Hence, three suitable values of the refrigerant mass flow rate have been detected in order to introduce the need of controlling the working fluid flow rate: for the first range of working points (#1 to #4) it ANA 12 was reduced by 50%, for the second range (#4 to #8) it was kept as it was designed and, finally, for the third range (#9 to #14) it was increased by 50%. This flow rate, on the other hand, can be easily changed because it is imposed by the pump which is of a rotary volumetric type so linearly correlated to the pump speed. Table 7 summarizes the results with these three different flow rates: fluid degradation is always avoided and working fluid at the outlet of the evaporator is almost always superheated, so suitable for expansions. Only for the tests #1 and #2 (at very low engine speed) refrigerant quality is too low for a good expansion: an even lower flow rate should be considered but the thermal power recovered by the gas would be really low.
Finally, results obtained demonstrate lymph hearts a model based control strategy applied to the working fluid flow rate is indeed suitable to manage the recovery unit.