Three existing pressure-drop models are validated and analyzed with experimental data compiled from the research database. From the analysis, it was found that the pressure-drop prediction results from the models are not very accurate and not consistent with all experimental datasets. A new pressure-drop model was consequently created based on the findings from the study, and experimental data from the database were used to validate the model to produce more accurate and consistent predictions. The new pressure-drop model was tested on experimental datasets that were in the database and also with experimental datasets that were not in the database. Good and consistent results were achieved, and the new model proved capable of predicting pressure drops for different pure refrigerants and refrigerant mixtures flowing inside different configurations of microin tubes for both condensation and evaporation.

Computational fluid dynamics (CFD) modeling was used to predict the gas-solid hydrodynamics of fluidized beds. An Eulerian-Eulerian multi-fluid model and granular kinetic theory were used to simulate fluidization and to capture the complex physics associated therewith. The commercial code ANSYS FLUENT was used to study two-dimensional single solids phase glass bead and walnut shell fluidized beds. Current modeling codes only allow for modeling of spherical, uniform-density particles. Owing to the fact that biomass material, such as walnut shell, is abnormally shaped and has non-uniform density, a study was conducted to find the best modeling approach to accurately predict pressure drop, minimum fluidization velocity, and void fraction in the bed. Furthermore, experiments have revealed that all of the bed mass does not completely fluidize due to agglomeration of material between jets in the distributor plate. It was shown that the best modeling approach to capture the physics of the biomass bed was by correcting the amount of mass present in the bed in order to match how much material truly fluidizes experimentally, whereby the initial bed height of the system is altered. The approach was referred to as the SIM approach. A flow regime identification study was also performed on a glass bead fluidized bed to show the distinction between bubbling, slugging, and turbulent flow regimes by examining void fraction contours and bubble dynamics, as well as by comparison of simulated data with an established trend of standard deviation of pressure versus inlet gas velocity. Modeling was carried out with and without turbulence modeling (k-ϵ), to show the effect of turbulence modeling on two-dimensional simulations. / Master of Science

We have studied gas flow and particle deposition in a realistic three-dimensional model of the bronchial tree, extending from the trachea to the segmental bronchi (7th airway generation for the most distal ones) using Computational Fluid Dynamics (CFD). The model is based on the morphometrical data of Horsfield et al. [J. Appl. Physiol., 31: 207-217, 1971] and on bronchoscopic and CT images, which give the spatial 3D-orientation of the curved ducts. It incorporates realistic angles of successive branching planes. Steady inspiratory flow varying between 50cm³/s and 500cm³/s was simulated as well as deposition of spherical aerosol particles (1 to 7 m diameter, 1g/cm³ density). Flow simulations indicated non-fully developed flows in the branches because of their relative short lengths. Velocity flow profiles in the segmental bronchi, taken one diameter downstream the bifurcation, were distorted compared with the flow in a simple curved tube, and wide patterns of secondary flow fields were observed. Both were due to the asymmetrical 3D configuration of the bifurcating network. Viscous pressure drop in the model was compared with results obtained by Pedley et al. [Respir Physiol, 9: 387-405, 1970], which are shown to be a good first approximation. Particle deposition increased with particle size and was minimal for approximately 200cm³/s inspiratory flow but it was highly heterogeneous for branches of the same generation.

A careful review of the literature showed that there is a serious lack of information (experimental or analytical) on the pressure losses during two-phase flow in combining tee junctions. Pipe networks in industrial applications involve combining and dividing junctions and knowledge of the pressure losses at these junctions is essential for analysis of the flow distribution in the network. To this end, the pressure losses of air-water mixtures passing through a horizontal, combining tee junction with a 37.8 mm diameter were experimentally studied with annular, wavy, and slug flow regimes in the outlet. The test matrix independently varied the outlet flow rates, the outlet mixture qualities, the gas distribution between the inlets, and the liquid distribution between the inlets. All experiments were conducted at room temperature and a nominal absolute pressure at the centre of the junction of 150 kPa. The pressure distribution in all three legs of the tee was determined using up to 49 pressure taps distributed among the three sides and monitored using pressure transducers to produce accurate measurements of the pressure losses. Time-averaged pressure measurements with annular and wavy flows are reported, while pressure measurements with slug flows were not repeatable. A new model and empirical coefficients is presented that allows accurate prediction of pressure losses for flows with either an annular or wavy outlet. Time-varying pressure measurements are presented and analyzed using probability density functions. Different distributions were found for differential measurements depending on whether or not slugging was present in the system. The probability density functions for cases with annular or wavy flow in the outlet followed Gaussian distributions, while cases with slug flow had skewed distributions. Time-varying pressure signals showed a time lag between slug events based on pressure tap locations. A visual study with slug flow present in the system showed upstream travelling waves induced in a stratified inlet when slug flow was present in the other, which led to unexpected slugging under certain flow conditions. / October 2016

Diploma thesis deals with numerical simulations of an air flow in a water cooled charge air cooler (WCAC), specifically with pressure drops in inlet/outlet chamber. The simulations have been performed in a proprietary software Star-CCM+. Physical phenomena have been solved by the Reynolds-averaged Navier-Stokes (RANS) equations and consequently a matrix of pressure drops for miscellaneous variations of chamber's geometry and the initial flow conditions has been created. Based on the CFD results, dependence between calculated pressure drops and changing parameters has been analyzed and finally a 1D solver has been developed and implemented into a software OpenModelica.

This study looked at the effect relative humidity had on respirator performance.

The Boosted Fast Flux Loop (BFFL) will expand the Advanced Test Reactor (ATR) at Idaho National Laboratory. Part of the BFFL is a new corrosion test cap section for testing in the ATR. The corrosion test cap section was designed with parallel channels to reduce the pressure drop and allow coolant contact with specimens. The fluid experiment conducted by Idaho State University found the pressure drop not characteristic of parallel channel flow but greater than without parallel channels. A Computation Fluid Dynamics simulation using STAR-CCM+ was conducted with the objectives of showing sufficient flow through the test cap section for a corrosion test, verifying the fluid experiment's validity, and explaining the abnormal pressure drop. The simulation used a polyhedral volume mesh and the k-e turbulent model with segregated equations. Convergence depended on a low continuity residual and an unchanging pressure drop result. The simulation showed the same pattern as the fluid experiment. The simulation provided evidence of flow through the test cap section needed for a corrosion test. The specimen holding assembly was found to be a small contributor to the pressure drop. The counterintuitive pressure drop was found to be the sum of many factors produced from the geometry of the test cap section. The inlet of the test cap section behaved as a diverging nozzle before a sudden expansion into the test cap section chamber with both creating a pressure drop. The chaotic flow inside the chamber gave rise to pressure loss from mixing. The fluid exited the chamber through a sudden contraction to a converging nozzle behaving exit, again, producing a pressure drop. By varying the flow rate in the simulation, a disturbance in the flow where the gap fluid separated into the parallel channels was found at high flow rates. At low flow rates the pressure drop anomaly was not found. The corrosion test cap section could be used in the ATR but with a higher pressure drop than desirable. The design of the corrosion test cap section created the abnormal pressure drop.

<p>Cake filtration is a unit operation to separate solids from fluids in industrial processes. The build up of a filter cake is usually accompanied with a decrease in overall permeability over the filter leading to an increased pressure drop over the filter. For an incompressible filter cake that builds up on a homogeneous filter cloth, a linear pressure drop profile over time is expected for a constant fluid volume flow. However, experiments show curved pressure drop profiles, which are also attributed to inhomogeneities of the filter (filter medium and/or residual filter cake).</p><p>In this work, a mathematical filter model is developed to describe the relationship between time and overall permeability. The model considers a filter with an inhomogeneous permeability and accounts for fluid mechanics by a one-dimensional formulation of Darcy's law and for the cake build up by solid continuity. The model can be solved analytically in the time domain. The analytic solution allows for the unambiguous inversion of the model to determine the inhomogeneous permeability from the time resolved overall permeability, e.g. pressure drop measurements. An error estimation of the method is provided by rewriting the model as convolution transformation.</p><p>This method is applied to simulated and experimental pressure drop data of gas filters with textile filter cloths and various situations with non-uniform flow situations in practical problems are explored. A routine is developed to generate characteristic filter cycles from semi-continuous filter plant operation. The model is modified to investigate the impact of non-uniform dust concentrations.</p>

Cake filtration is a unit operation to separate solids from fluids in industrial processes. The build up of a filter cake is usually accompanied with a decrease in overall permeability over the filter leading to an increased pressure drop over the filter. For an incompressible filter cake that builds up on a homogeneous filter cloth, a linear pressure drop profile over time is expected for a constant fluid volume flow. However, experiments show curved pressure drop profiles, which are also attributed to inhomogeneities of the filter (filter medium and/or residual filter cake). In this work, a mathematical filter model is developed to describe the relationship between time and overall permeability. The model considers a filter with an inhomogeneous permeability and accounts for fluid mechanics by a one-dimensional formulation of Darcy's law and for the cake build up by solid continuity. The model can be solved analytically in the time domain. The analytic solution allows for the unambiguous inversion of the model to determine the inhomogeneous permeability from the time resolved overall permeability, e.g. pressure drop measurements. An error estimation of the method is provided by rewriting the model as convolution transformation. This method is applied to simulated and experimental pressure drop data of gas filters with textile filter cloths and various situations with non-uniform flow situations in practical problems are explored. A routine is developed to generate characteristic filter cycles from semi-continuous filter plant operation. The model is modified to investigate the impact of non-uniform dust concentrations.

Annular flow is an important flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space-based systems. Annular two-phase flow is frequently present in the drilling, production and transportation of oil and natural gas, boilers and condensers, and in heating and refrigeration systems. The flow regime is also important for the refueling of space vehicles, and heating and refrigeration systems for space use. Past studies on annular flow have dealt with varying the gas or liquid Reynolds numbers and studying the effect of such changes on the flow regimes and pressure drops. The effect of two other relevant dimensionless groups, namely the gas-to-liquid density ratio and the gas-to-liquid viscosity ratio, on the film characteristics are noticeably absent. As well, with the increased interest in the space environment, studies on the effect of the gravitational acceleration on two-phase flow would be beneficial. The effect of the gas density and the gravitational acceleration on the annular flow average film thickness and frictional pressure drop are examined. The film thickness was measured using two-wire conductance probes. Experimental data were collected in microgravity and hypergravity aboard the Novespace Zero-G Airbus microgravity simulator and normal gravity data were collected at the University of Saskatchewan. Data were collected for a range of annular flow set points by changing the liquid and gas mass flow rates. The liquid-to-gas density ratio was examined by collecting annular flow data using helium-water and air-water. The gravitational effect on the film thickness characteristics was examined by collecting the data during the microgravity and pull-up (hypergravity) portions of each parabolic flight. A direct comparison is possible between the normal gravity data and the microgravity data, due to the matching of the liquid and gas mass flow rates and the flow regime. The reduction in gravity causes the average film thickness to increase between two and four times from the normal gravity values. The microgravity average frictional pressure drop is within approximately 20% of the normal gravity pressure drop for the same flow conditions. For all gravity levels, the air-water and the helium-water flows give similar results, for both average film thickness and frictional pressure drop, when based on the specific energy of the gas. The hypergravity average film thickness results are larger than at normal gravity for the same flow conditions. However, no flow regime map exists for the hypergravity condition, so the similarity of the flow regime cannot be confirmed. The hypergravity flow appears more chaotic, and may be in the transition from a churn type flow. The average frictional pressure drop is increased by approximately 20% due to the increase in the gravitational acceleration. New non-dimensional equations, which include the effect of the gas density, are presented for each gravity level to predict the average film thickness and the average frictional pressure drop.