Finite time exergy with generalised heat transfer law

The problem of maximal work that can be extracted from a system consisting of one infinite heat reservoir and one subsystem with a generalised heat transfer law {q∝[Δ(Tn)]m}, which includes the generalised convective heat transfer law [q∝(ΔT)m] and the generalised radiative heat transfer law [q∝Δ(Tn)], is investigated in this paper. Finite time exergy is derived for the fixed process duration by applying optimal control theory. The effects of heat transfer laws on the finite time exergy and the corresponding optimal thermodynamic process are analysed. Numerical examples for the cases with some special heat transfer laws are given, and the results are also compared with each other.