Undercurrent: The Alden Blog

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Industrial fluid dynamics insights


From Mountain Clouds to River Plumes: Observations and modeling of turbulent mixing in stratified flows
Mixing between fluids of different properties goes on all around us every day (e.g., think of stirring milk into your coffee or smoke billowing from a chimney).  In many flows of engineering relevance, velocity differences between fluid bodies generate turbulent motions that, in turn, greatly enhance the mixing process; small-scale chaotic eddies that characterize the turbulence are much more effective than molecular diffusion at mixing fluid properties such as momentum, heat, salinity, sediment load, or pollution concentration. When fluid bodies are of different densities the effects of gravity weigh heavily on the turbulent mixing process (pun intended).  For example, when warm air escapes from a chimney it accelerates upward in a turbulent billow because it is lighter (less dense) than the cooler air around it, and gravity acts to drive turbulence through buoyant convection.  On the other hand, in a stably-stratified lake, gravity acts to suppress turbulence at the thermocline where lighter, warm water overlies heavier cold water. The signatures of turbulent mixing in stratified flows are perhaps most obvious in the sky above us.  Clouds provide a convenient flow visualization ...

The Changing Energy Climate - Part II
In the last installment of this series, we discussed energy demand, energy supply, and the impact of the rapid growth of solar power on changing energy sources.  Today, we continue with the effects of power prices, the importance of power storage, and offer some conclusions. Price of Power A significant portion of the United States electricity markets is split into hubs.  Each hub is an independent energy market in which supply and demand set the price of electricity on a real time basis.   A map of United States hub zones is shown in the following figure. Daily electricity demand is primarily based upon the time of day and climate.  As shown in Part I, more electricity is used during daylight and evening hours than night time.  Very cold or very warm weather can add demand due to heating and cooling.  Additional constraints on fuel costs and available supply add an extra layer of complexity.  The cost of environmental mitigations for coal fired power plants, the lack of sufficient natural gas supply in certain markets like New England, and the recent addition ...

The Changing Energy Climate - Part I
As we discussed in our first blog post, there are many challenges facing the nuclear industry. One of the greatest is the current energy climate.  There are many contributing factors to the general state of flux in energy production, which we would like to explore today.  These challenges don’t just impact the nuclear industry, but also affect energy producers across generation types. Energy Demand It may surprise you, but US energy consumption has effectively plateaued over the last 15 years.  Below is a plot generated with the US Energy Information Administration Open Data Embedded Visualization Library.  The EIA provides a wide range of information and data products covering energy production, stocks, demand, imports, exports, and prices; and prepares analyses and special reports on topics of current interest. There are four sectors that are included when looking at total energy consumption.  These include Residential, Commercial, Industrial, and Transportation, all of which are shown in the figure.  As you can see, starting around the year 2000 the Total Energy Consumption has plateaued.  The largest changes in trends  have been experienced by the Industrial Sector, ...

NIAC Annual Meeting
In November 2016, the Alden Quality Assurance department attended the NIAC (Nuclear Industry Assessment Committee) annual meeting.  NIAC is the supplier equivalent to NUPIC (https://www.aldenlab.com/News/Blog/PostId/9/nuclear-procurement-issues-committee-annual-meeting) and the main benefit of membership is for suppliers to share audits of their sub-suppliers.  NIAC membership is open to suppliers with a 10CFR50 Appendix B or equivalent DOE quality program, and who demonstrate and agree to compliance with the NIAC Charter.  Alden joined NIAC in the fall of 2014 and the membership has helped reduce quality assurance costs while also staying in touch with current industry issues and maintaining a high quality product for our clients. The meeting was held in Jacksonville, Florida and featured the necessary business of setting the audit schedule for the upcoming year and providing auditor training.  The auditor training is important to ensure consistent and accurate audits that all members can share and rely on.  Additionally, there was a keynote address by Ben Marguglio of High Technology Seminars (http://hightechnologyseminars.com/).  Mr. Marguglio is a leading authority on human performance factors and human errors, including error prevention and reduction.  He ...

Pumped Energy Storage: Old Technology, New Demand
There is an interesting past and new future for the world’s largest batteries.  For decades pumped storage plants have helped stabilize large power grids by supplying peak power support to base loaded nuclear and fossil fuel power plants across the United States and the world.  Today, as many nations make a conscious move away from these generating sources toward renewable energy technology, such as solar and wind, and smaller micro grids, these behemoth batteries are finding new purpose.  Keeping in the spirit of this green power revolution, it is imperative to keep the environmental impact of pumped power plants, and other power storage technologies, as low as possible. Base loaded power plants, nuclear or fossil fuel, operate at full production 24 hours a day because they are difficult and slow to start and stop; however society’s power demand fluctuates dramatically throughout the day.  In the morning and during business hours when most people are running home appliances or working with tools and equipment, the base load power may not be able to keep up.  In contrast, at night when most ...

Venturi Design for a Circulating Dry Scrubber
One of Alden’s key business areas is designing, analyzing, and improving air pollution control equipment for fossil power plants.  Over the last decade, circulating dry scrubbers (CDS) have become a popular way to remove SO2 and other acids from the flue gas of coal-burning power plants.  A few of the benefits of CDS technology include a relatively low cost of installation, high removal efficiency, low water usage, and no wastewater that needs to be treated – in fact it can be a means to dispose of other wastewater from the plant. The technology works by injecting lime powder into a reaction vessel, and also spraying in a small amount of water (Figure 1).  The water coats the lime particles and eventually evaporates, which helps to improve acid removal.  The powder is suspended in the reaction vessel and mixed using a high velocity stream of flue gas entering from the bottom of the reactor.  Once mixed and reacted, the gas carries the solids out through the top of the reactor into a fabric filter, which acts like a vacuum bag to ...

Nuclear Procurement Issues Committee Annual Meeting
In June 2016, the Alden Quality Assurance department attended the annual NUPIC (Nuclear Procurement Issues Committee) vendor conference for the third year in a row.  NUPIC is an organization that provides a cost effective method for NRC (Nuclear Regulatory Commission) licensee's to maintain their approved suppliers lists by sharing audits of suppliers.  The vendor conference is an opportunity for utilities, suppliers and regulators to get together and discuss current issues which impact the processes of purchasing and supply of nuclear components and services.  This annual event has been beneficial for Alden QA to stay abreast with current nuclear quality issues and to maintain a high quality product for our clients. The NUPIC vendor conference is hosted each year by a different utility and in addition, the NRC sends representatives and holds a workshop on vendor oversight at the conference every two years.  The 2016 event was hosted by Ameren in St. Louis, Missouri at a hotel adjacent to the Jefferson National Expansion Memorial (U.S. National Park featuring the Gateway Arch and Old Courthouse, see photos).  Conference topics included an ...

The Future of Nuclear Power
As the US Nuclear fleet continues to age, and the availability of alternate sources of energy continues to rise, it is not surprising that we are seeing more news of permanent plant closures.  The most recent announcements come from Entergy, stating they will shut down Palisades permanently on October 1st, 2018, and Indian Point in 2021. For many of these plants announcing closures, the writing has been on the wall.  In 2013, economist Mark Cooper, a Senior Fellow for Economic Analysis at the Institute for Energy and the Environment at Vermont Law School published Renaissance In Reverse, an interesting read on the factors that affect the viability of nuclear power economically.  He provided a list of plants that face particularly significant challenges to operation, which is provided below. Palisades (Repair impending, local opposition) Ft. Calhoun (Outage, poor performance) Nine Mile Point (Site size saves it, existing contract) ...