Experimental investigation on a rotodynamic pump operating in the cogeneration system with a low-boiling working medium

The article presents the research carried out on the circulating rotodynamic pump (peripheral pump) operating in the organic Rankine cycle with or without regeneration. The low-boiling solvent HFE7100 was used as the working fluid. Its boiling point is around 61 ◦C at atmospheric pressure. An expansion valve, which simulated the operation of an expansion machine, was used to load the tested pump. The flow characteristics were given for the working media: a solution of glycol and HFE7100 in the condenser, thermal oil and HFE7100 in the evaporator and HFE7100 in the regenerator. The research results concerning the PK70 pump operating in an ORC cycle are reported for the HFE7100 temperature range 15-60 ◦C and the dynamic viscosity range of 0.132 to 0.66 mPas. The maximum flow rate and pressure of the pump during its operation in the ORC system were assessed. The analysis of the results demonstrates that the maximum efficiencies of the pump operating with or without regeneration were 44% and slightly below 37%, respectively. The impact of the selected physicochemical parameters of the working mediums on the pressure drops occurring in the ORC cogeneration installation was discussed. Based on the research conducted and the measurement results, the possibility to apply a PK70 unit as a circulating pump for the working medium in an ORC cycle was checked.