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In recent years, there has been a considerable interest in the application of solid-liquid fluidized bed heat exchangers in various process industries. The importance of these heat exchangers arises from their ability to remove large quantities of heat per unit time and area from a hot surface. The value of the heat transfer coefficient in solid-liquid fluidized beds can be up to 8 times higher than for single phase forced convection, due to the increase in turbulence level. In addition, in cases where severe fouling is expected, any deposits that may form on the heat transfer surfaces are immediately removed by the abrasive action of the particles. Accurate prediction of hydrodynamic design parameters, such as particle terminal velocity, bed voidage, minimum fluidization velocity and its corresponding bed voidage, and heat transfer coefficient is essential for sizing solid-liquid fluidized bed heat exchangers. In recent years, solid-liquid fluidized beds are also finding application in the chemical, petrochemical and mineral process industries in which the liquid phase is viscous with non-Newtonian behavior. In this investigation, after an extensive literature review of the subjects, a complete experimental set-up for measuring particle terminal velocity, bed voidage and heat transfer was constructed. Then, using Newtonian and non-Newtonian liquids experimental results on particle terminal velocity, bed voidage, minimum fluidization velocity and heat transfer were obtained. It is necessary to mention that the term of non-Newtonian in this investigation implies shear-thinning power law liquids. New experimental data were obtained where published results were insufficient. The results were systematically analyzed and compared with previously published models. Particle terminal falling velocity was measured for different spherical and cylindrical particles with Newtonian and non-Newtonian liquids. The results show that for predicting the particle terminal velocity with Newtonian liquids, the correlation suggested by Hartman et al. (1992) has the best accuracy and is suitable. Few attempts have been made to establish the functional dependence on the particle terminal Reynolds number for solutions with non-Newtonian behavior. Therefore, by analyzing the measured data, a correlation for predicting the particle terminal velocity in non-Newtonian liquids was developed that predicts the experimental results with very good accuracy. The minimum fluidization velocity point represents the transition between the fixed and fluidized states. In this study, the minimum fluidization velocity was obtained by plotting pressure drop gradient versus liquid phase Reynolds number for fixed bed and fluidized regime. The results of the present investigation show that the correlation proposed by Wen and Yu (1966) is the best correlation for predicting the minimum fluidization velocity for Newtonian and non-Newtonian solutions if the apparent viscosity is used for Remf and Ar in fluidization with non-Newtonian liquids. Bed voidage was studied for fluidization with Newtonian and non-Newtonian liquids. The different effects of particle and liquid properties such as particle size and density, and liquid viscosity on bed voidage were studied. A new semi-theoretical model was developed which predicts the bed voidage for fluidized beds with Newtonian and non-Newtonian liquids with very good accuracy. Convective heat transfer coefficients were measured for fluidization of various particles with Newtonian and non-Newtonian liquids under constant heat flux. Different effects of operational parameters such as particle size and density, bulk temperature, liquid viscosity and bed voidage were studied. A new model that is based on the findings of this study and on previous investigations was developed for predicting the heat transfer coefficient in solid- liquid fluidized beds with Newtonian and non-Newtonian liquids. This model predicts the experimental data with good accuracy. A data bank of published fluidized bed heat transfer data was obtained and completely revised. The measured heat transfer coefficients in this study and all results in the refined data bank were compared with the predictions of 39 published correlation and also with the present model. For both Newtonian and non- Newtonian liquids, the present model out-performs all others correlations.

The use of natural convection to effect heat transfers in enclosures is limited principally because of its low heat transfer coefficients. This study aimed to establish a better understanding of the heat transfers occurring in enclosures which are heated by cylindrical heat sources and to identify preferred heating arrangements for improving the rates of natural convection heat transfers. Experimental investigations including interferometric observations were carried out on a square-sectioned enclosure containing a rectangularsectioned, isothermal inner body and cylindrical, sheathed electrical heating elements. The locations of the heaters were varied and the effects on natural convection heat transfers established. The findings conformed to intuitive expectations, concluding that the maximum position for natural convection heat transfer was with the heaters located in the lower half of the sidewalls. The flow patterns and heat transfer characteristics of a single horizontal cylindrical (9.5mm dia) heater in a square-sectioned enclosure were studied by traversing the heater both horizontally and vertically across the enclosure at distinct Rayleigh numbers (7.5x104 and 1.1x105). Optimal positions for maximum and minimum Nusselt numbers were established with respect to heater diameter and vertical height, and horizontal offset from a vertical wall. Flow and Interferometric observations were also carried out on an enclosed single tubular 55mm dia. heater, and two 55mm dia. heaters. Improved arrangements for enhanced heat losses by natural convection from horizontal tubular arrays were deduced, applicable to arrays either totally enclosed or In the proximity of a vertical wall. A square-sectioned (35Ox35Oxl7OOmmtu)n nel oven was designed which would withstand operations under vacuum. Within this enclosure, the heating arrangements were located and varied essentially in the lower half of the enclosure, flow and thermal profiles obtained, a multi-surface radiation model developed and the convective heat transfers validated by evacuating the enclosure. At oven temperatures, over 40% of the heat input was achieved by natural convection.

The development and use of a'n experimental test rig is reported which is capable of modelling two- and three-dimensional wall-bounded air jets. This test rig was primarily produced in order to facilitate the experimental verification of computer codes for calculating convective heat transfer within mechanically- ventilated enclosures. Special attention was therefore given in the design of the rig to heat transfer measurements within such enclosures. The analogy between heat and mass transfer and the application of the naphthalene sublimation technique are explained. Also use of phase change paints in heat transfer measurements in general, and wall-jets in particular, is discussed and experimentally demonstrated. The boundary conditions for the application of each of the above two methods are then specified. The mass transfer method may be used for the case of a heated plate and a jet at ambient temperature while the phase change paint method is applicable to a heated jet. Heat/mass transfer studies are carried out for two different geometries. First beneath a plane wall-jet- obstructed by a normal flat-plate (Alamdari, Hammond and Montazerin (1986 bound paper)), where the data are compared with the computations of the 'intermediate-level' convection model of Alamdari and Hammond (1982) and the high-level 'elliptic' finite domain flow model of Pun and Spalding (1977). The comparison has been a clear demonstration of the capabilities of the computer codes and has shown that although their results over flat surfaces are in good agreement with the test data, their predictions for jets flowing round corners need further research. Secondly the flow and heat transfer characteristics of a three-dimensional jet parallel to a flat plate has been studied. In this case the flow field and mass transfer are modelled and an equation is finally derived which estimates the average heat transfer over a plate parallel to a bluff-jet for a variety of off-set heights, Reynolds numbers and nozzle aspect ratios and can readily be used by design engineers handling such flows.

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No description available.