Browsing by Author "Carr, A D"

Now showing 1 - 9 of 9
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    Dehydration of apple rings
    (1971) Promnitz, Richard Henry George; Carr, A D; Buhr, H O
    The effect of air humidity and velocity, tray surface and ring thickness, on the drying rates of apple rings, is reported. Drying rates for different apple slice thicknesses are correlated with the total moisture content of the fruit and the air relative humidity. Also reported are results on the simulation, both experimental and computational, for the parallel-flow industrial dehydrator drying process.
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    The equilibria and kinetics of certain ion exchange systems
    (1980) Kennet, Paul Charles; Carr, A D
    Fresh water is becoming increasingly scarce in the modern technological world, and thus alternative sources of potable water must be found. One possible source of water of relatively low total dissolved salt content is municipal effluent. This has been successfully desalinated using continuous countercurrent ion exchange systems, the design and structure of which depend largely on the resin types used, and in particular on their equilibrium and kinetic properties. In recent years new and improved resins, such as macroporous and high density resins, have come onto the market, and the vital properties of these have not been well investigated. With this in mind, the H⁺, Na⁺ and Ca⁺² equilibria and kinetics of both a gel type strong acid cation resin (Cation Fort) and a macroporous strong acid cation resin (Zerolit 625) were investigated and compared, as well as the Cl⁻, SO₄²⁻ and artificial COD kinetics of a macroporous normal density weak base, anion resin (Zerolit MPH) and a high density macroporous weak base anion resin (Senbrix). The COD kinetic tests were performed using a conductiometric apparatus, while all the inorganic ion studies were performed on a fractional sampling apparatus. The equilibrium isotherms were obtained using batch tests.
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    Heat transfer to liquid metals, with observations on the effect of super-imposed free convection in turbulent flow
    (1967) Buhr, Heinrich Otto; Carr, A D
    Evaluation of the different theories of heat transfer to liquid metals requires values of the ratio of eddy diffusivities of heat and momentum, which may be obtained from temperature and velocity profiles measured in the flowing liquid metal. Temperature profiles have been reported by a number of workers, but these results are in poor agreement and this investigation was undertaken to measure further profiles and thus obtain reliable eddy diffusivities. Chapter 1 introduces the background to liquid metal heat transfer theory, and Chapter 2 contains a discussion of the experimental apparatus that was constructed for the purposes of this investigation. A description of this equipment he-s been published (Ref. 64) and the material is included here with the permission of the candidate's supervisor. Chapter 3 discusses the unsuccessful attempts to measure velocity profiles, and then goes on to consider appropriate values of the eddy diffusivity of momentum, based on the universal velocity profile. The data of Nikuradse are recommended after a careful study of all the available data and the author believes that this is a conclusion which will be useful to other workers in the field, who usually make an essentially random choice of eddy diffusivities.
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    Liquid side flow characteristics in a packed absorption column
    (1965) Bryson, Anthony Watson; Carr, A D
    This thesis is primarily concerned with the study of techniques which enable flow conditions in complex geometrical arrangements to be measured and analysed. The liquid side in a packed absorption tower is chosen to illustrate the principles involved. The analysis of disturbance testing involves the evaluation of the moments of the resulting residence time distribution curves. It has in the past been found that this method often produces misleading results due to the magnification of experimental errors. An improved method of moment analysis is introduced in this work in an attempt to lessen this effect. It is also shown that much more useful information can be obtained by measuring the response to a disturbance at a number of selected positions in the bed rather than a single determination at the outlet from the column. Two mathematical models are chosen to describe the observed flow situation. The values of their characteristic parameters, as determined from the disturbance testing, are shown to exhibit a number of interesting features which enhance our knowledge of liquid side flow conditions. Finally, a technique is introduced to study flow behaviour from chemical reaction data. The experimental results obtained are shown to agree very closely with theoretically derived values.
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    Nucleation during boiling, with special reference to its cessation at low pressure
    (1962) Jawurek, Harald Hans; Carr, A D; Rallis, C J
    A critical review of the mechanisms, models and heat-transfer correlations for nucleate boiling is presented. The importance of nucleation is stressed. It is pointed out that the bulk of correlations are based on the erroneous notion that the energy transferred away from the heating surface by bubbles as such, in the form of latent heat, contributes insignificantly to the total flux. - A critical review of the correlations for the upper limit of the nucleate boiling regime - the peak flux is also presented. The theory of nucleation during boiling is reviewed and extended in an attempt to explain the complete absence of the nucleate regime, noted in preliminary tests conducted at low pressures.
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    The removal of organic waste matter from secondary sewage effluents by chemical coagulation
    (1977) Milis, Emmanuel; Carr, A D
    The removal of organic waste matter was investigated: a) On both a maturation pond effluent and a secondary clarifier effluent, collected from the same municipal sewage-treatment plant, and b) On a maturation pond effluent collected from a different municipal sewage-treatment plant. The inorganic coagulants alum, ferric chloride and lime as well as organic polyelectrolytes were tested for their ability to remove the organic waste matter from the above effluents under various conditions of pH and coagulant concentration. The tests were on laboratory scale and were conducted under constant room temperature, mixing and stirring conditions. A standard laboratory technique was employed which approximately simulates the large scale operation. Removal was evaluated in terms of Chemical Oxygen Demand (COD) of the wastewater. It was found that, among the inorganic coagulants tested, ferric chloride was, in all cases, the most effective coagulant for COD removal. In general, the final COD achieved with ferric chloride was between 10 and 40 milligrams per litre, depending on the initial COD level of the raw effluent.
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    Velocity and temperature distributions for mercury in turbulent flow
    (1971) Louw, Robert Alexander; Carr, A D; Buhr, Heinrich Otto
    Velocity and temperature profiles in mercury are reported for vertical flow in a pipe at Reynolds numbers of approximately 3.3 x 10⁴ and 5.4 x 10⁴ with variation in heat flux. At a Reynolds number ≈ 3.3 x 10⁴ profiles are reported for thermal calming lengths of approximately 17, 36, 61 and 84. The velocity profiles, temperature profiles and Nusselt numbers are shown to be strongly influenced by free convection effects. Correlations are presented whereby the amount of distortion of the velocity profile from the isothermal profile under given conditions may be estimated, and the value of the Nusselt number under given conditions may be predicted.
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    Velocity, temperature and turbulence measurements in air under combined free and forced convection conditions
    (1971) Connor, Michael Anthony; Carr, A D; Buhr, H O
    This thesis reports the results of an experimental investigation of the effect of buoyancy forces on turbulent upflow of air in a vertical pipe under condit.io:1s of constant wall heat flux at Reynolds numbers of 5000 to 14000. Preliminary velocity and axial turbulence intensity measurements in isothermal flows for Reynolds numbers of 5000 to 32000 are also reported. Velocity and temperature distributions were measured over a range of heat fluxes at Reynolds numbers of approximately 5000 and 8000 and at a single heat flux at a Reynolds number of 14000.