Search

An experimental study has been made of the adsorption of carbon dioxide from air using a bed of molecular sieve pellets (type 4A), the object being to compare the relative suitability of the various existing analytical solutions describing the dynamic behaviour of fixed-bed adsorbers, and to test the extent to which the simplifying assumptions may be relaxed before significant deviations occur. Data have been obtained for the concentration history at different bed depths and conclusions are drawn on the rate-determining mechanism of solid diffusion for this system. A programme for use with the Mercury Digital Computer for the analysis of such data, has been developed.

The design of a plant for the measurement of the specific enthalpy of steam up to temperatures of 75000 and pressures of 1000 bar is presented, and measurements are reported up to temperatures of 700°C and pressures of 1000 bar. Tile experimental method adopted was that of constant—flow calorimetry, and the plant designed included a boiler—feed pump, a boiler and superheater, pressure and temperature measuring stations, a set of throttling devices and a condenser-calorimeter. The measuring systems were designed so that the overall accuracy of measurement of specific enthalpy was approximately 0.1%. The method of operation of the completed plant and the computation of the results was arranged so that the stability of the system could be shown.

The thesis deals mainly with a study of the mechanism by which segregation may be made to occur in a granular mass composed of particles of the same composition but of two size ranges or a mass consisting of particles of the same size range but, of tyro differing densities: The object, was to ascertain whether by a suitable design of separator a continuous separation could be effected. The materials used were (a) sand of varying size ranges and (b) mixtures of Coal and Magnetite, The flair characteristics of these materials were examined and in particular measurements of the Angle of Repose of the single materials and of mixtures were carried out. A quantitative study was made of the segregation occuring when conical heap of material was formed by flow from a hopper. A series of separators were designed in which one section. consisted of a cone and the other a cylinder or coned of various angles. The separators were provided with a continuous feed arrangement and could be rotated about their longer axis at various speeds. The Angle of Repose of the feed material and the shape of the vessel were found to be important factors in effecting complete separation. The mechanism of separation, however, 'was found to be complex and -whilst complete separation could usually be obtained, the optimum conditions had to be found by experiment. The effects of feed rate, rate of revolution and residence time were determined.

Standard codes are available for the detailed design of high pressure plant operating at pressures up to about 250 atmospheres. For higher pressures there are no accepted codes and design must be based largely on experience and first principles. This work was under-taken to provide a rational basis for the design of a mechanical joint employing n cone ring gasket. To this end,the load-strain characteristics of such joints have investigated at pressures up to 500 atmospheres, using mild steel cone rings of various angles, radius ratios and axial lengths, located between seating surfaces of angles 0° to 30°. The main conclusions reached in the investigation are: firstly, the angle of the seating surface has little direct effect on the leakage pressure, but it is of major importance in determining the radial extension of the ring required for self sealing. Secondly, the minimum ratio of the radial extension per unit increase in hydraulic end load, required for self sealing, to that required to maintain contact with the seating surface, is 1.3:1 and the minimum ratio of applied load to hydraulic end load, is 1.2:1. Thirdly, the gasket factor of a mild steel gasket varies inversely with the initial stress and width of the contact surface, and fourthly, the minimum gasket seating stress is inversely proportional to the gasket width. Equations have been developed which may be used to determine the load-strain characteristics of a cone ring during precompression and when the joint is subjected to an internal pressure. These equations are used to determine the conditions which must be satisfied if a high pressure joint utilising a cone ring gasket is to function satisfactorily.

The investigations described in this thesis relate to some of the fundamental and characteristic properties of coarse granular solids and in particular to those which determine the rates of flow from hoppers, pipes and orifices. The internal frictional forces and the applied shearing forces necessary to overcome frictional resistance are important quantities in the investigation and the methods of measuring them will receive some consideration.

The dynamic response of a thin, flat metal disc to a transverse shock pressure load is studied and a theoretical analysis presented. The analysis predicts that the deformation mechanism of the disc is dependent upon the interaction of two interdependent wave motions, that of a plastic wave and an inertia wave. A model of this mechanism is described and used, together with a criterion of rupture, to develop a relationship between the minimum shock rupture pressure of a disc and its size and material properties. It is then shown analytically, that due to aerodynamic disturbances created by the violent disc motion, the applied pressure waveform is modified appreciably by rupturing discs and equations have been derived to determine the effect of such motion upon the rupture pressure. Several assumptions had to be made in the theoretical analysis which required experimental verification. For this purpose, three sets of experiments were conducted with the aid of a shock tube and the following phenomena were studied; the deformation mechanism and node of rupture of a disc, the minimum rupture pressures of annealed copper and aluminium discs of different sizes and the variation in the applied pressure with disc motion. Further experimental work had to be carried out to measure the characteristic stress-strain properties of the disc materials. Finally, the results of these experiments are compared with those predicted by the relationships derived from the theoretical study.

A Mach-Zehnder interferometer with 200 mm. mirrors has been designed and constructed for the study of refractive index fields. The instrument can accommodate large test-sections and is mounted on a sprung cradle to isolate it from any external vibration. Transient heat transfer phenomena occuring during evaporation and condensation in liquid vapour systems were studied, using : the inferometer to measure the temperature gradients existing adjacent to the surface. From these results values of the condensation coefficient were calculated for propyl alcohol, pure water and water with involatile contaminants. For all systems studied the calculated values of the coefficient were found to decrease as the rate of condensation increases and it was considered that this effect cannot wholly be attributed to the small quantities of air sometimes present near the liquid surface. Coefficients obtained for water during condensation were of the same order as those measured by other workers studying evaporation. Traces of sodium lauryl sulphate, a surface active agent, reduced the coefficient by a factor of about 3; a similar reduction was found for a normal solution of sodium chloride. Coefficients for propyl alcohol were less than those for water by a factor of 20. Evaporation and condensation yielded similar coefficients for all systems.

The separation of the boundary layer in a two dimensional convergent-divergent nozzle, discharging to atmosphere, has been investigated using an interferometer in conjunction with pressure measurements. It is shown that the variation in pressure rise across the separating boundary layer with Mach number is the same as that for separation over steps and wedges in wind tunnels. It is also shown that the position of transition in the boundary layer relative to the point of separation is the prime factor in determining the flow pattern at separation. Stable turbulent separation is obtained throughout the range of Mach numbers investigated by making the boundary layers turbulent artificially. The interferometric studies indicate that separation of boundary layers is accompanied by separation of the boundary layers on the adjacent glass walls. The flow pattern in the region of reverse flow under the separated layer is complex, the reverse flow being entrained from the atmosphere. The shape of the velocity profiles in the turbulent regions of the boundary layer are shown to be dependent on the Reynolds and Mach numbers of the flow. The flow upstream of the shock waves causing separation is not isentropic as the entropy change between the reservoir and a given point in the divergence increases with increase of the reservoir pressure.