Scroll expander model
The scroll expander model has been previously proposed by Lemort et al. [5] and partly validated by tests with steam. In this model, the evolution of the fluid through the expander is decomposed into the following steps (as shown in Fig. 3):
• Supply pressure drop (su^ su,1,1)
• Cooling-down in the supply port of the expander (su1,1 ^ su,1);
• Isentropic expansion from the supply pressure down to the adapted pressure imposed by the internal expansion volume ratio of the expander (su,1 ^ ad);
• Expansion at a fixed volume from the adapted pressure to the exhaust pressure (ad ^ ex,2);
• Mixing between suction flow and leakage flow (ex,2 ^ ex,1) and
•
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Cooling-down or heating-up in the exhaust port (ex,1 ^ ex).
The model requires only nine parameters (heat transfer coefficients, friction torque, leakage area, pressure drop equivalent diameter). Those nine parameters, defined for a specific type of expander and for a specific working fluid, are determined on the basis of experimental data.
