Browsing by Author "Rodriguez-Pascual , Marcos"

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    The effect of energy input on the aggregation rate in an oscillating multi-grid reactor
    (2014) Willis, Brian Mathew; Lewis, Alison Emslie; Rodriguez-Pascual , Marcos
    Aggregation is a size enlargement mechanism which can be either desirable or inconvenient depending on the process involved. It involves the coming together or collision of two or more particles to form a larger single particle. It is a mechanism which is poorly understood and much research is still required before the intricacies of the process are fully grasped. Although it is known that aggregation is influenced by energy input (amongst other factors), the relationship between the two has previously been measured in anisotropic turbulent environments. Thus although aggregation is a function of local energy input, it has yet to be measured in environments where the local energy dissipation is well understood, or else it has been studied in low Reynolds number environments. This thesis aims to address this deficiency by studying the effect of local energy input on the aggregation rate in a well characterised environment of isotropic and homogenous turbulence.
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    Heat and mass transfer effects of ice growth mechanisms in water and aqueous solutions
    (2013) Kapembwa, Michael; Randall, Dyllon G; Rodriguez-Pascual , Marcos; Lewis, Alison Emslie
    Research into ice crystallization processes is an important area of study. The desire to improve product quality and efficiency of processes involving ice crystallization in industries such as desalination by freezing, freeze drying, freeze concentration and freeze crystallization for food processing, requires insight into the ice growth mechanisms. More so, a novel technology called Eutectic Freeze Crystallization, where water is recovered in the form of ice, requires that ice crystals are of high purity as this directly determines the quality of the water obtained. During ice crystallization, ice growth mechanisms play an important role in determining the structure, size and morphology of ice which have an effect on separation processes and product purity. Heat and mass transfer play a fundamental role in ice growth processes as they affect the thermodynamics and kinetics of the crystallization process. Ice growth experiments were carried out in pure water, in 8.4 wt% and 16.8 wt% magnesium sulphate and in 8.4 wt% sodium nitrate using a 10x5x31 mm test cell made of Plexi-glass®. The Colour Schlieren optical technique was used to conduct the experiments. This is because of its capability to map refractive index gradients related to either temperature or/and concentration gradients of the solution during crystal growth.