• Admin
    UC Research Repository
    View Item 
       
    • UC Home
    • Library
    • UC Research Repository
    • College of Engineering
    • Engineering: Theses and Dissertations
    • View Item
       
    • UC Home
    • Library
    • UC Research Repository
    • College of Engineering
    • Engineering: Theses and Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of the RepositoryCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

    Statistics

    View Usage Statistics

    Heat transfer through cavity walls

    Thumbnail
    View/Open
    lishomwa_thesis.pdf (22.20Mb)
    Author
    Lishomwa, Lufwendo
    Date
    1977
    Permanent Link
    http://hdl.handle.net/10092/9452
    Thesis Discipline
    Chemical Engineering
    Degree Grantor
    University of Canterbury
    Degree Level
    Doctoral
    Degree Name
    Doctor of Philosophy

    The aims of this study were: (a) to develop a numerical method and (b) to develop an experimental method for the prediction of heat transfer in a cavity in which radiative transfer, gaseous and solid conduction are occurring. In the experiments, the thermal conductivities of various materials (perspex, durotherm and particle board) were measured to within 1%. The rates of heat transfer across the materials (specimens) were measured for different values of: (a) temperature difference across the specimens - dT varied between 1°C and 51°C (b) material (specimen) thickness - 5.6mm, 9.7mm, 11mm, 12mm and 19mm thick specimens were used (c) cavity size - 30.5mm, 34.925mm, 35.5mm and 40.5mm diameter holes were used. The results are presented in graphical and tabular forms (rate of heat transfer versus temperature drop). As expected, the rates of total heat transfer decreased with increases in the hole size and specimen thickness. The effects of radiation transfer were assessed by blocking the holes with aluminium foil. The results showed that radiation transfer was small (about 5% of the total heat transferred). For four different values of the emissivity of aluminium (0.04, 0.11, 0.2 and 0.5), the method computed: (a) the heat transferred by solid conduction - this was found to be constant for all values of emissivity (b) the heat transferred by gaseous (air) conduction - this too did not vary with emissivity (c) the radiation transferred between the surfaces in the hole - this varied significantly with emissivity (d) the total heat transferred. The results obtained from the numerical simulations are presented in graphical and tabular forms. Depending on the emissivity value used, the percentage of radiation transfer varied between 2 and 15% of the total heat transferred. Correspondingly, the air conduction varied between 9 and 17% of the total heat transferred. Hence solid conduction was the dominant mode of heat transfer (68 to 89% of the total heat transferred). When using the material durotherm, the experimental and the theoretical results were in agreement within the limits of experimental error. When using perspex, only half of the results were within the limits of experimental error. The discrepancies for the perspex runs varied between 2 and 26%. Reasons are advanced to explain these discrepancies.

    Collections
    • Engineering: Theses and Dissertations [2271]
    Rights
    https://canterbury.libguides.com/rights/theses

    UC Research Repository
    University Library
    University of Canterbury
    Private Bag 4800
    Christchurch 8140

    Phone
    364 2987 ext 8718

    Email
    ucresearchrepository@canterbury.ac.nz

    Follow us
    FacebookTwitterYoutube

    © University of Canterbury Library
    Send Feedback | Contact Us