Micro turbo expander design for small scale ORC

The Tesla expander was first developed by N. Tesla at the beginning of the 20th century. In recent years, due to the increasing appeal towards micro power generation and energy recovery from wasted flows, this cost effective expander technology rose a renovated interest. In the present study, a 2D numerical model is realized and a design procedure of a Tesla turbine for ORC applications is proposed. A throughout optimization method is developed by evaluating the losses of each component. The 2D model results are further exploited through the development of 3D computational investigation, which allows an accurate comprehension of the flow characteristics. Finally, two prototypes are designed, realized and tested. The former one is designed to work with air as working fluid. The second prototype is designed to work with organic fluids. The achieved experimental results confirmed the validity and the large potential applicative chances of this emerging technology in the field of micro sizes, low inlet temperature and low expansion ratios

Exergy Analysis of a Wood Fireplace Coupled with Thermo-Electric Modules

In recent years the climate change issue, coupled with the concern of resource depletion, are favouring the blossoming of renewable energy conversion systems. Particularly, the development of new technologies for the combustion of biomass, have drawn a special attention to the possibility of coupling thermoelectric modules with stove-fireplaces. The current thermoelectric generators have many attractive points, such as a solid structure, absence of noise, and no maintenance required, however, due to their very low efficiency (4–8%), they are still economically non-attractive. However, if the modules are applied to a heat source, which otherwise would be wasted, the interest of the solution certainly grows. In this study an exergy analysis of a stove-fireplace coupled with thermo-electric modules is performed, with the aim of identifying the critical issues of the overall system. The obtained exergy efficiency of the whole system resulted to be of 36.2%. A sensitivity analysis on the main parameters affecting the second law efficiency of the system (such as number of cells, dimension of the stove fireplace, heat input ...) is also carried out