Hey all if you want my made up wort chiller calcs to justify buying a 50 ft copper chiller or to compare chill water temps use the link below. I made several assumptions, but I have empirically tested several temps, lengths of chillers, and types of chiller (i.e. copper and stainless) and the calculator is approximately correct.
https://www.dropbox.com/s/h90mx6idjmvxoec/Wort%20Chiller%20Calcs.xlsx?dl=0