Thermodynamic evaluation of an ORC system with a Low Pressure Saturated Steam heat source

This paper presents a thermodynamic analysis for an ORC system with Low Pressure Saturate Steam (LPSS) as the heat source to evaluate the system performance characteristics in terms of actual system design. The results indicate that some design guidelines for general ORC systems may not be proper for an actual LPSS ORC system design. In a LPSS ORC system, the Pinch Point Temperature Difference (PPTD) in the evaporator is located at the working fluid inlet or outlet, rather than the bubble point, mainly due to the property characters of LPSS. The turbine inlet must be superheated and the pump inlet must be subcooled even for dry working fluids. The superheat has a negative effect on the output power, but a positive effect on the net system power. The required condenser outlet subcooling differs for different working fluids and need special attention when we select the working fluid for ORC system. The condensing temperature has an optimal value that gave the maximum net power. For the present system, higher evaporating temperatures increase the net power, but not the turbine efficiency, which indicate that the system optimization needed to carefully consider the key component parameters.