Classification and evaluation of heat transformation processes

Energy transformation occurs if, in contrast to simple energy conversion, a part of the available energy is transformed into a higher quality. Heat transformation processes are cycles in which the temperature level of at least one heat is raised. They can be categorised as syn- and disproportionation processes and subdivided into several groups depending on the acting potential differences and interactions in the inner of the cycles. From the special viewpoint of transformation, a decomposition of transformation processes into a lift and a drive part is useful for the evaluation of these processes. The introduction of a Carnot lift, i.e. the difference of the Carnot-factors of the lift hear, allows a uniform treatment of all cycles. In addition, it permits a statement about the change of the exergy of the heat due to the transformation effect. Transformation ratio and coefficient of transformation are the ratios of the energy and the exergy of the lift (upvalued) heat as use respectively to the consumed amount in the drive part as expenditure. The three transformation characteristics Carnot-lift, transformation ratio and coefficient of transformation form a thermodynamically consistent model for the evaluation of transformation processes. In contrast to the conventionally used evaluation characteristics of cycles, they lead to unified qualitative and quantitative thermodynamic statements. (C) Elsevier, Paris.