WS20-1 WORKSHOP 20 Radiation shield using VIEW entry NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation

WS20-2NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation

WS20-3NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation n Problem Description u View Factor calculation using CHBDYE elements: u Following is a model of exhaust pipe in the car. The objective of this analysis is using shield to block some portion of the radiation energy, so that the floor does not get exceedingly hot.

WS20-4NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation n The pipe section consists of CQUAD4 element ID from 121 to 220. The shield has CQUAD4 element from 221 to 420, and the rectangular plate has CQUAD4 element from 1 to 120. n Dimension : mm n n NASTRAN BULK DATA ENTRIES:RADSET,RADCAV,VIEW,VIEW3D,CHBDYE,RADM n The name of the model file is called:model1. txt n Name of the input file: shld2_noamb.dat

WS20-5NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation Exhaust pipe section Exhaust pipe Boundary Conditions: Temperature of the pipe is constant at 630 degree C

WS20-6NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation Problem 1: Solve the view factor calculation using two separate cavities: SOL 153 TIME 600 $ Direct Text Input for Executive Control CEND ANALYSIS = HEAT TITLE = MSC/NASTRAN job created on 16-Apr-98 at 16:37:43 ECHO = SORT MAXLINES = TEMPERATURE(INITIAL) = 1 $ Direct Text Input for Global Case Control Data SUBCASE 1 Subcase name : Default SUBTITLE=Default NLPARM = 1 SPC = 1 THERMAL(print)=ALL flux=all BEGIN BULK include 'model1.txt' PARAM,TABS, PARAM,SIGMA, NLPARM,1 $ Radiation Enclosures of Load Set : pipe_shld RADCAV,55,,NO VIEW,1,55,NONE $ Radiation Enclosures of Load Set : shld_pipe VIEW,2,55,NONE $VIEW3D ICAVITY GTTB GIPS CIER ETOL ZTOL WTOL RADCHK VIEW3D,55,4,4,4 RADCAV,65,,NO $ Radiation Enclosures of Load Set : shld_floor VIEW,5,65,NONE $VIEW3D ICAVITY GTTB GIPS CIER ETOL ZTOL WTOL RADCHK VIEW3D,65,4,4,4 $ Radiation Enclosures of Load Set : floor_shld VIEW,6,65,NONE RADSET,55,65 $CHBDYE EID EID2 SIDE IVIEWF IVIEWB RADMIDF RADMIDB CHBDYE,500,121,1,,1,,1 =,*1,*1,== =98 CHBDYE,600,221,1,5,2,2,2 =,*1,*1,== =198 CHBDYE,800,1,1,6,,2 =,*1,*1,== =118

WS20-7NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation $ Radiation Material Properties RADM,1,,.8 RADM,2,,.74 $ Referenced Coordinate Frames SPC,1,144,1,630.0 =,=,*1,== =108 $ TEMP,1,144,630.0 =,=,*1,== =108 $ Default Initial Temperature TEMPD,1,300.0 ENDDATA 3ce62818 PARTS:CAVITY NUMBERIVIEWFIVIEWB PIPE55 1 SHIELD INSIDE55 2 SHIELD OUTSIDE655 PLATE656

WS20-8NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation On the unix machine one can use the grep command To extract the view factor: For example, grep -SUM shld2.f06 > shld2. txt CHBDY ID AiFij Fij SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E SUM OF E E-01

WS20-9NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation T E M P E R A T U R E V E C T O R POINT ID. TYPE ID VALUE ID+1 VALUE ID+2 VALUE ID+3 VALUE ID+4 VALUE ID+5 VALUE 1 S E E E E E E+02 7 S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E+02

WS20-10NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation Problem 2: Previously the assumption of cavities is that the elements within cavity 1 cannot see cavity 2. Therefore, the view computation takes less time because there is no checking of elements required. However, in reality the pipe surface does see the floor directly. We will put all elements into one cavity, and assign a FLAG for the VIEW card: KBSHD – face can be shaded by other faces KSHD – face can shade other faces BOTH – face can both shade and be shaded by other faces NONE – face can neither shade nor be shaded by other faces PARTS:SHADE FLAGIVIEWFIVIEWB PIPEKBSHD 1 SHIELD INSIDEBOTH 2 SHIELD OUTSIDEBOTH5 PLATEKBSHD6 Test deck: shld2_both2. dat Problem 2: Turn on the shading calculation, and use a single cavity

WS20-11NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation RADCAV,55, VIEW,1,55,KBSHD VIEW,2,55,BOTH $VIEW3D ICAVITY GTTB GIPS CIER ETOL ZTOL WTOL RADCHK VIEW3D,55,4,4,4 VIEW,5,55,BOTH VIEW,6,55,KBSHD RADSET,55

WS20-12NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation Problem 3: Adding ambient elements using chbdyp,point elements Test deck is: shld2_chbdyp.dat In this problem we will add two ambient elements. One ambient element ID 7777 for cavity 55 and ambient element ID 8888 for cavity 65. We will also fix the temperature boundary conditions on element 7777 at 70 degree and 8888 at 30 degree.

WS20-13NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation Begin Bulk include 'model1.txt' PARAM POST 0 In this example,sigma is equal to 5.67E-14 Watt/mm**2.K**4 PARAM PATVER 3. PARAM AUTOSPC YES PARAM,TABS, PARAM,SIGMA, NLPARM,1 SPC,1,144,1,630.0 =,=,*1,== =108 $ Radiation Enclosures of Load Set : pipe_shld RADCAV,55,7777,no VIEW,1,55,NONE $ Radiation Enclosures of Load Set : shld_pipe VIEW,2,55,NONE $VIEW3D ICAVITY GTTB GIPS CIER ETOL ZTOL WTOL RADCHK VIEW3D,55,4,4,4 $ Radiation Enclosures of Load Set : amb_998 RADCAV,65,8888,no $ Radiation Enclosures of Load Set : shld_floor VIEW,5,65,NONE $VIEW3D ICAVITY GTTB GIPS CIER ETOL ZTOL WTOL RADCHK VIEW3D,65,4,4,4 $ Radiation Enclosures of Load Set : floor_shld VIEW,6,65,NONE RADSET,55,65

WS20-14NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation $ Initial Temperatures from Temperature Load Sets SPC,1,7777,1,70.0 SPC,1,8888,1,30.0 TEMP,1,7777,70.0 TEMP,1,8888,30.0 TEMPD,1,200.0 $ TEMP,1,144,630.0 =,=,*1,== =108 $ Default Initial Temperature TEMPD,1,300.0 $ CHBDYE elemnent $CHBDYE EID EID2 SIDE IVIEWF IVIEWB RADMIDF RADMIDB CHBDYE,500,121,1,,1,,1 =,*1,*1,== =98 CHBDYE,600,221,1,5,2,2,2 =,*1,*1,== =198 CHBDYE,800,1,1,6,,2 =,*1,*1,== =118 Define ambient points using SPOINT 7777 and 8888,notice that an area input is required on the PHBDY card. You should put an area that is bigger than your total radiation area. I put in for the ambient element area CHBDYP,7777,80,POINT,,,7777,,,+ +,777,,,,1.0,0.0,0.0 CHBDYP,8888,80,POINT,,,8888,,,+ +,777,,,,1.0,0.0,0.0 PHBDY,80, SPOINT,7777,8888 RADM,777,,1.0 $ Radiation Material Properties RADM,1,,.8 RADM,2,,.74 $RADM,3,,1. $ Referenced Coordinate Frames ENDDATA 3ce62818

WS20-15NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation we can see that by adding ambient elements, the temperature increase on the plate as compared to the problem 1 because now all the loss radiation now goes to a constant temperature of 70 and 30 degree instead of absolute zero degree Kelvins.

WS20-16NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation In the NASTRAN F06 file we can see that ambient element 7777 and 8888 received 6437 and 1207 watts in this problem. H E A T F L O W I N T O H B D Y E L E M E N T S (CHBDY) ELEMENT-ID APPLIED-LOAD FREE-CONVECTION FORCED-CONVECTION RADIATION TOTAL E E E E E E E E E E E E E E E E E E E E E E E E E+03

WS20-17NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation Problem 4: Test deck: shld2_noamb_both_gauss2_flux.dat We are changing the boundary conditions of the pipe. Instead of fixing the temperature contour to 630 degree. We will imposed a constant heat flux of value equal to 0.07 watt/mm**2 boundary conditions on the surface of the pipe. Since we are not changing the geometry of the problem, and therefore we can reuse the radiation matrix punch from problem 4. $Add heat flux to CHBDYE ID 500 to 599 $QBDY3 SID Q0 CNTRLND EID1 EID2 EID3 EID4 EID5 QBDY3,20,0.07,,500,THRU,599 include 'gauss2.pch' You can see the following messages in the F06 file: *** USER WARNING MESSAGE 6427 (VIEWD) VIEW FACTORS WILL NOT BE COMPUTED FOR RADIATION CAVITY ID= 55 BECAUSE A RADIATION MATRIX IS ALREADY DEFINED. USER INFORMATION: THE RADIATION MATRIX IS DEFINED ON RADLST OR RADMTX BULK DATA ENTRIES. Since the view factor calculation is not required, and thus the job can run much faster. Problem 4: rerun the model using the radiation punch file

WS20-18NAS104, Workshop 20, March 2004 Copyright 2004 MSC.Software Corporation T E M P E R A T U R E V E C T O R POINT ID. TYPE ID VALUE ID+1 VALUE ID+2 VALUE ID+3 VALUE ID+4 VALUE ID+5 VALUE 1 S E E E E E E+02 7 S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E S E E E E E E+02