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Thermodynamic analysis of a novel fossil-fuel–free energy storage system with a trans-critical carbon dioxide cycle and heat pump
This paper presents and analyzes a novel fossil-fuel–free trans-critical energy storage system that uses CO2 as the working fluid in a closed loop shuttled between two saline aquifers or caverns at different depths: one a low-pressure reservoir and the other a high-pressure reservoir. Thermal energy storage and a heat pump are adopted to eliminate the need for external natural gas for heating the CO2 entering the energy recovery turbines. We carefully analyze the energy storage and recovery processes to reveal the actual efficiency of the system. We also highlight thermodynamic and sensitivity analyses of the performance of this fossil-fuel–free trans-critical energy storage system based on a steady-state mathematical method. It is found that the fossil-fuel–free trans-critical CO2 energy storage system has good comprehensive thermodynamic performance. The exergy efficiency, round-trip efficiency, and energy storage efficiency are 67.89%, 66%, and 58.41%, and the energy generated of per unit storage volume is 2.12 kW·h/m3, and the main contribution to exergy destruction is the turbine reheater, from which we can quantify how performance can be improved. Moreover, with a higher energy storage and recovery pressure and lower pressure in the low-pressure reservoir, this novel system shows promising performance
Rifts in Spreading Wax Layers
We report experimental results on the rift formation between two freezing wax
plates. The plates were pulled apart with constant velocity, while floating on
the melt, in a way akin to the tectonic plates of the earth's crust. At slow
spreading rates, a rift, initially perpendicular to the spreading direction,
was found to be stable, while above a critical spreading rate a "spiky" rift
with fracture zones almost parallel to the spreading direction developed. At
yet higher spreading rates a second transition from the spiky rift to a zig-zag
pattern occurred. In this regime the rift can be characterized by a single
angle which was found to be dependent on the spreading rate. We show that the
oblique spreading angles agree with a simple geometrical model. The coarsening
of the zig-zag pattern over time and the three-dimensional structure of the
solidified crust are also discussed.Comment: 4 pages, Postscript fil
Impacts of magnetic permeability on electromagnetic data collected in settings with steel-cased wells
Electromagnetic methods are increasingly being applied in settings with steel
infrastructure. These include applications such as monitoring of CO2
sequestration or even assessing the integrity of a wellbore. In this paper, we
examine the impacts of the magnetic permeability of a steel-cased well on
electromagnetic responses in grounded source experiments. We consider a
vertical wellbore and simulate time and frequency domain data on 3D cylindrical
meshes. Permeability slows the decay of surface electric fields in the time
domain and contributes to a phase shift in the frequency domain. We develop our
understanding of how permeability alters currents within, and external to, the
casing by focussing first on the time domain response and translating insights
to the frequency domain. Following others, we rewrite Maxwell's equations to
separate the response into terms that describe the magnetization and induction
effects. Magnetic permeability impacts the responses in two ways: (1) it
enhances the inductive component of the response in the casing, and (2) it
creates a magnetization current on the outer wall of the casing. The
interaction of these two effects results in a poloidal current system within
the casing. It also generates anomalous currents external to the casing that
can alter the geometry and magnitude of currents in the surrounding geologic
formation. This has the potential to be advantageous for enhancing responses in
monitoring applications
New Icing Cloud Simulation System at the NASA Glenn Research Center Icing Research Tunnel
A new spray bar system was designed, fabricated, and installed in the NASA Glenn Research Center's Icing Research Tunnel (IRT). This system is key to the IRT's ability to do aircraft in-flight icing cloud simulation. The performance goals and requirements levied on the design of the new spray bar system included increased size of the uniform icing cloud in the IRT test section, faster system response time, and increased coverage of icing conditions as defined in Appendix C of the Federal Aviation Regulation (FAR), Part 25 and Part 29. Through significant changes to the mechanical and electrical designs of the previous-generation spray bar system, the performance goals and requirements were realized. Postinstallation aerodynamic and icing cloud calibrations were performed to quantify the changes and improvements made to the IRT test section flow quality and icing cloud characteristics. The new and improved capability to simulate aircraft encounters with in-flight icing clouds ensures that the 1RT will continue to provide a satisfactory icing ground-test simulation method to the aeronautics community
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