Mathematical models of wind tunnels are very useful, cost-saving tools in the field of aerodynamic testing. An entire test can be run on a mathematical model to predict the reaction of relevant flight variables and to ensure that the test can be run without any unexpected results or the need for an emergency shut down. They can also serve to train new operators of the wind tunnel by having them deal with potentially dangerous situations with no risk to the wind tunnel hardware. A mathematical model of a wind tunnel can be created from the basic fluid mechanic equations. To be sufficiently accurate, several engineering parameters must be determined experimentally and incorporated into the model. This thesis describes the development of a mathematical model of the thermal behavior for the Notre Dame 3 Foot Closed-Circuit Wind Tunnel. The results of experimental measurements of various engineering parameters is presented, as well as a comparison of the actual facility behavior to the prediction of the mathematical model.