A comprehensive correlating equation for laminar, assisting, forced and free convection

Churchill, Stuart W.

doi:10.1002/aic.690230103

Cited by 264 publications

(74 citation statements)

References 39 publications

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“…Other simulated results involved lower drying air temperatures. As can be seen, the numerical results do not differ from empirically correlated data obtained from Hilpert (cited by Incropera & Witt, 1992) and Churchill (1977). The numerical simulated results and Hilpert's and Churchill's data differ from …”

Section: Resultsmentioning

confidence: 32%

“…In the last decades, many researches related to food and grain drying and heat treatment have been carried on to obtain the required physical and thermal properties required for proper drier or process design (Churchill, 1977;Zahed & Epstein, 1992Muthu & Chattopadhyay, 1993;de Ville & Smith, 1996;Galan-Domingo & Martinez-Vera, 1996;Smith, 1996;Sotocinal et al, 1997;Tolaba et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

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Transport coefficients for low and high-rate mass transfer along a biological horizontal cylinder

Barreto¹,

Fortes

Ferreira

et al. 2006

Rev. bras. eng. agríc. ambient.

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Knowledge of heat and mass transfer coefficients is essential for drying simulation studies or design of food and grain thermal processes, including drying. This work presents the full development of a segregated finite element method to solve convection-diffusion problems. The developed scheme allows solving the incompressible, steady-state Navier-Stokes equations and convective-diffusive problems with temperature and moisture dependent properties. The problem of simultaneous energy, momentum and species transfer along an infinite, horizontal cylinder under drying conditions in forced convection is presented, considering conditions normally found in biological material thermal treatment or drying. Numerical results for Nusselt and Sherwood numbers were compared against available empirical expressions; the results agreed within the associated experimental errors. For high rate mass transport processes, the proposed methodology allows to simulate drying conditions involving wall convective mass flux by a simple inclusion of the appropriated boundary conditions. Key words: drying, heat transfer, convection, diffusion Coeficientes de transporte para baixas e altas taxas de transferência de massa ao longo de um cilindro biológico horizontal RESUMO O conhecimento dos coeficientes de transferência de calor e massa é essencial para o estudo de simulação de secagem e para o projeto de processamento térmico de grãos e alimentos, inclusive secagem. Este trabalho apresenta o desenvolvimento completo de um método de elementos finitos segregado para resolver problemas de convecção-difusão. O esquema desenvolvido permite que se resolvam as equações de Navier-Stokes incompressíveis em regime permanente, além de problemas convectivos-difusivos com propriedades dependentes da temperatura e da umidade. Apresenta-se o problema de transferência simultânea de energia, momentum e espécies ao longo de um cilindro horizontal, infinito sob condições de secagem em convecção forçada, considerando-se condições normalmente encontradas em tratamento tér-mico ou secagem de material biológico. Compararam-se resultados numéricos para Nusselt e Sherwood com expressões empíricas disponíveis; os resultados concordaram dentro dos erros experimentais associados. Para processos com altas taxas de transporte de massa, a metodologia proposta permite simular condições de secagem envolvendo fluxo convectivo de massa na parede, por meio de uma simples inclusão de condições de contorno apropriadas.

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Section: Resultsmentioning

confidence: 32%

Section: Introductionmentioning

confidence: 99%

Transport coefficients for low and high-rate mass transfer along a biological horizontal cylinder

Barreto¹,

Fortes

Ferreira

et al. 2006

Rev. bras. eng. agríc. ambient.

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“…Churchill's sum of cubes [146] approach as discussed in Chapter 5, for combining the hydr,.,clynamic contribution with background leads to the low power dependence reported. Previous researchers have not subtracted out background at ali [158], or have followed Beck's proposed linear summation [160].…”

Section: Electrical Testing Of the In-house Mmementioning

confidence: 99%

Micro-scale mass-transfer variations during electrodeposition

Sutija¹

1991

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“…In quiescent solutions or solutions with very low forced convection rates, the density difference between the (saturated) liquid-solid interface and the bulk solution drives a convection current which is the principal mechanism that moves solution away from the solid. The natural and forced convection terms are in general not directly additive (Pei 1965;Churchill 1977) in determining total convection or the dissolution rates.…”

mentioning

confidence: 99%

“…11 by [ 1 -(SJSf)3]5/12. This is a rough correction derived from Churchill (1977) for heat transfer with assisting forced and free convection.…”

mentioning

confidence: 99%

Plaster standards to measure water motion

Thompson

Glenn

1994

Limnology & Oceanography

127

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Plaster of paris blocks (clod cards) were re‐evaluated as devices to measure water motion in freshwater and marine environments. Clod cards, developed in 1971, have only been used as indicators of relative water motion. We generated standard curves relating the dissolution rates of clod cards to water speed, temperature, and salinity by attaching the cards to a mechanical arm rotating in a tank of water. Free convection experiments were also conducted by suspending clod cards in quiescent solutions held in ice chests. We describe calibration methods that use either forced convection or free convection to correct field results for the effects of temperature and salinity on dissolution rates of clod cards. Although dissolution rates were lower in freshwater than brackish or seawater, salinity in the range of 20–40‰ did not greatly affect dissolution. Properly calibrated, clod cards now offer a simple, practical method for measuring integrated water motion, expressed in readily visualized rate units, over a wide range of temperatures, salinities, and water speeds.

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A comprehensive correlating equation for laminar, assisting, forced and free convection

Cited by 264 publications

References 39 publications

Transport coefficients for low and high-rate mass transfer along a biological horizontal cylinder

Transport coefficients for low and high-rate mass transfer along a biological horizontal cylinder

Micro-scale mass-transfer variations during electrodeposition

Plaster standards to measure water motion

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