In this paper, a carbon dioxide refrigerating cycle is used to illustrate an application of the ‘Associated Reversible Transformation’ (A.R.T.) Method. It can be used to describe each real thermodynamic transformation of the working fluid inside a thermodynamic cycle, similarly to the well-known description of ideal gas adiabatic compression by means of a polytropic transformation. Once a complete set of independent parameters of the carbon dioxide refrigerating cycle has been identified through the A.R.T. formulation of processes and constraints, numerical simulation techniques may be employed to identify the origin of the malfunction and useful information can be obtained by a comparison with the approach based on pure exergy balances. The application of A.R.T. approach to the energy diagnosis of a carbon dioxide refrigerating cycle shows that the actual origin of the malfunction can be clearly identified in all cases.
