My reason for appearing here, was, a little over a week ago, I had posted a question on the Stirling Engine Forum I frequent: There was no response. So I thought perhaps the knowledgeable folks on this or another Science forum might have some input. I don't think I've received an unequivocal answer. Perhaps the equation can't be used because this engine doesn't behave in the expected way, and something about steam tables and not having a glacier or something along those lines. W