Evaluate conductance of CAD shape -> report total heat of constraint

Hello,

I would like to determine the thermal resistance of a CAD shape. (its a bipod made of titanium)

my approach:

I define a "hot" and a "cold" temperature boundary at the ends of the shape. Then I evaluate how much heat is needed to establish these boundaries.

my question:

How can I output the heat needed to establish a temperature boundary?

With reporting the "heat of constraint" I found a way to print the heat of each element, but not the total value.

Kind regards and thanks in advance

0 Daniel Chu over 3 years ago

Here is a box example on which one end is fix at 100 degree C, and the other end is fix at zero temperature,(box.bdf)

The spcforces = all in the case control will gives you the heat of constraint or (Reaction force analogy in structure analysis) for for the grids that you have fix with a boundary temperature.

You can export that into a Excel spreadsheet and and add them and you will get Energy In minus Energy Out = zero

However you can modify the model to have convection to one end with a big H value such as 100 watt/m2.C convecting to a node 46. And the other end ,convection to zero degree also with H = 100 with node 47, now you will get heat of constraints as 50 watt, and -50 watt respectively.

box_conv.bdf

SOL 153

CEND

$ Direct Text Input for Global Case Control Data

ANALYSIS = HEAT

TITLE = MSC.Nastran job created on 30-Jun-21 at 10:51:52

ECHO = NONE

TEMPERATURE(INITIAL) = 1

SUBCASE 1

  SUBTITLE=Default

  NLPARM = 1

  SPC = 1

  THERMAL(SORT1,PRINT)=ALL

  SPCFORCES(SORT1,REAL)=ALL

Using convection analogy: Only 2 nodes to look at: Energy In is equals to 50 watt,and -50 watt is leaving the body.

LOAD STEP = 1.00000E+00

                              F O R C E S  O F  S I N G L E - P O I N T  C O N S T R A I N T

      POINT ID.  TYPE     ID  VALUE    ID+1 VALUE    ID+2 VALUE    ID+3 VALUE    ID+4 VALUE    ID+5 VALUE

           43     S     0.0           0.0           0.0           4.995005E+01 -4.995005E+01

Attached Files (1)

box_conv.bdf.zip
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