The calculated efficiencies for the expansion machine are based on characteristic data available for use with
600°C exhaust gas.
From experience with the test rig the efficiencies for use with lower temperatures are about
10% to 15 % lower.
The efficiency for the compressor is accurate because the available characteristic data meets
similar conditions as there are at the test rig. Fig. 4 (right hand side) shows
simulated results for the COP-value with respect to different efficiencies for the expander while using real characteristic data for the compressor and the heat exchanger. As can be seen, efficiencies in the order of 0.8 are required in order to get a resonable COP.