Cooling capacity of a Co2 cartridge/powerlet

Science
#1

Hello science! I’m looking to figure out the cooling capacity of a standard Co2 cartridge, 12g or 16g, commonly used to inflate bike tires. Gas expansion from a pressurized vessel causes a localized temperature drop and all that. I’d like to know by how much.
There are two methods ahead of me.

  1. hit the thermodynamics text books like crazy to find/solve the required calculations
  2. vent a cartridge in a tub of water and measure the temp change.

Option 1 has me feeling ill just thinking of it… There’s liquid CO2 in a cartridge so phase changes, etc.

Therefore option 2 wins.
What does science have on hand at the space to further my experiment?
To ease the experimental burdens of a slow pressure ‘leak’ over a long duration I’m looking for a best case fast vent (1min total or less, hopefully, as long as it doesn’t cause the regulator to freeze and sieze) to limit heat transfer out of the water/container, in a safe manner that allows the liquid CO2 to phase change within the cartridge.
Bucket with fixed H2O volume, dump the reg and cartridge in the bottom, and a temp probe and stopwatch?

1 Like
#2

When I was very young I had a Crossman pellet rifle that used two cartridges. The plan was to tighten the cap by hand and dry fire the rifle. When I pulled the trigger in the back seat of a car, the cap blew off and left a dent in steel top of the door.

Be careful.

1 Like
#3

Yep, well aware of the…energetic capacity of Co2 capsules, haha. I knew a guy who used them as both propellant and projectile in a spud gun at the same time.
It’s going to be screwed into a regulator built for Co2, and vented as fast as the reg will allow without the reg freezing and failing. (Probably less than 100psi output through 1/8" bottleneck to prevent freezing?) Should make a nice stream of bubbles in the water though.

1 Like
#4

The heat of vaporization of CO2 is approximately 15.33kJ/mol, and the molar mass is about 44 g/mol. It takes about 5.57kJ to vaporize 16g liquid of CO2.

I believe it’s a reasonable assumption because the gas will make up a negligible portion of the mass of CO2, and the enthalpy change in boiling the liquid CO2 will be the majority of the total energy (a small fraction will be due to expansion from bottle pressure to 1atm).

#5

Wow! Thats great! Thank you so much!
I’m still gonna dump a cartridge into a bucket…for science. But now I have some working numbers. :slight_smile:

1 Like
#6

If you would like to experiment, you can get a CO2 dispenser from a keg shop for around $20, which is trigger released.

#7

If you are going to release a CO2 cartridge into a tub of water I really want to watch. Is this a design issue for a project or just an exercise in curiosity?? Do you have something in mind that needs cooling? or just wondering how much cooling could be done?

#8

Had an idea for portable equipment cooling… wanted to see if the math worked out. So bit of both. The numbers look decent enough to continue prototyping (thank you to michaelb for the quick answer)there’s so many real world variables that finding the actual efficiency of the system requires building and testing.
Still assembling the pieces for a bucket test… waiting to hear from anyone in the know about what kind of accurate temperature measuring equipment the space has.

#9

I think electronics has a data logger, and if they don’t have thermocouples, they’re pretty cheap.

Some fluke multimeters also can do temp through thermocouples via a dedicated port.

@Team_Electronics we got anything like that?

#10

ELab doesn’t have a readily usable data logger for this.
We do have a Fluke 572-2 courtesy of Mouser.
Link to manual is in the Tool Wiki.

#11

What parameters will you use for your experiment? Measuring equipment kind of relative to procedure. Do you need a data logger when a thermocouple or thermistor on a VOM will do?

#12

So the standard for HVAC calculations for a BTU is to raise 1lb of water 1 degree at atmospheric pressure.

I have a CO2 clean out tool with a hose. You are welcome to use it. It has a valve on it.

#13

I have an Arduino IDE compatible Wemos/Lilon D1 Mini with two waterproof DS18B20 temperature sensors you are free to borrow for the project. The program can be easily modified to display one or two temperatures on a PC screen at whatever rate you require. At completion, copy the data to a spreadsheet or whatever. Its not scientific quality but should be accurate to within 0.1F.

This project was used to transmit Big Thunders cooling unit temperatures to the IoT every 20 seconds for a few months last year.

Similar to this link but mine have one meter cables.

#14

It would be good to insulate the water bucket to minimize heat transfer even further.

And you’re going to need to let the temperature to distribute evenly throughout the volume of water for an accurate measurement by either mixing the water (while measuring the energy input done by the mixing device and subtracting that out) or by letting it sit for a bit (and determining the amount of warming from the ambient air through container and subtracting that out).

#15

Arduinos are not very good for precise voltage measurements unless you have a good reference voltage. Adafruit sells a 4.096V reference for like $8 plus their shipping. If the sensor doesn’t need a precise voltage reading or can compensate for it’s inaccuracy, then it doesn’t matter. Thermocouples, however, aren’t very good out of the box for measuring a specific tempature.

See: http://www.skillbank.co.uk/arduino/measure.htm and https://www.adafruit.com/product/2200?gclid=Cj0KCQjwu-HoBRD5ARIsAPIPenfYSg6LQB-8p88qdHcNpivHsb3acLeW5w3tv3eEuUiAQEiwu1WXsb0aAph8EALw_wcB

@artg_dms if electronics is looking for a data logger, DatsQ makes a decent one for ~90.

See: https://www.dataq.com/data-acquisition/starter-kits/ (I recommend the $90 one)

1 Like
#16

This is not a thermocouple. The Dallas Semiconductor DS18B20 is actually an awesome digital device with each one having their own serial number. Twenty can be connected to a three wire bus and addressed individually. The accuracy is about +/- 1.0F but the resolution, which is important here, can be 9-12 bits.

2 Likes
#17

Well thank you all for contributing, I will probably buy a styrofoam cooler as the vessel. Should help with insulation a bit. Honestly the temp recording can be as simple as getting a readout every 15sec via stopwatch, and once the Co2 is vented keep measuring for another minute or two, slowly stirring. I would assume that the Co2 bubbling out will mix the water pretty well until the gas stream is almost exhausted.
Not looking to do a complicated experiment, just looking for a ballpark and if need be I can always redo it with better methodology/equipment.
I have no idea what I’m doing regarding temperature measurement equipment so if any of you want to volunteer your knowledge and expertise in setting that stuff up, I’d really appreciate it.

I would assume I would need something with at least ±0.5F accuracy, dependant on the amount of water… if a less accurate probe is available/cost effective I can simply get a larger temp change by having a smaller water amount, to decrease equipment error affecting the final calc.

@bpamplin your Arduino setup should be more than adequate, otherwise a fluke + thermocouple and pen/paper recording at intervals should work as well.

I’m planning to run this sometime in July.

1 Like
#18

Keep in mind the resolution of Arduinos & raspberry pi. Since the ADC is only 10 bit. You need to take this into account in selecting your range of your temp sensor.

1 Like
#19

Check me if I’m wrong, but CO2 doesn’t have a liquid phase. It “sublimates” from solid to vapor. This is the principle used in a Dewers bottle (yes, the Scotch company). They put a brick of Dry Ice in the core bottle, it sublimates into the Outer Bottle, and supplies the fizzy to your soda drinks.

If you’re going to use a CO2 cartridge for cooling, then the Gas Laws are your friend:

1 Like
#20

CO2 has a liquid phase, but it doesn’t exist at atmospheric pressure. You can see from the diagram that liquid CO2 can’t exist until 5.1atm (75psi).

4 Likes