Analysis of Exergy Destruction of an Evaporator or/and a Condenser

Preliminary note This paper presents the exergy destruction of an evaporator or a condenser or evaporator and condenser. The exergy destruction can be analytically calculated by using the same non-dimensional variables which have been used by its energy analysis. The one additional variable is the ratio of absolute input temperatures of both streams. This means that the given model enables the simultaneous calculation of heat transfer effectiveness and exergy destruction respectively. The exergy destruction is put in the ratio to the heat capacity of the weaker stream. The limited values of the exergy destruction are estimated, taking into account the zero and infinite values of relevant variables. Further, exergy destruction for the case when both streams change phase is calculated, which means that the appropriate heat exchanger is condenser and evaporator simultaneously. The given model is derived as a special case of the model for calculation of exergy destruction by parallel and counter flow heat exchangers respectively. For all presented cases the only temperature differences between the streams have been taken into account. This means that the effect of a frictional pressure drop of the streams on exergy destruction has been neglected.