Scioly.org

harryk wrote:I've derived an equation that accounts for initial temp, ambient temp, volume of water, and time. All in one single equation that is based on a value taken from only one calibration plot. Though I'm too selfish to post it

That's impressive (and seriously hardcore ).

i was wondering if shrink wrap is allowed, and also what types of fiber glass was permitted in the box. also can we use duck tape on the inside of the box as well?

The open question is if the students are allowed to use the plugs for the 1.5 cm hole. W/o the plug, modeling shows that one would have an almost instant drop from say 90C to 80C by just heating the beaker, then heating the air outside. Majority of heat loss for any well-designed thermos are linear losses through the 1.5 cm thermometer hole.
Can we use the plug?

pawtre13 wrote:i was wondering if shrink wrap is allowed, and also what types of fiber glass was permitted in the box. also can we use duck tape on the inside of the box as well?

Look back through the thread, there was a discussion about fiberglass. As for shrink wrap and duck tape, the rules don't say anything against them.

istou wrote:The open question is if the students are allowed to use the plugs for the 1.5 cm hole. W/o the plug, modeling shows that one would have an almost instant drop from say 90C to 80C by just heating the beaker, then heating the air outside. Majority of heat loss for any well-designed thermos are linear losses through the 1.5 cm thermometer hole.
Can we use the plug?

The rules explicitly state that the hole must remain "open and unobstructed" during competition

Skink wrote:

harryk wrote:I've derived an equation that accounts for initial temp, ambient temp, volume of water, and time. All in one single equation that is based on a value taken from only one calibration plot. Though I'm too selfish to post it

That's impressive (and seriously hardcore ).

Actually, if the thermos is properly design to eliminate heat conduction by reducing the contact area between the beaker and the thermos body, mitigate radiation by using reflective material, like foil, then the main heat loss mechanism is convection, which behaves as dq = hc A dT. Then, the thermal plot after the initial fast cooling by exchange with the cold beaker and inner air by 10-15 C will become weak exponential, almost linear, especially after the 20 minutes when delta T is reduced.
If students were allowed to cover the stubborn hole, the heat retention improves quite a bit.
Apparently, it's not allowed, though, even the rules are ambiguous on that.

istou wrote: If students were allowed to cover the stubborn hole, the heat retention improves quite a bit.
Apparently, it's not allowed, though, even the rules are ambiguous on that.

Please explain how 'the hole must remain open and unobstructed during the competition' is ambiguous?

ignore post

What is the time constant of a plot?
I am really confused.

ScienceOlympian wrote:What is the time constant of a plot?
I am really confused.

Context?

And please make your sig smaller

harryk wrote:

ScienceOlympian wrote:What is the time constant of a plot?
I am really confused.

Context?

And please make your sig smaller

I am sorry for my sig.
I made it smaller.
An equation calls for the time constant.
In a thermal sense, it is like 63% of the ending time or something in a set of data.
It is for predicting the temperature of the insulated box.
How do you calculate the time consrant without actually testing it?
Sorry, I just started Keep the Heat. o_O