Experimental Study On Air-Cooled Finned-Tube Condenser With Liquid-Vapor Separators

In this thesis,a parallel flow condenser with tube pass arrangement of 14-9-5-2-6was designed based on the outdoor unit of 1.5HP air conditioner.Through the air-cooled condensation heat transfer experiments,the performance differences of parallel flow condenser without separator,liquid-vapor separation condenser with one U-type separator and two U-type separators using R134a as working medium were studied under different air speeds and temperatures.Because there were some limitations in liquid-vapor separation for the existing separator,a new liquid-vapor separation structure,adaptive separator,was designed,and its liquid separation characteristics were studied through cold water experiments.Finally,the performance differences between the liquid-vapor separation condensers with two adaptive separators and two U-type separators were analyzed through experiments under different air speeds and temperatures.The adaptability of the liquid-vapor separation condenser with two adaptive separators was studied under different heat loads.The results showed that the U-type separator greatly improved the heat transfer performance of single tube,hence improving the heat transfer performance of the condenser.The condenser could cool more refrigerant,and the increase of mass flow rate further improved the heat transfer performance of the condenser.Compared with the parallel flow condenser without separator,the liquid-vapor separation condenser with U-type separator had smaller pressure drop under the condition of larger inlet mass flow rate.The coefficient of performance of liquid-vapor separation condenser with U-type was greater than that of condenser without separator under different working conditions.In the cold water experiments of the adaptive separator,the effects of inner diameter of hollow tube,inner diameter of box and the number of holes on the liquid separation capacity were studied.In addition,the liquid separation capacity of the adaptive separator with different number of holes and the U-type tubes with inner diameters of 2 mm,4 mm and 6 mm were compared.Two adaptive separators with specification parameters of D_13-6-N₁₂ were selected to be added to the parallel flow condenser and processed into a two-stage adaptive liquid-vapor separation condenser.The comparative experimental study of liquid-vapor separation condenser with two U-type separators and liquid-vapor separation condenser with two adaptive separators under different working conditions showed that the adaptive separator could improve the heat transfer performance of a single tube to a greater extent,and further improved the heat transfer performance of the condenser.The liquid-vapor separation condenser with two adaptive separators had smaller pressure drop and larger coefficient of performance than the liquid-vapor separation condenser with two U-type separators.In addition,the heat transfer characteristics of the first three tube passes of the two-stage adaptive liquid separation condenser under different heat loads were experimentally studied.The results showed that the liquid-vapor separation condenser with two adaptive separators had good adaptability under different heat loads.