A partial differential–integral equation has been derived to connect vapor condensation and the development of condensate film thickness in both the tangential and axial directions in a horizontal circular condenser tube. A high-order explicit numerical scheme is used to solve the strongly nonlinear equation. A simple strategy is applied to avoid possible large errors from high-order numerical differentiation when the condensate becomes stratified. A set of empirical friction factor and Nusselt number correlations covering both laminar and turbulent film condensation have been incorporated to realistically predict film thickness variation and concurrently allow for the predictions of local heat transfer coefficients. The predicted heat-transfer coefficients of film condensation for refrigerant R134a and water vapor in horizontal circular mini- and macrotubes, respectively, have been compared with the results from experiments and the results from the simulations of film condensation using computational fluid dynamics (CFD), and very good agreements have been found. Some of the predicted film condensations are well into the strong stratification regime, and the results show that, in general, the condensate is close to annular near the inlet of the condenser tube and becomes gradually stratified as the condensate travels further away from the inlet for all the simulated conditions. The results also show that the condensate in the minitubes becomes stratified much earlier than that in the macrotubes.
Numerical Modeling of Film Condensation in Horizontal Mini- and Macrocircular Tubes
Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received November 28, 2017; final manuscript received June 4, 2018; published online August 20, 2018. Assoc. Editor: Amitabh Narain.
Li, J. (August 20, 2018). "Numerical Modeling of Film Condensation in Horizontal Mini- and Macrocircular Tubes." ASME. J. Heat Transfer. December 2018; 140(12): 121501. https://doi.org/10.1115/1.4040647
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