Multibubble Sonoluminescence from a Theoretical Perspective

In the present review, complexity in multibubble sonoluminescence (MBSL) is discussed. At relatively low ultrasonic frequency, a cavitation bubble is filled mostly with water vapor at relatively high acoustic amplitude which results in OH-line emission by chemiluminescence as well as emissions from weakly ionized plasma formed inside a bubble at the end of the violent bubble collapse. At relatively high ultrasonic frequency or at relatively low acoustic amplitude at relatively low ultrasonic frequency, a cavitation bubble is mostly filled with noncondensable gases such as air or argon at the end of the bubble collapse, which results in relatively high bubble temperature and light emissions from plasma formed inside a bubble. Ionization potential lowering for atoms and molecules occurs due to the extremely high density inside a bubble at the end of the violent bubble collapse, which is one of the main reasons for the plasma formation inside a bubble in addition to the high bubble temperature due to quasi-adiabatic compression of a bubble, where “quasi” means that appreciable thermal conduction takes place between the heated interior of a bubble and the surrounding liquid. Due to bubble–bubble interaction, liquid droplets enter bubbles at the bubble collapse, which results in sodium-line emission.

Technology Focus: Heavy Oil (April 2021)

After serving two terms for a total of 6 years, my time writing this column is coming to an end. This issue of JPT marks my last opportunity to share my thoughts, recap my observations, and make note of some final touch-ups to the research conducted over this 6-year period with regard to recent heavy oil practices. Here are some highlights to keep in our minds over the coming years. Despite all the recent negative and serious changes affecting the whole world and our industry, life goes on and we will increasingly be needing energy. One should recall that statistics predict oil will continue to be the main source of energy for the next 2 decades, with heavy oil constituting a great portion of that. That means that, while the oil industry is going through unprecedented and even unpredictable economic downturns, the status of heavy oil is still unquestionable. However, we have to face the fact that this energy should be tapped in a cheap, clean, and sustainable way. The best aspect of this effort is that heavy oil technologies have been established and tested over a long period of time, unlike other unconventional resources. Lowered steam consumption, down to zero if possible, has been under consideration to minimize the emission of greenhouse gases (GHGs) while simultaneously producing heavy oil. This green effort leads us to nonsteam techniques such as the use of water with chemicals (mainly polymer) and noncondensable gases and certain unconventional methods such as solvent injection and electromagnetic heating, the latter being unavoidable especially for extraheavy oil and bitumen. These areas have been critically considered by researchers and practitioners with a considerable number of applications existing at the field scale. At the same time, the oil industry must deal with mature steam projects in the near future. We have accumulated so much heat energy over the decades, yet a substantial amount of oil remains in these reservoirs. What can be done to reuse this energy? Can we recover different forms of energies using methods with no GHG emission? The current practices encountered in field-scale operations to improve the heavy oil recovery in mature steam applications use noncondensable gases; mainly, these techniques serve to pressurize steam-assisted gravity drainage wells, improve sweep and microscopic displacement by adding chemical additives to the steam (or hot water), and re-engineer well designs (flow control for efficient heating and sweep). My final example highlighting new practices is the increasing trend of offshore heavy oil practices. Of particular interest is polymer injection through vertical and horizontal wells and pilot steam applications, methods that are effective even if they occur at the pilot stage of the process. Recommended additional reading at OnePetro: www.onepetro.org. SPE 199947 - Enhanced Oil Recovery in Post-Cold Heavy Oil Production With Sand Heavy Oil Reservoirs of Alberta and Saskatchewan Part 2: Field Piloting of Cycling Solvent Injection by Gokhan Coskuner, Consultant, et al. SPE 199925 - Scalable Steam Additives for Enhancing In-Situ Bitumen Recovery in SAGD Process by Armin Hassanzadeh, Dow, et al. SPE 199927 - The Myth of Residual Oil Saturation in SAGD - Simulations Against Reality by Subodh Gupta, Cenovus Energy, et al.

Improvement of the RELAP5-3D Condensation Heat Transfer Model in the Presence of Noncondensable Gases

Condensation of steam on the primary side of steam generator in a pressurized water reactor is one of the means of removing decay heat during accident scenarios such as a small break loss of coolant accident. With the presence of noncondensable gases, the rate of removal of decay heat reduces, affecting the ability of the nuclear plant to remove heat in accident scenarios. Therefore, correct prediction of heat removal capability is very significant to predict the plant behavior. In this study, an analytical model is compared with a numerical solution with the use of experiments performed at University of California, Berkeley and at MIT. A modified correlation is proposed and compared to experimental observation for various noncondensable gases.

Characterization of bio-Oil produced by Microwave Pyrolysis of Karanja Seed.

Pyrolysis is one technique that produces three products in a short span of time in which both conventional and non-conventional method of heating (microwave irradiation) can be done. Karanja seed powder is taken as the feedstock in this microwave pyrolysis experiment. Proximate and Elemental analysis of karanja seed powder resulting volatile content of about 84.89% and moisture content of 10.11% whereas the Carbon of 52.08%, Hydrogen of 8.26%, Sulphur of 0.21%, Nitrogen of 4.02% and oxygen of 35.04%. Microwave pyrolysis for karanja seed was conducted for two power inputs of 700W and 800W in which bio-oil yield is high of 47% at 700W and noncondensable gases of 39% at 800W. The FT-IR results resembles the presence of aliphatic compounds. The TGA analysis was also taken for the produced bio-oil. The rheological study was made to determine the dynamic viscosity of the produced bio-oil at 50 rpm in room temperature which is averaged to 52 cP. The flash point of 90°C and fire point of 94°C was also determined for the produced bio-oil

Numerical Investigation of Natural Convective Condensation with Noncondensable Gases in the Reactor Containment after Severe Accidents

The heat and mass transfer processes of natural convective condensation with noncondensable gases are very important for the passive containment cooling system of water cooled reactors. Numerical simulation of natural convective condensation with noncondensable gases was realized in the Fluent software by adding condensation models. The scaled AP600 containment condensation experiment was simulated to verify the numerical method. It was shown that the developed method can predict natural convective condensation with noncondensable gases well. The velocity, species, and density fields in the scaled AP600 containment were presented. The heat transfer rate distribution and the influences of the mass fraction of air on heat transfer rate were also analyzed. It is found that the driving force of natural convective condensation with noncondensable gases is mainly caused by the mass fraction difference but not temperature difference. The natural convective condensation with noncondensable gases in AP1000 containment was then simulated. The temperature, species, velocity, and heat flux distributions were obtained and analyzed. The upper head of the containment contributes to 35.1% of the total heat transfer rate, while its area only takes 25.4% of the total condensation area of the containment. The influences of the mass fraction of low molecular weight noncondensable gas (hydrogen) on the natural convective condensation were also discussed based on the detailed species, density, and velocity fields. The results show that addition of hydrogen (production of zirconium-water reaction after severe accident) will weaken the intensity of natural convection and the heat and mass transfer processes significantly. When hydrogen contributes to 50% mole fraction of the noncondensable gases, the heat transfer coefficient will be reduced to 45%.

Analysis of Venting of a Resin Slurry

A resin slurry venting analysis was conducted to address safety issues associated with over-pressurization of ion exchange columns used in the plutonium uranium redox extraction (PUREX) process at the U. S. Department of Energy's Savannah River Site (SRS). If flow to these columns is inadvertently interrupted, an exothermic runaway reaction could occur between the ion exchange resin and the nitric acid used in the feed stream. This reaction generates significant quantities of noncondensable gases. To prevent the column from rupturing due to pressurization by these gases, rupture disks are installed on the column vent lines. The venting analysis models accelerating rate calorimeter (ARC) tests and data from tests that were performed in a vented test vessel with a rupture disk. The tests showed that the pressure inside the test vessel continued to increase after the rupture disk opened, though at a slower rate than prior to the rupture. The increase in the vessel pressure is modeled as a transient phenomenon associated with expansion of the resin slurry/gas mixture upon rupture of the disk. It is postulated that the maximum pressure at the end of this expansion is limited by energy minimization to approximately 1.5 times the rupture disk burst pressure. The magnitude of this pressure increase is consistent with the measured pressure transients. The results of this analysis demonstrate the need to allow for a margin between the design pressure and the rupture disk burst pressure in similar applications.