During the stable cavitation period, at the inlet the bubble ring reaches the maximum then becomes stable; Cd is determined only by CN, and infinitely close to a constant as pin increases.
The paper deals with the impact of inlet conditions on bubble to slug flow transition in mini systems.
The division of flows in the bed is determined by means of a modified two-phase theory which considers inlet gas jets, bubbles, free of particles, which develop at the top of the jets and grow in size as they rise, and an emulsion phase consisting of particles and the surrounding interstitial gas.
Two inlet conditions, controlled sized bubbles and uncontrolled sized bubbles, are conducted to study the characteristic behaviors of bubbles.
A comparison of the distribution of bubbles with equivalent diameter revealed the inlet mixer's strong impact on bubble size and bubble distribution along the mini-tube and thus, the bubble to slug flow transition.
Models for the assignment of void fraction into the grid, seeding of bubbles at the inlet, pressure change influence on the bubble size and turbulence effects on both phases have been assessed and compared with experiments for an upward vertical pipe scenario.
Also, pressure loss between the shell side outlet and inlet caused by air bubble injection was measured to know the power loss in heat exchangers under enhancement technique.
Based on the experimental data, the influence of mass flow rate and inlet temperature on the bubble behavior along the test section is observed.
The relevant processes, which include the pressure drop at the inlet orifice, nuclei formation, bubble growth inside the expansion chamber, pressure drop at the discharge orifice, the velocity slip between the bubbles and the liquid bulk, and the flow regime (sub- and choked-flow) at the discharge orifice, have been analyzed by using a one-dimensional model approach.
The effective parameters considered for optimization were air inlet velocity, liquid inlet velocity, bubble diameter, and viscosity.
