I must admit that I'm slightly perplexed about people talking about using ultra-low flow rates through a TEC chiller.
It doesn't make sense to me.
TEC's are more efficient when their delta T between Tc and Th (cold and hot sides of the TEC) is low.
Now, as many waterblock tests have shown, block performance (measured as C/W) improves as the flow rate goes up.
This means that the dT within the TEC is lower, because the cold side is warmer, thereby raising its effiency. Even though it may seem somewhat counter-intuitive at first glance, the cold side being warmer is actually drawing more heat out of the water due to the increase in TEC efficiency.
When one wants to build a TEC based chiller, we want to follow exactly the same principles as for cooling the hot side of the TEC. We want the cold side to be kept warmer than with a less efficient block. TEC dT will therefore drop, the TEC efficiency will go up, and more watts of heat will be pumped from the cold side to the hot side. Now that wattage is coming out of the water, hence the water will get colder, faster.
Remember too, we're talking about closed loop systems, so it matter little what the entry/exit temperatures of the TEC chiller is. Over time, more watts are being drawn out of a fixed quantity of water than with a less efficient cold-side setup utilising ultra-low flow rates.
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