My bad, I did not read the much more informative BBC article before speculating.
Having a closed circuit nitrogen heat exchanger is interesting because it is a heat exchanger... you still need to get rid of the heat somewhere. For the demo (per the BBC), they evaporated some of the nitrogen to get rid of the heat, but that means you need excess nitrogen to boil off enough to reject the heat. I wonder how they plan to get rid of the heat in a real aircraft.
It also makes me wonder how they can have enough surface area to absorb the heat in the precooler but maintain enough airflow to generate the thrust they would need.
Having a closed circuit nitrogen heat exchanger is interesting because it is a heat exchanger... you still need to get rid of the heat somewhere. For the demo (per the BBC), they evaporated some of the nitrogen to get rid of the heat, but that means you need excess nitrogen to boil off enough to reject the heat. I wonder how they plan to get rid of the heat in a real aircraft.
It also makes me wonder how they can have enough surface area to absorb the heat in the precooler but maintain enough airflow to generate the thrust they would need.