Simplified modelling of an open-type reciprocating compressor

The first part of this paper presents a detailed experimental analysis of an open-type reciprocating compressor equipped with internal sensors. The analysis reveals the main processes affecting the refrigerant mass flow rate as well as the compressor power and the discharge temperature. Based on these experimental results, a simplified steady-state model of the reciprocating compressor is proposed. The refrigerant mass flow rate is supposed to be affected by the clearance volume re-expansion, by a pressure drop occurring through a supply flow restriction and by a temperature increase due to some heat transfer from a supposed-to-be isothermal wall. The friction power loss is supposed to be transferred to this fictitious wall, which is also exchanging heat with the discharged gas and with the ambient. The model is able to determine the ambient losses and so, the exhaust temperature. The compression itself is considered as adiabatic, reversible and therefore isentropic. The friction power loss is decomposed into a constant contribution and another one proportional to the isentropic power.