With our clamp and backing finally working, we are at the final stage of testing to see if all our components work together. We know that its possible to freeze clear ice, and its also possible for us to freeze such large ice with the peltiers separately but now we will be testing to see if our overall prototype works as a complete functioning system.
We ran tests a few times with our codesys system, and these were the results we observed in Experiment 1:
Temperature dropped quite fast from 0 min to around 15 min before slowly decreasing for all peltiers. What we noticed immediately was that peltier 4 actually achieved far lower temperatures than the rest, with a maximum delta of about 6 degrees between peltier 1 and peltier4 after the first 30 minutes. To make sure that this wasn’t just an anomaly, we repeated the experiment again with these results:
Similar to the first one, peltier 4 achieved far lower temperatures than the other 3 and ice formed in the section of the ice mold attached to peltier 4 after 21min25s. We theorized that this may be because of
- Uneven compression of the peltiers by our backing and clamp
- Ice mold is not flat (sigh..) which decreases cooling efficiency as contact area is not optimal between ice mold and peltiers
- Peltier 1 and 3 have poor cooling capacity – might be faulty peltiers?
- Poor heat transfer capacity of the water cooling block
To test theory 3, we took out the peltiers from our ice mold and tested them one by one on another aluminium block with 0.9 pwm. However, we found that with peltier 1 (which might have been faulty), ice formed after 29 minutes which proved that the high temperatures were not due to the poor cooling capacity of peltier 1 nor a water cooling block issue. It might actually be due to the uneven compression of the peltiers by our backing as the tightened screws could not force the backing closer to the peltiers in the middle portion of the backing. We then attempted to design a new clamp to compress our peltiers better to check if that was the really the case.