So I decided to try using the new in-pipe thermal sensors to create a feed back loop allowing a single Thermo Aquatuner to bring a feed of liquid down to a specific temperature.  Using the free oil from a leaky oil fissure, I decided to create a pool of petroleum at around -50c.  Other uses include sending cold water to sleetwheat.  For the petroleum pool I want, the process is somewhat slow.  As it comes out of the refinery, petroleum is about 74c, so it has to go through the aquatuner about 9 times to reach -52c. On the left is a variation on @Luminite2's Method 2 cooling system. Rather than pumping coolant somewhere, I placed an aquatuner in the cold side to feed the petroleum through.  I'll not go into the details for that portion of the system and just focus on my feed back.  The location I built was not the best for easy pipe laying, so here's a simplified version. The thermal sensor is set to "above -45c."  As long as the temperature is above -45c, the liquid shutoff remains open, passing the petroleum back into the aquatuner.  The bridge connects after the shutoff, so that new petroleum will only be added if there's room for it.  Once the liquid drops below -45c, the valve closes and the cold liquid spills into the reservoir. For power reasons, I used a NOT gate in the cooler to make sure that only one of the aquatuners will run at a time.  So far, it works like a charm.  The average temperature of the output is about -50c, right where I wanted it. Hope this idea is useful to some of you.