A knowledge-based system for aiding in the construction of practical heat exchanger networks called SPHEN is presented in this article. The created network configurations feature low utility cost, low capital investment, rather stabie heat recovery during operation and rational distribution of pressure drops among the network branches. SPHEN consists of four component parts: network construction, simulator, flowsbeet diagram generation and user's feedback subsystem. So SPHEN is characterized by its hybridity, reflected in knowledge representation and abstraction, solving methods and implementation languages. The hybrid system is implemented through disk files and data files connecting different parts into one working space. An example of redesigning an energy recovery network of a large-scale crude oil unit is illustrated and the results obtained are successful.