Organic Rankine Cycle for Waste Heat Recovery Tests Complete using Air Squared E15H22N4.25 Scroll Expander.

Purdue University graduate student Brandon Woodland recently tested Air Squared’s E15H22N4.25 scroll expander as part of a research project on organic Rankine cycles with liquid-flooded expansion and internal regeneration for waste heat recovery.

An organic Rankine cycle is used to recover low-grade waste heat by transforming a portion of it into work. The recovery of low-grade waste heat is characterized by particularly low thermodynamic efficiencies. As a result, even small gains in efficiency can result in large improvements relative to the baseline. Also, the applications for waste heat recovery are typically small-scale, which makes it difficult to justify the complex efficiency enhancements typically employed in large-scale power plants. Therefore, it is desireable to improve the efficiency of organic Rankine cycles without dramatically increasing their complexity.

Three key elements are proposed to achieve this goal:

1. Selection of an appropriate expansion device is critical to the performance of the cycle. Scroll type expanders show particular promise in this area.
2. The employment of an internal regenerator can often have a dramatic effect on cycle efficiency.
3. using a liquid-flooded expansion process can potentially improve both the scroll expander and the internal regenerator. These two interaction effects can result in efficiency gains comparable to the traditional, more complex cycle enhancements.

Baseline performance tests without flooding or internal regeneration have been performed using Air Squared’s E15H22N4.25 expander. The results of these tests will be used to quantify the efficiency gains that result from internal regeneration and flooded expansion.