Direct and indirect heat transfer in water network systems

This paper addresses direct/indirect heat recovery network design for water network systems. A particular water network case of two different temperature fresh water sources is analysed. A new systematic heat recovery design approach based on thermodynamics is proposed for water stream sets leading to energy pinch problems. The concept of direct/indirect heat transfer decomposition is introduced to explore the design of heat exchanger network (indirect heat transfer) and non-isothermal mixing. This concept is illustrated through a new graphical segregation of the composite curves. To overcome the limitations associated with the representation of stream mixing in the composite curves, a new tool, source–demand energy composite curves, is introduced to evaluate the complexity of direct heat recovery and design different mixing scenarios.