Thesis (Ph. D.)--Landbouwhogeschool te Wageningen, 1981. / Summary in Dutch. Includes bibliographical references (p. 170-176).

<p> CHF and Post-CHF tests were performed in water at 9.7 MPa using two vertical test assemblies having identical, internally heated annular flow channels, one heated directly, the other indirectly. Experiments were conducted to determine the effect of these methods of heating on CHF and Post-CHF heat transfer. </p> <p> For the range of the test conditions investigated, the results show that the direct and indirect heaters have similar CHF performance. At heat fluxes above CHF and mass fluxes of 2.0 and 3.5 Mg.s^-1 .m^-2 , the indicated maximum wall temperatures of the heaters were similar, but at the highest mass flux for the tests, 5.0 Mg.s^-1 .m^-2 , the indirect heater had lower indicated maximum wall temperatures than the direct heater for a given heat flux above CHF. </p> <p> A multi-fluid model, of the type used previously in the prediction of CHF, was derived and tested against the experimental data. The model, which considers droplet entrainment, deposition and evaporation in the annular flow regime, assumes dryout to occur when the liquid film flow on the inner rod approaches zero. The CHF predictions were in fairly good agreement with the experimental results. In general, the model under-predicted CHF at low inlet subcoolings and over-predicted CHF at high inlet subcooling. The error trend is consistent with that of the CHF prediction models of other researchers. </p> <p> In addition to the CHF prediction model, a Post-CHF model to predict the vapour temperatures, and hence, the heated wall temperature is also presented in the report. The theory is based on a physical model of heat transfer in the liquid deficient regime. In the model, heat in the dry region is assumed to transfer from the heated wall to superheat the steam and some of this heat, in turn, is used to evaporate the droplets which are entrained in the vapour core. Droplet entrainment and deposition at the shroud (outer tube) film-vapour interface are modelled. Heat transfer enhancement due to increased turbulence downstream of the rod centering spacers is incorporated through an empirical correlation. The predicted results were compared to the direct heater experiments. In general, the predicted wall temperatures were in agreement with those in the experiments. </p> / Thesis / Master of Engineering (MEngr)

According to the statistics about civil transportation aircraft Environmental Control system (ECS), the three-wheel high pressure water separation system (HPWS) and low pressure water separation system (LPWS) are the most common choices for the 150-seat airliners. Although the former has become the mainstream configuration for air conditioning pack, the latter is still used on Boeing 737-600/700. In order to compare the two configurations and choose the better one for a specific aircraft, simulation and analysis are done. The cabin heat load is calculated at first in order to calculate required engine bleed air mass flow. Then a specific aircraft is defined so that required structural dimensions and cabin comfort indexes can be obtained based on Airbus 320. Thirdly, the component models are built by Matlab/Simulink according to the fundamental knowledge of heat transfer and aerodynamics, the working principles and mechanical dimensions of the components, the ambient environmental parameters and some data from Airbus 320. Consequently, the complete system model can be assembled. After confirming the validity of the model by checking the required ram air mass flow and temperature deviation of the state points referred to Airbus 320, the simulation model is used to do analyze the specific aircraft. Finally, through comparing the different values of ram air mass flow and turbine expansion ratio, as well as the system mass, economic cost and reliability, the better configuration is selected. It can be summarized that the three-wheel LPWS requires less ram air mass flow (0.012kg/s) and a little lower expansion ratio (0.02) than the HPWS, and it also has lower weight (63% of HPWS), lower (83% of HPWS) cost and higher reliability (140% of HPWS), thus it is the suitable configuration for the specific aircraft.

Magister Scientiae - MSc (Environ & Water Science) / There are growing concerns around the environmental issues related to processed water as the demand for potable water is on the increase in South Africa. Effluents discharged from various sectors such as water treatment facilities pose a constant threat to the environment and natural water resources, including rivers and groundwater due to their poor chemical and physical composition. As a result, the demand for predicting the elevated concentrations of salts in a spatial and temporal dimension is constantly growing. The effluent at the eMalahleni water reclamation plant in Mpumalanga, South Africa, is being processed through a triple reverse osmosis that improves the water quality of the mine water to potable standards. Two water quality streams emerge from this process, i.e. a potable standard and the other a brine concentrate which is stored in ponds. Brine ponds are used for inland brine disposal in the eMalahleni water reclamation plant. The large volumes and limited capacity to store brines has placed great emphasis on enhanced evaporation rates to increase the efficiency of the ponds. In order to improve the rate of brine evaporation in the pond, an understanding of the effect of brine salt content and other parameters affecting the rate of evaporation is required. This study aimed at establishing the physical and chemical behaviour of the brine from the eMalahleni plant in a controlled environment. The investigation incorporated actual brine from the eMalahleni plant as well as synthetic salts typical of the major components of the eMalahleni brine.

This diploma thesis deals with the unconventional technology of cutting water jet. The aim of this thesis is analysis of technological possibilities of water jet, possible operating modes (techniques) and entering technological data and influence of technical parameters on quality and accuracy of cutting. The thesis contains several experiment at which was examined achieved quality and accuracy of cuts, and simultaneously there is solved technoeconomic evaluation of this technology.

Dans cette thèse, nous étudions la stabilité et les propriétés des glaces d’eau de haute pression (entre 5 et 300 GPa) et de haute température (entre 300 et 2000 K) comportant ou non des inclusions de NaCl dans leur structure cristalline. Pour attendre ces conditions propres aux intérieurs des exoplanètes océans, nous utilisons une approche théorique basée sur des dynamiques moléculaires ab initio. Nous montrons que l’analyse de la dynamique des liaisons entre hydrogènes et oxygènes permet de distinguer toutes les phases de la glace présentant une structure cubique volume-centrée. En particulier, nous présentons la première description ab initio de la phase plastique, et nous mettons en évidence la présence de multiples transitions dans la phase superionique. Ensuite, nous montrons que jusqu’à 5.9 % en masse de NaCl peuvent être inclus dans la structure de la glace à 1600 K. L’inclusion des ions Na+ et Cl- stimule le désordre orientationel des molécules d’eau par rapport à la glace d’eau pure. À partir de 2.5 % en masse de NaCl, la conduction superionique s’étend à l’ensemble de la gamme de pression étudiée, et la symétrisation des liaisons hydrogènes se produit à plus haute pression. Enfin, nous décrivons les structures de cœur des dislocations vis ayant des vecteurs de Burgers <110> et <111> dans la glace X à 80 GPa, ce qui constitue une étape préliminaire importante à la construction de lois rhéologiques pour les glaces cubiques de haute pression. / In this thesis we study the stability and the properties of pure and NaCl-bearing dense water ices at high pressure (between 5 and 300 GPa) and high temperature (between 300 and 2000 K). To reach these conditions that correspond to the interiors of ocean exoplanets, we employ a theoretical approach based on ab initio molecular dynamics simulations. We show that a detailed analysis of the hydrogen bond dynamics allows to distinguish all the different ice phases presenting a body-centered cubic sub-lattice of oxygen atoms. In particular, we present the first ab initio description of the plastic phase of water ice. We also reveal the multiple transitions that occur in the superionic domain. Next, we show that ice VII' can incorporate up to 5.9 wt% NaCl in its structure at 1600 K. The inclusion of Na+ and Cl- ions enhances the orientation disorder of the water molecules in comparison to the pure ice. From 2.5 wt% NaCl, superionic conduction expands over the entire pressure range studied, and the hydrogen symmetrisation is shifted towards higher pressures. Last, we describe the <110> and <111> screw dislocation core structures of ice X at 80 GPa. This constitutes a first step towards the construction rheological laws for high-pressure cubic ices.

In diploma thesis there is elaborated the analysis of assumed development of water jet technology and there is analyzed the level of water jet method in production. There are introduced the possibilities of new applications of water jet machining and the possibilities of it’s future development. There is think over the enlargement of this method in next 5 years. Simultaneously there is solved the question of techno economic operation severity of this technology.