Wirsbo software modelling tool - is way tool cool!

rb_6

I just can't say enough about the Wirsbo folks and their commitment to continually raise the bar.

This past week I had one of my career highlights which was to become the student of ‘Dr. D’ – aka one of Europe’s foremost experts on building thermal modeling. What an incredible tool to add to the arsenal of design programs and from what I witnessed – my class mates have this stuff pegged!

Thanks again to Tim Doran and the entire crew and guest including Gary, Ryan, Him Li, and Elaine. I can’t wait to see what you do with the new toys and your life long adventures in radiant heating and cooling.

Here’s one of several graphics we created from the class. If Hot Rod ( ala Mark “Consolidated pics Ltd. Eatherton) would post the thermography stuff we’ll get to see the software and reality comparison – so far it look very close!

Also – thanks to Mr. John Barba for letting me witness his wildly entertaining class – I owe ya Mr. Allstate!

Great to see Dave Holdorf, Steve Z ,Todd "thanks for the lift" , the Kraft Man and his daughter and the rest of the full house.

Outstanding!

RB

jerry scharf_3

Fine white elephants?

Is this an FE tool? That would be a nice addition to the stable. Can I put Dale's plates into it? Then we could have a three way bake off.

jerry

Mark Eatherton1

Your wish....

Is my command...

Did I get it right?

ME

rb_6

close Mr. E...

The FEA simulation is a staple up...but its a interesting comparison to the plates...

We should be able to match each thermography pic from Hot Rods lab pics up to a FEA run simulation...lets have some fun!

Will work with Mr. Doran to do the simulations and will post - post haste.

hehe...can't get enough of those sugar crisp...

rb_6

I remember waaaaay back when...

Dale was doing his FEA stuff...(ahead of the curve as usual!)

Mark Eatherton1

Fixed suspended tube FEA vs Infrared

ME

siggy

FEA

Robert, It looks like there are three thin rectangular areas just beside and below the tubing in the FEA crossection. What are they? It appears they have a strong temperature gradiant across them, which would not seem possible if they represented air.

Siggy

Tim Doran

Tube

In this program the tube is approximated by a square with the same total outside surface and the lines that you see represent the resistance of the tube wall.

Tim D.

rb_6

FEA vs Thermography

There we go ME...

...realty and modelling - love it! On the surface - (pun intended) - it looks like a good representation.

hr

My question, Tim

is that a staple up or suspended tube? Dosen't look like a good conduction connection?

If so I have some suspended pic also.

Great, and important work you have undertaken, thanks

I'm meeting up with the IR camera tomorrow afternoon to film some "above floor" products, in an actual installation, for performance comparisons.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Tim Doran

Staple up

Mr. Bean did this one. It looks like a staple up. All in all staple up applications have a relatively poor conduction patch. Even though these types of programs represent the tube with a square they understand the actual dynamics of a circle in which case the contact patch would be very small even directly above a staple,
also the tube tends to sag a bit between staples further decreasing conductivity.

Tim D.


Tim D

hr

Does Wirsbo

approve a direct pexstaple up application? Seem the pex movement through the staples would be a wear problem?

Seems like suspended tube would be a safer, yet possibly weaker transfer, method.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Tim Doran

NO

We do not promote direct staple up applications. Lots of issues to be considered with them not only around transfer and noise but also around protection of the tube from nails ans screws from above, etc. The transfer of a suspended tube system is equal too that of a staple up system and the potential for stripping is non-existent.

Tim D.

Unknown

how comprehensive is this analysis?

Judging from what I can see in the modelling, it appears that the software is modelling radiation and conduction, but is not taking convection into account, is this correct?

For instance, I would expect that the air temperature in the joist bay cavity to be hotter near the top of the airspace, yet this model would seem to indicate that the middle of the center of the joist cavity is hotter than the top of the center of the joist cavity, and the center bottom is hotter still.

If the modelling cannot model convective currents, I am not sure how far to trust its analysis of systems with air spaces included in their assemblies (such as most joist installs). What do you think, Tim?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Tim Doran

Convective

The program handles convection as well as conduction and radiation. The trick with air spaces is setting up the resistances and transfer coefficients in layers. In a very small air space such as the air gap in suspended applications the convection will be very small and the overall gradient across such a small area would be hard to measure.

Tim D.

rb_6

Steady State and Transient Modelling

The use of the program reminds of the exercise we did for the very first Foothills Conference and subsequently the first RPA conference where designers were given identical projects with the objective of seeing how close everyone’s numbers would be...the graphic comparison to the thermography (ala filmographer Hot Rod and cut and paste man ME) visually shows a close resemblance (the air temperatures within the space are closer than they appear in both methods)...but it could easily be modeled with different results by changing the load, fluid temperatures, cycle time (start and stop) and the way the conductive, convective and radiant layers are setup pre simulation...that's where experience plays a role and from what I've learned it looks like Wirsbo's professor gives them some awesome bench strength in the modeling department...I know Tim's has a number of "North American" building blocks that he worked on with the good Doctor...can't wait to see them on the Wall.

ahhh - its great to be a student again!

Dale Pickard

Thanks for the recognition

Robert

It was me and my crew. Getting real information from such models takes some real engineering intuition and skill with the FEA software, niether of which are necessarily my forte'. At the time, 10 years ago, we didn't know what we know now from experience about the heat transfer characteristics of our plates and staple up applications. The FEA studies help put us in the ball park and predict success with the technique.

Something folks need to understand about these numerical methods is that the honesty with which you build your model strongly influences your results. As one is responsible for defining specifying the heat transfer relationships between elements. So if you put garbage into it that is what you will get out. It is best to bracket FEA runs with several sets of conservative and liberal assumptions so as to paint a realistic picture.

Something else that is important relates to scaling. What is useful about FEA is the accuracy with which it predicts temperatures in a scale model, so you can predict temperature at a given distance from the tube wall, for example. The nodes in the elements are deliberatly placed at key positions that are identifiable as coordinates in the scale model. The isotherms in the model are like the elevation lines of a topo map. Lines of constant temperature.

However, fea software is limited with respect to the range of scale that may be considered in the model. For example, a model that works well on the scale of the large elements in the floor, like the connection of the plates to the plywood, does not model well other connections like the connection of the tube to the plate.
The holy grail would be a 3d fea model of a radiantly heated room which is accurate to the scale of the fit of the plate to the tube.....verstahen?

Comparing the thick plates to the thin plates on the scale of the floor is similarly difficult. The flooring elements and the plate elements have to be very finely meshed to get good output. And the thermal relationships between elements have to be carefully defined. One can vary these input variables one at a time to study the effects of changes in the variables.

Typically, there are major simplifications and approximations made in terms of geometry. For example, Tim's tubes are square and not round. I see that his heat transfer plates are similarly crude, not the fine geometry that comes out of cad. Software like CosmosM can take the geometry directly out of detailed cad files without the need to produce crude approximations.

I don't know this but I suspect that the software that he is using would have difficult time resolving differences in detail, as in accurate predictions of thermal resistance between the tube and the plate (air spaces on the order of (.005"-.030") in a model scaled to the size of the larger elements in the floor, e.g. 3'.

These days I am more enamored of direct measure as with the thermal imaging. In a decent study program one would seek to tune the fea model with real world measurement and experimentation. Look at Hot Rod's photos like the one Mark posted of the TFin. You can see how important good contact of the plate with the floor is! It's easy to see how heat transfer at the fasteners is enhanced where the fit is tight and lost at the edges where the fit is not "tight". You'll play bloody hell modeling this in 3d in fea like the thermal photo shows. It would take a very skilled modeler and some very sophisticated software to recreate the image shown in the thermal image. The thermal image is a direct measurement. It is incontrovertable. Does that make sense?

I think that a study program based on thermal imaging combined with some simple data logging could provide a great deal of useful information.
At the same time, one could play with these toys and generate pretty pictures forever and still not pick up the kind of real information that comes from being there and directly experiencing and evaluating the results of one's "experiments". Nothing like hanging out in a boiler room at -30f. My hat's off to the contractors and the service guys. Their education is not virtual. Some things work and some things really don't.

Dale

rb_6

Fun Tools

The gent who taught our class uses several 3D programs including a few FDM programs which are way beyond my skill level... and you're right - its zippy stuff - great for those who get paid to play.

I believe the majority of your comments would find agreement with anyone who has or is in the process of adding these modeling tools to their services…I also believe its important to put things into perspective…we’ve lived the past 25 to 30 years as witnesses to radiant field experiments ala the consumer to informal research ala our own houses to formal research and then into hand calculations to the first Excel spreadsheets to the fancy programs we see marketed today including the loop draw stuff. I don’t know this as fact but I think you were first in using the FEA for this industry. The first really good radiant thermography pics I saw came from Dan Chiles and from Hot Rod’s participation (others may have existed but I am not aware of them)…in that time frame our industry like many others has moved into a world where we (using a quote from Tim at Wirsbo)…measure with calipers, mark with chalk and cut with an axe…given more time will the axe will get sharper and the chalk a little more pointed? I have to believe they will.

In many ways, this dialogue reminds me of the heated discussions that come out of our design courses on the ‘magnitude of errors’ related to how many decimal points to carry on head loss or flow rate calculations. This flows into the same stream of thought as Dr. Petijeans famous quote, “ If we are not prepared to measure the head losses in the field to verify our calculations – why crunch the numbers at all?” So just how do we know we have the differential pressure we’ve calculated unless we verify it with gauges, how do we know we have the temperatures unless we measure it with thermometers and how do we know we have the thermal distribution unless we scan it with thermography. Maybe we’ll see Schlieren imagery come next as design tool.

See this link to a sample picture (credit to Dr. Settles from Penn State)

http://www.healthyheating.com/blog/

I’ll be playing with the FEA programs over the next year or so and will definitely be in more classes -- my predications on the tool (which have been wrong before) -- given identical pre run setups with ‘small’ errors in geometry will generate a ‘small’ magnitude of error…that in the field is insignificant due to the flexibility of hydronics. But, like you said, “…a study program based on thermal imaging combined with some simple data logging could provide a great deal of useful information.” It certainly would expose the errors made in all types of design assumptions, software and product performance specifications but more importantly establish the magnitude of the error in relationship to the field performance.

So when did you say you were going to join our merry band of ASHRAE TC 6.5 members? You know I’ve hounded you before about this…next meeting is in Denver.

Mark Eatherton1

Denver....

is MY kind of town... Buy you an adult barley based beverage or two???

ME

rb_6

Snap Gulp and Pop

It’s the newest of barley cereals...

Snap is for the arm twisting,

Gulp...is the consumption technique

and Pop is for another one please.

You bet...and since we have free trade you have to let me return the offer.