In order to save energy chimneys should have an innertupe for the incoming flow of air. Due to the COUNTERCURRENCY principle this air will be preheated a lot. For direct heating the house or assisting the stove.

This seems like a good idea, but there might be some problems to overcome. These just came to my mind : How can you insure the airflow down the tube you propose to feed the fire? Wouldn't some kind of fan be needed? And how can you insure the separation between the intake air and exhaust air at the intake mouth? Maybe they should be distanced. And lastly, cooling the exhaust air with the airflow from the inner tube wouldn't create higher back-pressure and also speed up the clogging of the chimney?