I was trying to reason it out, you have the thermal mass of the heat exchanger material, that you aren't going to be able to tune to every temp differential.
at the start of the cycle, it may be very efficient, but at the end of the cycle where the heat exchanger temperature is going to approximate the temperature of the air, efficiency is going to drop, and that would be happening along the length of the heat exchanger, so by the end of the cycle the inlet would be basically doing nothing, and the exhaust quickly getting to that point (in the best case).
I was starting to confuse myself at this point, so the constant temp model seemed easier to reason about.
Although, having written all this the model would basically be a constantly shortening counter flow heat exchanger? with a thermal mass not necessarily tuned to the temp diff.
So its still going to be worse than a counterflow heat exchanger, at least theoretically.
I was trying to reason it out, you have the thermal mass of the heat exchanger material, that you aren't going to be able to tune to every temp differential.
at the start of the cycle, it may be very efficient, but at the end of the cycle where the heat exchanger temperature is going to approximate the temperature of the air, efficiency is going to drop, and that would be happening along the length of the heat exchanger, so by the end of the cycle the inlet would be basically doing nothing, and the exhaust quickly getting to that point (in the best case).
I was starting to confuse myself at this point, so the constant temp model seemed easier to reason about.
Although, having written all this the model would basically be a constantly shortening counter flow heat exchanger? with a thermal mass not necessarily tuned to the temp diff.
So its still going to be worse than a counterflow heat exchanger, at least theoretically.