The main objective of this experimental work is to investigate
the effect of pipe surface roughness on frictional component
of gas-liquid two phase pressure drop. The pressure drop
measurements are carried out with air-water two phase flow in
two different flow loops. First flow loop consists of 12.7 mm
I.D. (smooth pipe), 12.5 mm (rough pipe) while second flow
loop consists of both smooth and rough pipes of 27.8 mm I.D.
The smooth and rough pipes are made up of polycarbonate and
stainless steel material, respectively. Thus, all experiments are
carried out for four different combinations of relative roughness.
The gas and liquid flow rates are varied systematically so as to
generate all key flow patterns observed in two phase flow. Experimental
results show that the increase in the relative roughness
increases the frictional pressure drop as a function of both gas
and liquid flow rates. This effect is substantial for inertia driven
flows (annular flow) compared to bubbly and slug flow patterns.
It is also seen that the effect of increase in relative roughness on
the frictional pressure drop increases with decrease in the pipe
diameter. Moreover, the measurements carried out in 12.7 mm
and 12.5 mm I.D. pipes at upward and downward inclinations
show that the effect of relative roughness on frictional pressure
drop is independent of the pipe inclination. The general trends
of frictional pressure drop for different relative roughness are
found to be in agreement with the experimental observations
reported in literature. Evaluation of the existing two phase flow
models developed for smooth pipes show that these correlations
under predict the frictional pressure drop in rough pipes.
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.