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You searched for subject:(radial waveguides). Showing records 1 – 2 of 2 total matches.

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Virginia Tech

1. Narayan, Aditya. Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination.

Degree: MS, Mechanical Engineering, 2017, Virginia Tech

This thesis presents investigations on air-cooled air gap membrane distillation for desalination and the application of radial waveguides based on total internal reflection for solar thermal desalination. Using an air-cooled design for an air gap membrane distillation (AGMD) process may result in significantly lower energy requirements for desalination. Experiments were conducted on AGMD module to study the effect of air gap, support mesh conductivity and hydrophobicity, condensing surface hydrophobicity. A novel modular design was used in which modules could be used in a series configuration to increase the flux value for the distillate. The output from the series configuration was found to have about three times the production from a single pass water-cooled system with the same temperature difference between the saline and clear water streams. The results also indicated that the mesh conductivity had a favorable effect on the flux value whereas the hydrophobicity of the mesh had no significant effect. The hydrophobicity of the condensing surface was favorable on two accounts: first, it led to an increase in the flux of the distillate at temperatures below 60 °C and second, the temperature difference of the saline feed when it enters and leaves the module is lower which can lead to energy savings and higher yields when used in a series configuration. The second part of the thesis considers use of low-cost radial waveguides to collect and concentrate solar energy for use in thermal desalination processes. The optical-waveguide-based solar energy concentrators are based on total internal reflection and minimize/eliminate moving parts, tracking structures and cost. The use of optical waveguides for thermal desalination is explored using an analytical closed-form solution for the coupled optical and thermal transport of solar irradiation through a radial planar waveguide concentrator integrated with a central receiver. The analytical model is verified against and supported by computational optical ray tracing simulations. The effects of various design and operating parameters are systematically investigated on the system performance, which is quantified in terms of net thermal power delivered, aperture area required and collection efficiency. Design constraints like thermal stress, maximum continuous operation temperature and structural constraints have been considered to identify realistic waveguide configurations which are suitable for real world applications. The study provides realistic estimates for the performance achievable with radial planar waveguide concentrator-receiver configuration. In addition to this, a cost analysis has been conducted to determine the preferred design configurations that minimize the cost per unit area of the planar waveguide concentrator coupled to the receiver. Considering applications to thermal desalination which is a low temperature application, optimal design configuration of waveguide concentrator-receiver system is identified that result in the minimum levelized cost of power… Advisors/Committee Members: Pitchumani, Ranga (committeechair), Mahajan, Roop L. (committee member), Huxtable, Scott T. (committee member).

Subjects/Keywords: Air Gap Membrane Distillation; hydrophobic surface; desalination; air-cooled module; series configuration; planar waveguides; radial waveguides; concentrated solar thermal applications

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Narayan, A. (2017). Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78779

Chicago Manual of Style (16th Edition):

Narayan, Aditya. “Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination.” 2017. Masters Thesis, Virginia Tech. Accessed December 08, 2019. http://hdl.handle.net/10919/78779.

MLA Handbook (7th Edition):

Narayan, Aditya. “Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination.” 2017. Web. 08 Dec 2019.

Vancouver:

Narayan A. Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2019 Dec 08]. Available from: http://hdl.handle.net/10919/78779.

Council of Science Editors:

Narayan A. Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78779


McMaster University

2. Azizur-Rahman, Khalifa M. Simulation of III-V Nanowires for Infrared Photodetection.

Degree: PhD, 2016, McMaster University

The absorptance in vertical nanowire (nw) arrays is typically dominated by three optical phenomena: radial mode resonances, near-field evanescent wave coupling, and Fabry–Perot (F-P) mode resonances. The contribution of these optical phenomena to GaAs, InP and InAs nw absorptance was simulated using the finite element method. The study compared the absorptance between finite and semi-infinite nws with varying geometrical parameters, including the nw diameter (D), array period (P), and nw length (L). Simulation results showed that the resonance peak wavelength of the HE1n radial modes linearly red-shifted with increasing D. The absorptance and spectral width of the resonance peaks increased as L increased, with an absorptance plateau for very long nws that depended on D and P. Near-field coupling between neighbouring nanowires (nws) was observed to increase with increasing diameter to period ratio (D/P). The effect of F-P modes was more pronounced for shorter nws and weakly coupled light. Based on the collective observation of the correlation between nw geometry and optical phenomena in GaAs, InP, and InAs nw arrays, a periodic array of vertical InSb nws was designed for photodetectors in the low-atmospheric absorption window (λ = 3-5 μm) within the mid-wavelength infrared (MWIR) spectrum (λ = 3-8 μm). Simulations, using the finite element method, were implemented to optimize the nw array geometrical parameters (D, P, and L) for high optical absorptance (~0.8), which exceeded that of a thin film of equal thickness. The results further showed that the HE1n resonance wavelengths in InSb nw arrays can be tuned by adjusting D and P, thus enabling multispectral absorption throughout the near infrared (NIR) to MWIR region. Optical absorptance was investigated for a practical photodetector consisting of a vertical InSb nw array embedded in bisbenzocyclobutene (BCB) as a support layer for an ultrathin Ni contact layer. Polarization sensitivity of the photodetector was examined. Lastly, how light flux enters the nw top and sidewalls on HE11 resonance was investigated.

Dissertation

Doctor of Philosophy (PhD)

Advisors/Committee Members: LaPierre, Raymond R., Engineering Physics.

Subjects/Keywords: III-V nanowires; nanophotonics; photodetectors; waveguides; photonic crystals; optical simulation; nanoelectronics; multispectral detector; nanoscience; nanotechnology; infrared; MWIR; nanowires; optical coupling; guided modes; leaky modes; radial modes; near field coupling; photonic crystal modes; vertical nw array; InSb; GaAs; InP; InAs

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Azizur-Rahman, K. M. (2016). Simulation of III-V Nanowires for Infrared Photodetection. (Doctoral Dissertation). McMaster University. Retrieved from http://hdl.handle.net/11375/20703

Chicago Manual of Style (16th Edition):

Azizur-Rahman, Khalifa M. “Simulation of III-V Nanowires for Infrared Photodetection.” 2016. Doctoral Dissertation, McMaster University. Accessed December 08, 2019. http://hdl.handle.net/11375/20703.

MLA Handbook (7th Edition):

Azizur-Rahman, Khalifa M. “Simulation of III-V Nanowires for Infrared Photodetection.” 2016. Web. 08 Dec 2019.

Vancouver:

Azizur-Rahman KM. Simulation of III-V Nanowires for Infrared Photodetection. [Internet] [Doctoral dissertation]. McMaster University; 2016. [cited 2019 Dec 08]. Available from: http://hdl.handle.net/11375/20703.

Council of Science Editors:

Azizur-Rahman KM. Simulation of III-V Nanowires for Infrared Photodetection. [Doctoral Dissertation]. McMaster University; 2016. Available from: http://hdl.handle.net/11375/20703

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