Design and Experimental investigation of a Small scale organic Rankine using a scroll expander

The world is facing a historical increase in energy demand and energy consumption. As consequence the conventional fossil fuels are depleting faster with an inherent pollution causing sever damages to our environment. Renewable energy sources are considered as a solution to both environmental issue and energy demand. At the same time a lot of waste heat is witnessed in processes in industries and other thermal devices such internal combustion engines. Our objective is to propose a solution to recover this heat wasted. The organic Rankine cycle appeared to us as a solution.

This paper presents a study carried out on a prototype of small scale organic Rankine cycle (ORC) driven by two waste heat hot air streams. The prototype was designed using a diaphragm pump, a set of plate heat exchangers and an oil-free scroll compressor adapted to run in expander mode.

The available literature on Organic Rankine Cycles only proposes theoretical studies of fluid selection for a given application. This study aims at comparing fluids experimentally. Therefore, several fluids (including R245fa and R123) were tested in the prototype and the performance was measured.

The tests were performed to study the performance of the ORC system and the expander over a wide range of working conditions. The temperature of the heat sources varied between 150°C and 200°C. The maximum expander shaft power was above 2kW and maximum expander efficiency was 70%. These tests allowed to point out the critical characteristics that should be taken into account while selecting the components for the design of an ORC.