Calorimeter Design

[Aulex]

For a science project after my AP chemistry test we are supposed to design a calorimeter (not bomb). For fuel we are burning a cheese puff and you can design the calorimeter however you want. I attached a crude blueprint of what we've come up with. So design is that the cheese puff is in a container with a low heat capacity such as aluminum which will dissipate the heat from the flame to the water. The co2 from the flame will rise through the copper tubing (there will be two more on the sides not seen in the 2d drawing) so some of the heat will dissipate from the co2 to the water while keeping the co2 from smothering the flame. The copper tubing will be sealed with most likely a solder and the bottom of the aluminum container holding the cheese puff will be a mixture of solder and epoxy. The entire calorimeter will be raised on stilts allowing for oxygen to flow from the bottom, and the tiny bit of heat that falls will be reflected by the aluminum or any other material back up towards the water. The cheese puff will sit on a wire mesh making it easier to burn and transfer the heat. The entire container holding the water will be covered in insulation all around except for the openings and around the flame (this includes the bottom exposed to where the oxygen is going to flow through).

All the materials can be changed accordingly

 

Now what i'm most worried about is lighting cheese puff efficiently, allowing for the most amount of heat to transfer from the co2 to the water while minimizing margin of error and for the cheese puff not suffocate.

 

Do you guys have any suggestions on how to make this design more efficient.

[imatfaal]

This is not my area at all - but a few thoughts nonetheless

 

1. I presume you want to ensure that the gas entering (which I presume is air rather than Oxygen) and the gas leaving (CO2 enriched air) must be as close as possible to the same temperature? Would using warmed air/cooled air to introduce make this easier or harder?

 

2. Will CO2 laden air (even if hot) rise nicely through your copper tubes? What about a driven air-flow? - might allow for much longer tubes than passive; and thus more opportunity to exchange heat.

 

3. How do you go about maximising the surface area (internal and external) of the tubes to increase exchange?

 

4. If the object burning is nestled in a cradle of conductive material that is connected to water bath then some heat transference will occur more directly (ie other than via the gases around)

 

5. Does it matter what temperature your water bath is to start with?

 

Just a few ideas - dunno if that much good really. But good luck with your project

[Aulex]

This is not my area at all - but a few thoughts nonetheless

 

1. I presume you want to ensure that the gas entering (which I presume is air rather than Oxygen) and the gas leaving (CO2 enriched air) must be as close as possible to the same temperature? Would using warmed air/cooled air to introduce make this easier or harder?

 

2. Will CO2 laden air (even if hot) rise nicely through your copper tubes? What about a driven air-flow? - might allow for much longer tubes than passive; and thus more opportunity to exchange heat.

 

3. How do you go about maximising the surface area (internal and external) of the tubes to increase exchange?

 

4. If the object burning is nestled in a cradle of conductive material that is connected to water bath then some heat transference will occur more directly (ie other than via the gases around)

 

5. Does it matter what temperature your water bath is to start with?

 

Just a few ideas - dunno if that much good really. But good luck with your project

 

1. Yes, we want to transfer as much heat from the co2 enriched air as possible, using cooled air would be better because it would mean that co2 enriched air would be slightly less hot, slowing the rate of rising and increase the time for the co2 to transfer the heat to the water (i'm not sure about this)

 

2. We want to keep it as simple as possible to try and lower margin of error, we were originally going to do this, but we scratched it due to it's complexity

 

3. We want to keep the tubes as narrow as possible, but still wide enough for the co2 to leave, so we'll probably experiment with different sizes

 

4. it is connected (the clear portion is where the flame is and blue is the water), along with the heat transferred from the flame directly, we are trying to absorb as much heat and absorb some heat from the co2

 

5. Higher temperature means more vaporization meaning more heat loss, lower the calculated heat transferred (we're going to try and remove this issue as much as possible by using an air sealed container, or as close to this as possible)

[John Cuthber]

It's probably more trouble than it's worth , but I always thought that the ice calorimeter was a neat idea.

http://en.wikipedia.org/wiki/Calorimeter

[ACUV]

A way to circulate the water to have a more even temperature of the coolant is usually used. This may be a triviality to you but some calorimeters have an electric motor which connects to a shaft through cogs or tensioned elastic and at the end is a small paddle. But, as you use the paddle to move the coolant around you are providing a heat source which you must then factor into your calculations.

 

Have a look at some older ( 100 years ) designs of steam boilers and you may get some good thoughts for heat transfer!