So many questions on this topic....but I guess the starting point would be to explain the reason for the question. That way, maybe someone can help me work backwards to answer the question....and thus I can apply that to other situations. I have a friend who thinks he can make a personal cooling system, using frozen water (0c) as the coolant. I say that the amount of heat sink capacity of say 128oz of frozen water, is probably way too small to matter, in terms of cooling a person off while climbing a mountain, in 90 F degree heat, for 3 hours. Add to that the weight of the water itself is 8 pounds. It seems to me the ice would be melted and assume the ambient temp so quickly, that little would have happened in terms of cooling the person off....over a 3 hour period of exertion. So, I'm trying to understand (maybe there's a solid formula for this) how much heat sink is possible, using ice as the sink, and an ambient temp. or 90F....or 99F I guess, since the purpose is to sink energy from the person, which is surely 99F. I have another question, which is related.....but I'll ask it separately. Thanks in advance as always!