Justincase, I think you maybe misunderstanding what your instructor means by referencing water as a refrigerant and what the posting means by high heat capacity.
I think your instructor is refering to the latent heat of vaporization of water, and it's use as a refrigerant in absorbtion refrigeration. The latent heat value for water in that application is aprx. 1100 +/- BTU/LBS. Compared to R-22 at 70 BTU/LBS for typical A/C applications or 500 BTU/LBS for ammonia for similar temperatures. Water kicks BUTT!!
The heat capacity that Gepman and myself are refering to is the specific heat value of the water: in that when you are storing sensible heat BTUs in a mass(water) for every BTU you add or remove from one pound water(liquid state) the temperature of the water will change only one degree F. This is excellent compared to air with a specific heat value of .24 BTU/LBS/F.
Hope that didn't muddy the waters too much, but I thought it was important to note the difference.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI