements. A significant focus of the work was to investigate and explain the modification of these heat transfer phenomena through the addition of silica and diamond nanoparticles to the working fluid. Bubble departure diameter and frequency, growth and wait times, and nucleation site density were measured for every nucleation site during nucleate pool boiling at multiple superheats. The data were compared with decades-old and poorly-validated models and correlations, and were used to evaluate the relative contribution of the superheated liquid layer and microlayer evaporation to bubble growth. Deterioration in nucleate boiling heat transfer of water-based nanofluids was observed. It was determined that a reduction in the static contact angle, caused by nanoparticle deposition on the surface during boiling, created a larger energy barrier for nucleation, which in turn reduced bubble departure frequency and nucleation density, thus resulting in a reduced heat transfer coefficient.(cont.) Critical heat flux enhancement in nanofluids of up to 100% was experimentally observed. The cause of this enhancement was determined to be the decreased static contact angle of nanofluid boiled surfaces. The increased wettability modified the growth of bubbles prior to CHF and promoted rewetting of hotspots at CHF. In parallel quenching tests, rewetting temperatures and velocities were simultaneously measured for the first time. Surfaces that had been pre-boiled in nanofluids were found to have significantly higher rewetting temperatures and velocities than clean surfaces. Interpretation of the experimental data was conducted with consideration of the governing surface parameters and existing models. It was found that there is significant room for improvement of most pool boiling models, especially with regard to surface effects. The research performed in this thesis help demonstrate the power of the infrared thermography technique and its potential for future improvement of boiling models.by Craig Douglas Gerardi.Ph.D

Proceedings of the 2011 Space Cryogenics Workshop: "Poised for the Future, Reflecting on the Past"

The 24th Space Cryogenics Workshop was held at the Best Western Coeur d Alene Inn and Conference Center, Coeur d Alene, Idaho, June 8-10, 2011. The workshop was organized and sponsored by NASA Kennedy Space Center and NASA Marshall Space Flight Center, with a theme of "Poised for the Future, Reflecting on the Past." Over 100 scientists and engineers from around the world came together to discuss space applications for cryogenics, renew old acquaintances, and meet new practitioners in the field of space cryogenics

National Aeronautics and Space Administration (NASA)/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program, 1993, volume 2

The JSC NASA/ASEE Summer Faculty Fellowship Program was conducted by Texas A&M University and JSC. The objectives of the program, which began nationally in 1964 and at JSC in 1965, are (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of participant's institutions; and (4) to contribute to the research objectives of the NASA centers. Each faculty fellow spent at least 10 weeks at JSC engaged in a research project in collaboration with a NASA/JSC colleague. A compilation of the final reports on the research projects completed by the faculty fellows during the summer of 1993 is presented