If I understand correctly (history shows I probably don't), then the only reason why the absorption chiller evaporators are restricted (I hope that's the right word) to extract just enough heat so the chilled water exits at around 3 Celsius is so that the danger of the chilled water becoming frozen, and thus not being able to be pumped, is avoided by a safe margin.
Other than that I understand that most of the heat transfer at the evaporator takes place not because of the temperature gradient, but because the refrigerant water is kinda forced to evaporate due to the vacuum headspace (okay, your eyes bleed, but you're the physicist, not me). So I suppose if the flow rate in the chilled water pipes is lower, and every molecule of water passing through can lose more heat, the chilled water could essentially freeze?
This leads me to my question: If water in the chilled water pipe, is replaced by air, can't we use it to freeze things in a freezer? Is it possible?