This work addresses the challenges in design of heat integrated low-temperature separation processes. A novel, systematic and robust methodology is developed, which contributes to the design practice of heat-integrated separation sequence and the refrigeration system in the context of low-temperature separation processes. Moreover, the methodology exploits the interactions between the separation and refrigeration systems systematically in an integrated design context. The synthesis and optimisation of heat-integrated separation processes is complex due to the large number of design options. In this thesis, task representation is applied to the separation system to accommodate both simple and complex distillation columns. The stream conditioning processes are simulated and their associated costs are included in the overall cost of the process. Important design variables in separation systems, such as the separation sequence, type and operating conditions of the separation units (e.g. the operating pressure, feed quality and condenser type) are optimised. Various refrigeration provision strategies, such as expansion of a process stream, pure and mixed multistage refrigeration systems and cascades of multistage refrigeration cycles, are considered in the present work. A novel approach based on refrigeration system database is proposed, which overcomes the complexities and challenges of synthesis and optimisation of refrigeration systems in the context of low-temperature separation processes. The methodology optimises the key design variables in the refrigeration system, including the refrigerant composition, the number of compression stages, the refrigeration and rejection temperature levels, cascading strategy and the partition temperature in multistage cascaded refrigeration systems. The present approach has selected a matrix based approach for assessing the heat integration potentials of separation and refrigeration systems in the screening procedure. Non-isothermal streams are not considered isothermal and stream splitting and heat exchangers in series are taken into account. Moreover, heat integration of reboiler and condenser of a distillation column through an open loop heat pump system can be considered in this work. This work combines an enhanced simulated annealing algorithm with MILP optimisation method and develops a framework for simultaneously optimising different degrees of freedom in the heat integrated separation and refrigeration processes. Case studies extend the approach to the design of heat integrated separation sequences in above ambient temperature processes. The robustness of the developed framework is further demonstrated when it is utilised to design the LNG and ethylene plant fractionation trains.

This thesis investigates changes in temperature extremes between 1950-2005, analysing gridded data sets of observations and climate model simulations. It focuses on changes in the frequency of extreme temperatures occurring in single days or over periods of six or more consecutive days. The study aims to quantify the significance of changes in extreme temperature events and answer the following questions. Are external or human-induced forcings together with natural forcings responsible for the observed change in temperature extremes or can these changes be explained due to natural climate variability alone? Are the observed changes consistent with those from climate model simulations? And are the changes in extremes linked only to changes in the mean climate, or only to those in climate variability or both? The analysis concentrates on changes from global to regional scale and from annual mean to seasonal scale. A detection method is applied to assess if changes are significantly different with respect to the internal climate variability. Results show that there has been a significant increase in warm daily extremes and a decrease in cold ones, both on large and small spatial scales. The increase in warm extremes has been found to be highly correlated with the increase in mean temperature. The changes in daily extremes are well represented in climate model simulations. Changes in the persistent extremes show a detectable increase in the frequency of warm and a decrease in cold events and are reproducible by models.

Target Acquisition Weapons Software (TAWS) Version 3.4 is a joint Tactical Decision Aid (TDA) used to predict performance of electro-optic and electro-magnetic (EM/EO) munitions and navigation systems. TAWS is the USAF and USN mission-planning standard for laser-guided, infrared, and TV munitions and navigation systems TDAs. As TAWS continues to deploy through the mission planning community there is a need to establish a systematic approach to assessing TAWS accuracy. This study was an operational assessment of TAWS Infrared (IR) model performance and consisted of two parts: a comparison of model predictions to pilot observations of IR detection range of a static tank target and an assessment of physical temperature predictions. Limiting factors of this project are similar to those encountered in real world utilization of TAWS mission planning TDAs. This evaluation found TAWS predicted detection ranges and target scene model output were representative forecasts of observed values. The TDA provided a good description of background thermal behavior and highlighted the necessity of careful evaluation of the target scene because of component facet complexity and the geometry of facets exposed to the sensor view. The resulting component analysis illuminated the benefit of focusing new TAWS development on improving the target physical model.

A systematic examination of 1836 images of the sky constructed from scans made by the Infrared Astronomical Satellite has resulted in the detection of 466 objects which are shown to be in Earth orbit. Analysis of the spatial and size distribution and thermal properties of these objects, which may include payloads, rocket bodies and debris particles, is being conducted as one step in a feasibility study for space -based debris detection technologies.

No description available.

Digitized by Kansas Correctional Industries

A research report submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science. Johannesburg, 2017. / Lesotho, being a mountainous area and due to the level of poverty and the dependency of its economy largely on agriculture, is particularly vulnerable to the impacts of climate change. This study examined maximum, minimum and mean temperature trends at various altitudes in Lesotho so as to determine possible implications of recent (70 - 80 years) altitudinal climate trends on the agricultural sector. Using seven stations at various altitudes across Lesotho, trends in maximum, minimum and mean temperatures were analyzed at monthly, annual and seasonal scales. The significant warming of minimum temperatures (Mokhotlong (p=0.000), Oxbow (p=0.013) and Qachasnek (p=0.002)) and maximum temperatures (Mokhotlong (p<0.0001), Oxbow (p=0.007) and Qachasnek (p=0.000)), were observed at the highland stations, located on the eastern side of Lesotho, while at the lowland stations as well as in the foothills, located on the western side of Lesotho, significant increases were only observed with minimum temperatures (Maseru (p<0.0001) and Mejametalana (p=0.000), Butha Buthe (p=0.017), located on the western side of Lesotho. In Mohaleshoek, located in the Senqu river valley, no significant trends were observed. In addition, a significant decrease in the number of days with frost was observed in both the highlands and the lowlands. With significant increases in maximum and minimum temperatures, a decline in agricultural production can be expected in the lowlands while a potential increase in areas suitable for agricultural production can be expected in the highlands. / LG2017

Student Number : 0413336G - MSc(Eng)dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / This dissertation reports systematic work aimed at determining the plastic deformation mechanisms that led to strains at fracture as high as 4.7% in WC-Co alloys at 1000°C when subjected to 3-point bending tests. The three grades investigated have a Co content of 15wt% and WC grain sizes of 1.3, 0.35 and 0.3 μ m respectively and were received after they were tested in bending. Fractography, macrostructural and microstructural investigations were carried out in attempts to identify the mechanisms leading to the large strains. Techniques used included light microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and quantitative image analysis. Through comparisons of the results from the three grades at various temperatures, it was possible to establish that the large strain at 1000°C are mainly due to cracking and cobalt drift. During the fractographic investigations it was found that the grades which contained VC as a grain refiner exhibited steps on the WC grains and that fracture propagated preferentially along the stepped WC grain boundaries.

Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries