Last Updated: 2/21/09
Excel/VBA Spreadsheet for View Factors
If you click on either of the
links below, a Microsoft Excel workbook will be downloaded to your computer.
Each of the worksheets making up this workbook will compute the radiation view
factor for a particular geometry using the inputs you supply. In addition, each
worksheet draws your geometry to scale so that you can verify your inputs and
also appreciate the numerical values of the computed values returned. The four
geometries covered in this workbook are those that are usually presented in
graphical form in textbooks. This workbook was written under Windows, but
should work under MS Office running on a Macintosh. Earlier versions of MS
Office on both platforms may not support all features used in this workbook
and, as noted below, Office 2007 requires a separate version.
Disclaimer
No warranties, expressed or
implied, are made that this program is free from error, or is consistent with
any particular standard of merchantability, or will meet your requirements for
any particular application. This program should not be relied on for solving
problems whose incorrect solution could result in injury or lost property. If
you use this program in such a manner, it is at own risk. The author disclaims
all liability for direct or consequential damages resulting from your use of
this program, i.e., SOFTWARE THAT IS FREE HAS NO GUARANTEE!
These Excel workbooks contains
several macros written in Visual Basic for Applications (VBA), so that when you
open it you will probably see a warning like, "[filename] contains macros.
Macros may contain viruses. It is always safe to disable macros, but if the
macros are legitimate, you might lose some functionality." Then you are
given the choices: "Disable Macros", "Enable Macros" and
"More Info". In the case of this spreadsheet, you must select
"Enable Macros" or it will not work at all! (If you not even offered
this choice, then your security is probably set at "High." You must
have your security level in Excel set at "Medium," which allows you
to "choose whether or not to run potentially unsafe macros.") My
virus checker is set to update automatically every day (yours should be too!).
You might scan these materials (and anything else containing macros you might
download from the Internet) before opening them, but then you MUST enable
macros!
Radiation
View Factors - Perpendicular Plates
The first of the four worksheets
finds the view factor for perpendicular plates with a common edge (from the
well-known analytical solution) and draws an isometric view of them on the
screen. The user inputs the length of the common edge as well as the second
dimension of the two plates. This worksheet and the one for parallel plates
were developed in part to help in verifying the view factor values computed by
our much more versatile Visual Basic view factor module.
Radiation
View Factors - Coaxial Disks
The viewfactor for coaxial,
parallel disks is computed from the analytical solution and then they are drawn
to scale on the screen. The user inputs the radii of the two disks (emitter and
receiver) and the separation distance.
Radiation View Factors - Coaxial Cylinders
View factors for finite-length, coaxial cylinders are computed using a combination of analytical solutions and view factor algebra. The user inputs the radii of the two cylinders and their length. All nine relevant view factors and a scale drawing are returned.
Radiation
View Factors - Parallel Rectangles
NOTE: Because of differences in the graphics
calls between Office 2007 and earlier versions, there are currently two
separate versions of the view factor spreadsheet:
Download
View Factor Spreadsheet (Office 1997-2003)
Download View Factor Spreadsheet (Office 2007)
References:
Howell, J.R., A Catalog of Radiation Heat
Transfer Configuration Factors
Modest, M.F., Radiative Heat Transfer, 2nd Ed.,
McGraw-Hill, 2003.
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