A working fluid selection program for Organic Rankine Cycle

Abstract: This thesis handles the problem with fluid selection in organic Rankine cycles application. The main goal was to write a program that based on user defined variables finds the maximum power output from a range of fluids. The program was programmed in Matlab and is coupled with REFPROP that return the fluids characteristics as enthalpy and entropy etc. The program is preloaded with the fluids found from the literature review. These fluids were the best to use according to the respective authors. The result is generated with the main code of the program but using a different solver. The result section consists of multiple temperatures while the main program is designed to be used with one fix heating and one cooling temperature. Also a turbine calculation was written to be coupled with the main program. The results show that superheating have a negative impact on the output power and should be kept as small as possible. Some fluids however should have some superheating to avoid moisture in the expansion process. There are three types of fluids that is found: wet, dry and isentropic. The wet fluids are the ones that should have a degree of superheating as their expansion process otherwise might end in the wet region of the T-s diagram i.e. moisture at the end. The cooling has a major impact on the performance. A fluid that’s the best performing with a low cooling temperature isn’t necessary the best if the cooling temperature is increased. As the superheating should be kept low the main program uncertain parameter, if the user should define the pinch-point to the heating media or the amount of superheating, is set to last the mentioned