The effect of tube diameter on two-phase flow patterns was investigated in circular tubes with inner diameters of 0.6, 1.2, 1.7, 2.6, and 3.4 mm using air and water. The gas and liquid superficial velocity ranges were 0.01-50 and 0.01-3 m/s, respectively. The gas and liquid flow rates were measured and the two-phase flow pattern images were recorded using high-speed CMOS camera. The flow patterns observed were dispersed bubbly, bubbly, slug, slug-annular, wavy-annular, stratified, and annular flows. These flow patterns were not observed in all the test diameters, but were found to be unique to particular tube diameters, confirming the effect of tube diameter on the flow pattern. The data obtained were compared to existing experimental data and flow regime transition maps which show generally reasonable overall agreement at the larger diameters, but significant differences were observed with the smaller diameter tubes. © 2010 Canadian Society for Chemical Engineering.

Sarit Kumar Das

Department of Mechanical Engineering

Arcot R. Balakrishnan

AIR-WATER SYSTEM

Annular flows

Circular tubes

CMOS CAMERA

Experimental data

FLOW MAPS

FLOW REGIME TRANSITION

GAS AND LIQUID FLOWS

High-speed

Inner diameters

LIQUID SUPERFICIAL VELOCITIES

Micro-tubes

MINI TUBES

Tube diameters

TWO-PHASE FLOW PATTERNS

Liquids

Ternary systems

Tubes (components)

Two phase flow

WATERWORKS

Flow patterns

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Canadian Journal of Chemical Engineering

Geometric parameters of a microchannel such as cross-sectional area, shape and aspect ratio are important factors in determining the two phase flow characteristics. Two phase flow analyses were carried out experimentally for microchannel T-junction geometries at low values of capillary number. Three hydraulic diameters were used, namely 250, 400 and 550 μm, while the aspect ratio was varied between 0.1 to 1. Experiments were performed for the gas volume flow rate ranging from 2 to 30 ml/min while the liquid volume flow rate ranged between 0.1 to 10 ml/min. Slug length was estimated from the processing of high speed images of slug flow and pressure drop was simultaneously recorded. For constant mass flux in rectangular channels, an increase in the aspect ratio leads to an entrapment of continuous phase at the corner. This influences the transport characteristic of such channels. The effects of aspect ratio on slug length and pressure drop are reported. A simplified scaling model based on the geometric parameters of microchannels as well as gas and liquid flux is proposed which agrees reasonably well (within ±15%) with the present experimental data as well as data available in literature. A flow based pressure drop prediction model was developed which agrees well (within ±10%) with the experimentally measured two phase pressure drop. It is believed that a priori information on slug length and pressure drop in a given flow through a microchannel will help to design the flowing system better. © 2018 Elsevier B.V.

Chemical Engineering and Processing - Process Intensification

Effect of geometrical parameters on slug behaviour and two phase pressure drop in microchannel T-junctions

Two-phase flow in parallel minichannels finds a number of applications. Maldistribution between parallel channels reduces both the thermal and fluid-dynamic performances. To reduce the maldistribution effect, it is important to have information about the phase split in individual channels. The present study brings out the effects of various parameters like the channel diameter, number of channels, two-phase flow regimes, and void fraction on the flow split in two-phase flow inside a system of parallel channels for a U-type configuration. Experiments are carried out with the plug and slug regimes typical to minichannel flows. High speed photography is used for flow visualization and the pressure drop values in individual channels are measured with a differential pressure transmitter to quantify maldistribution. The time averaged void fraction is found using an image processing technique. A counterintuitive non-monotonous distribution of the void fraction in the channels brings out the fact that in two-phase flow splitting, the relative distribution of the two phases does not depend on pressure drop alone. Flow configuration and the two-phase flow regime in the header play a key role. An analysis with the existing separated flow model modified for minichannels reveals that although it is possible to estimate the orders of magnitude with respect to splitting, better splitting models still need to be developed. An empirical correlation for variation of the normalized pressure drop in the parallel minichannels, as a function of dimensionless distance along the header, is developed for each of the investigated flow regimes. © 2017 Canadian Society for Chemical Engineering

Experimental investigation on two-phase flow maldistribution in parallel minichannels with U-type configuration

The effect of tube diameter on two-phase frictional pressure drop was investigated in circular tubes with inner diameters of 0.6, 1.2, 1.7, 2.6 and 3.4. mm using air and water. The gas and liquid superficial velocity ranges were 0.01-50. m/s and 0.01-3. m/s, respectively. The gas and liquid flow rates were measured and the two-phase flow pattern images were recorded using high-speed CMOS camera. Unique flow patterns were observed for smaller tube diameters. Pressure drop was measured and compared with various existing models such as homogeneous model and Lockhart-Martinelli model. It appears that the dominant effect of surface tension shrinking the flow stratification in the annular regime is important. It was found that existing models are inadequate in predicting the pressure drop for all the flow regimes visualized. Based on the analysis of present experimental frictional pressure drop data a correlation is proposed for predicting Chisholm parameter " C" in slug annular flow pattern. For all other flow regimes Chisholm's original correlation appears to be adequate except the bubbly flow regime where homogeneous model works well. The modification results in overall mean deviation of pressure drop within 25% for all tube diameters considered. This approach of flow regime based modification of liquid gas interaction parameter appears to be the key to pressure drop prediction in narrow tubes. © 2010 Elsevier Inc.

Experimental Thermal and Fluid Science

Effect of diameter on two-phase pressure drop in narrow tubes

Two phase flows in mini channels occur in many industrial applications such as electronic cooling, compact heat exchangers, compact refrigeration systems and in micro propulsion devices. Due to its significance, research on two phase flow in mini channels has become attractive. However, in recent times a controversy exists whether flow in minichannel is different from macro flow because there are still substantial disagreements among various experimental results. In the present study an experimental investigation is carried out for fluid flow and boiling heat transfer characteristics of mini channels with tube diameters ranging from 1-3mm. The tubes were made of SS with water as the working fluid. The variation in friction factor and Nusselt number with decrease in tube diameter for single phase flow was systematically studied. The point of Onset of Nucelate Boiling (ONB) was identified based on wall temperature profile. The effect of heat flux and mass flux on two phase pressure drop with three different tube diameters during sub cooled boiling were investigated. The results reveal that there is an unmistakable effect of tube diameter on fluid friction and onset of boiling during sub cooled boiling in tubes of mini channel dimensions. © 2010 by ASME.

2010 14th International Heat Transfer Conference, IHTC 14

Fluid flow and boiling heat transfer in mini channels

Artificial Neural Network (ANN) based techniques for the classifications of flow regimes in air-water flow through 1–5 mm tubes are presented. 218 data points are based on the experimental investigation in 3 and 4 mm tubes and 2114 data points from various experimental results from the published literature for airwater two-phase flow in small diameter tubes have been used. Five different well known artificial neural network models have been used to predict the flow regime. The ANN model based on Radial Basis Function and Principal Component Analysis gives better predictability over the other networks used. © Springer India 2015.

Advances in Intelligent Systems and Computing

Flow regime prediction using artificial neural networks for air-water flow through 1â€“5 mm tubes in horizontal plane

Chemical Engineering Science

Flow regimes for adiabatic gas–liquid flow in microchannels

Renewable and Sustainable Energy Reviews

A review of two-phase gas–liquid adiabatic flow characteristics in micro-channels

International Journal of Thermal Sciences

Fundamental data on the gas–liquid two-phase flow in minichannels

Heat Transfer Engineering

State-of-the-Art Overview of Boiling and Two-Phase Flows in Microchannels

Applied Thermal Engineering

Experimental study on two-phase flow and pressure drop in millimeter-size channels

Effect of tube diameter on two-phase flow patterns in mini tubes

Journal	Canadian Journal of Chemical Engineering
ISSN	00084034
Open Access	No