To reduce work in assessing alternative system structures in low-energy design, a Branch and Bound method is proposed. The bound is based on exploiting the thermodynamic constraint of exergy destruction along a heat flow path. A novel derivation of exergy in a flow system is provided and used to show its fundamental relationship with temperature and primary energy. The method is applied to two simple systems.
Practical application:
In novel low-energy design, there can be many structural solutions that meet the client brief, especially at early stages in design, before full simulation/optimisation can be efficiently applied. The technique presented offers an application of the Branch and Bound algorithm that can be implemented on a spread sheet and which usually reduces the number of full structural solutions that have to be produced. It relies on working in exergy as the metric rather than temperature, and the work explains why this approach, common in optimising services components, can be applied to heating systems.
