This thesis describes investigations into cryofixation by the plunge-cooling technique, at ambient pressure. The objective was to characterise coolants which are commonly used for cryofixation, so that the structure and chemistry of biological specimens may be preserved in a more life-like state. The work began with the design of a suitable cooling device. This was developed further into a large test-bed apparatus which was used in both biological and methodological experiments. The large cooling apparatus demonstrated for the first time that ethane was a superior coolant under forced convection, compared to propane or Freon 22, for bare thermocouples, for exposed hydrated specimens and for metal-sandwiched hydrated specimens. Ice crystal formation was monitored in sandwiched specimens and found to correspond closely to modelling predictions. A biological application was the X-ray microanalysis of body fluids in "indicator" species of Chaetognaths, where results obtained from cryoscanning electron microscopy revealed ecophysiological differences. The use of low thermal mass supports demonstrated that good freezing can occur in the centre of specimens. A new cryomounting method was developed to load well-frozen specimens into the microscope. The effect of post-freeze processing temperature was investigated by monitoring ice crystals in red blood cells. Exposure to 213 K (-60°C) over a 48 hour period did not induce crystal growth and exposure to 233 K (-40°C) for 8 days showed minimal ice crystal damage. The progress of cryosubstitution was monitored over 48 h at 193 K ( -80°C), this showed that uranium ingressed to a depth of 320 µm which could be doubled when shrinkage was allowed for. The conclusion was that observed ice crystal damage originated during the initial freezing and not during subsequent cryoprocessing.

The continuing requirement for computational processing power, multi-functional devices and component miniaturization have emphasised the need for thermal management systems able to maintain the temperature at safe operating condition. The thermal management industry is constantly seeking for new cutting edge, efficient, cost effective heat transfer enhancement technologies. The aim of this study is to utilize the electron beam treatment for the improvement of the heat transfer area in liquid cooled plates and experimentally evaluate the performance. Considering the complexity of the technology, this thesis focuses on the design and production of electron beam enhanced test samples, construction of the test facility, testing procedure and evaluation of thermal and hydraulic characteristics. In particular, the current research presented in this thesis contains a number of challenging and cutting edge technological developments that include: (1) an overview of the semiconductor industry, cooling requirements, the market of thermal management systems, (2) an integral literature review of pin-fin enhancement technology, (3) design and fabrication of the electron beam enhanced test samples, (4) upgrade and construction of the experimental test rig and the development of the test procedure, (5) reduction of the experimental data and analysis to evaluate thermal and hydraulic performance. The experimental results show that the capability of the electron beam treatment to improve the thermal efficiency of current untreated liquid cooled plates is approximately three times. The highest heat transfer rate was observed for the sample S3; this is attributed to the irregularities of the enhanced structure, which improves the heat transfer area, mixing, and disturbs the thermal and velocity boundary layers. Enhancement of heat transfer for all three samples was characterised by an increase of pressure drop. The electron beam enhancement technique is a rapid process with zero material waste and cost effective. It allows thermal management systems to be produced smaller and faster, reduce material usage, without compromising safety, labour cost or the environment.

Wave power has been increasing the interest of many researchers looking for alternative sustainable energy sources since the reserves have proved to be capable of satisfying a considerable percentage of the world´s energy demands. This option has not been adopted as a sustainable source since there are some challenges in the process of designing a low cost device that converts the kinetic energy of the waves into electric energy and that could still be efficient enough to be competitive against other options. A new proposal from Anders Hagnestål looks like a very promising way of moving forward in this field. The structure of this newly proposed generator includes neodymium magnets that at temperatures over 60°C might suffer irreversible demagnetization, compromising the normal functioning of the machine. Because of the electrical losses in iron components, overheating is a possibility that must be studied. The aim of this study is to find the temperature distribution of the components that are subject to changing magnetic fields (where the losses will occur). This will be done for a variety of cases regarding environmental and working conditions with the purpose of determining if the generator will need a cooling technique to avoid damage to the magnets. The studied structure consists of a stator and a translator conformed by iron, FR4, glass fiber and, of course, the magnets. The task at hand was carried out first through a one-dimensional analytical model, then through a two-dimensional analytical model and finally by means of simulations on Comsol Multiphysics (Computer-Aided-Engineering software). All of the aforementioned methods implicate assumptions that deviate from reality, but are still useful for the task at hand. Results from the 1D calculation turned out to be unreliable due to the numerous approximations but helped to prove and understand the effect of each of the environmental conditions on the temperature distribution. On the other hand, the 2D calculations and the simulations had a very good agreement which provides some reliability. Furthermore, said results showed that the components might even reach temperatures as high as 380°C under certain conditions. As this number is clearly over the safe limit of the magnets, it was concluded that cooling techniques are needed to ensure the safety of the generator. After some discussion with Hagnestål, cooling methods were proposed. In addition to this, the seemingly most appropriate option was pointed out with the intention of achieving a low-enough temperature and keeping the costs as low as possible. This alternative was a combination of modifying geometric parameters (which would ultimately reduce heat generation) and inducing a low velocity air flow. / Vågkraft är en hittills outnyttjad förnybar energikälla som i framtiden kan tillgodose i storleksordningen 10 % av världens energibehov, om de tekniska utmaningarna kan lösas så att vågkraft kan levereras till konkurrenskraftiga priser. Därmed finns också ett starkt intresse från både akademi och näringsliv att lösa dessa utmaningar. Anders Hagnestål håller på att utveckla en ny linjär generatortyp som enligt beräkningar slår alla befintliga lösningar för effektomvandling för vågkraft med bred marginal. Maskinen har dock komplex geometri, och det är svårt att beräkna dess prestanda. Maskinen innehåller neodymmagneter, vilka kan avmagnetiseras om de blir för varma där 60°C kan ses som en gräns då magneterna börjar påverkas. Om magneterna avmagnetiseras blir maskinen svagare. Eftersom magneterna upphettas av virvelströmmar i magneterna och förluster i omgivande elektroplåt, är det av intresse att göra en termisk analys av maskinen vilket är syftet med detta examensarbete. Målet är att beräkna temperaturutbredningen i maskinens olika delar vid olika driftsfall, och se om man behöver tillföra extern kylning av maskinen för att skydda magneterna. Maskinen består av en translator som omsluter den inre statorn där magneterna är lokaliserade, vilka är byggda av fiberkompositer, elektroplåt, rostfritt stål och neodymmagneter. Beräkningar gjordes först med en endimensionell analytisk modell, därefter med en tvådimensionell analytisk modell och slutligen med numeriska beräkningar i 2D med det kommersiella finita elementmetodberäkningsprogrammet Comsol Multiphysics. Samtliga dessa modeller har avvikelser från det verkliga fallet, men är ändå användbara och ger en fingervisning om hur den termiska situationen för maskinen kan se ut. 1D-beräkningarna visade sig innehålla lite för grova approximationer för att ge pålitliga resultat, men gav en del intuitiv insikt om problemet. Den analytiska 2D-beräkningen stämde bra överens med Comsol-beräkningen, vilket indikerar att beräkningarna är korrekta. Resultaten visade på mycket höga temperaturer i vissa driftsfall utan kylsystem, 380 °C, vilket är en indikator på att antingen någon form av kylning förmodligen behövs, i.a.f. i en del driftsfall, eller att värmeförlusterna i den delen av generatorn behöver minskas genom t.ex. att pollängden ökas. En kombination av luftflöden med låg hastighet och förändrad geometri har föreslagits i examensarbetet för att minska temperaturen.