Heat detector device

[gforney]

Please complete the following lines...

FDS Version:5
SVN Revision Number:
Compile Date:11/3/2015
Smokeview Version/Revision:5
Operating System:Windows 7

Describe details of the issue below:

I model 2 circular tanks. I set one tank as a burner but only at the top side and another
tank with a heat detector device at side.
However, the temperature increase of the divice is very small even when I put both
tank very near to each other.
Please help.

Original issue reported on code.google.com by fatnab77 on 2015-03-11 10:31:43

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• Attachment: smv.png
  
• Attachment: 2tank.fds

[gforney]

A heat detector in FDS only uses the standard RTI algorithm.  This is based solely on
local gas temperature, it does not use radiant heat. The device is behaving as expected.
You should probably use a heat flux device.  

Original issue reported on code.google.com by drjfloyd on 2015-03-11 12:02:40

[gforney]

And you should use FDS 6 because we have added devices that might be of use to you.

Original issue reported on code.google.com by mcgratta on 2015-03-11 12:37:15

[gforney]

Thanks for your fast response.
Can you suggest what device should I use? I have referred to fds user guide but I'm
still not sure what device for heat flux.

Original issue reported on code.google.com by fatnab77 on 2015-03-11 13:19:34

[gforney]

16 Output
16.10 Special Output Quantities
Section 16.10.5 Heat Fluxes and Thermal Radiation

16.12 Summary of Frequently-Used Output Quantities
Table 16.3 Summary of frequently used output quantities (search for HEAT FLUX)

Original issue reported on code.google.com by drjfloyd on 2015-03-11 13:22:55

[gforney]

&MATL ID='metal', DENSITY=XXX, CONDUCTIVITY=XXX, SPECIFIC_HEAT=XXX /
&SURF ID='metal sphere', THICKNESS=XXX, MATL_ID='metal', GEOMETRY='SPHERICAL' /
&PART ID='heat detector', SURF_ID='metal sphere', STATIC=.TRUE. /
&INIT ID='hd', XB=..., N_PARTICLES=1, PART_ID='heat detector' /
&DEVC ID='Temp', INIT_ID='hd', QUANTITY='WALL TEMPERATURE' /

XB should be a small box where you want the detector to be located. These lines create
a small metal sphere that serves as a heat detector. You would have to choose the properties
and thickness to mimic a particular RTI. 

Original issue reported on code.google.com by mcgratta on 2015-03-11 13:38:01

[gforney]

Thanks! I've tried it and the results are promising.

But just for clarification, if i put the properties and thickness of the tank as properties
and thickness of the small metal sphere, will it be correct?

Original issue reported on code.google.com by fatnab77 on 2015-03-11 15:35:56

[gforney]

Why would the tank material properties be related to those of the detection device?
The small metal sphere is a model of a heat detector or slug calorimeter. This has
nothing to do with the tank.

Original issue reported on code.google.com by mcgratta on 2015-03-11 15:54:59

[gforney]

What are you trying to do with this device?

-Obtain the exposure to the top of the tank?  In this case put a wall heat flux device
on the tank top.

-or, attempt to mimic the behavior of a heat detector (which is generally a metal mass
with a temperature measuring device attached to it)?  In this case as Kevin notes use
the particle method and replicate the measurement device.

Original issue reported on code.google.com by drjfloyd on 2015-03-11 15:58:13

[gforney]

I want to use the device to detect the temperature rise at the adjacent tank so that
I can use link temperature to see the time of the adjacent tank will ignite when its
temperature is at a certain temperature.

Original issue reported on code.google.com by fatnab77 on 2015-03-11 16:51:06

[gforney]

If that is the case,  isn't the critical variable really the tank temperature?  That
is at some steel temperature of the adjacent tank you will presume there is an ignition?
In which case why use a heat detector instead of just using the tank temperature?

Original issue reported on code.google.com by drjfloyd on 2015-03-11 17:03:41

[gforney]

I choose heat detector at the first place because I want to use the link temperature.
The temperature of ignition will be temperature ignition of fuel inside the tank.
So I followed the fds5 user guide.

"&DEVC ID='HD_66', PROP_ID='Acme Heat', XYZ=2.3,4.6,3.4 /
&PROP ID='Acme Heat', QUANTITY='LINK TEMPERATURE', RTI=132., ACTIVATION_TEMPERATURE=74.
/"

If i use the metal mass with temperature measuring device, how do I make the link temperature?
Tried a few times but it doesn't work.

Original issue reported on code.google.com by fatnab77 on 2015-03-12 04:01:40

[gforney]

If you are concerned about the next tank, why are you bothering with a detection device.
Follow Jason's advice in Comment #10 and monitor the temperature of the tank itself.
You need to develop some plausible "failure temperature" that indicates a likelihood
of ignition. I cannot tell you what that is. This is your job. We can only help you
set up the FDS calculation.

Original issue reported on code.google.com by mcgratta on 2015-03-12 12:49:40

[gforney]

Alright. Thanks for your help.

Original issue reported on code.google.com by fatnab77 on 2015-03-12 15:03:09