Changing the material from PP to Al grade, thermal conductivity enhances thousands of time. But keeping the design same, actual water time performance is hardly impacted.
Kindly share your thoughts and comments, maybe suitable literature to contradict above statement.
Thanks in advance.
You can easily test this at home. I have suggested it as a science fair project. What's happening here is that the thermal conductivity (or resistance) of the ice tray is not the limiting factor, so the material has less impact than one might expect. The cool down from initial temperature to 0C is small compared to the freezing part of the overall process; because the latent heat of fusion is about 144 times the specific heat. Conduction through the water as it freezes at near constant temperature is the bottleneck in the process. You can simulate this fairly well with a little FDM in an Excel spreadsheet.
The conduction heat transfer depends not only on the thermal conductivity of the material but also on the thickness of that material.
Though the thermal conductivity of aluminium is almost one thousand times of the polypropylene, due to the very small thickness of the tray the contribution of the resistance of the tray material to the conduction heat transfer in the overall resistance to heat transfer in this problem may not make much difference. I think the contract resistance is the significant one; there is always a thin layer of air in between the tray bottom surface and evaporator surface. In the present case, no convection currents are set up in the water in the tray, the heat flows by conduction through the water layer to the bottom of the tray. The thermal conductivity of water is about 400 times less than aluminium and since the thickness of the water layer is much greater than thickness of the tray material, the resistance of water layer to the conduction heat transfer is also significantly greater than that of the tray material.
As far as convection heat transfer from the water surface is concerned, it is independent of the tray material.
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