Atkinson, B.J., Stephens, D.W., Harris, J.A., and Schneider, P.A. (2000) The net pressure driving force due to boiling in calandria tubes. In: Proceedings of the 22nd Annual Conference of the Australian Society of Sugar Cane Technologists. pp. 449-455. From: ASSCT 2000: 22nd Annual Conference of the Australian Society of Sugar Cane Technologists, 2-5 May 2000, Bundaberg, QLD, Australia.

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Abstract

Vapour formation due to boiling in calandria tubes provides the driving force for natural circulation in vacuum pans. The net pressure difference generated across a calandria tube is determined by the average density deficit in the tube relative to the downcomer (i.e. the aount of vapour in the tube) and the pressure loss due to friction and acceleration. This paper presents a mathematical model of the two-phase flow of molasses and vapour in a calandria tube assuming equilibrium thermodynamics and steady state conditions. The model can predict the net pressure driving force and the evaporation rate produced by a tube as a function of parameters such as the heat input, mass flow rate, liquid height above the calandria and boiling point elevation. Additionally, the model yields detailed profiles of temperature, absolute pressure, volume fraction and other variables as a function of distance along the calandria tube. Results are presented in the form of characteristic curves representing the net pressure difference available to drive natural circulation as a function of applied heat and mass flow rate. The circulation rate and evaporation rate in a natural circulation loop may be determined by matching the appropriate characteristic curve to the system resistance curve for the loop. An example is presented to illustrate the application of the method.

Item ID:	14542
Item Type:	Conference Item (Research - E1)
ISBN:	0726-0822
Keywords:	boiling; calandria tube; mathematical modelling; natural circulation; two-phase flow
Related URLs:	Organisation
Funders:	Sugar Research and Development Corporation (SRDC)
Projects and Grants:	SDRC project JCU021
Date Deposited:	15 Dec 2017 01:46
FoR Codes:	09 ENGINEERING > 0915 Interdisciplinary Engineering > 091505 Heat and Mass Transfer Operations @ 100%
SEO Codes:	86 MANUFACTURING > 8601 Processed Food Products and Beverages (excl. Dairy Products) > 860199 Processed Food Products and Beverages (excl. Dairy Products) not elsewhere classified @ 100%
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