This paper presents an airtoair heat exchanger that is designed by taking into account the bad working environment of the open air. The internal cabinet temperature is regulated and the external circumstance is isolated effectively by the present device with the features of intelligent control, selfdiagnosis, compact structure and convenient maintenance. Meanwhile, a flow network model of the entire system is constructed by MacroFlow which is based on the Flow Network Modeling (FNM). Accordingly, longtime operation can be guaranteed and the application of the airtoair heat exchanger has a promising future.