As I know next to nothing about textile technology, in giving my answer here I assume that the air-to-air heat exchanger is for heat recovery in a stenter. I also assume that the hot air is in the range of 100 deg C. 

As air is a poor medium for convective heat transfer, it requires fins on the air side. With air-to-air heat exchange, you require fins on both sides. There is only one construction of heat exchanger that permits fins on both sides. It is called plate-fin heat exchanger. (Please avoid confusion with Plate Heat Exchanger which is a plate-and-frame type). Results of a great deal of research on plate-fin heat exchangers can be found in the classical book on Compact Heat Exchangers by Kays and London. Images in Google may also help to understand the construction.

Tubular heat exchangers are just not the best choice as fins can be placed only on the outside. If you pose a more specific question with respect to the factors that affect air-to-air heat exchangers, perhaps a more pointed answer can be given.

Also you can use regenerative hear exchanger. It consists of porous media of high thermal conductivity material . Both hot and cold flue gases are alternated through it.

Mr. Alatyar is right. The porous media must have high heat diffusivity. You must necessarily have two units and operate them in transient mode with flow switching controls, solenoids, more complicated ducting etc. Instead, you could use rotary regenerative heat exchangers (heat wheels). I did not suggest the regenerative type because, for the rather low temperatures which are involved in your work, the recuperative, plate-fin heat exchanger will work out much more economical. 

Thank you for comments .