9

CHAPTER 2

LITERATURE REVIEW

2.1 GENERAL

This chapter presents a discussion of the literature studied on

two-phase flow (predominantly liquid-liquid flow and liquid-gas flow), heat

transfer in spiral plate heat exchangers, and thermal modeling of spiral plate

heat exchangers. It summarizes some of the key observations that place the

current work in the context of the literature reviewed.

2.2 LITERATURE STUDIED

There are four broad topics under which the literature studied is

grouped:

• Flow Patterns in Liquid-Liquid Mixtures

• Flow in Liquid-Gas Flows

• Heat Transfer in Liquid-Liquid Mixtures

• Spiral Plate Heat Exchangers

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2.2.1 Flow Patterns in Liquid-Liquid Mixtures

Charles et al. (1966) investigated the Lockhart and Martinelli

parameters, found to be useful in correlating data for stratified flow of two

immiscible liquids in the laminar-turbulent regime. The curves through

liquid-liquid data were available with a maximum deviation of 24%.

They studied water-oil mixtures in a pipeline, measured pressure drop and

flow regimes, and developed correlations.

Schael et al. (1996) studied water-kerosene mixtures in a vertical

pipe and demonstrated the application of a hot-film anemometer for

two-phase flow measurement.

Hewitt (1998) discussed about liquid-liquid flows and their flow

patterns. The predicted pressure drop and holdup in the respective regimes

were also discussed.

Yaws (1999) presented all the properties of pure chemical

substances and developed correlations.

Lum et al. (2004) experimentally studied the flows of

water-exxsol D 140 oil at ±5º inclination and compared with existing

horizontal flow data. The dual continuous regime prevailed at the flow

conditions used and appeared at lower mixture velocities. They measured

pressure gradient, hold up and flow pattern and developed models.

The models used predicted pressure gradient values higher than the

experimental.

Zhao et al. (2006) studied the flow pattern and the process of

formation mechanism of the dispersed phase with dyed deionized

11

water-kerosene in a horizontal rectangular microchannel. The flow patterns

map was correlated by interfacial tension and inertia force and developed

correlations.

Lum et al. (2006) experimentally investigated the effect of

upward and downward inclination during two-phase flow with water-exxsol

D 140 oil in a stainless steel pipe on flow pattern hold up and pressure drop.

A new flow pattern, oil plug flow was found at both +5o and +10º

inclinations.

Rodriguez and Oilemans (2006) conducted two-phase

experiments with water-diesel, water-oil in an slightly inclined steel pipe.

The steady-state data on flow patterns, two-phase pressure gradient and

holdup were obtained and developed models. A stratified wavy flow pattern

with no mixing at the interface was identified in downward and upward

flow.

Domanski and Hermes (2006) experimentally studied R-22 and

R0410a mixtures in a straight tube. They developed a new correlation for

two-phase flow pressure drop in 180º return bends for two refrigerants.

The correlation consisted of a two-phase pressure drop for straight tubes and

a multiplier that accounted for the bend curvature. Buckinham π theorem

was used.

Huang et al. (2007) analyzed water-oil mixtures with an intrusive

method for the measurement of water holdup based on water layer thickness

in horizontal pipes. Four flow patterns with continuous water were reported.

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Kashid and Agar (2007) experimentally studied

water-cyclohexane mixtures in Y-junction and investigated the effect of

various operating conditions on the flow regimes, slug size, interfacial area

and pressure drop. Different Y-junction mixing elements with various

downstream capillaries were used for experiments and developed models.

Salim et al. (2008) studied water-MACROL 82 Mineral oil

mixture in an microchannels of 793 and 667 µm hydraulic diameters made

of quarts and glass. They identified different flow patterns and mapped and

the corresponding two-phase pressure drops were measured. The measured

pressure drops were interpreted using the homogeneous and

Lockhart-Martinelli models for two-phase flows in pipe. They also

developed correlations and models.

Lozano et al. (2008) analyzed the flow between two plates of an

oil-water, water-glycerin in a plate heat exchanger and designed for the

automotive industry. They studied the flow structure using planar laser-

induced fluorescence (PLIF) to visualize and simulated with a CFD code.

Kumara et al. (2009) experimentally studied water-exxsol D60 oil

in horizontal and inclined pipes. They performed experiments at different

mixture velocities and water cuts. The time-averaged cross-sectional

distributions of the oil-water were measured with a traversable single-beam

gamma densitometer. Eight different flow patterns were observed as flow

regimes. The measured water hold-up and pressure drop data were compared

with two simple flow-pattern-dependent models.

Xu et al. (2010) experimentally investigated shell vitre 10 diesel

oil-water mixtures in a acrylic resin pipe and measured pattern transition and

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holdup behaviors. Two-fluid model for stratified flow and the homogeneous

model for dispersed flow were used to predict the flow patterns transition

and water holdup.

2.2.2 Flow in Liquid-Gas Flows

Lockhart and Martinelli et al. (1949) studied air-benzene,

kerosene, water and oil mixtures in a pipe, measured pressure drop and

boiling/ condensing heat transfer calculations. They developed various flow

mechanisms and were correlated. Finally they proposed a correlation for the

isothermal two phase flow.

Chisholm and Laird (1958) conducted experiments with water-air

mixtures in a circular tube and the experimental results were compared with

the Lockhart-Martinelli correlation and Akagawa's correlation and proposed

a correlation obtained by introducing a separated flow model in a rectangular

channel. This correlation gave accurate predictions of the pressure drop.

Ede (1961) predicted the heat transfer coefficient for flow of

water-air in a straight pipe. The pipes were horizontal, of different diameters

from 1.27 to 508 cm with Re numbers 30-100000. The temperature

differences were small. The results for laminar and turbulent flow were

compared with conventional formulae. For laminar flow, considerably

higher than predicted by elementary theory because of natural convection

effects. They also investigated the local heat transfer coefficient.

Koh et al. (1961) experimentally studied water-air in a tube and

investigated the effects of the interfacial shear on heat transfer for Prandtl

numbers of ten or greater.

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Emerson (1963) illuminated water-air mixtures in baffle type heat

exchanger, measured flow rate, pressure drop and heat transfer. They also

developed empirical correlations.

Plecher and McManus (1968) experimentally studied water-air

mixtures in a horizontal annular pipe and measured pressure drop and wall

temperature. They analysed sizeable circumferential variations in tube wall

temperatures at low air flow rates. The pressure drop data agreed well with

the Lockhart-Martinelli correlation.

Vermeulen and Ryan (1971) studied water-air mixtures in a

horizontal and inclined tube and developed a semi empirical theory based on

a simple model. The characteristics of flow, pressure fluctuations, slug

velocity and frequency were studied. They also developed correlations.

A comparison of the prediction of the theory and two published correlations

showed that the proposed theory showed better agreement with the data.

Frisk and Davis (1972) experimentally studied water-air

two-phase flow mixtures in a flat plate and investigated the effects of

different flow regimes on the effectiveness of the heat transfer. The results

for smooth liquid film flow and two-dimensional wavy flow of the liquid

phase shown to agree with the theoretical analysis of heat transfer to smooth

films.

Agarwal et al. (1973) studied light oil-gas mixtures in a pipe,

measured pressure drop, liquid volume fraction and flow pattern.

They developed equation to describe the stratified cocurrent flow of

gas-liquid mixtures in 101 ft long acrylic pipe. The pressure drop and

average in situ liquid volume fraction presented as a function of the

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superficial gas velocity and compared with predicted results. The visual

observation of flow patterns and their transitions indicated on the tentative

flow pattern map of Govier and Aziz.

Spedding and Nguyen (1980) experimentally studied water-air

mixtures in a tube, measured volumetric ratio and flow regime map.

They developed flow regime mapping for conditions from vertically

downward flow to vertically upward flow.

Chung and Olafsson (1984) experimentally investigated water-air

mixtures in a tube, measured radiation heat transfer, vapour droplet and wall

temperature. They developed a model for non-linear energy equation of the

vapor phase with droplets and also solved numerically.

Ho et al. (1995) experimentally investigated water-air mixtures in

a spiral coil heat exchanger, measured flow rate and temperature differences.

They developed two theoretical models to predict the performance of heat

exchanger, based upon unmixed and mixed air-flow considerations.

The results of experimental studies on a laboratory model, well agreed with

the predicted performance of the theoretical models.

Awwad et al. (1995) studied water-air mixtures in a horizontally

helicoidal pipe, measured pressure drop and developed correlations.

Fourar and Bories (1995) experimentally investigated water-air

mixtures in a artificial horizontal fracture channels, measured pressure drop

and liquid volume fraction and reported the Lockhart and Matinelli model

predicted a good fit.

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Awwad et al. (2000) studied the experiments in horizontal

helicoidal pipes with air-water system. It was found that the pressure drop

multiplier relates strongly to the superficial velocities of air or water, and

that the helix angle had almost no effect on the pressure drop, correlation for

two-phase flow in the horizontal helicoidal pipes also established based on

the experimental data.

Rezkallah and Zhao (1995) experimentally studied water-air,

glycerin-air mixtures in a tube, measured two-phase patterns. They analyzed

the two-phase flow under reduced gravity and classified into four flow

patterns viz., bubbly, slug, frothy slug-annular and annular flow.

Wijeysundera et al. (1996) experimentally studied the flow of

cold water-air mixtures in a spiral coil heat exchanger, measured flow rate

and temperature differences. They obtained an expression for the

effectiveness. They conducted an experimental study in a closed-loop test

set-up. The computed effectiveness agreed well with the measured values

Rahman et al. (1996) studied water-air mixtures in a tube of

horizontal in-line and staggered bundles. They experimentally determined

the interfacial friction data from pressure drop, void fraction and mass flux

in horizontal tube and developed correlations.

Boomkamp and Miesen (1996) studied parallel two-phase flow of

water-air mixtures in a tube, measured stratified flow, two-phase flow, and

linear stability. They developed a classification scheme for the various

instabilities arising in parallel two-phase flow. They modified the original

Kelvin-Helmholtz model to allow for variation in the fluid velocities with

distance from the interface.

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Ohnuki and Akimoto (1996) experimentally studied on

developing two-phase flow with water-air mixtures in a large vertical pipe

with the effect of air injection method. They obtained different flow

structure range of bubbly to slug flow.

Mishima and Hibiki (1996) experimentally investigated the

characteristics of two-phase flow of water-air mixtures in a vertical tube.

They observed different flow regimes. The overall trends of the boundaries

between flow regimes were predicted well by Mishima-Ishii's model.

The rise velocity of the slug bubbles was also correlated well by the drift

flux equation.

Xin et al. (1997) experimentally studied water-air mixtures in a

annular helicoidal pipes. They performed the experiments for superficial

water Reynolds in the range of 210 to 23,000 and superficial air Reynolds

Numbers in the range of 30 to 30,000. The effects of coil geometry and the

flow rates of air and water were experimentally investigated.

They developed a correlation for friction factor in different flow regimes.

Schmidt et al. (1997) studied mixtures of air and water, aqueous

glycerol, watery calcium nitrate and Freon 12 in a tube, measured pressure

drop. They introduced a new model to calculate the two-phase pressure drop

across a sudden contraction in a duct area.

Samways et al. (1997) experimentally studied water-air mixtures

in a vertical test section tube, measured hydrodynamic pressure and flow

patterns. They established both experimentally and theoretically that the

dispersed phase created low fluctuating hydrodynamic pressures.

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Ghiaasiaan et al. (1997) studied air-water, air-mineral oil and

air-paraffinic oil mixtures and experimentally investigated the flow patterns,

countercurrent flow limitation (flooding) and gas hold-up (void fraction) for

countercurrent flow in vertical and inclined channels and developed

correlations.

Fore et al. (1997) experimentally studied air-water and 50%

aqueous glycerin mixtures in a tube. They found the enhancement of the

heat transfer coefficient over single-phase liquid flow, increased with

increasing void fraction and were to some extent larger for 50% glycerin

solution than for water and developed correlations.

Alcock and Webb (1997) studied steam-air mixtures in an

industrial shell and tube heat exchanger, measured and analyzed the

performance of the heat exchanger for step changes in five key parameters

such as the inlet pressure, steam flow rate, air flow rate, coolant flow rate

and coolant inlet temperature.

Xu et al. (1998) experimentally studied the hydrodynamics of

two-phase flow in water-air mixtures in vertical-up and down-flow across a

horizontal tube bundle, measured void fraction, pressure drop and flow

pattern maps. They obtained flow patterns in the cross-flow zones and

constructed flow pattern maps. The data of average void fraction were

well-correlated in terms of the Martinelli parameter and Froude Number.

The two-phase friction multiplier was well correlated with the Martinelli

parameter.

Xu et al. (1999) experimentally investigated water-air mixtures in

a rectangular channel and observed the gas-liquid two-phase flow regimes

19

with mini/micro gap using a CCD camera and identified by examining the

video images.

Triplett et al. (1999) investigated water-air mixtures in a circular

microchannel. The overall flow patterns and flow pattern maps using gas

and liquid superficial velocities as coordinates were similar for all the test

sections. The visible flow patterns were bubbly, churn, slug, slug-annular

and annular.

Triplett et al. (1999) studied water-air mixtures in horizontal

micro-channels, measured two-phase friction factor and flow regimes.

They presented two-phase friction factor based on the homogeneous mixture

assumption provided the best agreement with the experimental data for

bubbly and slug flow patterns. It was compared with relevant flow regime

transition models and correlations.

Noghrehkar et al. (1999) studied water-air mixtures in a tube

bundles in a vertical upward flow. They also studied the use of probability

density function (PDF) of local void fraction to identify two-phase flow

regimes and constructed flow regime maps.

Yan Yi-Yie et al. (1999) studied the condensation heat transfer

and pressure drop of refrigerant R-134a liquid and vapour phases in a

vertical plate heat exchanger, measured vapour quality, pressure, friction

factor and heat flux, and developed correlations. The correlations were

provided for the measured heat transfer coefficients and pressure drops in

terms of the Nusselt Number and friction factor.

Wolk et al. (2000) carried out the experimental study for

air-water two-phase mixtures in one circular tube and four different

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non-circular channels, measured flow pattern and flow pattern map, and

developed correlations.

Narrow et al. (2000) experimentally investigated the two-phase

flow water-air mixtures with six distinct flow patterns such as bubbly,

plug/slug, froth, stratified-intermittent, annular-intermittent and annular in a

horizontal micro-rod bundle. The other flow patterns namely, complete

stratification, in individual sub channels did not occur. The frictional

pressure drops were strongly dependent on flow pattern.

Jaberi and Mashayek (2000) experimentally studied the

two-phase turbulent flow. The results indicated, the variance of the fluid and

particle temperatures, the dissipation rate of the fluid temperature and the

high wave number values of the fluid temperature spectrum were increased

as the magnitude of turbulence increases.

Gradeck and Lebouche (2000) experimentally investigated the

flow of two-phase water-nitrogen gas mixtures in horizontal corrugated

channels. The analysis revealed a flow structure modification from

monophonic to two-phase flow.

Bao et al. (2000) studied the experiments of two-phase

non-boiling water-air mixtures in a narrow conduit, measured pressure drop,

gas superficial velocity and liquid superficial velocity and wall heat flux,

and developed correlations. The pressure drops in these adiabatic non-

boiling two-phase flows estimated with good accuracy.

Badie et al. (2000) experimentally studied water-air and oil-air

mixtures in a horizontal pipe, and measured pressure gradient and gas hold

up. They studied the addition of very small liquid flow and was found to

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result in a considerable increase in the pressure gradient compared with

single phase gas flow. The pressure gradient and the holdup data were

compared with predictions of the apparent rough surface and the

‘double-circle’ models.

Zhao and Bi (2001) experimentally investigated air-water

mixtures in vertical equilateral triangular channels with various hydraulic

diameters. The flow regimes were identified by both visual observations and

using a high speed motion analyzer and also measured pressure drop.

The results showed various typical flow patterns in the conventional, large

sized vertical tubes, such as bubbly flow, slug flow, churn flow and annular

flow were also observed. The flow regime transition boundaries were

compared with relevant flow regime models.

Guo et al. (2001) experimentally studied water-steam mixtures in

a helically coiled tube, measured pressure drop, and developed correlations.

The pressure drop oscillation in various steam generator inclinations showed

the influence of oscillating boundaries on gravity.

Kim et al. (2001) experimentally studied the two-phase flow of

commercial water-air in a vertical round tube with wire coil inserts.

The flow pattern and slug rise velocity measured visually with a video

camera. The void fraction measured by the quick-closing valve method.

By introducing a simple assumption on considering the effective flowing

area, the measured void fractions in a wire-coil inserted tube were in

relatively good agreement with the predicted result based on the drift flux

model

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Ju Lee and Yong Lee (2001) studied water-air mixtures in a

rectangular channel with small gaps, measured mass flux, gas size and

two-phase pressure drop, and developed correlations. They developed a

correlation for pressure drop characteristics of two-phase flow and the

two-phase frictional multiplier expressed using the Lockhart-Martinelli type

correlation but with the modification of parameter C. The correlations with

the modified C successfully covered wide ranges of the Martinelli parameter

and liquid Reynolds Number based on the hydraulic diameter with a

deviation of ± 10 %.

Zhao and Bi (2001) experimentally studied and presented for the

gas velocity, the void fraction, and the pressure drop of upward co-current

air-water mixtures through a vertical miniature triangular channels.

A correlation was developed for predicting pressure drop of single-phase

laminar and turbulent flow. Their work the pressure drop of two-phase row

was well predicted by Lockhart-Martinelli correlation.

Scott Downing and Kojasoy (2002) experimentally investigated

the single-phase and two-phase flow pressure drop and heat transfer

characteristics with refrigerant R134a and its vapour. The effect of curvature

on these parameters was analyzed in relation to miniature channels.

The results were correlated to appropriate parameters of helical channels of

different curvatures. They presented the pressure drop results for single and

two-phase flow in linear and curvilinear passages.

Qu and Mudawar (2002) discussed several aspects of fluid flow

and heat transfer in two-phase R-113 and FC-72 or deionized water mixtures

in a micro-channel heat sink. They obtained correlations to predict

23

two-phase pressure drop and saturated convective boiling heat transfer in

micro-channel heat sinks.

Vlasogiannis et al. (2002) experimentally studied water-air

mixtures in a spiral plate heat exchanger. They recorded various visual

observations by a high-speed video camera for the construction of a flow

regime map. They also measured the heat transfer coefficient of the air/water

stream as a function of air and water superficial velocities.

Rani Hemamalini and Sundaram (2002) experimentally

investigated air-water, air-palm oil, air-kerosene mixtures in a horizontal

pipe, measured visual observations and construction of flow regime map.

The findings showed Lockhart-Martinelli parameter decreased with quality.

Guo et al. (2002) experimentally investigated water-steam

mixtures in a closed-circulation helical-coiled tube steam generator.

They examined the non-uniform property of local heat transfer with steady

flow. They reported the pressure drop type oscillations and their threshold

for steam-water two-phase flow in a uniformly helical tube.

Guo et al. (2002) conducted a linear instability analysis on the

interface of a stratified gas-liquid two-phase flow in a circular pipe

employing a two-fluid model. They investigated the effects of flow rates of

gas and liquid, liquid viscosity, surface tension and tube inclination on the

stability of interface, and developed correlations.

Kawahara et al. (2002) experimentally studied water-nitrogen

mixtures in a circular tube. They studied the two-phase flow patterns by

video recording. The flow was in the transparent silica capillary tube, and

developed correlations.

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Yu et al. (2002) studied water-vapour mixtures in a small

horizontal tube, measured two-phase pressure drop, boiling heat transfer and

critical heat flux. They presented the experimental results and compared

with recent predictive correlations. They made modifications to the

Chisholm two-phase multiplier correlation and to the Argonne National

Laboratory small-channel boiling heat transfer correlation for better

representation of the experimental data.

Park and Kang (2002) investigated the heat transfer

characteristics of FC-72 (C6F14) in liquid and vapor form mixtures in a

two-phase closed thermo siphon, measured the heat transfer characteristics.

The condenser heat transfer coefficients showed some increase with the

increase of fill charge ratio by the expanded working fluid pool.

Agostini et al. (2002) conducted an experimental study with

R134a along with its vapour in a flat aluminum multi port extruded tube,

measured friction factor and heat transfer coefficient. They compared their

results with the literature for conventional tubes and mini-channels and

discussed.

Naphon and Wongwises (2003) studied water-air mixtures in a

spiral-coil finned tube heat exchangers, measured water flow rate, air inlet

temperature and humidity efficiency. They investigated the performance of

heat transfer characteristics and derived a mathematical model by including

fin efficiency. They discussed the effects of various inlet conditions of

fluids.

Wang et al. (2003) studied water-air mixtures in a T-junction and

analyzed several measurement methods to analyze differential pressure

25

fluctuations of two-phase flow through a T- junction. They investigated

three kinds of flow pattern including bubble flow, churn flow and annular

flow in the inlet tube. The two-phase flow splitting at a T-junction was a

complicated non-linear dynamic system.

Hibiki and Ishin (2003) studied water-air mixtures in a large

diameter pipe, measured distribution parameter and drift velocity for vertical

upward two phase flow. They developed two types of inlet-flow regime

dependent drift-flux correlations for two-phase flow.

Rani Hemamalini and Sundaram (2003) experimentally studied

air-liquid mixture two-phase mixtures in a horizontal pipe. They determined

pressure drop for air-kerosene and air-diesel system and also determined

two-phase flow parameters namely quality, two-phase multiplier and

Lockhart-Martinelli parameter. They developed a correlation between L-M

parameter and two-phase multiplier.

Zhao et al. (2003) experimentally studied steam-water mixtures

in a horizontal helically coiled tube, measured frictional pressure drop,

boiling heat transfer, mass flux and heat flux. They obtained a new

two-phase frictional pressure drop correlation from the experimental data

using Chisholm’s B-coefficient method. They found boiling heat transfer,

was dependent on both mass flux and heat flux.

Goda et al. (2003) studied water-air mixtures in a tube, measured

distribution parameter and drift velocity for downward two-phase flow.

The consecutive equations specified the distribution parameter in the

downward flow derived by taking into account the effect of the downward

mixture volumetric flux on the phase distribution.

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Hetsroni et al. (2003) studied water-air and water-steam mixtures

in a parallel triangular microchannels, measured temperature, gas hold up

and flow pattern. They reported the results for holdup as a function of flow

rates, flow pattern and pipe inclinations. They compared various techniques

for measuring holdup and discussed. They also compared the flow pattern

and shut-in holdup with the predictions of a mechanistic model. The results

showed close agreement between observed and predicted flow pattern and a

reasonable level of agreement in holdup.

Oddie et al. (2003) experimentally investigated the flow of

two-phase and three phase flow in an inclined pipe. They conducted

steady-state and transient experiments of oil-water, oil-kerosene, oil-tap

water and oil-nitrogen multiphase flows. They reported the extensive results

for holdup as a function of flow rates, flow pattern and pipe inclinations.

They compared various techniques for measuring holdup and also compared

the flow pattern and shut-in holdup with the predictions of a mechanistic

model.

Weilin and Mudawar (2003) studied water-vapour mixtures in a

micro-channel heat sink, measured pressure drop, critical heat flux and

hydrodynamic instability, and developed correlations. They identified two

types of two-phase hydrodynamic instability. They identified severe

pressure drop oscillation could trigger pre-mature critical heat flux and

eliminated simply by throttling the flow upstream of the heat sink.

Zhao et al. (2004) experimentally studied and presented a new set

of experimental data for air-water flow patterns in a channel with a cross

section of 1x1 mm2 with different ranges of gas and liquid superficial

velocities. They observed different flow patterns. The Bond Number was in

27

the same order for the experimental data obtained from microgravity

experiments.

Yang et al. (2004) experimentally studied water-air two-phase

flow patterns in a miniature square channel. They identified the flow

patterns in both vertical upward and horizontal flows using a high-speed

motion analyzer. The visualization showed the typical flow pattern

encountered were bubbly flow, plug flow, slug flow and annular flow.

They found four transitional flow patterns such as bubbly-plug flow,

bubbly-slug flow, plug-slug flow and slug-annular flow. They also presented

the flow regime maps for various liquid volumetric fluxes in terms of the

mass quality and volumetric flux of gas phase.

Rogak and Faraji (2004) experimentally studied water-oxygen

mixtures in a horizontal, smooth, electrically-heated tube, measured constant

pressure heat capacity and forced convection heat transfer coefficient.

The magnitude and temperature for the peak heat transfer decreased, was

consistent with changes in the heat capacity.

Vist and Pettersen (2004) conducted an experimental study with

Refrigerant R134a and its vapour in a compact heat exchanger manifolds,

measured two-phase flow distribution, electrical input, evaporator heat and

mass flow rate.

Rani Hemamalini et al. (2005) experimentally studied palm

oil-air mixtures in a horizontal pipe, measured pressure drop and volume

fraction. They studied the effect of two-phase flow on pressure drop across

the control valve for different volume fractions of the fluids.

28

The Lockhart-Martini parameter and the quality were found to correlate well

with the two-phase multiplier, based on pressure drop with gas phase.

Hetsroni et al. (2005) experimentally investigated water, R-134a,

methanol, isopropanol-air, N2, He, Ar in a circular, rectangular, trapezoidal

and triangular micro-channels. They analyzed the pressure drop in different

channels with hydrodynamic diameter ranging from 1.01 µm to 4010 µm.

For each flow, they considered the Reynold`s Number and compared with

the predictions of the conventional theory with the experimental data.

Saravanan (2005) studied mixtures of air with kerosene, palm oil,

diesel and caster oile mixtures in a 1-2 shell and tube heat exchanger and

stabilized correlations between heat transfer coefficient, two phase

multiplier, L-M parameter and quality. These correlations were useful in

finding out the heat transfer coefficients for two phase flows from pure

phase fluid properties.

Wang et al. (2005) experimentally studied water-air mixtures slug

flow in a small diameter tubes in the presence of vertical U-type return

bends. They proposed dimensionless correlations for upward and downward

flows and described the variation in the translational velocity.

Shen et al. (2005) studied water-air mixtures in a vertical large

diameter pipe, measured flow conditions, phase distribution patters, void

fraction and bubble size. They also studied the experimental and theoretical

flow conditions. They suggested two basic phase distribution patterns in the

vertical large diameter pipe were namely, wall peak and core peak.

Lee and Mudawar (2005) explained the predictions of the

homogeneous equilibrium flow model and prior separated flow models.

29

The correlations yielded relatively poor predictions of pressure drop.

They suggested a new correlation scheme, incorporated the effect of liquid

viscosity and surface tension in the separated flow model.

Wongwises and Naphon (2006) conducted experiments with

water-air mixtures in a spirally coiled finned tube under dehumidifying

conditions. They also measured mass flow rate, temperature, enthalpy

effectiveness and humidity effectiveness. They developed a mathematical

model to simulate the flow and heat transfer characteristics of working

fluids. The model showed reasonable agreement with the experimental data.

Palm and Claesson (2006) described the design of plate heat

exchangers and the connection between the geometric parameters and their

thermal and hydraulic performance, in single phase flow and in flow boiling.

They measured pressure drop, heat flux, and flow boiling and heat transfer

performance and developed correlations. They correlated the heat transfer

performance by pool boiling correlations.

Kim and Sin et al. (2006) experimentally studied the air-water

flow distribution and the effects of tube outlet direction, tube protrusion

depth, mass flux and quality in a parallel flow heat exchanger.

The explanations were provided based on the flow visualization.

Saravanan et al. (2006) experimentally studied the gas-gas,

two-phase flow in 1-2 shell and tube heat exchanger. The experimental

results showed the two phase multiplier, increased with quality, quality

increased with heat transfer coefficient and the two phase multiplier

decreased with the increase in L-M parameter. They developed a correlation

between L-M parameter and two phase multiplier.

30

Kabiri-Samani et al. (2007) studied the experiments of two-phase

flow with water-air mixtures in a horizontal and inclined pipeline.

They studied the pressure fluctuations inside a circular, horizontal and

inclined pipe (90 mm inside diameter and 10 m long) carrying air-water slug

flow based on an experimental model. They presented, the forecasting

pressure as a function of flow characteristics, pipe, pipe geometry,

longitudinal and cross-section positions and head water.

Park and Hrnjak (2007) investigated the flow boiling heat transfer

coefficient, pressure drop, and flow pattern in the horizontal smooth tube for

CO2 and R410A and R22 mixtures. They described the relation between

pressure drop and properties for each refrigerant by applying the

Muller-Steinhagen and Heck correlation.

Hrnjak and Tu (2007) studied the single phase pressure drop in

microchannels. In their experiments, they used R134a liquid and vapour as

the testing fluids. The Reynolds Numbers varied between 112 and 9180.

They used pressure drop data to characterize the friction factor in different

flow regimes. For low surface roughness, both the laminar friction factor

and the critical Reynolds Number approached the conventional values and

there was no indication of deviation from the Navier-Stokes flow theory.

Vijayarangan et al. (2007) studied R-134a liquid-vapour mixtures

in a vertical tube, measured mass flux, fluid temperature, vapour

temperature, flow pattern, pressure gradient and void fraction.

They developed a flow pattern-based model for the prediction of the

pressure.

31

Marchitto et al. (2008) studied water-air mixtures in compact heat

exchangers, measured flow distribution and void fraction. They analyzed the

two-phase distributions in a cylindrical horizontal headed supplying 16

vertical channels for upward flow. They studied time varying, void fraction

data with video records of different flow patterns.

Oriol et al. (2008) studied water-air mixtures in a tube, measured

void fraction, axial dispersion; velocity and trace response. They designed

and tested a photo attenuation technique for the non-intrusive two-phase

flows characterization. They used designed sensor to characterize the flow

behavoiur in horizontal and vertical tubes. The Peclet Number showed a

huge variation with increasing of superficial gas velocity.

Shannak (2008) experimentally studied water-air mixtures and

developed a new prediction model for frictional pressure drop of two-phase

flow in pipes. The results demonstrated the frictional pressure drop

increased with increasing relative roughness of the pipe. The model defined

a new definition of the Reynolds Number and friction factor of two-phase

flow. The proposed model fit the presented experimental data very well, for

vertical, horizontal, smooth and rough pipes.

Vashisth and Nigam (2009) investigated the local variables and

interfacial phenomena for water-air mixtures in a coiled tube. They carried

out 3D CFD simulations using volume of fluid approach to predict the

development of velocity fields, local and average friction factor, interfacial

friction factor, phase distribution and entry length using a commercial CFD

package.

32

Bhramara et al. (2009) studied refrigerants R22, R134a and

R407C and its vapor mixtures in a horizontal pipe. Using FLUENT, they

modeled single component and two-phase flow. They evaluated the average

properties of the refrigerants using homogeneous model for each quality.

Lima et al. (2009) investigated ammonia liquid (R7117) and gas

mixtures in a tube. They described the flow patterns observed during their

study were stratified-wavy, slug-stratified-wavy, slug, intermittent and

annular. They compared the flow structure observations against the

predictions of the flow pattern map model of Wojtan et al.

The experimental results showed the traditional pressure drop trends.

Kabiri-Samani and Borghei (2010) experimentally investigated

the two-phase water-air slug flow to study the frictional pressure loss in a

circular pipeline. The experimental results of pressure loss for different

hydraulic and geometric properties indicated Weber Number (We), Froude

Number (Fr), and air concentration parameters affecting the pressure loss

and developed correlations and models.

Zhang et al. (2010) studied water-air mixtures in a mini-channel.

They developed alternative correlations of two-phase friction pressure drop

and void fraction based on the separated flow model and drift-flux model.

They applied the artificial neural network and picked out the dominant

parameters to correlate the two-phase friction multiplier and void fraction.

The non-dimensional Laplace constant was a main parameter to correlate the

Chisholm parameter as well as the distribution parameter

Muzychka and Awad (2010) investigated water-air mixtures in a

pipe. They examined the two-phase flow pressure drop from the point of

33

view of asymptotic modeling and developed an alternative approach for

predicting two phase flow pressure drop using superposition of three

pressure gradients. They modeled the interfacial pressure drop for each type

of flow regime.

2.2.3 Heat Transfer in Liquid-Liquid Mixtures

Grover and Knudsen (1955) studied liquid-liquid immiscible

mixtures in a pipe and injected in various ways. They observed the overall

heat transfer coefficient depended on the total mass flow rate but it was

independent of dispersed-phase volume fraction and inlet temperature.

They described, it was difficult to evaluate because the liquids were in

turbulent and mixed in the entrance region and only separate out later,

depending on the injection method.

Gollan and Sideman (1970) experimentally illuminated fluid flow

of water in an inclined plane and observed the direct contact heat transfer

with change of phase and measured heat transfer coefficients for stratified

laminar flow down in an inclined plane.

Somer et al. (1973) studied the heat transfer between immiscible

liquid mixtures in direct contact. They studied heat transfer to an immiscible

liquid mixture for desalination of sea water, with the mineral oil Energol

WM-2. They studied three regimes, namely, heat transfer to individual water

drops, heat transfer to immiscible liquids in cocurrent turbulent flow without

phase change, and heat transfer to immiscible liquids in cocurrent laminar

and turbulent flow with evaporation of water. They measured pressure drop

and estimated Fanning friction factor, and fit a correlation between Nusselt

Number, Reynolds Number and Prandtl Number.

34

Shahidi and Ozbelge (1995) investigated the direct contact heat

transfer between two immiscible liquids of water-oil under non-boiling

conditions in co-current turbulent flow through a horizontal concentric

annulus. They determined the overall volumetric heat transfer coefficient

and increased with increasing dispersed phase volume fraction at each

constant mixture velocity. They obtained an empirical expression for the

volumetric heat transfer coefficient within the ranges of the experimental

parameters.

Lang and Auracher (1996) experimentally studied the phase

distribution and heat transfer in n-heptane-water mixture flowing upward in

a vertical tube, for different volumetric fractions of n-heptane, inlet

velocities and inlet temperatures, measured phase distribution.

They observed an abrupt change in the heat transfer from water-dominated

heat transfer to n-heptane-dominated heat transfer at n-heptane volume

fractions between 0.6 and 0.7.

Farrar and Brunn (1996) studied water-kerosene mixtures in a

vertical pipe flow and demonstrated the application of a hot-film

anemometer for two-phase flow measurement.

Ha et al. (2004) studied the two-phase natural circulation flow

through the annular gap between a reactor vessel and insulation system.

The measured the liquid mass flow rates driven by the natural circulation

loop by varying the wall heat flux, upper slot area and water head condition.

The simple loop analytical results shown the natural circulation mass flow

rates between the reactor vessel wall and the insulation qualitatively agreed

with the experimental one as the wall heat flux increased.

35

Ramachandran et al. (2006) experimentally studied

water-dodecane mixtures in a spiral plate heat exchanger, measured flow

rate and mass fraction. They developed a correlation between the two-phase

multiplier and Lockhart-Martinelli parameter, to predict two-phase heat

transfer coefficients, helps to optimally design the heat exchanger.

The experimental studies were in laminar range. They related the two phase

heat transfer coefficients with Reynolds Numbers and fitted into a relation in

the form h = a Rem

.

Ramachandran et al. (2006) experimentally investigated the heat

transfer correlations for a two-phase system in a compact heat exchanger.

The experimental studies were in laminar range with hot water and mixture

of water-nitrobenzene in different mass fractions. They correlated the

experimental heat transfer coefficients on the process side with Reynolds

Numbers and fitted into an equation. They correlated the two-phase

multiplier with the Lockhart-Martinelli parameter.

Wang et al. (2008) studied heat transfer micro-dispersing hot

octane and hexane into cold water, by cross flow of the oil phase into water

through a membrane, measured Murphree efficiency, oil volumetric fraction

and Ca Number, and developed correlations and models. They observed the

significant enhancement in heat transfer due to dispersion with up to 15-20

increased in volumetric heat transfer coefficients compared to conventional

dispersed system.

Ramachandran et al. (2008) experimentally investigated the heat

transfer coefficients in a spiral plate heat exchanger. They related the heat

transfer coefficients to the quality of the two-phase systems.

The correlations between quality and L-M parameter showed a good

36

agreement with experimental data and used for the prediction of two phase

heat transfer coefficients and were useful in the design of heat exchangers

for two-phase flow in the Reynolds Numbers and temperature ranges

investigated.

Habchi et al. (2009) studied the heat transfer in liquid-liquid

system and the study focused on water-oil dispersions produced by

continuous water injection into a main oil flow, for small Dean Numbers.

The chaotic advection generated in twisted pipe, produced smaller and more

homogeneous droplets than a helically coiled mixer.

Habchi et al. (2009) examined the liquid-liquid dispersion,

droplets formation and breakup, and direct-contact heat transfer between

immiscible liquids by facilitating mixing in straight flow, helically-coiled

flow and twisted-pipe flow. They introduced n-butanol in calculated

quantities to modify the organic phase-oil and observed the reduction of

continuous phase viscosity, intensified the emulsification process, and

enhanced mass transfer as well as provided a smaller droplet size

distribution than in regular Dean Flow.

Lemenand et al. (2010) studied water-mineral oil mixtures in a

direct-contact heat exchanger, measured the heat transfer enhancement,

turbulent mixing and high efficiency vortex. They developed a

phenomenological model for heat transfer and validated with experimental

data and identified the longitudinal embedded vortices as the main

intensification factor for heat transfer.

Janes et al. (2010) studied the heat transfer in both gas-liqiud and

liquid-liquid two-phase plug flow systems with water-air, oil-air and

37

oil-water mixtures in mini-channel heat sinks. In spiral plate heat

exchangers, the changes in flow patterns from smoothly stratified flow to

more mixed flow were expected at lower velocities, resulting in enhanced

heat transfer even at low velocities and developed correlations.

Asthana et al. (2011) conducted experimental studies for

convective heat transfer in serpentine microchannels with segmented

water-mineral oil mixtures. The significant Nusselt Number enhancement in

microchannel heat sinks compared to that obtained using single phase liquid

cooling. They employed Laser Induced Fluorescence (LIF) to measure

temperature of the coolant with and without droplets, and micro-PIV used to

determine velocity field. They observed the increase of the Nusselt Number

up to four fold and compared to pure water flow.

2.2.4 Spiral Plate Heat Exchangers

Wen-Jei Yang (1964) investigated theoretically for

incompressible viscous fluids in logarithmic spiral channel. The various

parameters like velocity, temperature and concentration profiles were

calculated. Numerical results were obtained for shear stress and the rates of

heat and mass transfer at the channel walls.

Minton (1970) studied the theoretical investigations in a spiral

plate heat exchanger, measured the heat transfer coefficient, friction factor

and pressure drop. They also developed empirical correlations.

Chowdhury et al. (1985) conducted analytical studies on the

temperature distribution in a spiral plate heat exchanger. A countercurrent

cascade of n concurrent heat exchangers (n = number of turns of the spiral

exchanger) was a useful approximation for the thermal behavior of spiral

38

exchangers and derived straightforward formulae for LMTD correction

factor and temperature profile for balanced countercurrent heat exchanger

(equal heat capacities) and generalized the model for other heat capacity

ratios. They found a physical model and represented the overall behavior of

a spiral plate heat exchanger.

Xuan et al. (1991) developed a thermal analysis of shell and tube

exchangers. They derived temperature equations and used for the calculation

of thermal effectiveness, mean temperature difference, correction factor and

the temperature at a given location on the exchanger surface and developed

correlations..

Martin (1992) studied the influence of flow configuration in a

spiral plate heat exchangers, measured temperature profile, mean

temperature difference, pressure drop and heat transfer. They proposed

algorithms for designing spiral plate heat exchangers.

Bes and Roetzel (1992) developed an analytical method for the

calculation of thermal changes in countercurrent flow in a spiral plate heat

exchanger. They measured the thermal changes in countercurrent flow and

investigated the influence of various geometrical parameters and were more

accurate.

Bes and Roetzel (1993) developed simple, approximate analytical

expressions to examine heat transfer in a counter flow spiral plate heat

exchanger. They proposed a new criterion number, based on which they

estimated the LMTD correction factor for the exchanger geometry.

They developed expressions for thermal effectiveness as a function of NTU

for spiral exchangers.

39

Devois et al. (1995) developed a thermal modeling of the heat

exchanges in both steady-state and time dependent cases with 2D spiral

geometry, allowing computation with different materials, forced convective

heat transfer models in turbulent flow and geometrical parameters options.

They also performed numerical simulations on a spiral mesh.

Manglik and Bergles (1995) studied single phase and developed

heat transfer and pressure drop correlations for the rectangular offset strip fin

compact heat exchanger. A rational design equation for f and j were

presented in the form of single continuous expressions covering the laminar,

transition, and turbulent flow regimes.

Zhang et al. (1996) developed and implemented an accurate

computational method for the calculation of flow and heat transfer in

compact heat exchangers and developed correlations.

Wang et al. (1998) conducted experiments with water, activated

carbon-methanol system in a spiral plate heat exchanger for adsorption

refrigeration system. The expected ice making power density per kg

adsorbent was further improved.

Kapur and Meloy (1998) examined the model of the working of a

spiral with various parameters and assumed the particles eventually attain

dynamic equilibrium in the forward longitudinal direction and static

equilibrium in the transverse direction. The model reflected the present

empirical spiral design philosophy for treating different feeds.

Perry (1998) represented a correlation for spiral plate heat

exchangers. The heat transfer coefficient was calculated using an appropriate

40

correlation for spiral plate heat exchangers as

( ) ( )17.0

w

25.08.0PrRe0315.0Nu

µµ

= .

Strelow (1999) reviewed and developed a general calculation

method for plate heat exchangers and developed correlations.

Marcus Reppich (1999) conducted a literature survey and

reviewed the usage of plate heat exchangers in chemical process industries.

Naphon and Wongwises (2002) studied heat transfer with

water-air mixtures in spirally coiled tubes of different curvature ratios under

cooling and dehumidifying conditions, with constant wall temperature and

constant radius examined for temperature profiles, heat transfer rate, heat

transfer coefficients and pressure drops. They compared the results with

those calculated from correlations available in the literature. They developed

a new correlation.

Dongwu (2003) developed geometric calculations for the spiral

heat exchanger. They modeled a spiral plate heat exchanger as semi-circled

spirals, i.e., two spirals generated by splitting sets of concentric circles along

any diametric axis, and displacing the center of one of the set of the

semicircles by a fixed distance with respect to the center of the other set.

Gut and Pinto (2003) studied the configuration of plate heat

exchangers and developed a mathematical model in algorithmic form.

The main simulation results were temperature profiles in all channels,

thermal effectiveness, distribution of the overall heat transfer coefficient and

pressure drop.

41

Thome (2003) reviewed the recent advances in modeling of

two-phase flow and heat transfer. The general thermal design methods for

two-phase heat exchangers were based on local two-phase flow patterns and

the flow structure of the two-phases. These methods were more accurate and

reliable for predicting two-phase heat transfer coefficients and pressure

drops.

Naphon and Wongwises (2005) investigated the heat transfer

characteristics and the performance of a spiral coil heat exchanger under

cooling and dehumidifying conditions, measured heat transfer

characteristics, enthalpy and humidity effectiveness. They developed a

mathematical model based on mass and energy conservation and solved by

using the Newton-Raphson iterative method to determine the heat transfer

characteristics. The results obtained from the model were in reasonable

agreement with the present experimental data.

Egner and Burmeister (2005) determined the laminar flow and

heat transfer in three-dimensional spiral ducts of rectangular cross section

with various aspect ratios and use of the FLUENT computational fluid

dynamics program. The peripherally averaged Nusselt Number was

presented as a function of distance from the inlet and of the Dean Number.

Fully developed values of the Nusselt Number for a constant-radius-of

curvature duct either toroidal or helical with small pitch, were used to

predict the quantities for the spiral duct in postentry regions.

Naphon and Wongwises (2006) reviewed the heat transfer and

fluid flow studies in helical, spiral and coiled tubes and summarized the

predictions of single-phase heat transfer coefficients and friction factors in

both single-and two-phase flows.

42

Burmeister (2006) studied the liquid-liquid mixtures in a spiral

plate heat exchanger and derived a formula for the dependence of heat

exchanger effectiveness on the number of transfer units for a exchanger with

equal capacitance rates.

Ramesh K. Shah (2006) summarized the theory, analysis, design

and optimization manufacturing and technology of compact heat exchanger

and assessed the advantages in many specific areas and developed

correlations and models.

Ramachandran et al. (2006) developed a correlation to predict

two-phase heat transfer coefficients, and helped to optimally design the heat

exchanger. The experimental studies were in laminar range. The two phase

heat transfer coefficients were related with Reynolds Numbers and were

fitted into a relation in the form h = a Rem. They developed correlations

between the two-phase multiplier and the Lockhart-Martinelli parameter.

Ramachandran et al. (2006) experimentally investigated the heat

transfer correlations for a two-phase system in a compact heat exchanger.

The experimental studies were in laminar range with hot water and mixture

of water-nitrobenzene in different mass fractions and flow rates were carried

out. The experimental heat transfer coefficients on the process side were

correlated with Reynolds Numbers and were fitted into an equation

h = a Rem. The heat transfer coefficients were also related to the mass

fraction of nitrobenzene for identical Reynolds Numbers. The two-phase

multiplier was correlated with the Lockhart-Martinelli parameter.

Ramachandran et al. (2006) experimentally investigated heat

transfer coefficients and related to the quality of the two-phase systems.

43

The correlations between quality and L-M parameter showed a good

agreement with experimental data and used for the prediction of two phase

heat transfer coefficients and were useful in the design of heat exchangers

for two-phase flow in the Re and temperature ranges investigated.

Ramachandran (2006) experimentally investigated eight

two-phase immiscible systems in a spiral plate heat exchanger, measured

mass fraction and flow rate of cold fluid. He developed totally four

correlations.

Picon-Nunez et al. (2007) developed the design approach for

spiral plate heat exchanger. They performed a numerically study using CFD

to rate the performance of the geometry and developed correlations.

Naphon and Suwagrai (2007) studied single phase flow of cold

water in horizontal spirally coiled tubes. They investigated the effects of

curvature ratios on the heat transfer and flow development. The turbulent

flow and heat transfer developments were simulated by using the k-ε

standard turbulence model. The predicted results for the convective heat

transfer and flow characteristics were reasonable agreement with the

experiments.

Guo-Yan et al. (2008) examined the design and economic

analysis of three compact exchangers, viz., plate-fin, plate and spiral plate

heat exchangers, measured overall heat transfer coefficient, heat transfer

equation, pressure drop, optimization, annual cost and worth and developed

correlations. The criterion for optimization was minimum pressure drop for

a given capacity. They studied material purchasing, equipment abrasion, and

44

power consumption. From an energetic point of view, all compact

exchangers were found to be feasible.

Picon-Nunez et al. (2009) developed a rapid design methodology

for spiral plate heat exchangers on the basis of full utilization of pressure

drop and heat utilization. The width and plate spacing were determined, and

the final exchanger dimensions were matched to standard dimensions.

The approach used empirical correlations for calculation of heat transfer

coefficients and friction factor based on average curvature of the exchanger.

Adamski (2009) developed correlations to predict heat transfer

coefficients and Fanning friction factor for air flowing through a

longitudinal flow spiral recuperator and also examined thermal efficiency,

heat transfer coefficient and Nusselt Number of the exchanger.

da Silva et al. (2006) described the wetting wall behaviour of the

pipe wall through contact angle measurements for oil-water-stainless steel,

galvanized steel, commercial steel and PVC surface system in an contact

angle measurement apparatus, measured contact angle, wettability,

temperature effect, pH effect and salt effect. They investigated with various

metallic surfaces, salt, pH, temperature effects on the wetting behaviour.

2.3 KEY OBSERVATIONS FROM LITERATURE

The following are some of the key observations obtained from

studying the above literature:

• Liquid-gas and liquid-vapor flows have been studied extensively

by visualization and measurement of flow distributions, phase

distribution patterns, boiling and condensing phenomena,

45

pressure drops, and heat transfer. Most of the common flow

geometries (over a flat plate, circular, rectangular/square, and

triangular cross-sections, helicoidal, spiral, inclined channels and

microchannels) have been studied. Effects of curvature, surface

roughness, and corrugations, heat exchanger geometry, junctions,

extended surfaces and including a third liquid phase have been

examined. Laminar, transition and turbulent flow velocities have

been studied. Interesting physics has been observed and

interpreted, and these are presented along with key features of

each study in the “Remarks” section of each entry in the tables.

• On the contrary, there are fewer studies on liquid-liquid

two-phase mixtures. Among the geometries considered for

studies include horizontal pipes, flow through inclined pipes,

180º return bends, rectangular microchannels and mixing at a

Y-junction. Flow distribution and pressure drops have been

studied.

• There are even fewer studies on heat transfer to liquid-liquid

mixtures. Heat transfer in pipe flow of liquid-liquid mixtures has

been studied only till the 70’s barring a publication in 1996.

Other studies include direct contact heat transfer (where the hot

and cold fluids and mixed and then separated), heat transfer in

direct contact with microdispersion, microchannels and

minichannels. Finally, recently, there have been studies of heat

transfer to liquid-liquid mixtures in a spiral plate heat exchanger,

similar to the present work.

46

• A study of heat transfer in spiral plate heat exchangers requires

good understanding of thermal theory of these exchangers.

The literature presented in this topic primarily concerns the

thermal theory of spiral plate heat exchangers. There are some

single-phase experimental studies and liquid-vapor two-phase

heat transfer studies in spiral plate heat exchangers discussed in

this topic, in addition to recent studies on liquid-liquid mixtures.

Thus, it is concluded that the present study on heat transfer to

liquid-liquid mixtures in a spiral plate heat exchanger fills a much-needed

gap in the literature. The present study attempts to characterize the heat

transfer to liquid-liquid mixtures in spiral plate heat exchangers through the

development of predictive correlations and a mixing rule, as well as

characterize the exchanger’s thermal performance when liquid-liquid

mixtures are used.