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Organic Rankine Cycle(ORC) can effectively recover the low grade heat source due to its distinctive thermodynamic performance. Based on Genetic Algorithm, net power output per unit mass of geothermal water is set as the objective function. Evaporation pressure, superheating of the steam, the minimum temperature in the evaporator are analyzed to obtain the optimal performance of the system. The results indicate that under the assumption condition that the optimal level constitution of system parameters is determined as the working fluid of R227ea, the power output of the system of 596kw and the corresponding power output per unit mass of geothermal water of 11.91kJ/kg. R245ca has the maximal efficiency of 5.75% among the selected 6 working fluids (Butane, R236fa, R227ea, R236ea, R245fa, R245ca). The effect of pinch temperature in evaporator on power output per unit mass is more seriously than that of superheating. It is about 7 times in terms of increasing 1K of R227ea.

In this study, the quick-freezing model and heat transfer model of quick-freezing of strawberries with dry ice at different flow speeds were proposed to ensure the quality of quick-frozen strawberries and control the jetting amount of dry ice. The aim of this study was to investigate the changes of internal and external temperature in the process of quick-freezing strawberries by jetting dry ice. The quick-freezing experiment platform of strawberries based on dry ice jetting was built for a quick-freezing experiment of strawberries at a dry ice jetting flow speed of 0.30 m/s. As indicated by the results, the temperature of strawberries was more uniform under the dry ice jetting speed of 0.30 m/s. The highest and lowest temperature differences between the surface and center of strawberries (the simulated) were 15.7 and 39.7 C, respectively, and the quick-freezing time of strawberries was 345 s. Compared with the experimental result, the error of quickfreezing completion time was 5.79%. The differences measured in the experiment were 15.1 and 37.7 C, and the error accounted for 4.73% and 7.89%, respectively. The accuracy of the model was measured, mean relative error = 6.31% and root mean square error = 10.78%. As revealed by the results, the model had high universality and precision and could be used to analyze the temperature change during dry ice jetting-based quickfreezing of strawberries. The quality indexes of quick-frozen strawberries before and after dry ice jetting were found to be better than the standard of quick-frozen strawberries. Thus, the research results can provide a reference for a further development of energy-saving and environmental dry ice jetting-based quick-freezing equipment.

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