Design, fabrication, and operation of a system to control FC-72 refrigerant condensation by means of manipulating exiting liquid and vapor flow rates.

摘要

Annular, internal-condensing flow is one of the most common two-phase (vapor-liquid) flow regimes encountered in industrial equipment, such as heat exchangers, engines, and capillary pump loops. For the condensing flow occurring through these processes, little is known about the stability and dynamics of the condensing film, the specifics of heat transfer rates during forced condensation as well as the behavior of the condensing flow with regards to variations of the surrounding process. Applications where two-phase internal condensation occurs happen throughout many engineering disciplines. In most cases, however, more information is needed to understand how temperature and pressure changes within the surrounding flow loop affect the condensing flow within the condensing section.; The internal condensing flow examined here is one of in-tube condensation in a vertical, downward flow configuration where full condensation as well as partial condensation can be achieved under certain entrance and exit conditions (controlled or uncontrolled). In a closed system, the dynamic behavior of the condensing section is affected by the tube inlet, tube wall, and exit conditions, but these conditions are affected by the process of flow loop outside the condensing section.; The work presented here deals specifically with the mechanical design, construction and operation of a closed-system flow loop for experiments corresponding to inlet vapor Reynolds numbers in the range of 10,000-40,000 and the means to control temperature, pressure, and flow such that a two-phase condensing zone could be developed for unspecified (natural) and specified (forced) exit condition. This work also deals with the operations and attainment of partial condensation cases with natural and forced vapor/liquid splitting, Ze, which are then compared to that of existing and forthcoming simulations.; This system is able to produce stable full and partial condensation cases with a maximum inlet vapor flow rate of 2.0 g/s, and cooling water temperatures in the range of 25-60°C. Full condensation cases with various inlet vapor flow rates and cooling temperatures were produced and show that the system can attain a steady state and maintain it for an extended period of time. Partial condensation cases were attained with an experimental natural Ze value of 0.73 and a simulated value of 0.75. The system was also able to produce a forced partial condensation case, with the same inlet and cooling conditions as for the natural case, to a Ze value of 0.60, showing that multiple exit conditions can be attained while holding all inlet and cooling parameters constant.