Theoretical And Experimental Investigation On Thermodynamic Performance Of Air-cooled Condenser With Liquid-vapor Separators

In this thesis,based on the application of the air-cooling condenser,the researches on the thermodynamic performance and the characteristics of the liquid-vapor separation were carried out theoretically and experimentally.A theoretical model was established to optimize the circuitry design and analyze the heat transfer performance of the condenser.An air-cooling condensation experimental system was built to measure,calculate and analyze the main parameters of the thermodynamic performance of the condenser.The thermodynamic characteristics of the serpentine condenser and the liquid-vapor separation condensers with one separator and two separators were compared.Based on the Nusselt theory,a theoretical liquid film growth model of the flow condensation of the refrigerant vapor inside a horizontal smooth circular tube was established.The model was based on the convection boundary condition and considered the effects of gravity and shear force to express the feature of the condensate growth inside the tube.The thicknesses of the liquid film and the local heat transfer coefficients at each locality were calculated by dividing the tube circumference and the tube length into several average segments,forming multiple calculation cells.The model was validated by comparing the predicted heat transfer coefficient and the experimental data.Then,based on the assumptions of the situations of the liquid-vapor separation in the header,the circuitry design of the liquid-vapor separation condenser unit was optimized and the vapor quality and the heat transfer coefficient of the condenser employing the optimal circuitry design were calculated by the model It was shown that the circuitry design had a big influence on the flow uniformity.The inlet vapor quality of the second channel pass could be improved by the separator.As a result,the heat transfer coefficients of the second channel pass and the total condenser could be improved.An air-cooling condensation experimental system driven by a compressor was built and the liquid-vapor separation condenser with one separator was designed and made based on the prototype serpentine condenser.The refrigerant R134a was used as the working fluid.In the experimental condition,the mass flow rate of the separated condensate,the separation ratio,the heat transfer load,the heat transfer coefficient,the vapor quality,the pressure drop and the penalty factor of the liquid-vapor separation condenser were measured and calculated.These parameters were compared with those of the serpentine condenser.It was shown that compared with the serpentine condenser,the liquid-vapor separation condenser could greatly improve the thermodynamic performance.Based on the liquid-vapor separation condenser with one separator,an extra separator was added between the second and the third channel passes.In the same experimental condition,the main parameters of the thermodynamic performance of the liquid-vapor separation condenser with two separators were measured and calculated too,and these parameters were compared with those of the liquid-vapor separation condenser with one separator.It was shown that the heat transfer performance of the third channel pass was improved by the new separator,but the liquid-vapor separation efficiency of the first separator and the heat transfer performance of the second channel pass were deteriorated by the new separator.In summary,the second separator could improve the thermodynamic performance of the liquid-vapor separation condenser slightly.