Low grade waste heat recovery using diethyl ether thermo-fluid diaphragm engine

The recovery of low grade waste heat for power generation is getting more attention due to its large magnitude in the industrial sector. Commonly proposed solutions include Organic Rankine Cycle (ORC), transcritical carbon dioxide (T-CO2) cycle and Kalina cycle but with complex architectures. Special type Stirling liquid piston engines such as the Fluidyne and thermo-fluid oscillator can also recover low grade waste heat below 150 °C with simple construction. In this study, a novel two-phase thermo-fluid engine with single chamber and diaphragm was developed and tested experimentally. The engine was characterized at different heat source temperatures ranging from 50 °C up to 100 °C and maximum pressure in the range of 1.2-2 bar. Highest indicated efficiency was 10.3% compared to 25.5% Carnot efficiency with maximum indicated power of 70 W at 10 RPM engine speed. A crankshaft mechanism was installed with flywheel and rope brake dynamometer to measure engine brake power. Maximum brake power measured was about 0.4 W at 8 RPM due to the high friction losses in the power delivery mechanism.