Not long and no. It's not a liquid, it's a frozen gas. It could be contained within a loop once it's thawed but there'd be no way for a water pump to circulate it. Also, once it's thawed/melted it would no longer have any cooling potential. And you can't pump it while it's frozen because it's a solid at that point. Without active refrigeration to keep it in solid form it'd last some time measured in hours and minutes, depending on the ambient temps you have.