Patreon livestream #2: Testing heat capacity of phase change materials
Added 2024-05-20 15:53:46 +0000 UTCI'll be going live at this link in 10-20mins. Hope to see you there!
Comments
I'm pretty sure that the ice had a lot of time to warm to 0c, it is more thermally conductive than liquid water.
Jedediah Kivi
2024-05-21 01:03:33 +0000 UTCI think there may be a flaw in your method. It is true that the surface of the ice must be at 0C because it is melting but the bulk of the mass will likely be much colder. This is important because, assuming the ice is allowed to melt completely, the measured temperature drop of the surrounding water is measuring the amount of work done to the ice. Melting 10g of -40C ice must require more work than melting 10g of ice at -20C even if the surface temperature of both pieces of ice is the same.
Oliver
2024-05-20 21:35:16 +0000 UTCI ran my experiment again, and this time I remembered to turn the temp logging on! I also improved the experiment with a control cup containing the same amount of water so I could see the natural thermal loss and subtract that from the temp change in the cups containing my samples. The control lost 11C over the test period, so I subtracted 11C from the delta observed in my samples. My ice sample was calculated to have cooled the water by 6.88 J/g•C. My PCM sample registered a cooling of 12.7 J/g•C! Almost 2x the cooling capacity of ice! I'm not sure what to call this measurement since it's a combination of both the specific heat of the substance and the heat of fusion. If anyone wants to check my work, I used 400g of water per sample with a start temp of 91C. My control cooled to 80C over the test period, a delta of 11C. My ice sample was 14.3g, starting temp 1C, ending temp 75C. PCM sample was 20.3g, starting temp 1C, ending temp 68C. I tested the 15g sample of cement also, but it only cooled the water by 1C more than the control. That calculates to a specific heat (in this case it really is the specific heat) of 1.43 J/g•C which is a little high. Usually cement measures between 0.84-1.17 J/g•C, but I doubt the accuracy of this test because the measured difference in temp was small enough for the imprecision of my thermometers to throw it off. I could recheck using a bigger piece of cement but I think 1.43 J/g•C is close enough to the normal range that I trust the results of my ice and PCM tests to be fairly accurate. The PCM seems to be waaaay better than ice. Unless one of you spots an error!
NightHawkInLight
2024-05-20 20:59:24 +0000 UTC
