Performance evaluation of a micro partial admission impulse axial turbine in a combined ammonia-water cooling and electricity absorption cycle

The integration of an expander in an absorption machine allows it to produce cooling and electricity simultaneously. This technology holds great promise for its ability to harness low-temperature heat sources more efficiently than production with separate cycles. The integration of a turbine is currently being studied in an experimental ammonia-water absorption chiller at CEA INES. Given the very small mass flow rate and enthalpy drop, a partial admission impulse axial turbine has been selected for the application. Due to lack of experimental data, a 3D model of the impulse turbine was generated and its functioning studied with CFD simulations using pure ammonia. A compressible real gas 1D model of the turbine was later developed in EES & REG; for the ammoniawater mixture and compared to CFD simulation, adjusting loss term parameters to match CFD results, thus achieving an average discrepancy below 7% in the considered range of operating conditions (inlet pressure 1410 bar, outlet pressure 5 bar, inlet temperature 120 degrees C and rotational speed of 10-100 thousand RPM). The tuned 1D expander model was then integrated in a previously developed 0D model of the absorption cycle to demonstrate its robustness and potential to be used in the study of complex combined cycles. An overall energy efficiency is introduced and used to map the performance of the cycle for changing operating conditions. Results show the potential of the combined cycle to produce both power and cooling even at small scale, highlighting at the same time, the constraints imposed by this type of expander on the combined cycle.

Automated summary

Integrating an expander in an absorption machine enables simultaneous cooling and electricity production, making more efficient use of low-temperature heat sources compared to separate cycles. An experimental ammonia-water absorption chiller at CEA INES is currently studying the integration of a turbine. Through CFD simulations and 1D modeling, the turbine's functioning and performance with the ammonia-water mixture were analyzed and its integration in a 0D model of the absorption cycle demonstrated its robustness and potential for studying complex combined cycles.