Modelling of organic Rankine cycle system and heat exchanger components

Abstract

Numerical models of a standard organic Rankine cycle (ORC) system and the heat exchangers comprising the system are developed as a design tool platform for a flexible design. The objective is design of an efficient, cost-effective ORC power plant that can effectively exploit low-grade industrial waste heat or low to medium-temperature geothermal fluid. Typical heat exchanger configurations were modelled, including the circular finned-tube evaporator, air-cooled condenser, and flat-plate preheater. A published ORC configuration and process conditions from experiments are used for the thermodynamic cycle analysis in order to validate of the system model. Heat transfer correlations and friction factors are described for the modelling of the heat exchangers. The simulation results of the ORC system provide the design requirements for the heat exchangers. Geometric specifications and performance of the heat exchangers are determined by iterative simulations.

Keywords:

• numerical modelling
• organic Rankine cycle
• finned-tube evaporator
• air-cooled condenser
• plate type heat exchanger
• thermal system modelling

Acknowledgements

The authors would like to thank the New Zealand Heavy Engineering Research Association for supporting this work.