Abstract Pool boiling process is frequently encountered in a number of engineering applications. However, it is difficult to exactly predict the heat transfer coefficient. This is because the boiling phenomenon is rather complex and influenced by many factors, such as surface condition, heater size, geometry, material, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure diameter, frequency and nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. The present study is ain at providing the pool boiling data for plasma coating and helical wire wrapped enhanced tubes. Furthermore, more fundamental of the physical phenomenon can be obtained. This study was performed experimentally. R-134a and R-600a were used as refrigerants. The surface condition will be changed with plasma spray coating and helical wire wrapped. It is expected that the surface condition can affect the nucleate boiling heat transfer in certain degree. In addition, boiling visualization was also made to broaden our basic understanding of the bubble diameter and dynamics while growing. Thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results will hopefully be helpful not only for the academia but for the industry.

Abstract Pool boiling process is frequently encountered in a number of engineering applications. However, it is difficult to exactly predict the heat transfer coefficient. This is because the nucleate pool boiling phenomenon is rather complex and influenced by many factors, such as surface roughness, areas of heater, material, geometry, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure frequency, diameter and active nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. This study was performed experimentally. R-134a was used as refrigerants, and the present study is aim at providing the pool boiling data for smooth and plasma coating enhanced tube bundles. It is expected that the surface condition, amount of test tubes, geometric of bundles and different heat flux can affect the nucleate boiling heat transfer in certain degree. In addition were calculated and developed that heat transfer coefficients and relevant corrections. Furthermore, more fundamental of the physical phenomenon can be obtained. According to the results of experiments, Boiling curves and calculations of the bundle factors and geometry factors were subsequently secured. The enhanced heat transfer coefficients with coated tube bundles are 1.1-2.0 times higher than smooth tube bundles. The 1.5-2.3 and 1.1-3.8 bundle factors obtained from the smooth tube bundles and coated tube bundles respectively. The geometry factors were about 1 for all arrangements studied herein. Thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results will hopefully be helpful not only for the academia but for the industry.

Abstract Pool boiling process is frequently encountered in a number of engineering applications. It is difficult to exactly predict the heat transfer coefficient. This is because the boiling phenomenon is rather complex and influenced by many factors, such as surface condition, heater size, geometry, material, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure diameter, frequency, velocity and nucleation site density will be varied in such different heated rod pitches resulting in the different effect of heat transfer. Furthermore, more fundamental of the physical phenomenon can be obtained. Pool boiling heat transfer of R-134a is investigated experimentally on twin tube arrangement. The tube pitch is 1.65 and 2.5. The surface condition was prepared with plasma spray coating. In addition, using the high-speed digital camera and LDV, the bubble diameter and dynamics of R-134a were measured while growing. The boiling curves in different twin-tube pitches were drawn and the influence of bubble velocity on heat transfer coefficients was also examined. Finally, to broaden our basic understanding of different arrangement of heated rods and heat transfer mechanisms, thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results would hopefully be helpful not only for the academia but also for the industry.

The transient two-dimensional thermocapillary convection and molten pool shape in melting or welding with a time-dependent and distributed incident flux are numerically predicted in this study. Determination of the molten pool shapes is crucial, because of its close relationships with the strength, microstructure, and mechanical properties of the fusion zone. In the work, the time-dependent incident flux is assumed to be a function of scanning speed and energy distribution parameter. Transport processes at the time corresponding to the maximum cross section can be identical to those under steady three-dimensional condition. The computed flow patterns and molten pool shapes under the flat free surface exhibits distinct regions for different Marangoni and Prandtl numbers. The effects of Peclet number and beam power on flow and temperature fields and fusion zone shapes are also presented. The computed results are confirmed by comparing the predicted peak speed on the free surface and molten pool width with those obtained from scale analysis provided in the literature.

Barton Springs Pool (BSP) is an important ecological and recreational resource to the City of Austin (CoA). Due to sediment accumulation, excessive algal growth, and concern for water velocities through salamander habitat, improving the flow regime of BSP was identified as an important focus for future infrastructure development in Barton Springs Pool. The CoA commissioned this project to develop and test a hydrodynamic model to provide a basis for understanding the flow dynamics of BSP, and to aid in future infrastructure developments in BSP. This phase of the project included the collection of bathymetric and velocity data, creating a hydrodynamic model of BSP that dynamically represents space-time varying 3D velocities, and testing the model using the default settings and an adjustment of the outlet coefficients. The model was run with three targeted inflow scenarios to determine both how the model responds with varying inflows, and to provide a general idea of how flow in BSP is affected by the magnitude of the inflow. The model used was the Fine Resolution Environmental Hydrodynamic Model that solves the 3D non-hydrostatic Navier-Stokes equations in a split hydrostatic/non-hydrostatic approach. The model was run using the default settings and the outputs were compared to available data. Results from these initial runs showed that further calibration is necessary. Model runs under the targeted inflow scenarios showed that as inflow increases, velocities in the upstream portion of BSP increase correspondingly, but this is not reflected in the downstream portion of BSP. / text

Transportation accidents and the resulting fires are an important field of study. At the University of Waterloo Live Fire Research Facility (UWLFRF), an experiment was conducted in partnership with Sandia National Laboratories in Albuquerque, New Mexico. This experiment was designed to simulate an aircraft accident where fuel is spilled on the runway and is subsequently ignited. A crosswind pushes the 2.0 m diameter pool fire towards the aircraft fuselage and the conditions around the fire are monitored. Literature on the subject is examined first, examining the relationship between the fire, the crosswind, and the 2.7 m diameter blocking object (aircraft fuselage). A full wind characterization is then presented of the UWLFRF both with and without the blocking object in place, using five distinct wind speeds ranging from 3 m/s to 13.5 m/s. Turbulence intensity measurements are made on the centerline of the facility when possible. Details about the two sets of live fire tests are presented, a control experiment without the blocking object in place and then fire tests with the blocking object in place. Additionally, the control experiment has two different setups, one involving a floor surround in order to diminish the effect of the forward facing step on the front of the fuel pan. The fuel regression rate, the wind speed, the ambient conditions and the heat flux near the fuel pan are monitored during each live fire test. The fuel regression rate, defined as the rate at which the height of the liquid fuel level decreases as the fire burns, is then analyzed versus all other monitored variables. During no blocking object tests, trends of increasing wind speed and increasing heat flux on some gauges and decreasing flux on others was observed with increasing fuel regression rate when the floor surround was in place. During no blocking object tests without the floor surround and tests with the blocking object in place, no strong trends were observed when comparing the monitored variables. The ambient conditions were not observed to have an effect on any test. The average fuel regression for tests without the blocking object in place is 4.0 mm/min without the floor surround, and 4.4 mm/min with it in place. With the blocking object in place the average fuel regression rate was measured to be 4.8 mm/min using load cells and 4.1 mm/min using the sight glass.

The Devonian (419-359 million years ago) is the geological period when the terrestrial biota fully established. Early representatives from a terrestrial and continental aquatic biota have previously been reported from the Upper Devonian (Famennian) Strud quarry in Belgium, in the shape of seed-bearing plants and vertebrates (fish and early tetrapods). The palaeoenvironment is interpreted as a floodplain with slow accumulation of sediment in the river channels and adjacent shallow pools, subject to seasonal flooding and desiccation. This thesis presents the upper Famennian Strud ecosystem with representatives from the largest animal phylum – the Arthropoda. Pancrustaceans are dominating the arthropod assemblage by two eumalacostracans (previously described), three groups of branchiopods, and a putative insect, all collected in fine shales likely deposited in the shallow pools. The branchiopods from Strud comprise new members from all three extant clades, i.e. notostracans, anostracans, and spinicaudatan diplostracans. The notostracan Strudops goldenbergi is remarkable for its close resemblance with the extant genus Triops by the overall body plan and telson morphology. A phylogenetic analysis including modern and extinct notostracans and anostracans was performed, where Strudops appears as the earliest undisputed notostracan ever found. In addition, new genera of Anostraca (Haltinnaias serrata) and Spinicaudata (Gesvestheria pernegrei) are described herein. The insect Strudiella devonica consists of a single specimen and is interpreted to have been a nymph due to its minute size and wingless appearance. The chelicerates are represented by one or several species of eurypterids. So far unnamed juvenile eurypterid remains have also been found within the pool strata, and fragments of adult individuals in the coarser river deposits. The branchiopod community displays a unique insight to the ecosystem that these crustaceans inhabited. This is partly because of their co-occurrence, but mainly because they are preserved in close association to draught-resistant encysted eggs, in the same manner as modern day branchiopods do to survive and disperse during periods of drought and freezing. Altogether, the arthropod assemblage offers insight to Late Devonian freshwater ecosystems, and provides further understanding of the evolution of respective groups.

Being able to predict the future had been an invaluable competitive advantage for any corporation. Forecasting is a vital part of any business, hence a good forecast allows enterprises to invest in a beneficial way. However, there are several ways to prepare forecasts and the forecast methodology can vary. An industry that is dependent on forecasts is the energy industry. By predicting consumers' energy consumption, Swedish energy companies can hedge on the Nordic power market Nord Pool. To know how much volume to hedge, the most accurate forecast possible is needed.A tool used for forecasting in the energy market is normal correction with degree days. The method aims to neutralize the effects of temperature on energy consumption and allows the actors in the electricity trade to see how the energy usage looks like if the weather is considered "normal". The method unfortunately has a couple of pitfalls, and should therefore be evaluated before it is implemented.This study has evaluated whether normal correction method with degree days should be implemented in a case study at Karlstad Energi. The results show that the method does not improve the forecast and the conclusion is that the method should not be implemented. Key words: Business forecasting, Nord Pool, Future, Forward

Previous research has demonstrated that pool-riffle bedforms play a critical role in channel stability and ecosystem health in many natural gravel-bed channels. Although the bedform length is known to scale with channel width, no experimental research has yet isolated the effect of bedform length on pool-riffle hydrodynamics. To improve the understanding of the hydrodynamics of these bedforms so that they can be better incorporated in restoration practices, flume experiments were conducted testing the flow at seven different bedform lengths. Velocity profiles are measured in a 17 m flume with movable PVC bedforms using ultrasonic velocity profilers (UVPs). Smooth two-dimensional (no sinuosity) bedforms are used in order to isolate the key dynamics in convective acceleration and deceleration. The angle of transition between pool and riffle heights was 7°, so that permanent flow separation did not occur. Parameters calculated from the velocity and turbulence profiles include the Coles’ wake parameter (a measure of the deviation from the log law), shear stress estimated from the velocity profile, shear stress estimated from the Reynolds shear stress, and vertical velocity. From the individual velocity time series, the integral length scale and the integral time scales are also calculated. Overall, the length of riffles and pools exert a fundamental control on the distribution of flow and turbulence within a channel. In the pool, energy is dissipated both through turbulence and as the flow is redistributed to uniform flow conditions. In the riffle, kinetic energy increases as the flow velocity increases, and as the length increases, the flow moves towards a new uniform flow condition. The results start to explain the reasons behind the persistent scaling relation between width and bedform length. It can be concluded that uniform flow conditions exist at the end of the pool when the bedform length ratio is greater than approximately 1:5.0 when the riffle length is held constant, and that uniform flow conditions are no longer observed at the end of the pool when the bedform length ratio exceeds 1:7.0 when the pool length is held constant. Future research should concentrate on extending the results to include three-dimensional pool-riffle configurations, repeating bedform configurations, internal scaling parameters, and sediment transport. Ultimately, as the hydrodynamics of pool-riffle sequences are better understood, better bedform designs can be implemented in restoration projects.

Thesis (Ph.D.)--Tufts University, 1996. / Adviser: Frances S. Chew. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 173-184). Access restricted to members of the Tufts University community. Also available via the World Wide Web;