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Re: Keep the Heat B/Thermodynamics C

Posted: October 24th, 2012, 8:13 pm
by iwonder
It's plastic and not plastic foam, no type of foam is allowed.

Re: Keep the Heat B/Thermodynamics C

Posted: October 25th, 2012, 12:25 pm
by LMayeski84
Is down considered a commercial insulator?
Could chemicals be used as insulators?

Re: Keep the Heat B/Thermodynamics C

Posted: October 25th, 2012, 12:32 pm
by foreverphysics
LMayeski84 wrote:Is down considered a commercial insulator?
Could chemicals be used as insulators?
If you mean stuff like chicken down, then no.
As for chemicals...there is a specific part in the rules that says, "no chemical reactions". Since it says that, I would play on the safe side and just leave out any chemicals. Also, chemicals tend to spill and ruin your box. I know that from experience...

Re: Keep the Heat B/Thermodynamics C

Posted: October 26th, 2012, 2:07 pm
by retired1
retired1 wrote:Just an opinion. A glass vacuum container is moderately thin glass and the reflector coating is extremely thin. I think that if you make a vacuum jar ( a Dewar)out of metal or normal thickness glass, the outer layer will suck up an immense amount of heat.
A high vacuum will crush a normal container. So how much are you going to gain? The lightest thing that you can come up with with just atmospheric pressure will probably work better.

About half of the event score is on the test. the other half is mostly on how well you can predict your final temps. A small percent of the score 5%+/- is on how effective your insulator is. A great insulator will help on the prediction score if it is very consistent.
Again, just an opinion from a practical standpoint.
I will partially modify this. I have a 20 Oz coffee cup that is anodized aluminum outside and a "spun" aluminum inside. It does a nice job of keeping 140F coffee warm for an extended period. I sort of doubt if it is a true vacuum cup.
I think that it succeeds by having a large volume to give up heat to an slow approach to an equilibrium temperature.
I do know that it does not work any where near as well with a partial cup full. Since this event will normally be close to 100 ml of liquid and the beaker will suck up a lot of that heat, I would like to privately hear how you plan on obtaining a vacuum cup. I suspect that it would have quite a bit of mass. I will hazard a guess that some event supervisors will consider a commercial vacuum cup or dewar to be commercial insulation. If you are seriously thinking of going this route, You would be well advised to get a rules clarification.

Re: Keep the Heat B/Thermodynamics C

Posted: October 27th, 2012, 1:56 pm
by awesome90220
For those who were in this last year, what kind of conversions do you think I need

Re: Keep the Heat B/Thermodynamics C

Posted: October 27th, 2012, 2:31 pm
by siciscio
awesome90220 wrote:For those who were in this last year, what kind of conversions do you think I need
Definitely have a list of conversions of all the different temperature you can find. ( they generally keep it down to Fahrenheit, Kelvin and Celsius sometimes Rankine, but I think I've seen test with some others as well :shock: )

I'd also recommend having conversions between Calories, calories (there's a difference apparently), Joules and BTU. The mainly ask for the conversions of joules and calories but then again you never know ;)

Lastly, I'd have a conversion between the different units of pressure. I.e. Pascal and atmospheres. It's for the different forms of the gas law they might give you.

Anyone else want to add(or edit) to that? Hope it helps :roll:

Re: Keep the Heat B/Thermodynamics C

Posted: October 28th, 2012, 12:12 pm
by sciencegeek999
Can we use electrical tape, aka insulating tape? I heard that some had fiberglass cloth on it something.
If so, is it used as a fastener or actualy insulator? Eg. wrapped around beaker when placed in but not sticking to it
Also, if you go to wikipedia, you can find temperature conversions for other units such as Newtons and Reaumers, not just degrees F and C.

Re: Keep the Heat B/Thermodynamics C

Posted: October 28th, 2012, 6:22 pm
by retired1
My thoughts. Electrician's tape is normally a vinyl, but there is a rubber based one. Fiberglass reinforcement such as in some package tape would not be considered an insulator-no air pockets. You would be treading on troubled water if you tried to use "flame spray" tape. Also it is expensive.
I seriously doubt if you would be allowed to wrap either beaker with tape, however, it could slide down into something like a shell after you get your hot water. The intriguing part would be making the shell.

Re: Keep the Heat B/Thermodynamics C

Posted: October 29th, 2012, 5:09 pm
by sciencegeek999
I meant a shell. Last year, I made a shell out of a wool sock and duct tape. I got third place, division b varsity using that idea. :)

Re: Keep the Heat B/Thermodynamics C

Posted: October 30th, 2012, 6:22 am
by foreverphysics
I am fairly sure my entire device is made out of cardboard, paper, cotton, a few sheets of aluminum foil, and some glue. I think that at 22˚ C room temperature, 100 mL of water at 80˚ C, on a 40 minute time interval, it goes down to ~54˚C.
That being said, there's no need to creatively make a bunch of materials. Using simple materials will often get you the farthest, and really, the rules allow for plenty of tweaks and edges here and there.