CFD evaluation of the pressure losses in a reciprocating compressor: a flexible approach

Abstract: Pressure losses in the suction and discharge components of a reciprocating compressor are the main irreversibilities that affect the global system efficiency; their prediction is a critical issue for the evaluation of the absorbed power. Flow coefficients for automatic valves are often derived from experimental data obtained on a dedicated test bench. Conversely, there is a lack of information concerning the flow behavior in the other components along the gas path and their losses are often taken into account by correcting the valve's flow coefficient by means of an empirical correlation. CFD simulation of the entirety of the suction and discharge systems is a viable alternative for the prediction of the global pressure losses, although these simulations are very demanding in terms of computational resources. This paper presents an approach to reducing the computational effort required to perform the CFD analysis of a reciprocating compressor. A set of CFD simulations with different suction system geometry configurations has been performed in order to evaluate the dependence of a component pressure loss on the losses of the upstream components. The losses along the suction system can then be evaluated separately from the valve loss by neglecting the presence of the valve itself. The valve can be replaced by an equivalent porous region that straightens the outgoing flow. This approach leads to a decrease in both the mesh size and complexity, and an increase in general applicability.