http://cgi.ebay.com/30-plate-Beer-and-Wort-Plate-Chiller-Heat-Exchanger-/250780072234?pt=LH_DefaultDomain_0&hash=item3a63a8392a#ht_894wt_903
they have a simple performance chart for wort plate chiller.
if link doesn't work, it's item #250780072234 on ebay.com.