Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: The thermal regulation response of a neonate has to maintain temperature homeostasis, thus resisting the changes to core temperature caused by the unstable external environment. In this thesis a theoretical thermal regulation response model for human infants subject to a well-defined environment is presented. This model will aid in understanding the influences of environmental effects on core and skin temperature. The respiratory system was also included in the thermal regulation response model. A literature study was undertaken emphasising thermal regulation of neonates. The blood circulation system, skin tissue physiology and the respiratory system physiology were reviewed and helped to provide a better understanding of the thermal regulation mechanisms and how heat transfer theory can be used to analyse heat loss in neonates. The thermal heat transfer properties of skin tissue was specified and used in the development of the theoretical simulation model. The bioheat equation developed by Pennes was reviewed as well as a mathematical model developed by Fiala et al. The theoretical model was developed by applying the conservation of energy and the applicable properties to one dimensional layers to generate a set of time dependent differential equations. The set of equations was solved using an explicit numerical finite difference method, given the initial conditions. The mathematical model included heat loss through the skin, heat loss through the respiratory system, as well as the effect of environments (in incubator or in a bassinette) with different temperatures, relative humidity’s and air velocities. Clothing was also incorporated. A clinical trial was conducted to facilitate a better understanding of thermal stability in neonates. The data acquired during the clinical trial was also used to verify/validate the theoretical simulation model. The results from the simulation temperatures were compared with the average outer skin layer temperature measured during the clinical trial and an average deviation of only 0.22 °C was found, thereby proving that the simulation model gives realistic results. An experimental respiratory model was designed to simulate the respiratory system and illustrate the functioning thereof with regards to heat transfer. This was done by designing an experimental mechanical lung apparatus. The apparatus was tested and successfully imitated the respiratory system with regards to heat transfer. The results obtained from this experiment indicated that the trachea must be moistened continuously in order to condition inhaled air. The outcome of this project identified two possible applications. For the first application it can be used as a test tool for quickly evaluating the influence of different environmental conditions in the transient temperature distribution of neonates. The second application would be to enable medical professionals to monitor the influence of the thermal environment, including the temperature, relative humidity and air velocity, on the neonate’s temperature change to allow for a speedier thermal intervention strategy. / AFRIKKANSE OPSOMMING: Die hitte regulering reaksie van 'n pasgebore baba moet temperatuur homeostase handhaaf, en sodoende die veranderinge aan die kern temperatuur weerstaan wat veroorsaak word deur ‘n onstabiele eksterne omgewing. In hierdie tesis word 'n teoretiese hitte regulerings reaksie model vir menslike babas, onderhewig aan 'n goed-gedefinieerde omgewing, aangebied. Hierdie model sal help met die verstaan van die invloed wat omgewings effekte het op die kern en vel temperatuur. Die respiratoriese sisteem is ook ingesluit in die hitte regulering reaksie model. 'n Literatuurstudie is onderneem met die klem op hitte regulering van pasgebore babas. Die bloed sirkulasie sisteem, vel weefsel fisiologie en die respiratoriese sisteem fisiologie is hersien en help met beter begrip van die hitte regulering meganismes en hoe hitteoordrag teorie kan gebruik word om hitte verlies in pasgebore babas te analiseer. Die hitte-oordrag eienskappe van vel weefsel is gespesifiseer en word gebruik in die ontwikkeling van die teoretiese simulasie model. Die ‘bioheat’ vergelyking ontwikkel deur Pennes is hersien asook 'n wiskundige model wat ontwikkel is deur Fiala et al. Die teoretiese model is ontwikkel deur die toepassing van die behoud van energie tesame met die gebruik van toepaslike eienskappe en een dimensionele lae om 'n stel tyd afhanklike differensiaalvergelykings op te wek. Die stel vergelykings is opgelos met behulp van 'n eksplisiete numeriese eindige verskil metode, gegewe die aanvanklike toestande. Die wiskundige model sluit in die hitte verlies deur die vel, hitte verlies deur die respiratoriese stelsel, sowel as die effek van die omgewing (broeikas of in 'n bassinette) met verskillende temperature, relatiewe humiditeit en lug snelhede. Klere is ook in ag geneem. 'n Kliniese proef is gedoen om 'n beter begrip van termiese stabiliteit in pasgebore babas te fasiliteer. Die data wat tydens die kliniese proef verhaal is, is ook gebruik om die die teoretiese simulasie model te verifieer. Die resultate van die simulasie temperature is vergelyk met die gemiddelde buitenste vel laag temperatuur gemeet tydens die kliniese proef en 'n gemiddelde afwyking van slegs 0.22 °C is gevind, wat dus bewys dat die simulasie model realistiese resultate gee. 'n Eksperimentele respiratoriese model is ontwerp om die respiratoriese stelsel te simuleer en die funksionering daarvan te illustreer met betrekking tot hitte-oordrag. Dit is gedoen deur die ontwerp van 'n eksperimentele meganiese long apparaat. Die apparaat is getoets en slaag daarin om die respiratoriese stelsel suksesvol na te boots met betrekking tot hitteoordrag. Die resultate verkry uit hierdie eksperiment het aangedui dat die tragea kostant klam gemaak moet word om ingeasemde lug te kondisioneer. Die uitkoms van hierdie projek het twee moontlike toepassings geïdentifiseer. Die eerste is dat dit as 'n toets instrument vir die vinnige evaluering van die invloed van verskillende omgewingsfaktore in die temperatuur verspreiding van pasgebore babas gebruik kan word. Die tweede toepassing sal wees om medici in staat te stel om die invloed van die termiese omgewing te monitor, insluitend die temperatuur, relatiewe humiditeit en lug snelheid, om die neonaat se temperatuur verandering te monitor en voorsiening te maak vir 'n vinniger verwarmings intervensiestrategie.

Previous studies have shown how endothermic organisms have a range of environmental temperatures in which energy used for thermoregulation is relatively low. If the temperature exceeds this specific range, the individual needs to thermoregulate. The demand for thermoregulation depends on several factors, for instance the intensity of solar radiation. Species which have little opportunity to avoid incident solar radiation at their breeding sites, such as cliff-nesting seabirds, could thus be exposed to temperatures outside of their preferred range. In 2019, cameras were installed on the cliffs of Stora Karlsö, which has the Baltic Sea’s largest colony of common guillemots (Uria algee). These cameras made it possible to study the thermoregulatory behavior of common guillemots. Due to seabird species adaptation for minimal heat loss and a rise in global temperature, the common guillemot constitutes an interesting study species. This study aimed to answer the two following questions: How often do common guillemots exhibit thermal regulation? Which variables affect the frequency of thermal regulation in common guillemots? To investigate thermoregulatory behavior and potential drivers, this study included a basic pilot study, behavioral analyzes and regression analyzes to explore potential causal relationships. Due to previous studies five behavior were suggested to indicate thermal regulation in common guillemots of Stora Karlsö; Panting, Raising scapular feathers, “Screaming”, Orientation toward the sun and Seeking shadow. During June 2019, the guillemots showed thermoregulatory behavior 22 of 28 days. Two separate regression analyzes indicate that 18,57 % of the variability of the thermal regulation can be explained by temperature and 84,83 % of the variability can be explained by direct solar radiation. This study observed possible trade-offs and thermal adaptations.

With the world’s increasing usage of electronic devices such as mobile devices and batteries, improving the reliability and performance of these devices has become more and more important. Besides the common overheating issues, low-temperature environments can also cause performance degradation or failure to these devices. Research on thermal switches and thermal regulators aims to improve the thermal management of electronic devices across a range of operating conditions. However, continuous tuning of thermal transport with all-solid-state systems is still challenging. The primary purpose of this work is to propose and demonstrate compressible foams as novel variable thermal resistors and thermal regulators to control device temperature under various input heat flux and ambient temperature. The graphene/PDMS foam is first tested in this work to demonstrate promising performance as a thermal regulator, with continuous tuning capability and a system switching ratio over ~4. Then, the dependence of the thermal conductivity of polymer foams during compression is studied, where the thermal conductivity is measured using a customized system based on an infrared microscope. Unexpectedly, the thermal conductivity decreases slightly at a compression level of more than 10x, in contrast to common theories that the thermal conductivity would increase with the mass density. A simple “spring model” is proposed as a limit where the ligaments do not build contacts during compression. Our results now fall in between the “spring model” and other common theories and can be explained. To gain further insights, a molecular dynamic simulation is performed on a graphene random nanofoam on the nanoscale. The result also shows that the effective thermal conductivity along the compression direction is not sensitive to the mass density, consistent with our experimental data on the macroscopic scale. This work provides useful insights into dynamic thermal management of electronic devices.

Thermal adaptation in freshwater planktonic crustacean Daphnia pulex has been investigated by means of heatshock (35°C) experiments using individuals acclimated to different water temperatures (18, 24, and 28°C). Retention of mobility and survival during the heatshock experiments differed among clones and strongly depended on acclimation temperature: clones acclimated to substressful temperature (28°C) survived significantly longer than clones acclimated to lower temperatures. Both retention of mobility and survival correlated with geographic latitude of the clones' origin. There was, on the other hand, no significant correlation between clones' performance in heatshock experiments and hemoglobin content. Clones do not differ in the degree of the effect of acclimation on survival during heatshock but differ with respect to the effect of acclimation on mobility retention.

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One of prospective procedures of absorbing thermal energy and releasing it during the required time is the application of phase change materials known as PCMs in building envelopes. High thermal energy storage (TES) materials has been a technology that effects the energy efficiency of a building by contributing in using onsite resources and reducing cooling or heating loads. Currently, many TES systems are emerging and contributing in building assemblies, however using an appropriate type of TES in a specific building and climate requires an in-depth knowledge of their properties. This research aims to provide a thorough review of a broad range of thermal energy storage technologies including their potential application in buildings. Subsequently, a comparative study and simulation between a basecase and an optimized model by PCM is thoroughly considered to understand the effect of high thermal storage building's shell on energy efficiency and indoor thermal comfort. Specifically this study proposes that the incorporation of PCM into glazing system as a high thermal capacity system will improve windows thermal performance and thermal capacity to varying climatic conditions. The generated results by eQUEST energy modeling software demonstrates approximately 25% reduction in cooling loads during the summer and 10% reduction in heating loads during the winter for optimized office building by PCM in hot arid climate of Arizona. Besides, using PCM in glazing system will reduce heat gain through the windows by conduction phenomenon. The hourly results indicates the effect of PCM as a thermal energy storage system in building envelopes for building's energy efficiency and thermal regulation. However, several problems need to be tackled before LHTES can reliably and practically be applied. We conclude with some suggestions for future work.

Ce travail s'inscrit dans le cadre d'une thèse Cifre, en partenariat avec la société VIESSMANN Faulquemont SAS, dont l'objectif est d'aboutir à une couche absorbante de nouvelle génération qui vise à réguler de manière passive et réversible la température d'un capteur solaire. Cette couche absorbante est à base de dioxyde de vanadium (VO2), un matériau thermochrome qui présente une transition de phases de type semi-conducteur/métal en fonction de la température. Dans un premier temps, l'élaboration de films de VO2 à 500°C sera présentée puis nous montrerons un procédé inédit et original permettant d'obtenir une phase pure VO2 à partir d'un dépôt effectué à température ambiante. L'étude en température des propriétés optiques et électriques de ces deux types de revêtements sera discutée ainsi que les effets sur la transition de phases de paramètres tels que, la taille de grains ou encore les contraintes internes. Enfin, nous étudierons les propriétés physiques du système biphasé du type VO2+V4O9 qui sous forme de couche absorbante se trouve, in fine, être très avantageux pour la régulation thermique d'un panneau solaire / This work is incorporated within the framework of a Cifre thesis with the partnership of the VIESSMANN Faulquemont SAS society to end in a new generation of absorbent layer in order to regulate the temperature of a solar cell in a passive and reversible way. This absorbent layer is based on vanadium dioxide (VO2), this thermochromic material exhibits a phase semiconductor to metal transition depending on its temperature. In a first step, the synthesis of VO2 films at 500 °C will be exposed and then we will present a new process to obtain a pure VO2 phase with a film deposited at room temperature. The study in temperature of the optical and electrical properties of these two kinds of coatings will be discussed, same as the effects on the phase transition of parameters such as the grain size or the internal stresses. Eventually, we will study the physical properties of a VO2+V4O9 two-phase system as an absorbent layer which is, in fine, very beneficial for the thermal regulation of a solar panel

La présente étude a pour objet de savoir si le Maroc en tant que pays en voie de développement dispose de dispositifs juridiques lui permettant de construire durablement.Le rapport Meadows publié en 1972 annonçant « les limites de la croissance » a incité la communauté internationale à prendre conscience de l’urgence écologique et à agir. Ainsi, plusieurs conférences internationales ont été organisées afin de mettre en place une nouvelle vision de l’avenir de l’humanité. C’est dans ce contexte international marqué par l’accroissement du conflit entre les préoccupations environnementales et le développement économique que la notion de développement durable a vu le jour. Le secteur de la construction parait-il le mieux à pouvoir intégrer ces préoccupations.Un bâtiment durable doit être pensé dès sa conception. Tout le cycle de vie de l’ouvrage a un impact sur l’environnement. C’est pourquoi son développement est subordonné à l’adoption d’un cadre juridique imposant le recours à des matériaux de construction écologique, à la gestion des déchets, à la préservation de la qualité de l’eau, du sol et de l’air et à la réalisation de la performance énergétique. Ces dispositions impliquent de nouvelles exigences qui vont changer les méthodes et pratiques des intervenants et contribuer à une coopération renforcée dans le cadre de la construction. Ainsi, il sera primordial de mettre la lumière sur la responsabilité de ces professionnels. La construction durable a un coût. Son développement doit être appuyé par des règles d’urbanisme, par des incitations financières et par la normalisation et la certification des bâtiments selon les référentiels de l’association haute qualité environnementale. / This study aims to explore the possibility for Morocco as developing country and booming economy to succeed in integrating sustainable development in the construction sector in the same way as his French counterpart.The Meadows report published in 1972 announcing « the limits togrowth » was intended to encourage international community to become aware of the ecological emergency and to act.Thus, a number of international conférences were organized in order to establish a new vision for the future of humanity. It is in this international context marked by the increase conflict between environmental concerns and economic development that the concept of sustainable development was born. The construction fiel dit seems able to integrate these concerns.A sustainable building must be thought fromits conception. All the life cycle of the work has an impact on the environment.That’s whyhis development is subordinated to the adoption of a legal frame work imposing the use of environment-freindly construction materials, waste management, conservation of the quality of the water, the ground and the air and to realization of the energy performance. These rules involve new requirements which are going to change the methods and the practices and contribute to an enhanced coopération gram work or construction. It is there forevery important to shed light on liability of professionals. Sustainable construction has a cost.It’s development must be supported by rules of urban construction, by Financial incentives and by normalization and certification of buildings according to the reference tables of the high quality environmental association.

The challenge of climate change is twofold: to mitigate (prevent) the causes of climate change and to prepare (adapt) to the inevitable effects and consequences. Building and construction are key sectors for decarbonisation (mitigation). The increase in intensity, frequency and duration of heat waves threatens indoor comfort and constitutes a health and comfort risk (adaptation).Therefore, regulations are being changed to take into account related emissions and extreme episodes through new indicators. However, up to now, past climate observations are still used in the calculation of these indicators. This raises the question of how to integrate future climate predictions into regulations. This work aims at characterising the vulnerability of buildings to climate change and aimsat taking into account future climate predictions in building design. It establishes a method for constructing standard weather data based on climate projections and for identifying vulnerable building typologies that are at risk. This project stands out for the use of a large number of building and meteorological data. 77 residential buildings from the Centre Scientifique et Technique du Bâtiment (CSTB) database and 78 years (1981-2058) of weather data for 9 climate models (RCP8.5 scenario) are crossed for Dynamic Thermal Simulations (DTS) on COMETh. The study first highlights the relevance of using reference and extreme years, representative of the climate data, to reduce the number of simulations. The reference year makes it possible to observe the average needs over a period. The extreme year estimates the range of values around this mean.The report then raises the issue of cooling systems as one of the major challenges for energy needs. Under the effect of climate change, heating requirements are decreasing and largely compensate the increase of cooling needs. But few buildings in France are already equipped with cooling systems and the creation of a need exceeding a threshold leads to the purchase of new units. This raises a problem of social equity in access to thermal comfort. Moreover, the environmentalimpact of these systems is more related to refrigerants necessary for the manufacturethan to energy consumption.The research finally proposes a method to classify passive or active buildings (in the sense of cooling needs), that are adapted or not adapted to future extreme weather conditions. This involves applying a clustering algorithm (k-means) to group similar buildings together in terms of energy requirements for different climate models. This method already makes it possible to identify the buildings at risk and to prioritise the measures to be taken (energy renovation). This classification also opens up the possibility of extending this work to newer, larger and more diversified samples. Similar encouraging results were obtained from 2470 offices. They could helpidentify technical and architectural characteristics and assist in the design of efficient passive buildings.

Des films minces de pérovskites NdNiO3 et SmxCa1-xMnO3 ont été synthétisés par co-pulvérisation magnétron et leurs propriétés thermochromes ont été étudiées dans le domaine infrarouge. Dans un premier temps, l'étude du nickelate NdNiO3 a montré la possibilité de synthétiser la phase pérovskite en utilisant un recuit de cristallisation sous air à basse température (550°C). Nous avons mis en évidence une cristallisation compétitive entre la phase orthorhombique thermochrome et une phase rhomboédrique non thermochrome qui est largement influencée par les paramètres d'élaboration : pression de dépôt, épaisseur des couches, température de recuit... L'obtention de ces deux phases a permis d'étudier plus précisément les mécanismes d'oxydation et de réduction intervenant lors du dépôt et lors du traitement thermique respectivement. Parallèlement à cette étude, des couches minces de SmxCa1-xMnO3, ont été également synthétisées par co-pulvérisation. Après une optimisation des conditions expérimentales permettant d'obtenir des films stoechiométriques et des analyses structurales (MEB, DRX), les comportements électriques et optiques des films ont été suivis en fonction de la température (mesure 4 pointes et IRTF). Le composé Sm0,5Ca0,5MnO3 présente une température de transition proche de la température ambiante ainsi qu'un contraste optique dans le très proche et le moyen infrarouge. Les mesures de la transmittance optique dans le domaine visible-proche infrarouge ont permis d'évaluer la dépendance du gap optique avec la température. A 20°C, celui-ci est proche de 0,7 eV. Le manganite SmxCa1-xMnO3 est donc un bon candidat pour la régulation thermique et la furtivité infrarouge / NdNiO3 and SmxCa1-xMnO3 perovskites thin films were synthesized by magnetron co-sputtering process and the thermochromic properties have been studied in the infrared range. At first, the study of the NdNiO3 nickelate has established the timeliness to synthesise the perovskite phase using a subsequent annealing crystallisation in air at moderate temperature (550°C). We have demonstrated a competitive crystallisation between the thermochromic orthorhombic phase and a non-thermochromic rhombohedral phase largely influenced by experimental parameters: deposition pressure, layer thickness, annealing temperature... The presence of these two phases allowed to clarify more precisely the oxidation mechanisms involved during the deposition process and the reduction mechanisms occurring during the heat treatment. At the same time, the SmxCa1-xMnO3 system was synthesised also as thin films. The first step includes developing the experimental conditions to obtain stoichiometric films using two separate targets. After structural analyses (SEM, XRD), the electrical and optical behaviours of films were analysed using the four probe configuration and the FTIR spectroscopy versus temperature respectively. As result, the metal-insulator transition of the Sm0,5Ca0,5MnO3 compound is close to the room temperature and the film shows an interesting optical contrast in the near and mid-infrared ranges. The optical transmittance measurements in the visible-near infrared range were used to evaluate the optical gap dependence with temperature. At room temperature, the optical gap is close to 0.7 eV. Finally, SmxCa1-xMnO3 manganite is a good candidate for thermal regulation and infrared furtivity