Influence of supercritical ORC parameters on plate heat exchanger design

The applications of Organic Rankine Cycle (ORC) appear to be growing in the field of waste heat utilization. This thermodynamic cycle can be successfully used in the field of biomass combustion, geothermal systems or solar desalination systems, providing efficient systems. In the last years, a very intense investigation on the utilization of low temperature waste heat for supplying ORC systems has brought new research potential in the area of thermodynamic optimisation of this cycle. More specifically, the use of supercritical fluid parameters in the ORC processes seems to become more and more attractive leading to lower exergy destruction systems together with higher heat utilization systems. However, the investigation of the heat exchanger design and the heat exchange coefficients is of high importance for these applications as the effective heat transfer reflects on the overall process energetic and exergetic efficiency. It is important to study the relatively unknown heat transfer mechanisms around the critical point to improve both the heat exchanger surface and the design algorithms. The aim of this paper is to investigate the influence of the ORC parameters on the heat exchanger design. More specifically, the basic parameters of the design of the heat exchangers will be defined in the cases of supercritical fluid parameters and the convective coefficients as well as resulting heat transfer surface will be calculated for various fluid parameters.