Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study is an introductory investigation into vaporizer technology as implemented in micro gas turbines. Experimental investigations are aimed at the development of expectations concerning the internal flow structure though vaporizers by generating application specific flow maps. Consolidation of these maps with other experimental data suggests that annular flow leads to increased evaporation rates. In addition, it was discovered that flow structure is affected by the injection angle and air and fuel flow rates. An investigation into the numerical modelling of vaporizers is based on two phase flow theory using a flow structure approach. The numerical behaviour is observed for parametric variations to establish the impact of assumptions. A final numerical model is formulated with empirically determined coefficients with fair correlation to experimental data. The results of this study yield recommendations towards the implementation and analysis of vaporizers with applied use in micro gas turbines. / AFRIKAANSE OPSOMMING: Hierdie studie is 'n inleidende ondersoek na verdamper tegnologie soos toegepas in mikro gasturbines. Eksperimentele ondersoeke is gerig op die ontwikkeling van kennis rakende die interne vloeistrukture deur verdampers met die bou van toepassingspesifieke vloeikaarte. Konsolidering van hierdie kaarte met verdere eksperimentele data dui daarop dat annulêre vloei lei tot verhoogde verdampingstempo’s. Daar is ook bevestig dat die vloei struktuur deur die inspuitingshoek en vloeitempo’s affekteer word. 'n Ondersoek na die numeriese modellering van verdampers is gebasseer op twee-fase vloei met 'n vloeistruktuur benadering. Die numeriese gedrag is waargeneem vir parametriese variasies om sodoende die impak van aannames te bevestig. Die numeriese model is voltooi met empiriese bepaalde koëffisiënte en lei tot goeie korrelasie met eksperimentele data. Resultate van hierdie studie lei tot aanbevelings rakende die implementering en ontleding van verdampers met spesifieke toepassing op mikro gas turbines.

A lithium vaporizer for a high-power magnetoplasmadynamic (MPD) thruster is modeled using a parallel approach. A one-dimensional, thermal-resistive network is developed and used to calculate the required vaporizer length and power as a function of various parameters. After comparing results predicted by this network model with preheat power data for a 200 kW MPD thruster, we investigate performance over a parameter space of interest for the Advanced Lithium-Fed, Applied-field, Lorentz Force Accelerator (ALFA2) thruster. Heater power sensitivity to cathode tube emissivity, mass flow rate, and vapor superheat are presented. The cold-start heater power for 80 mg/s is found to range from 3.38 to 3.60 kW, corresponding to a vaporizer (axial) length of 18 to 26 cm. The strongest drivers of vaporizer performance are cathode tube emissivity and a conduction heat sink through the mounting flange. Also, for the baseline ALFA2 case, it is shown that increasing the vapor superheat from 100 K to 300 K has the effect of lowering the vaporizer thermal efficiency from 57% to 49%. Also, a finite-volume computational fluid dynamic (CFD) is implemented in FLUENT 6.2 which includes conjugated heat transfer to the solid components of the cathode. This model uses a single-fluid mixture model to simulate the effects of the two-phase vaporizer flow with source terms that model the vaporization. This model provides a solution of higher fidelity by including three-dimensional fluid dynamics such as thermal and momentum boundary layers, as well as calculating a higher resolution temperature distribution throughout the cathode assembly. Results from this model are presented for three mass flow rates of interest (40 mg/s, 80 mg/s, and 120 mg/s). Using a fixed power and length taken from the conceptual ALFA2 design, the dryout point ranges from 12.3-17.6 cm from the base of the cathode assembly for 40 mg/s and 80 mg/s, respectively. For the 120 mg/s case, the two-phase flow never reaches dryout. Finally, results two modeling approaches are compare favorably, with a maximum disagreement of 13.0 percent in prediction of the dryout point and 4.2 percent in predictions of the exit temperature.

The aim of this diploma thesis is the construction design of the steam boiler burning pellets. Set parameters: 450°C; 5,2 MPa; 30t/h. Decision procedure: stoichiometric calculation, energy balance, calculation of combustion chamber and heat delivery surface.

This diploma thesis deals constructional and calculation design of the steam boiler 60t/h of clean burning wood. For the parameters of the stoichiometric calculations are carried out and enthalpy calculations of combustion and air. The collected data is then made It a diagram of air and flue gas. The following are the calculations with the heat balance calculations of losses and determination of the boiler thermal efficiency of the boiler. It is made of the combustion chamber design and its thermal calculation. After determining the main dimensions of the combustion chamber moves continue the calculation of boiler heating surfaces. At the end of the calculations are controlling the overall energy balance. Boiler output parameters as temperature, pressure and quantity of the steam.

This master thesis designes the calculation of fluid boiler with specific part - the circular fluid bed. The heat is given by combustion of wood biomass. The thesis is devided into several parts. All necessary elementary results are going to be reached within these parts: an analysis of solid fuel, stechiometry calculation, discussion on output limits and the environmental point of view, definition of elemental heat losses and general heat efficiency, calculation and design of a combustion part and its heat loads and calculation of enthalpies with different ash concentrations. All these phases get to a successful design of the fluid boiler heat balance and sizes of heat-flow surfaces. The composition of the boiler shows the added drawing.

Thin layers are widely used in many fields of technology and today we can say that they are found in all modern technologies. Thin layers can be created in two ways, namely by chemical or physical means. This work focuses on the latter method, more particularly a technology of thermal evaporation of thin layers in a vacuum. The work focuses on the process principles during and after the evaporation. Much of the work focuses on the development and design of experiments. These experiments illustrate some of the phenomena that take place on thin films produced by the aforementioned technology. Work helps to better understand processes during formation of thin layers and properties that influence the quality and stability of thin films. In conclusion we describe results of experiments and new developments in the field of thin films deposition using evaporation under vakuum are summarized.