This experim ental project aims to describe the influencing factors in the vacuum boiling o f w ater in w ater vapour refrigeration system s Testing was conducted using a 2 kW three-stage steam je t ejector system, w ith barom etric condensers, as the com pression device. Three direct-contact evaporators were used to investigate the boiling phenom ena. T hese were : a through-flow evaporator w here heal and mass transfer rates were established for boiling m echanism s at various positions within the evaporator; a vertical cylinder where small quantities o f w ater were subjected to rapid decom pression and the effects m easured, and a sim ple channel for photographic studies o f the process. Boiling in direct-contact water vapour systems is described herein The vacuum boiling proo ss was found to be controlled by a com bination o f the w ater surface tem perature and the hydrostatic pressure gradient, these being governed by the w ater vapour flow geometry between the w ater surface and ejector suction and convective heat transfer below the boiling region. The contributions o f the various boiling regim es to the total heat transfer are discussed. Heat and mass transfer coefficients and their applicability to evaporator design are presented

Steam property evaluations may represent a significant portion of the computing time necessary for power system simulations. The iterative nature of the solutions for heat transfer and kinetic equations often requires thousands of steam property evaluations during the execution of a single program. Considerable savings may be realized by simplification of property evaluations. Empirical equations have been obtained for the thermodynamic properties of water in the region of interest. To maintain thermodynamic consistency, the compressibility factor Z, in terms of pressure and temperature, was obtained by curve fitting, and the enthalpy, entropy, and internal energy were derived by standard relationships. Formulations for heat capacity, saturation temperature as a function of saturation pressure, the specific volume of saturated water as a function of saturation pressure, and specific volume of saturated water as a function of the saturation temperature were determined by curve fitting of independent equations. Derivatives were obtained by differentiation of the appropriate formulations. Evaporator and superheater components of a liquid metal fast breeder reactor power plant simulator were chosen as test cases for the empirical representations. Results obtained using the empirical equations were comparable to those obtained using tabular values, but significant savings in computational costs were realized. Execution time for the evaporator program with the empirical forms was approximately 27 percent less than for the program with tables. Execution time for the super-heater program was approximately 23 percent less.