DIY chiller

[hillegom]

I don't think slowing the water down will make the unit more efficient. It would be better if you could attach the peltier device to the glass. Because heat will travel through glass faster than plastic.
Because this device is on the outside, why not try a thin layer of that thermal paste they use on the cpu of a computer? That would make the heat transfer more efficient, Just don't get any into the water.