Experiment Investigation On Vertical Heat Exchanger With Inside Tube Condensation

The heat transfer characteristics of liquid-vapor separation condenser and its effects on the cooling system using R410A as the refrigerant are fully detected via experimental methods in this thesis. A water-cooled in-tube-condensation liquid-vapor separation condenser(ILSC) is designed based on short tube effect for air conditioning and heat pump systems. The heat transfer performances of ILSC with in-tube condensation of refrigerant are examined through the condenser testing system (CTS). Meanwhile, the influences of ILSC on system pressure, system power dissipation, system heat transfer and system COP are also probed. The results are compared with that in horizontal shell-tube condenser (HSC). A vertical shell-tube condenser (VSTC) with in-tube condensation, which utilizing internally threaded pipes for the refrigerant and also possessing liquid-vapor separation structure is also designed for testing. The heat transfer characteristics and the influences on the cooling system of it are tested and compared with the HSC which possesses external threaded pipes. Finally, a subcooled section with liquid-vapor separation structure is designed and added to ILSC condenser. The condensers with and without subcooled section are compared on heat transfer of the system, power dissipation of the compressor, subcooling degree of the refrigerant at the condenser outlet, cooling capacity of the system and COP of the system.Changing of the heat transfer coefficients of ILSC with the mass flow rates are investigated experimentally when the refrigerants mass flow rates vary from220-330kg/h and the saturation temperatures are at35,40and45℃. Moreover, the effects of the liquid-vapor separation structure on the system performance are detected when the mass flow rate of and the temperatures of the cooling water is0.7kg/s and vary from27-33℃respectively and the temperature and the mass flow rate of the cooled-water is12℃and0.5kg/s respectively. The results is concluded as followed, firstly the heat transfer coefficients of ILSC increases with the refrigerant flow rate linearly and decreases with the refrigerant saturation temperature. Secondly the heat transfer coefficients of ILSC and HSC are nearly the same at low refrigerant flow rate and the former overwhelms the latter when the refrigerant flow rate gets higher. Finally, the liquid-vapor separation structure enhances the exhaust pressure, condensation heat transfer, cooling capacity and COP of the cooling system significantly.The heat transfer performance of VSTC with in-tube condensation of refrigerant and is compared with that of HSC experimentally and the heat transfer area on the cooling water side of the both condensers are identical. It is found that the heat transfer coefficient of VSTC with in-tube refrigerant condensation increases linearly with the mass flow rate of the refrigerant and decreases when the saturation temperature of the refrigerant increases. In addition, the heat transfer coefficient of the condenser with internally threaded pipes is lower than that of the condenser with externally threaded pipes and the heat transfer performance of the former is improved comparing to that of the latter when the refrigerant flow rate is higher increasingly. The transition mass flow rates are250kg/h,235kg/h and228kg/h at the three refrigerant saturation temperatures, respectively. Comparing with the results obtained in the experiments conducting in ILSC, it is concluded that the condenser with threaded pipe enhances the performance of the condenser with liquid-vapor separation structure.Besides the experiments mentioned above, the influence of the subcooled section on the heat transfer performance of ILSC (ILSCS) is also investigated in the present thesis. The results show that the effect of subcooled section on the condensation heat transfer and power dissipation of system is tiny. However, it provides positive influence on refrigerant subcooling, cooling capacity and COP of system. In summary, the subcooled section makes the refrigerant subcooled at the condenser outlet and enhances the system performance.