BUBBLE PUMP MODELING FOR SOLAR HOT WATER HEATER SYSTEM DESIGN OPTIMIZATION
Solar thermal water heating systems reduce household energy bills by using the free solar radiation provided by the sun to heat water for residential needs. In order to eliminate the need for electricity to run a pump to drive the fluid circulation in these systems, fluid buoyancy effects can be employed to move the fluid from lower elevations to higher elevations. There are several operational challenges with conventional “thermosyphon” systems, such as reversing flow and overheating, which can all be addressed by using a bubble pump mechanism. Although the solar thermal bubble pump water heating system has been on market, little research has been done on the optimization of the system to improve its efficiency. Engineering Equation Solver software is used to implement a mathematical model for the bubble pump system operation. The model allows for parametric studies of the design attributes to investigate optimum efficiency conditions for the thermally driven pump.
A general design equation for air lift pumps operating in slug flow
Air lift pumps are finding increasing use where pump reliability and low maintenance are required, and where corrosive, abrasive, or radioactive fluids must be handled. Although air lifts are used in nuclear fuel reprocessing plants, no general, theoretically sound equation has been proposed in the literature for tall air lift design. Such an equation is developed from two-phase flow theory to predict the height to which an air lift pump operating in the slug flow regime can lift a given volumetric flow rate of liquid, given the air flow rate and pressure at the point of gas introduction. The widely used drift-flux model for the prediction of holdup is combined with an approximate relationship to predict pressure loss, and is substituted into the total pressure differential. Integration of the resulting equation provides an explicit formula for the calculation of lift. Experimental work using a variety of liquids in a 38 mm dia. air lift test installation supports the new design equation and demonstrates its flexibility.
Physical Processes in Inorganic Scintillators
BASIC PRINCIPLES AND PROCESSES Physical Mechanism of Scintillation Creation of Electron Hole Pairs Excitation and Emission of Luminescence Centers Scintillation Materials Halides Oxides and Oxide Systems Chalcogenides Glasses Interaction of Ionizing Radiation with Scintillators High Energy Photons Charged Particles Neutral Particles General Characteristics of Inorganic Scintillators Light Yield Duration of Scintillation Pulse Afterglow Temperature Response Optical Properties Radiation Hardness Density Emission Spectra Mechanical and Chemical Properties Physical Parameters Cost Consideration Scintillator Requirements in Various Applications High Energy Physics Intermediate Energy Physics Positron Emission Tomography Gamma Spectroscopy Energy Resolution Intrinsic Scintillator Resolution Nonproportional Response Time Resolution Low Energy Quanta and Electrons CONVERSION OF ELECTRONIC EXCITATIONS IN SOLIDS Charge Carrier Behaviors Delta Rays Secondaries Excitation of Luminescence Centers Effect of Ionization Density Energy Losses Simple Phenomenological Model Plasmon Model Polaron Model Scintillation Yield Spectra Vacuum Ultraviolet Region Ultrasoft X-Rays X-Rays Gamma Rays Heavy Ionizing Particles INTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Excitonic Luminescence Alkali Halide Crystals Alkaline-Earth Fluorides Ternary Halide Compounds Excitonic-Like Luminescence Cesium Iodide Tungstate and Molybdate Phosphors Core-to-Valence Transitions First Evidence for Radiative Core-to-Valence Transitions Excitation Spectra Emission Spectra Experiment Theory Luminescence Kinetics Experimental Theoretical Investigations Temperature Dependence of Luminescence Parameters Conditions of Detection Prospects for Research EXTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Thallium-Activated Halide Scintillators Crystals with NaCl-Type Structure Crystals with CsCl-Type Structure Other Thallium-Based and Thallium-Doped Crystals Crystals Containing Other ns2 Ions Bismuth Germanate (BGO) Sodium-Activated Cesium Iodide Rare-Earth-Activated Crystals General Considerations Europium-Activated Crystals Cerium-Activated Compounds Preliminary Comments LaF3-CeF3 Systems Cerium Chloride Barium Fluoride Gadolinium-Containing Crystals Lu- and Y-Containing Crystals Nd- and Pr-Activated Crystals DEFECT FORMATION BY IONIZING RADIATION Effect on Scintillator Characteristics Mechanisms of Defect Formation Efficiency of Defect Production Geometrical Factor Separation between F and H Centers Temperature Dependence of Production Efficiency Role of Halogen Ion Impurities Effect of Cation Impurities Formation Time of F-H Pairs Closing Comments References Index