I want to circulate cold water through copper tubing curled in a spiral about a fan. I'll cool the water with a large block of ice that I can remove and replace like a battery. To avoid making a mess I can freeze the ice inside of a copper housing, and pump the water in copper tubes around that housing to make it removable. I'm wondering if there's a better choice of liquid than water for this? One that would melt slower, thus, need to be replaced less often? Also, what would that quality be called?