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The paper presents experimental and theoretical investigation of the outflow of liquids from single-outlet vessels incorporating a vertical downcomer. In such vessels the liquid leaving through the outlet of the downcomer is replaced by another fluid, which enters the vessel-downcomer system through the same opening. Experimental results of the variation of the void fraction and pressure in the vessel with elapsed time are presented. It is shown that the flow is generally oscillatory, and the conditions required for the establishment of the fully developed oscillatory flow are reported. A theoretical model of the fully developed oscillatory flow is developed. The model describes well the frequency of the oscillatory flow and the variation of the gas void fraction in the vessel with elapsed time. The model somewhat overpredicts the amplitude of the pressure oscillations. Thermodynamic aspects of this flow are also considered.

An experimental and theoretical study recently investigated the transient processes that occur when hot liquid spray droplets are suddenly injected into air contained in a closed chamber [1]. The analysis gathered all important parameters governing droplet heat transfer in a single dimensionless group, denoted by K2. The work has been extended by redefining K2, and introducing a new dimensionless group KN2, and by using helium as the surrounding gas. The dimensionless group KN2 is, to a first approximation, independent of all parameters investigated in the present work, including the properties of the surrounding gas, and approximately equal to 0.12. The dimensionless group KN2 =0.12 should be used instead of the Nusselt number as the primary dimensionless group in analysing the heat transfer performance of spray injection nozzles in closed chambers.

There are many processes in engineering in which a physical parameter y normally varies linearly with another physical parameter x, but where, on occasion, a step change in the variation of parameter y may occur. A typical example of this phenomenon is the variation of the pressure drop along an obstructed straight pipe. It is the purpose of this paper to develop a direct method for determining this step change and to consider the implications.

This paper analyses the outflow of liquids from single-outlet vessels. In such vessels the liquid leaving the vessel through the outlet is replaced by another fluid, which enters the vessel through the same opening. A theoretical model is developed for the general case of gas—liquid systems. The model, based on a simplified description of the system, is derived from first principles, and contains one adjustable parameter. Irrespective of the numerical value of this parameter the model describes qualitatively the various phenomena observed experimentally, such as the linear variation between the large-scale gas void fraction in the vessel and the elapsed time. A correlation for the adjustable parameter is presented and its significance discussed. The model is in excellent agreement with the available experimental data on the variation of the large-scale gas void fraction in the vessel and the large-scale gas pressure in the vessel with elapsed time. The application of the model is also discussed.

This paper considers the oscillatory behaviour of liquids in single-outlet vessels, i.e. vessels in which the outflowing liquid is replaced by another fluid which enters the vessel through the same opening. A theoretical model is developed and an equation for the natural frequency of oscillations obtained. The model is in good agreement with the available experimental data. It is shown that the natural oscillations of the liquid govern the hydrodynamic processes involved.

This paper considers the influence of viscosity and circulation on the effect of vortices on the liquid outflow from open vessels. One of the simplest possible arrangements is investigated: an axisymmetric vertical cylindrical vessel with an outlet in its base with the vortex flow generated by supplying the liquid through pipes located at the perimeter of the vessel. It is shown that for low liquid levels in the vessel the vortex provides a hindrance to the flow, but that for high liquid levels it is the vortex flow which discharges more freely. It is also shown that the liquid level in the vessel is proportional to the liquid flowrate, with the constant of proportionality being a function of viscosity and initial circulation.