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Research on Improved Low-temperature Solar Organic Rankine Cycle (ORC)

Author: WangJianLi
Tutor: ZhaoLi
School: Tianjin University
Course: Thermal Power Engineering
Keywords: Solar Low temperature Rankine cycle Non- azeotropic refrigerant mixtures Recuperator
CLC: TB61
Type: Master's thesis
Year: 2009
Downloads: 216
Quote: 0
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Abstract

On the basis of theoretical and experimental analysis of pure refrigerants and non-azeotropic refrigerant mixtures, expand the study of solar the cryogenic thermoelectric conversion system designed to clear back to the heater on the degree of influence of the different working fluid system performance, thereby to improve the energy conversion efficiency. First low temperature of the pure refrigerants R245fa solar Rankine regenerative cycle theory analysis, analysis showed that the larger expander lack gas superheat, has a large potential for regenerative. Back to the heat, the thermal efficiency of the system and thermodynamic sophistication has been increased, the collector area and the cooling water flow rate can be decreased by 7.00% and 13.17%, and thus the economics of the system has also been improved. Based on the theoretical analysis, low-temperature Rankine R245fa as the working fluid solar heat recovery loop experimental study, the experimental system including solar flat plate collectors, expansion valve, condenser, accumulator, and the working fluid pump. Experimental studies have shown that the constant flow of the working fluid, the regenerative cycle did not significantly improve the efficiency of the Rankine cycle, but due to the collector outlet superheat the working fluid has increased, resulting in decreased efficiency of the collector. When appropriate increase in the flow of the working fluid of the system, the system output power and efficiency of the collector has been markedly improved overall system efficiency of up to 2.42%, compared with recuperator increased nearly twice as much. Non-azeotropic used in solar low-temperature Rankine cycle system can reduce the irreversible loss of the system, thus improving cycling performance under different mixing ratio R245fa/R152a theory. Studies have shown that the efficiency of the cycle of non-azeotropic refrigerant mixtures to below pure refrigerants R245fa, but with the increase in the component of R152a refrigerant mixtures output power is higher than pure refrigerants R245fa. The recuperator use export lack of expander gas sensible heat, as the R152a component increases, the decrease in mixed working fluid back to the heat, and the pinch point is moved to the inside of the heat exchanger. Meanwhile, the use of the different mass ratio can be obtained having a larger volume flow and the smaller expansion ratio of the working fluid can be designed to the high efficiency, low rotational speed of the expander. Finally, the experimental studies were conducted for the a non azeotropic solar low-temperature Rankine cycle, studies show that having a large latent heat of evaporation due to the mixed refrigerants, the same solar radiation the mixed refrigerants M3 (R245fa/R152a, 0.7 / 0.3) the average efficiency of the collector higher than the pure refrigerants R245fa 7.91%, while the refrigerant mixtures showed a smaller degree of superheat, so the cycle efficiency and the overall efficiency of the system are higher than the pure refrigerants. The increase in refrigerant mixtures condensing heat dissipation and heat transfer performance degradation, the working fluid M3 condenser outlet appeared incomplete condensation.

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