Analytical modeling and numerical solution of a simple solar still

Even though most part of the planet is covered by water, many regions experiences situation of severe draught. Solar still devices presents as a solution to scarcity of water in hot climate regions, where electricity does not reach. These devices are very simple and present ability of converting available saline or low quality water into potable water. In this work, multiphysics of an inclined square solar still device are numerically studied through finite volume method. The phenomenon of double-diffusion natural convection is considered for problem modeling. Velocities, temperature and concentration fields are obtained when Rayleigh number is varied from 104 to 107. Solar still capacity is analyzed through condensation rate parameter, for the mentioned Rayleigh number range.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Small Radial Compressors: Aerodynamic Design And Analysis

This paper presents a computational procedure for the analysis of steady one-dimensional centrifugal compressor. The numerical model is based on the conservation principles of mass, momentum and energy, and has been utilized to predict the operational and aerodynamic characteristics of a small centrifugal compressor as well as determining the performance and geometry of compressor blades, both straight and curved. © 1998 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.43189200Bammert, K., Rautenberg, M., Wittekindt, W., Matching of turbo-components described by the example of impeller and diffuser in a centrifugal compressor, Part I: Aerothermodynamic coupling of impeller and diffuser, Part II: Optimised stage efficiency of a centrifugal compressor (1979) Transactions of the ASME, Journal of Engineering for Power, pp. 59-65. , Paper No. 79-GT/Isr-9Benevenuto, F.J., (1996) Estudoparamétrico de Uma Mini Turbina a Gás do Tipo Radial, , São Carlos, SP, Brasil. 182 p. M.Sc. Thesis, Escola de Engenharia de São Carlos, Universidade de São PauloCame, P.M., The development, application and experimental evaluation of a design procedure for centrifugal compressors (1978) Proceedings of the Institution of Mechanical Engineers, 192 (5), pp. 49-67Clements, W.W., Artt, D.W., The influence of diffuser channel geometry on the flow range and efficiency of a centrifugal compressor (1987) Proceedings of the Institution of Mechanical Engineers, Part A, 201 (A2), pp. 145-152Cohen, H., Rogers, G.F.C., Saravanamutoo, H.I.H., (1987) Gas Turbine Theory, 3rd Ed., p. 114. , Longman Scientific & Technical, EnglandKenny, D.P., The history and future of the centrifugal compressor in aviation gas turbines (1984) Society of Automotive Engineers, , Oct. SAE Paper 841635, 15 pRosolen, C.V.A.G., (1994) Desenvolvimento Analítico e Numérico de um Compressor Centrífugo Subsônico de Baixa Potência, , São Carlos, SP, Brasil. 148 p. M.Sc. Thesis, Escola de Engenharia de São Carlos, Universidade de São PauloSenoo, Y., Pressure losses and flow field distortion induced by tip clearance of centrifugal an axial compressors (1987) JSME International Journal, 30 (261), pp. 375-385Stow, P., The development of advanced computational methods for turbomachinery blade design (1989) International Journal for Numerical Methods in Fluids, 9 (8), pp. 921-941Takeda, A.S., (1987) A Centrifugal Compressor Design Assessment for a Small Gas Turbine, , Cranfield. 161 p. M.Sc. Thesis, School of Mechanical Engineering, Cranfield Institute of Technolog

Experimental study of fusion and solidification of phase change material (pcm) in spherical geometry

The objective of this work is to investigate the parameters affecting the time for complete solidification and fusion in spherical capsules and develop correlations between this time and the investigated parameters. These correlations will be used in the numerical simulations of latent heat storage systems of the fixed bed type having the phase change material, PCM encapsulated in spherical containers. Four spherical shells of 35, 76, 106 and 131 mm diameter were used at temperatures ranging from -20°C to -5°C for solidification process and temperature of 10°C, 18°C, 25°C for the melting process. Water and mixtures of water and polyethylene glycol in percentages ranging from 7.5% to 50% were used as PCM. Based on the experimental results correlations of the time for complete solidification and complete fusion were developed and compared with the experimental measurements showing good agreement and confirming the suitability of using these correlations to predict the complete phase change times. These correlations are applicable in the ranges: 0.076 m Diameter of spherical capsule 0.131m, 0.1% concentration of polyethylene glycol 0.5%, -20°C Initial temperature of PCM -5°C, 10°C Thermal bath temperature 25°C. The differences between the values predicted by the correlation and the experimental measurements are below 10%.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Comparative Study On Finned And Finless Tubes Immersed In Phase Change Material

In an attempt to increase the heat transfer rate and reduce the convective currents during freezing in PCM storage tank, externally finned circular tubes submersed in PCM were studied both theoretically and experimentally. The analytical formulation of the problem was done by applying control volume technique to the enthalpy formulation of the phase change problem controlled by conduction. The equation obtained is applicable to the phase change material in the solid, liquid phase as well as to the metallic fins. Numerical calculations were done using ADI approach for finned and for one- dimensional unfinned cylinder. The parameters analyzed include: number of fins, fin length, fin width, compactness ratio and degree of superheat. An experimental rig was designed and instrumented to permit comparing with the numerical results and establish the validity of the model proposed. The numerical results were found to agree well with experiments.28129

Numerical Prediction Of Ice Crystal Growth Due To Film Flowing Down A Vertical Cooled Plate

A finite volume numerical code has been developed to numerically represent the rate of ice crystal growth in a laminar falling film flowing down a cooled vertical plate. The governing energy equation contains the phase energy as the source term. Enhancement of heat transfer due to suspended ice crystals is accounted for in the use of effective values of thermal conductivity, viscosity, thermal difiusivity, and specific heat as function of volumetric concentration of ice crystals in the falling film. Nusselt number, overall heat transfer coefficient between the fluid and cooled plate, and ice crystal growth rate were calculated for different film thickness with and without axial diffusion. Nusselt number and ice crystal growth rates were found to be dependent on film thickness. Axial diffusion effects were found to be negligible for larger film thickness (large flow rate).35733744Ahuja, A.S., Augmentation of Heat Transport in Laminar Flow of Polystyrene Suspensions -I. Experiment and Results (1975) Journal of Applied Physics, 46, pp. 3408-3416Burns, A.S., Stickler, L.A., Stewart, W.E., Solidification of an Aqueous Salt Solution in a Circular Cylinder (1992) ASME Transactions. J. Heat Transfer, 114, pp. 30-33Charunyakorn, P., Sengupta, S., Roy, S.K., Forced Convection Heat Transfer in Microencapsulated Phase-Change Marterial Slurries: Flow in Circular Duct (1991) Int. J. Heat Mass Transfer, 34, pp. 819-832Fang, L.J., Cheung, F.B., Linehan, J.H., Pedersen, D.R., Selective Freezing of a Dilute Salt Solution on a Cold Surface (1984) Journal of Heat Transfer, 106, pp. 385-393Hale, D.V., Hoover, M.J., O'Neil, M.J., (1971) Phase-change Materials Handbook, , NASA CR-61363Hart, R., Thornton, F., Microencapsulation of Phase-Change Materials (1982) Final Report Contract No. 82-80, , Department of Energy, OhioKasza, K.E., Chen, M.M., Improvement of the Performance of Solar Energy or Waste Heat Utilization Systems by Using Phase-Change Slurry as an Enhanced Heat-Transfer Storage Fluid (1985) Journal of Solar Energy Engineering, 107, pp. 229-236Leal, L.G., On the Effective Conductivity of Dilute Suspension of Spherical Drops in the Limit of Low Particle Peclet Number (1973) Chem. Engng. Commun, 1, pp. 21-31Levich, V.G., (1962) Physiochemical Hydrodynamics, pp. 669-672. , Engle-wood Cliffs, NJNir, A., Acrivos, A., The Effective Thermal Conductivity of Sheared Suspensions (1976) J. Fluid Mech., 78, pp. 33-48Rutgers, I.R., Relative Viscosity of Suspensions of Rigid Spheres in Neotonian Liquids (1962) Rheologica Acta, 2 (4), pp. 305-348Patankar, S., (1980) Numerical Heat Transfer and Fluid Flow, , Hemisphere Publishing Co., New YorkSohn, C.W., Chen, M.M., Heat Transfer Enhancement in Laminar Slurry Pipe Flows with Power Law Thermal Conductivities (1984) Journal of Heat Transfer, 106, pp. 539-542Stewart Jr., W.E., Kaupang, R.L., Tharp, C.G., Wendland, R.D., Stickler, L.A., An Approximate Numerical Model of Falling-Film Ice Crystal Growth for Cool Thermal Energy Storage (1993) ASHRAE Transactions Research, 99 (PART I), pp. 347-354Vand, V., Viscosity of Solutions and Suspensions (1948) J. Phys. Coll. Chem., 52, pp. 300-32

Complete Model For The Laminar Flow Of Supercooled Liquid (water)

The solidification process of liquid flowing in laminar regime in a duct under supercooling conditions is studied both theoretically and experimentally. The model proposed is based upon the energy balance equations for the solid and liquid regions as well as across the solidification front admitting temperature dependent physical properties. The Landau transform is used to immobilize the interface and hence facilitate the numerical calculations. The results obtained were verified experimentally. Comparisons with the exact solution due to Neumann as a special case, apparent thermal capacity method due to Bonacina and the energy equation model due to Goodrich were included and discussed.33534

Numerical Solution Of Finned Geometries Immersed In Phase Change Material

The Stefan problem in regions bounded by fins is formulated using the enthalpy approach. The equations obtained are parabolic with coefficients varying with time and space. The differential equations were reduced to a set of algebraic equations by using the method of control volume. The numerical solution was obtained by using an alternating direction implicit scheme together with an iterative procedure. Three cases of interest were treated, including a cylinder with axial fins, cylinder with transverse fins and rectangular finned plane geometry.109313

Semi Analytical Model For Heat Transfer In Liquid Fluidized Bed.

This paper presents a semi analytical model for heat transfer in liquid fluidized bed using big particles. The accuracy of the model and its validity are verified by experiments. Using a one dimensional general formulation of the energy equation, a system of coupled differential equations is obtained. This system represents the temperature distribution in the solid particles and in the fluid along the axis of the bed. These equations were solved numerically using an iterative finite difference technique. The heat transfer coefficient between the solid particles and fluid is obtained experimentally.167968

Frost Formation Over A Flat Plate

This paper models the frost formation process on a cold flat surface exposed to the flow of warm moist air. The model is a one dimensional transient formulation of flow, heat and mass transfer based upon the local volume averaging technique. This model enables predicting the frost temperature, density and thickness distribution along the plate as well as the void fraction. Available experimental data were used to validate the model. Also numerical experiments were realized to choose the best initial values of the diffusivity and initial radius of the ice crystals and the frost diffusion parameter Fs.71071

Evaluation Of Internal And External Environments: Comfort Issues And Climate Analysis For Building Project

This research investigates the evaluation of methods of thermal performance of the a construction envelope classrooms of Brazilian Universities, University of Campinas Unicamp and University of São Paulo Polytechnic School USP SP. This is related with the internal environment in the thermal human sensations of the users in the university building. Moreover, this research proposes a methodology for evaluation of ambient comfort At the university building. The influences of the conditions external climatological in the renewal of air and the conditions climatological of internal environments were evaluated. Some comparatives studies on classrooms with and without thermal conditioning was been carried through; the limits between the zones of comfort of the human metabolism based in the collected ones of internal data had been determined, for the o air volume of the constructed environment, and for the identification of the bands where if they concentrated the heat sources.National Grid,Syracuse University,Carrier,Corning,IBMFanger, P.O., (1970) Thermal Comfort, , Copenhagen: Danish Technical PressGivoni, B., (1962) Influence of Work and Environmental Conditions on the Physiological Responses and Thermal Equilibrium of Man, , Haifa: Israel Institute of Technolog