Summary
A unified model of multiphase heat transfer is developed for different flow
patterns of gas/liquid pipe flow at all inclinations –90° to +90° from
horizontal. The required local flow parameters are predicted by use of the
unified hydrodynamic model for gas/liquid pipe flow recently developed by Zhang
et al. (2003a, 2003b). The model prediction of the pipe inside
convective-heat-transfer coefficients are compared with experimental
measurements for a crude-oil/natural-gas system in horizontal and
upward-vertical flows, and good agreement is observed.
Introduction
As oil and gas production moves to deep and ultradeep waters, flow-assurance
issues such as wax deposition, hydrate formation, and heavy-oil flow become
very crucial in transportation of gas, oil, and water to processing facilities.
These flow-assurance problems are strongly related to both the hydraulic and
thermal behaviors (such as liquid holdups, local fluid velocities, pressure
gradient, slug characteristics, and convective-heat-transfer coefficients
corresponding to different phases and flow patterns) of the multiphase flow.
Therefore, multiphase hydrodynamics and heat transfer need to be modeled
properly to optimize the design and operation of the flow system.
Compared to experimental and modeling studies of multiphase hydrodynamics,
very limited research results can be found in the open literature for
multiphase heat transfer. Davis et al. (1979) presented a method for predicting
local Nusselt numbers for stratified gas/liquid flow under
turbulent-liquid/turbulent-gas conditions. A mathematical model based on the
analogy between momentum transfer and heat transfer was developed and tested
using heat-transfer and flow-characteristics data taken for air/water flow in a
63.5-mm-inside-diameter (ID) tube.
Shoham et al. (1982) measured heat-transfer characteristics for slug flow in
a horizontal pipe. The time variations of temperature, heat-transfer
coefficients, and heat flux were reported for the different zones of slug flow.
Substantial difference in heat-transfer coefficient was found to exist between
the bottom and top of the slug.
Most previous modeling studies were aimed at developing heat-transfer
correlations for different flow patterns (Knott et al. 1959; Kudirka et al.
1965; Aggour 1978; Shah 1981; Ravipudi and Godbold 1978; Rezkallah and Sims
1987). Kim et al. (1997) evaluated 20 heat-transfer correlations against
experimental data collected from the open literature and made recommendations
for different flow patterns and inclination angles. However, these recommended
correlations did not give satisfactory predictions when compared with
experimental results by Matzain (1999).
Manabe (2001) developed a comprehensive mechanistic model for heat transfer
in gas/liquid pipe flow. The overall performance was better than previous
correlations in comparison with experimental data; however, some
inconsistencies in the hydrodynamic model and the heat-transfer formulations
for stratified (annular) and slug flows need to be improved.
A unified hydrodynamic model has been developed for gas/liquid pipe flow at
the Tulsa U. Fluid Flow Projects (TUFFP) (Zhang et al. 2003a, 2003b). The major
advantage of this model compared with previous mechanistic models is that the
predictions for both flow-pattern transition and flow behavior are incorporated
into a single unified model based on slug dynamics. Multiphase heat transfer
depends on the hydrodynamic behavior of the flow. The objective of this study
is to develop a unified heat-transfer model for gas/liquid pipe flow that is
consistent with the unified hydrodynamic model.
© 2006. Society of Petroleum Engineers
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