LAUSR

Abstract This work aims to investigate the operation characteristics of an organic Rankine cycle (ORC) system under the variable mass flow rate of the working fluid ( m wf ), such as the flow excursion in the field of direct vapor generation (DVG) systems. Besides, the mass flow rate of cooling source ( m cs ) was verified as an effective manipulated variable to respond the variation of m wf , which was an easily available freedom in the ORC system. The operation characteristic was tested respectively for m wf and m cs , where the change form of the single variable was rectangular-wave steps with different amplitudes. To verify the effectiveness of regulating m cs , the operation characteristics under the changes of multiple variables including the m wf and m cs were tested. The results indicate that the m wf dominates the variation of operation parameters of the ORC apparently, especially the evaporation pressure. Specifically, the evaporation pressure increases about 26.10 kPa as the m wf increases about 0.01 kg/s. The m cs also affects the operation parameters, which shows the opposite trend in evaporation pressure and condensing pressure compared with the increase of m wf . The results show that when the m wf increases, the increase of pressure can be reduced and the thermal efficiency can be improved by regulating the m cs in the same direction simultaneously. The increase of the theoretical thermal efficiency of the system is about 11.21% when only the m wf is inclined 0.01 kg/s, while it is 18.00% when the m cs is inclined 0.12 kg/s at the same time. The experimental findings enable to give a reference on designing control strategies for the DVG ORC systems.