Keep the Heat B/Thermodynamics C

[harryk]

Ok, I think I found what you are talking about: Thermal Time Constant

In order to calculate the time constant you will need to know a few easily measurable factors, and then the Heat Transfer Coefficient. However the heat transfer coefficient is very complex and difficult to calculate accurately. An easier way to calculate the time constant would be to run a calibration test and work backwards through the prediction formula.

[istou]

Good point chalker, thanks! How about keeping the thermometer in all the time vs. only inserting it at a measurement point? We have seen both at LA county open.

[Luo]

Good point chalker, thanks! How about keeping the thermometer in all the time vs. only inserting it at a measurement point? We have seen both at LA county open.

This actually might be something worth submitting an official clarification about. My interpretation is that keeping the thermometer in all the time would be considered an "obstruction" and therefore against the rules, but this one isn't so clear-cut. I hope that a clarification comes out so that we know what to expect at nationals.

[chalker]

Good point chalker, thanks! How about keeping the thermometer in all the time vs. only inserting it at a measurement point? We have seen both at LA county open.

This actually might be something worth submitting an official clarification about. My interpretation is that keeping the thermometer in all the time would be considered an "obstruction" and therefore against the rules, but this one isn't so clear-cut. I hope that a clarification comes out so that we know what to expect at nationals.

This is explicitly allowed in rule 4.a.vii "Supervisors may leave thermometers/probes in the devices for the entire cooling period". Do you all not have copies of the rules to look at?

[Luo]

Good point chalker, thanks! How about keeping the thermometer in all the time vs. only inserting it at a measurement point? We have seen both at LA county open.

This actually might be something worth submitting an official clarification about. My interpretation is that keeping the thermometer in all the time would be considered an "obstruction" and therefore against the rules, but this one isn't so clear-cut. I hope that a clarification comes out so that we know what to expect at nationals.

This is explicitly allowed in rule 4.a.vii "Supervisors may leave thermometers/probes in the devices for the entire cooling period". Do you all not have copies of the rules to look at?

I thought he was referring to the competitor's thermometer. We've found that it makes a difference in the cooling whether we leave the metal thermometer probe in the device throughout the cooling period. I submitted a clarification about this awhile back but it was not answered.

[chalker]

I thought he was referring to the competitor's thermometer. We've found that it makes a difference in the cooling whether we leave the metal thermometer probe in the device throughout the cooling period. I submitted a clarification about this awhile back but it was not answered.

Hmmm.. I don't recall seeing one about that. Regardless, and unofficially of course since this is not the proper forum for clarifications, it seems obvious to me that since the rules say both the hole must remain open and unobstructed, as well as that you may only measure the starting temp of the water with your own thermometer, you won't be allowed to leave it in the hole.

[istou]

Dear Chalker,

Here is a true ambiguous and undefined rule. How do the event supervisor measure the temperature?
Last year at LA county and South Cal they measured the temp inside the cattle and then poured the water into beakers, which seemed to be very logical.
Today at South Cal they pour some amount of water in the beaker, then measure the temperature, then announce it to the world. Please tell me it's not ambiguous! It makes a huge difference in predictions!
Another topic. At LA county, some were allowed to keep a thermometer in and some not. Today, at LA county - nobody is allowed to keep thermometer in.
It is impossible to calibrate any thermos by having thermometer in and out say every 2-3 minutes, because thermometer temperature affects the water temperature and ultimately prediction.
Depending on the volume and temperature of water and time it shifts the plots by degrees. Agreed?
I can see your answer to Lou below, but I hope you agree that it is not possible to properly calibrate the thermos while taking thermometer in and out.
For example, if the event supervisor announces 110 ml at 75C at 28 minutes, one must have a calibration point where a student did not put a thermometer in and out before that 28 minutes 3-4 times to get more points on the curve.
Hope it helps to improve.


Sincerely,

Thermal expert.

[harryk]

Dear Chalker,

Here is a true ambiguous and undefined rule. How do the event supervisor measure the temperature?
Last year at LA county and South Cal they measured the temp inside the cattle and then poured the water into beakers, which seemed to be very logical.
Today at South Cal they pour some amount of water in the beaker, then measure the temperature, then announce it to the world. Please tell me it's not ambiguous! It makes a huge difference in predictions!

This is exactly why students are allowed to bring there own thermometers for measuring the initial temp. I never trust the temp the supervisors give, sometimes its within a couple degrees and once it was almost fifteen degrees off.

Another topic. At LA county, some were allowed to keep a thermometer in and some not. Today, at LA county - nobody is allowed to keep thermometer in.
It is impossible to calibrate any thermos by having thermometer in and out say every 2-3 minutes, because thermometer temperature affects the water temperature and ultimately prediction.
Depending on the volume and temperature of water and time it shifts the plots by degrees. Agreed?
I can see your answer to Lou below, but I hope you agree that it is not possible to properly calibrate the thermos while taking thermometer in and out.
For example, if the event supervisor announces 110 ml at 75C at 28 minutes, one must have a calibration point where a student did not put a thermometer in and out before that 28 minutes 3-4 times to get more points on the curve.
Hope it helps to improve.


Sincerely,

Thermal expert.

Technically the thermometer is not supposed to be left in during competition as chalker clarified(unofficially of course) above. It also would not be wise to be repeatedly removing/replacing the thermometer during a calibration test, as you pointed out. However, I've always done my calibration tests with the thermometer in the entire time and at almost every competition I've been to the thermometer was not left in, and my predictions are usually within one degree. While yes, having the thermometer in during calibration and out during competition will produce some error, it is a minor factor and will be overshadowed by the numerous other uncontrolable variables. And if it really bugs you, then figure out how to calculate out the error in your prediction formula.

Lastly, look at this, and other problems in SO, from the rule writers perspective. If they really wanted to account for every single variable and make sure every competition was run exactly the same, rules would come in textbooks and all equipment would have to be ordered from SOInc. The result would be a less enjoyable experience for all, and a large decrease in popularity.

[istou]

Dear Chalker,

Here is a true ambiguous and undefined rule. How do the event supervisor measure the temperature?
Last year at LA county and South Cal they measured the temp inside the cattle and then poured the water into beakers, which seemed to be very logical.
Today at South Cal they pour some amount of water in the beaker, then measure the temperature, then announce it to the world. Please tell me it's not ambiguous! It makes a huge difference in predictions!

This is exactly why students are allowed to bring there own thermometers for measuring the initial temp. I never trust the temp the supervisors give, sometimes its within a couple degrees and once it was almost fifteen degrees off.

Another topic. At LA county, some were allowed to keep a thermometer in and some not. Today, at LA county - nobody is allowed to keep thermometer in.
It is impossible to calibrate any thermos by having thermometer in and out say every 2-3 minutes, because thermometer temperature affects the water temperature and ultimately prediction.
Depending on the volume and temperature of water and time it shifts the plots by degrees. Agreed?
I can see your answer to Lou below, but I hope you agree that it is not possible to properly calibrate the thermos while taking thermometer in and out.
For example, if the event supervisor announces 110 ml at 75C at 28 minutes, one must have a calibration point where a student did not put a thermometer in and out before that 28 minutes 3-4 times to get more points on the curve.
Hope it helps to improve.


Sincerely,

Thermal expert.

Technically the thermometer is not supposed to be left in during competition as chalker clarified(unofficially of course) above. It also would not be wise to be repeatedly removing/replacing the thermometer during a calibration test, as you pointed out. However, I've always done my calibration tests with the thermometer in the entire time and at almost every competition I've been to the thermometer was not left in, and my predictions are usually within one degree. While yes, having the thermometer in during calibration and out during competition will produce some error, it is a minor factor and will be overshadowed by the numerous other uncontrolable variables. And if it really bugs you, then figure out how to calculate out the error in your prediction formula.

Lastly, look at this, and other problems in SO, from the rule writers perspective. If they really wanted to account for every single variable and make sure every competition was run exactly the same, rules would come in textbooks and all equipment would have to be ordered from SOInc. The result would be a less enjoyable experience for all, and a large decrease in popularity.

Dear Harryk,

I agree that this is not Scientific Lab or a business, where we have to be precise. Everyone appreciates the efforts of volunteers including Dr.Chalker, that they put into this very important event. I wish we had more people like that, who bring that "light of science" to our children.
The problem is changing the rules year to year, like measuring the temperature in the kettle or right after pouring water in the beaker (the difference is on average ~15C!). Our team spent 100+ hours calibrating the thermos they built. Last year in both county and South Cal, they got both predictions within 0.2 C. This year at LA county - 5 degrees off. Impossible! Now, we know why. The event supervisors (really nice and friendly guys, by the way) changed the initial temperature measurement method, which caused on average 5-6 C error at about 30 minutes point for about 100 ml volume.

Anyway, let's hope the event will continue forever!

Best luck

[chalker]

The problem is changing the rules year to year, like measuring the temperature in the kettle or right after pouring water in the beaker (the difference is on average ~15C!). Our team spent 100+ hours calibrating the thermos they built. Last year in both county and South Cal, they got both predictions within 0.2 C. This year at LA county - 5 degrees off. Impossible! Now, we know why. The event supervisors (really nice and friendly guys, by the way) changed the initial temperature measurement method, which caused on average 5-6 C error at about 30 minutes point for about 100 ml volume.

Anyway, let's hope the event will continue forever!

Best luck

Keep the Heat and Thermodynamics are rotating out next year. We keep events in typically for 2 years in the Physics track. It'll be quite a while before they come back in.

Also, no matter how detailed we make the rules, there will always be event supervisors who interpret them slightly differently or deliberately change their local implementation either due to logistical reasons or because they don't pay attention to all the details. There isn't much we can do from a national level about that.