Cardiac surgery implies harsh conditions for the lungs, which are normally disconnected from the patient’s body during the procedure. A better understanding of lung’s heat transfer may allow to reduce potential tissue injuries. In order to analyze heat transfer for dynamic heat flows and temperature inputs, thermal two-port network formalism is used. Asymptotic behavior of the impedance elements of this model are analyzed and approximated by using fractional-order operators. The same ide ais combined with Pennes bio-heat equation to also take into account blood’s flow effect on heat transfer. A global circuit model for the lungs is proposed. On the other hand, recursive identification methods for fractional-order continuous-time systems are proposed and tested.