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This paper presents an experimental investigation of variation tendency of heat transfer coefficient, log-mean temperature difference and differential pressure of pure R123 and 20 nm Al2O3-R123 nanorefrigerants with four various volume concentrations, 0.03%, 0.13%, 0.18%, 0.23% flowing inside the evaporator of organic Rankine cycle system under the conditions of various heat source temperatures and flow rates. Heat source temperatures are in the range of 50–90 °C at an interval of 10 °C, and heat source flow rates are 0.7 m3/h, 1.3 m3/h and 1.8 m3/h. Results show an increment of heat transfer coefficient along flowing direction for both pure R123 and four Al2O3-R123 nanorefrigerants with the increment of heat source temperature and flow rate, and that of four nanorefrigerants are higher than that of pure R123. There is no optimum value of heat transfer coefficient when operation condition is changed for the loading carrying capacity increasing with the increasing intensity of operation condition. Meanwhile, suspending nanoparticles and increasing heat source temperature can change the variation tendency of heat transfer coefficient along flowing direction except pure R123 and 0.18 vol% nanorefrigerant. In addition, 0.13 vol% as a whole is the optimum volume concentration for both log-mean temperature difference and differential pressure.

Solar enhanced natural draft dry cooling tower(SENDDCT) is a new heat rejection device that uses solar energy to increase the cooling efficiency of natural draft dry cooling tower. In this paper, an experiment study was carried out t under natural conditions to investigate the effect of solar radiation intensity on the performance of SENDDCT. Meanwhile, a same-size CFD model was developed by using FLUENT to analyze the influence of ambient temperature on the cooling performance of SENDDCT. The results verified that SENNDCT can enhance heat transfer rate of natural draft dry cooling tower when ambient temperature was high at noon, solar radiation increased heat transfer rate by an average of 16.5% during the experiment. Air mass flow and heat transfer rate decreased with the increase of ambient temperature.

In this study, the optimum flash and evaporation temperatures have been selected for the following four geothermal power generation systems: single-flash system (SF), double-flash system (DF), flash-organic Rankine cycle system (FORC), and double-flash-organic Rankine cycle system (DFORC). Optimization is based on the maximum net power output of each system, with the pump and fan consumptions being taken into account. Under the given geofluid’s condition (temperature= 170oC; dryness= 0.2), the optimum flash temperature of SF, the optimum 2nd-stage flash temperature of DF, the optimum evaporation temperatures of FORC and DFORC are found to be 150oC, 100oC, 100oC, and 70oC, respectively. More scenarios have been analyzed for geofluid’s temperatures ranging from 80oC-260oC and geofluid’s dryness values of 0, 0.2, and 0.4 respectively. The result shows that the optimum 2nd-stage flash temperature of DF is close to the optimum evaporation temperature of FORC under the same geofluid’s condition, especially when the geofluid’s temperature is below 170oC and the dryness is below 0.2.