Dans cette étude, nous souhaitons aborder toutes les activités de François et François-Charles Joullain qui ont été, entre autres activités, graveurs, éditeurs et marchands d'estampes. Nous replacerons ces deux personnages dans le contexte du commerce de l'art à paris au XVIIIe siècle et nous tenterons d'évaluer leur participation à la diffusion de la création artistique par la gravure et, dans une moindre mesure, par les tableaux. La place centrale qu'ils occupent dans le monde de l'art parisien sera également pour nous l'occasion de nous intéresser au domaine du collectionnisme ainsi qu'au goût pour l'estampe dans la capitale au début du XVIIIe siècle. L'étude de ces deux marchands, encore mal connus des chercheurs, nous permettra donc d'aborder conjointement le monde de l'édition d'estampes et celui des amateurs, de plus en plus nombreux, afin d'en apprendre davantage sur l'histoire du goût et ses fluctuations au cours du XVIIIe siècle. / In this study, we wish to approach all the activities of François and François-Charles Joullain which were, among others activities, engravers, publishers(editors) and traders of prints

The purpose of this research program was to measure the efficiency of evacuated tube solar collectors under various operating conditions including: the angle of inclination towards the incident solar radiation, heat transfer fluid flow rate, glazing installation, and number of evacuated tubes. The operating conditions and configurations were chosen to represent realistic or probable installation scenarios and environmental conditions. Furthermore, the research aimed to identify the suitability of evacuated tube solar collectors to each of the scenarios. The scope of the research project was limited to the efficiency of a single tube, and various configurations of a 32-tube panel, not the entire solar domestic hot water or space heating system. Thus, factors such as heat loss in the tubing, solar storage tank, and heat exchanger efficiency were not investigated. The findings indicated that efficiency varied by approximately 5% in general between the different collector configurations.

The purpose of this research program was to measure the efficiency of evacuated tube solar collectors under various operating conditions including: the angle of inclination towards the incident solar radiation, heat transfer fluid flow rate, glazing installation, and number of evacuated tubes. The operating conditions and configurations were chosen to represent realistic or probable installation scenarios and environmental conditions. Furthermore, the research aimed to identify the suitability of evacuated tube solar collectors to each of the scenarios. The scope of the research project was limited to the efficiency of a single tube, and various configurations of a 32-tube panel, not the entire solar domestic hot water or space heating system. Thus, factors such as heat loss in the tubing, solar storage tank, and heat exchanger efficiency were not investigated. The findings indicated that efficiency varied by approximately 5% in general between the different collector configurations.

Hybrid solar systems as well as concentrating solar collectors are promising solar technologies. To run them efficiently in northern countries is a task Solarus AB is working on.The objective of this MSc project is to investigate and experimentally evaluate the option of implementing a light diffusing sheet in acompound parabolic concentrator (CPC) solar collector, called the “Scania Model”. This component should improve the non-uniform illumination of the photovoltaic cells in concentrating solar collectors.Therefore, scientific publications on this kind of solar collectors were read up on, e.g.Adsten, M. Brogren, M., Roos, A., Karlsson, B. Nilsson, J. and Leutz, R.After researching and procuring possible diffuser materials, experimental tests were carried out and the different materials were reviewed. Implemented in a solar simulator the IV curves of the collector with the different diffusers were generated. Furthermore, the influence of the materials on light was reviewed using daylight, laser light and an artificial light source. In the following, the light intensity distribution on the absorber of the Scania Model was defined and evaluated.The results of this project show that the main problem regarding diffuser material is to provide sufficient diffusion without much transmission losses.

A novel type of parabolic trough collector was characterised using a very basic theoretical model. This model looked at an ideal case and provided a basic expectation that was compared to actual measurements. The model showed that greater improvements can be achieved if heat losses to the environment are limited or omitted. This can be achieved by using a glass shield to insulate the receiver in a vacuum to limit the effect wind has and therefore limit convective losses. The experimental characterisation of the PTC consisted of taking six different temperature measurements to better understand the energy balances taking place. Four different configurations were tested, using two different types of concentrator and in each case a receiver that was either unpainted or painted with a semi matte black paint. The different types of concentrator were either stainless steel sheet metal or discretised glass mirror strips, similar to a linear Fresnel collector. Experimental runs were conducted on cloudless days for an hour and 15 minutes. This allowed for three runs to be performed on a single day. Using the theoretical model and comparing it to the experimental data, an efficiency was calculated. This efficiency averaged 14 % when the receiver was unpainted and 13 % when the receiver was painted for the metal sheets. The glass mirror strips had average efficiencies of 54 % and 45 % for an unpainted and painted receiver respectively. The model is very basic and can be improved upon if more variables are taken into consideration, such as convective heat losses. It was also recommended that wind measurements are taken in future tests. A property looked at to evaluate the effectiveness of each type of configuration was the average energy supplied to the thermal heating fluid over the course of an experimental run. For this the averaged values over all the experimental runs conducted for stainless steel sheet metal were 258 W and 332 W for an unpainted and painted pipe respectively. When using the glass mirrors an average energy value of 1049 W was supplied when the pipe was unpainted and an average of 1181 W was gained in the runs conducted after the pipe had been painted. Painting the receiver had little to no effect. The surface temperature of the receiver after painting the pipe was not higher and a slight increase in the energy gained by water was observed. This was explained by inaccuracies during testing as scattered light may have caused an interference on some of the measurements. There were also human inaccuracies in testing which should be omitted in future tests by implementing, for one, a functional tracking system. Future tests should be designed in such a way to completely omit irradiance affecting the thermocouple taking the measurement. Glass mirrors fared far better than the stainless steel sheet metal counterpart. It was recommended that they are used as the concentrator of choice. Higher efficiencies were achieved and in some cases almost four times the energy was supplied to the water in the pipe. This was attributed to a much lower concentrator temperature, on average 11 °C lower than the temperature of the metal sheets, as well as a much better ability to concentrate sunlight onto a single focal point. However, the glass mirror strips were proven to be very fragile and as such, require protection from the elements. While the strips were lighter and caused less of a load during windy conditions, they were susceptible to oscillations from gusty wind. This led to a number of strips breaking and needed to be replaced. By discretising the strips into individual pieces, they had the benefit of only needing to replace the strips that were damaged. This is also true for all future runs. It is still recommended that a tarp be used to protect the glass mirrors. Using glass mirror strips as a concentrator combined LFC technology with PTC technology and a novel PTC design was achieved. The design still required the installation area of a PTC. The novel design was compared to Industrial Solar’s industrial LFC module, LF-11, as it shares many similarities to LFC technology. The peak thermal output of the rig was significantly lower at 346 W/m2 compared to the industrial value of 562 W/m2. However, the noteworthy differences in design and optimisation between the two modules meant the results achieved were comparable. It is expected that better and more comparable results can be realised once the inherent flaws in the design, such as tracking the sun, aperture size and adding a vacuum absorber, are addressed. It is recommended that more research and emphasis is put into this field as an alternative energy power plant for South Africa. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

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Ranney radial collector wells consist of an array of horizontal lateral wells arranged radially around and connected to the base of a vertical well. They offer numerous advantages over traditional vertical wells with application in both the petroleum industry and hydrologic sciences. This study improved the understanding of the interaction of collector wells and the aquifers/reservoirs they tap by numerically modeling flux exchanges between a collector well and a river in an unconfined aquifer with regional background flow. Modeling demonstrated that flux along each horizontal lateral increased with distance from the vertical well stem following a third order polynomial function. Ultimately these models demonstrated that in the collector well/aquifer/river system, the pumping rate of the collector well was the dominant factor in controlling flux between the river and aquifer under various conditions. This study can be used to project the maximum allowable pumping rate without causing an initially gaining river to become a losing river.

Ranney radial collector wells consist of an array of horizontal lateral wells arranged radially around and connected to the base of a vertical well. They offer numerous advantages over traditional vertical wells with application in both the petroleum industry and hydrologic sciences. This study improved the understanding of the interaction of collector wells and the aquifers/reservoirs they tap by numerically modeling flux exchanges between a collector well and a river in an unconfined aquifer with regional background flow. Modeling demonstrated that flux along each horizontal lateral increased with distance from the vertical well stem following a third order polynomial function. Ultimately these models demonstrated that in the collector well/aquifer/river system, the pumping rate of the collector well was the dominant factor in controlling flux between the river and aquifer under various conditions. This study can be used to project the maximum allowable pumping rate without causing an initially gaining river to become a losing river.

Collector well designs are necessary to maximize groundwater uptake and riverbank filtration without negatively impacting an aquifer. Unfortunately, there is a lack of information and research regarding the implementation of collector well design parameters. In the past, collector well installation was too costly, but recent advances in well technology have made collector wells more cost effective. This research will contribute a set of guidelines to optimize riverbank filtration and groundwater remediation. This study models the hydrodynamics surrounding collector well configurations in riverbank filtration and groundwater remediation. Visual Modflow® was utilized to run a variety of numerical models to test four areas: flux along the laterals of a collector well, collector well interactions with a river, collector well yield, and collector well remediation capability. The two design parameters investigated were lateral length (25 m, 50 m, and 100 m) and number of laterals (3 and 4). The lateral flux tests confirm flux increases towards the terminal end of each lateral and pumping rate is the controlling factor in flux amount obtained along the laterals. The analysis of the flux-river interaction shows the main factor in determining flux amount is the initial river geometry, followed by the pumping rate, regional background flow, and collector well design, respectively. The models suggest that the 4-lateral collector well design is more effective than the 3-lateral design and in addition, 100 meter length laterals provide the highest amount of yield with the least amount of drawdown. The remediation tests investigate the application of vertical well equations to evaluate collector well designs in two areas: minimum pumping rate to capture line source of particles and first arrival time of particles. The remediation models show 100 meter length laterals provide both the lowest pumping rate and the highest residence time with the surrounding aquifer for maximum remediation. Ultimately, these models provide basic design guidelines and explain which designs are most effective, depending on the collector well purpose.