No,you can't go below air temperature,even if you have fan the size of airplane engine lol ,if you believe otherwise get yourself a thermodynamic book and read.
Even if you put 1000 fans,the fans move the air through the radiator.The water takes the heat from waterblock and moves it into radiator.The air generated by fans takes the heat from radiator blades.
So if you have room temperature of 20 degrees the radiator will be cooled in ideal case to 20 degrees and the water will have 22-23 degrees because of the imperfect thermal transfer.The delta from idle to load depends on how many junctions you have ,for example direct die contact means one thermal junction,if you have standard IHS that means 2 thermal junctions,one between die and IHS and next one between IHS and waterblock. The more junctions the more losses you have.
Tehnically your submission is valid only if you had 1 juntion,liquid metal between die and waterblock,great CPU and i mean really golden one with also low-leakage,excellent waterflow and excellent fans. Also 5 degrees ambient or maybe lower.