Forced convection flow transient

Kaka9 S., 1975, A general solution to the equation of transient forced convection with fully developed flow, Int. J. Heat Mass Transfer 18, 449-1453. 

Kaka9 S., Y. Yener, 1983, Transient Laminar Forced Convection in Ducts, in S. Kaka9, R. K. Shah, A. E. Bergles (eds). Low Reynolds Number Flow Heat Exchangers, pp. 205-227, Hemisphere, New Yourk. 

The present lecture summarizes some of tiie most recent joint research results from tiie cooperation between the Federal University of Rio de Janeiro, Brasil, and tiie University of Miami, USA, on tiie fransient analysis of both fluid flow and heat transfer within microchannels. This collaborative link is a natural extension of a long term cooperation between the two groups, in the context of fimdamental work on transient forced convection, aimed at tiie development of hybrid numerical-analytical techniques and tiie experimental validation of proposed models md methodologies [1- 9]. The motivation of this new phase of tiie cooperation was thus to extend the previously developed hybrid tools to handle both transient flow and transient convection problems in microchannels within the slip flow regime. 

This work discusses hybrid numerical-analytical solutions and mixed symbolic-numerical algorithms for solving transient fully developed flow and transient forced convection in micro-channels, making use of the Generalized Integral Transform Technique (GITT) and the Mathematica system. 

Santos, C.A.C., Medeiros, M.J., Cotta, RM., and Kaka9, S. (1998), Theoretical Analysis of Transient Laminar Forced Convection in Simultaneous Developing Flow in Parallel-Plate Channel, 7 AIAA/ASME Joint Themophysics and Heat Transfer Conference, AIAA Paper 97-2678, Albuquerque, New Mexico, June. Cheroto, S., Mikhailov, M.D., Kaka , S., and Cotta, R.M, (1999), Periodic Laminar Forced Convection -Solution via Symbolic Computation and Integral Trmsforms, Int. J. Thermal Sciences, V.38, no.7, pp.613-621. Kaka, S., Santos, C.A.C., Avelino, MR., and Cotta, R.M. (2001), Computational Solutions and Experimental Analysis of Transient Forced Convection in Ducts, Invited Paper, Int. J. of Transport Phenomena, V.3, pp. 1-17. 

Cotta, R.M. and Ozisik, M.N. (1986) Transient Forced Convection in Laminar Channel Flow witii Stepwise Variations of Wall Temperature, CanJ. Chem. Eng., Vol. 64, pp. 734-742. 

Gondim, R.R., Cotta, R.M., Santos, C.A.C., and Mat, M. (2003) Internal Transient Forced Convection with Axial Diffusion Comparison of Solutions Via Integral Transforms, ICHMT International Symposium on Transient Convective Heat And Mass Transfer in Single and Two-Phase Flows, Cesme, Tmkey, August 17 - 22. 

The scientific program starts with an introduction and the state-of-the-art review of single-phase forced convection in microchannels. The effects of Brinkman number and Knudsen numbers on heat transfer coefficient is discussed together with flow regimes in microchannel single-phase gaseous fluid flow and flow regimes based on the Knudsen number. In some applications, transient forced convection in microchannels is important. 

The mechanisms of mass transport can be divided into convective and molecular flow processes. Convective flow is either forced flow, for example, in pipes and packed beds, or natural convection induced by temperature differences in a fluid. For diffusive flow we have to distinguish whether we have molecular diffusion in a free fluid phase or a more complicated effective diffusion in porous solids. Like heat transport, diffusion may be steady-state or transient. 

This equation shows that vorticity is a maximum at the moving wall (which acts a source of vorticity) and decays exponentially on a length scale 0(l/Re) by the action of viscous forces. Thus for Rey 1 the flow is effectively irrotational. In this respect the problem is atypical as we normally expect vorticity to decay on a diffusive length scale of 0( / J Re) (cf. oscillatory Couette flow). The reason for this difference is that in the present probiem we have a balance between convective inertia and viscous forces as opposed to a balance between transient inertia and viscous forces. 

For prediction of subassembly coolant flow rate and temperature distributions a wide range of coolant flow and thermal convection regimes must be considered including laminar and turbulent flow natural, forced and mixed (forced + natural) convection and steady state and transient reactor conditions. 

Heat conduction, convection, boiling heat transfer, radiation, transient heat transfer, forced flow in pipes and packed beds, mass transfer by diffusion, and diffusion in porous solids. 

Transient simulations of SEALER have been carried out using the SAS4A/ SASSYS-1 codes as well as BELLA, a code written specifically for the purpose of safety-informed design of LFRs. Analysis shows SEALER to withstand unprotected withdrawal of a single control rod, loss of forced flow and loss of heat sink, thanks to its low power density, the capability of natmal convection for decay heat removal, and reliance on thermal radiation from the vessel as the ultimate heat sink. 

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