How Birds Fly Over the Himalayas

Birdman

Thanks, that's fascinating. Here is a video that shows how it works. Since the air flows one way through the lungs and blood flows the opposite way so there is always a gradient in oxygen and carbon dioxide concentration.

The same principle is employed in a counterflow heat exchanger. Heat diffuses from a hot fluid to a cold fluid flowing in the opposite direction, just as O₂ and CO₂ diffuse in and out of the bloodstream in the bird's lungs.

A counterflow heat exchanger can allow airflow into and out of a building without the loss of heat or air conditioning.

Wading birds use counterflow exchange to avoid losing heat from their bodies to the cold water.

https://www.allaboutbirds.org/news/how-do-gulls-deal-with-cold-feet/

I installed a double pass counter flow heat exchanger with a reversing valve and a waste dump cycle between cycle reversal. This kept the tubes cleaner for a longer period of time.

It was a rather small unit (400 GPM)@160F that utilized the cooling water from the compressors and waste water from a dying range. There was a supplemental steam source to keep the exit water at 160F and it was sent to a 75000 gallon storage tank and from there to the boiler room as needed.

One wing at a time....