A semi-empirical model for the unsteady-state simulation of reciprocating compressors for household refrigeration applications

The current work presents a semi-empirical mathematical model to simulate the unsteady behavior of mass flow rate and power of reciprocating compressors. The model is based on thermodynamic equations fitted to thirteen calorimeter data sets of two compressors with different capacities. The curve fitting suggests linear correlations between the measured values and the thermodynamic equations, indicating that only two calorimeter data sets are necessary for curve fitting. Additionally, the proposed model was also fitted to data sets of 21 other compressors obtained directly from the catalog of two different manufactures. Besides, comparisons of computed and measured values of mass flow rate and power, in transient regime, were conducted for the two fitted compressor curves. A good agreement of results was found for both compressors in either cycling or start-up tests. It was found that the proposed semi-empirical model can be satisfactorily applied to dynamic simulations of the whole refrigeration system.

Research highlights
► A model to predict the transient performance of reciprocating compressors is proposed.
► The actual-to-ideal volumetric efficiency ratio is a linear function of the pressure ratio.
► The power is a linear function of the product of mass flow rate and compressor isentropic work.
► The pressure changes affect quite instantly the mass flow and the compressor power.
► There is good agreement of the dynamic model results with experimental values.