Thermodynamics B/C Build

[JonB]

I feel that would be so difficult to keep consistent due to the difficulty of making sure there actually is a vacuum created within the device walls. Did they keep the vacuum bag on it during testing??

But, if it works, great!

I didn't see it in action, but it was a rigid container rather than a bag and it had a barometer which I assume helped with consistency.

The problem with homemade vacuum devices is that they are very unpredictable. Sure, it might work really well, but if there's an issue with the vacuum, it leaks and your prediction is messed up.

This was the problem we ran into when Thermo was an event years ago and only natural products could be used as insulation. We honestly put a good amount of time and effort into the idea of a vacuum device but never got it to work as well as we were hoping. Almost impossible to keep the vacuum and very difficult to tell if the vacuum is maintained. I honestly think it is possible, but the amount of time it would take to build a predictable device could (and probably should) be used for testing and data collection of a device that is simple and gives results that are easy to replicate given the same parameters (water volume, temp, etc).

[someone1580]

So states are coming up next week and I made a completely new box because of a rules clarification that made my old box's heat retention quite terrible. I wanted to know if a starting temperature of 70 degrees at 125 ml ending at 62.8 is going to be good for state competition

[wec01]

So states are coming up next week and I made a completely new box because of a rules clarification that made my old box's heat retention quite terrible. I wanted to know if a starting temperature of 70 degrees at 125 ml ending at 62.8 is going to be good for state competition

That sounds like it'll be fine. I would be more concerned with making sure you can make a good prediction.

[CookiePie1]

So states are coming up next week and I made a completely new box because of a rules clarification that made my old box's heat retention quite terrible. I wanted to know if a starting temperature of 70 degrees at 125 ml ending at 62.8 is going to be good for state competition

That sounds like it'll be fine. I would be more concerned with making sure you can make a good prediction.

You should probably be cramming in a bunch of trials right now, with a new box. Just make sure the box cools in between and that you're getting consistent results.

[sciencekid27]

Just wondering, would it be better to have a higher start temperature, maybe 67-72, than to have a lower start temperature, around 60? I know that if you have a higher start temperature, the water decreases to a lower end temperature. For example, if you start at 70, it may drop to 55 (random value btw), which is a 15 degree drop. However, if you start at 60, it would drop to maybe around 50, which is a 10 degree drop. Which one of these is better in terms of the heat score in the competition? Thanks!

[CPScienceDude]

Just wondering, would it be better to have a higher start temperature, maybe 67-72, than to have a lower start temperature, around 60? I know that if you have a higher start temperature, the water decreases to a lower end temperature. For example, if you start at 70, it may drop to 55 (random value btw), which is a 15 degree drop. However, if you start at 60, it would drop to maybe around 50, which is a 10 degree drop. Which one of these is better in terms of the heat score in the competition? Thanks!

Ultimately it depends on your box, but personally my box preformed exceptionally better with lower starting temps. In terms of competition, it really doesn’t matter because most other teams’ boxes will also follow this pattern.

[sciencekid27]

Also, the k value that is closest to zero is best, right?

[CPScienceDude]

Also, the k value that is closest to zero is best, right?

Yup

[sciencekid27]

What do y'all think is a good prediction for nats? We are getting about 0.5 off in practice.

[CookiePie1]

What do y'all think is a good prediction for nats? We are getting about 0.5 off in practice.

That's really good! I mean, at nats, you'd probably want to get within 1.5 degrees. Otherwise, you should be pretty much fine if you can repeat those results.