The impact of component performance on the overall cycle performance of small-scale low temperature organic Rankine cycles

Abstract

Experimental and numerical assessment of normal heat flux first wall qualification mock-ups under ITER relevant conditions J Du, A Bürger, G Pintsuk et al. Email: Martin.White.1@city.ac.uk Abstract. Low temperature organic Rankine cycles offer a promising technology for the generation of power from low temperature heat sources. Small-scale systems (~10kW) are of significant interest, however there is a current lack of commercially viable expanders. For a potential expander to be economically viable for small-scale applications it is reasonable to assume that the same expander must have the ability to be implemented within a number of different ORC applications. It is therefore important to design and optimise the cycle considering the component performance, most notably the expander, both at different thermodynamic conditions, and using alternative organic fluids. This paper demonstrates a novel modelling methodology that combines a previously generated turbine performance map with cycle analysis to establish at what heat source conditions optimal system performance can be achieved using an existing turbine design. The results obtained show that the same turbine can be effectively utilised within a number of different ORC applications by changing the working fluid. By selecting suitable working fluids, this turbine can be used to convert pressurised hot water at temperatures between 360K and 400K, and mass flow rates between 0.45kg/s and 2.7kg/s, into useful power with outputs between 1.5kW and 27kW. This is a significant result since it allows the same turbine to be implemented into a variety of applications, improving the economy of scale. This work has also confirmed the suitability of the candidate turbine for a range of low temperature ORC applications.

Improving the economy-of-scale of small organic rankine cycle systems through appropriate working fluid selection

“…The focus of this paper is to combine this turbine performance map with thermodynamic cycle analysis in order to investigate the interaction between the selected working fluid and the turbine performance under different heat source conditions. Preliminary investigations have already been conducted by the authors [32], and this paper extends this analysis by implementing the modified and more accurate similitude model, updating the turbine performance map to account for additional loss mechanisms not accounted for during the CFD simulation, whilst also including a consideration of how the pump and heat exchanger performance varies with different working fluids under different heat source conditions. The main novelty in this work is the ability establish the full range of heat source mass flow rates that could be accommodated using a particular turbine design and working fluid.…”