• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Investigation of Heat Transfer and Entropy Production of High Temperature Molten Chloride Salts Circulation in Concentrating Solar Power Systems

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_etd_19567_sip1_m.pdf
    Size:
    2.274Mb
    Format:
    PDF
    Download
    Author
    Zhang, Ye
    Issue Date
    2022
    Keywords
    Energy storage
    heat transfer
    Molten salt
    Solar Energy
    thermal energy
    thermal systems
    Advisor
    Li, Peiwen
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    The global warming and worsening environment on the earth has been a great concern to human society in the last two decades. The major solution to the problem is to use clean and renewable energies for electricity generation, thus reducing the use of fossil fuels and cutting emission of CO2. One of the most feasible approaches for accomplishing the goal is to significantly increase the harvest and utilization of solar energy, using Concentrating Solar Power (CSP) technology combined with Thermal Energy Storage (TES) systems.Heat transfer fluids (HTFs) are used in CSP plants to receive heat from solar concentrator and then transfer it to heat exchanger, power turbine, or thermal storage system. To achieve higher energy efficiency from the CSP systems, the development of a new generation HTF to approach a higher temperature limit by using eutectic high temperature molten chloride salts is sponsored by the U.S. Department of Energy. The first part of this dissertation is the experimental study of the convective heat transfer of the molten salt at high temperatures. For the first time, a circulation system and instrumentation of flow and heat transfer was designed and constructed to measure the heat transfer coefficient of the . Experimental measurement of the convective heat transfer coefficients of NaCl-KCl-ZnCl2 (molar fraction: 13.8%-41.9%-44.3%) inside tubes has been accomplished to find the most suitable heat transfer correlations. This provides valuable information for the design of heat transfer devices in CSP plants that use molten chloride salts as heat transfer fluid and thermal energy storage material. The second part of this dissertation mainly focuses on the analysis to the transient heat transfer phenomenon between the hot fluid and the cold pipe. Currently, most of the modern concentrated solar thermal power plants employ molten salts as the heat transfer fluid to carry the thermal energy from solar concentrators and deliver to thermal storage systems or thermal power plants for the need of power generation. For the startup operation of solar concentrators, molten salts need to be pumped to flow into the pipes which may have lower temperature than the molten salt due to cold ambient overnight or over the suspend period of operation. As the freezing point of various molten salts ranges from 220 oC to 430 oC, preventing the freezing of molten salt flowing in cold pipe is a very important requirement for the safe operation of a concentrated solar thermal power plant. A basic heat transfer analysis of transient heat exchange between molten salts and the flow pipe is conducted to find a criterion or the critical condition of preventing molten salt from freezing. The effects of molten salt flow velocity, heat capacities of molten salt and pipe, dimensions of pipes, and the initial temperatures of salts and cold pipes are all correlated theoretically in the analysis through modeling of transient heat transfer between a pipe and the fluid. The results are very helpful to the understanding and management of a safe startup of hot molten salt flowing in cold pipes on cyclic operations. The third part of this dissertation introduces details about the modeling that provides a fundamental approach for the comparison of various heat transport systems which may have different designs and using different heat transfer fluids/media (gas, liquid, or solid particles) in CSP systems. For various high temperature heat transfer fluids, such as, synthetic oils, various molten salts, and liquid metals, a general criterion is proposed in this work to evaluate the merit of fluids regarding their transport properties. For the goal of transferring a desired amount of heat, a fluid that causes less entropy production is believed to have better figure of merit (FOM). This is due to the fact that entropy production is associated with the destruction of exergy or useful energy. The entropy production in a heat transfer system in a solar thermal power plant includes the part due to the processes of heat addition and removal and the other part due to pressure losses in the flow in heat exchangers and pipes. Theoretical analysis and relevant equations for total entropy production are derived. As an example, the FOM for several heat transfer fluids used in CSP industry are compared for the goal of heat transport in the range of 50 MWth to 600 MWth. This work offers one very important approach leading to the development and optimization of a heat transport system for CSP plant with all factors considered. The investigations included in this dissertation for the heat transfer and system analysis in concentrating solar power technology are of particular interest to the renewable energy engineering community. It is expected that the proposed methods can provide useful information for engineers and researchers.
    Type
    text
    Electronic Dissertation
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Mechanical Engineering
    Degree Grantor
    University of Arizona
    Collections
    Dissertations

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.