field function report new value each iteration

hebeldebel · July 1, 2014, 10:14

Hi,

I created a field function with a variable from a report ${nameofthereport} , I created a monitor for the report as well. Do I need to set an option for ccm+ to read in the value of ${nameofthereport} each iteration, or does this happen on its own?

Thanks for your help

kind regards
hebeldebel

This is the field function I wrote:

(9E-05)*${TemperaturKupferMitteReport}*${TemperaturKup ferMitteReport}-0.0144*${TemperaturKupferMitteReport}+10.382

I use it to define a volumetric heat source as a function of the temperature on a specific point. When I do the same calculation with my calculator I get approx. 9.8 Watt, when i do a heat transfer report on the region with the volumetric heat source, I get ~ 17 Watt. As ${TemperaturKupferMitteReport} lies between 60 and 130, something must be wrong with my field function.

me3840 · July 1, 2014, 14:25

No, this happens every time the field function is calculated, you don't have to specify an update frequency.

Are you sure your report contains no other heat transfer from other places in the region? That sounds like it's happening to me.

hebeldebel · July 3, 2014, 08:57

Thank you for your answer

Quote:

Originally Posted by me3840

No, this happens every time the field function is calculated, you don't have to specify an update frequency.

And the field function is automatically recalculated, after every iteration, right?

Quote:

Originally Posted by me3840

Are you sure your report contains no other heat transfer from other places in the region? That sounds like it's happening to me.

I double checked the report of the volumetric heat source. There are two interfaces (as there should be).

me3840 · July 3, 2014, 11:23

The field function is automatically calculated every time it needs to be. When it is called, it is calculated. How often it is called depends on how you've implemented it. If it's in a monitor that's updated every iteration, that would then calculate it every iteration.

Well, I don't know what your field function really means since there's a few constants in there, but it doesn't look like the 1d HX equation I've seen many-a-times.

hebeldebel · July 11, 2014, 08:56

It is a formula I derived from the datasheet of a LED manufacturer and its power output varies with the temperature. I typed the same equation into excel, created a monitor for the boundary I took the temperature and did the calculation with excel. I got the right wattage, but the output of the heat transfer report (of the volumetric heat source) shows a much higher number for the following iteration, than expected.

Something must be wrong with the way, I wrote the field function.

Here is another point:
the input ${TemperaturKupferMitteReport} is a temperature in C, while the field function I try to write is defined as Power [W] is this a problem?

the excel formula reads as:
=0.00009*L53*L53-0.0144*L53+10.382

L53 is the cell with the temperature value

me3840 · July 14, 2014, 01:56

It's a problem if the report outputs something other than C. I would just make everything in Kelvin and see if you get the same answer.

hebeldebel · July 14, 2014, 08:23

Hi me3840,

thanks for your answer, I tried it but still got some weird results, so I tried it all again, . . . turns out I had some rounding errors in my calculation and therefore got wrong values

. Everything works now.

lj0812 · September 6, 2017, 03:01

Hi hebeldebel,
What's rounding errors you mentioned in star? It's maybe a answer of my difficulty for a long time.

July 1, 2014, 10:14	field function report new value each iteration	#1
hebeldebel Member Join Date: Jan 2014 Posts: 40 Rep Power: 12	Hi, I created a field function with a variable from a report ${nameofthereport} , I created a monitor for the report as well. Do I need to set an option for ccm+ to read in the value of ${nameofthereport} each iteration, or does this happen on its own? Thanks for your help kind regards hebeldebel This is the field function I wrote: (9E-05)${TemperaturKupferMitteReport}${TemperaturKup ferMitteReport}-0.0144${TemperaturKupferMitteReport}+10.382 I use it to define a volumetric heat source as a function of the temperature on a specific point. When I do the same calculation with my calculator I get approx. 9.8 Watt, when i do a heat transfer report on the region with the volumetric heat source, I get ~ 17 Watt. As ${TemperaturKupferMitteReport} lies between 60 and 130, something must be wrong with my field function. Last edited by hebeldebel; July 1, 2014 at 11:06. Reason: Added the equation*

July 11, 2014, 08:56		#5
hebeldebel Member Join Date: Jan 2014 Posts: 40 Rep Power: 12	It is a formula I derived from the datasheet of a LED manufacturer and its power output varies with the temperature. I typed the same equation into excel, created a monitor for the boundary I took the temperature and did the calculation with excel. I got the right wattage, but the output of the heat transfer report (of the volumetric heat source) shows a much higher number for the following iteration, than expected. Something must be wrong with the way, I wrote the field function. Here is another point: the input ${TemperaturKupferMitteReport} is a temperature in C, while the field function I try to write is defined as Power [W] is this a problem? the excel formula reads as: =0.00009L53L53-0.0144L53+10.382 L53 is the cell with the temperature value Last edited by hebeldebel; July 11, 2014 at 10:02. Reason: more information*

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July 1, 2014, 14:25		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	No, this happens every time the field function is calculated, you don't have to specify an update frequency. Are you sure your report contains no other heat transfer from other places in the region? That sounds like it's happening to me.

July 3, 2014, 11:23		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	The field function is automatically calculated every time it needs to be. When it is called, it is calculated. How often it is called depends on how you've implemented it. If it's in a monitor that's updated every iteration, that would then calculate it every iteration. Well, I don't know what your field function really means since there's a few constants in there, but it doesn't look like the 1d HX equation I've seen many-a-times.

July 14, 2014, 01:56		#6
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	It's a problem if the report outputs something other than C. I would just make everything in Kelvin and see if you get the same answer.

July 14, 2014, 08:23		#7
hebeldebel Member Join Date: Jan 2014 Posts: 40 Rep Power: 12	Hi me3840, thanks for your answer, I tried it but still got some weird results, so I tried it all again, . . . turns out I had some rounding errors in my calculation and therefore got wrong values . Everything works now.

September 6, 2017, 03:01		#8
lj0812 New Member LIU JUN Join Date: Sep 2017 Posts: 4 Rep Power: 9	Hi hebeldebel, What's rounding errors you mentioned in star? It's maybe a answer of my difficulty for a long time.