Table Of ContentAdvances in Multiphase Flow and Heat Transfer
Vol. 2, 2009
Lixin Cheng and Dieter Mewes (Editors)
Bentham Science Publishers Ltd.
Advances in Multiphase Flow and Heat Transfer Vol. 2
Contents
Preface i
Contributors vi
Research and Review Studies vii
Chapter 1 Passive Condensers 1
Shripad T. Revankar
Chapter 2 Phase Inversion in Liquid-Liquid Pipe Flows 38
Panagiota Angeli
Chapter 3 Heat Transfer and Friction in Helically-Finned Tubes
Using Artificial Neural Networks 62
Louay M. Chamra, Pedro Mago and Gregory Zdaniuk
Chapter 4 The Heat Transfer Characteristics of CO2 and CO2-Oil
Mixture in Tubes 107
Rin Yun
Chapter 5 Nonlinear Analysis and Prediction of Time Series from
Fluidized Bed Evaporator 148
Mingyan Liu, Aihong Qiang and Juanping Xue
Chapter 6 Air-Water Two-Phase Flows with Applications to
Drainage System 177
S.W. Chang and D.C. Lo
Chapter 7 Convective Boiling Heat Transfer of Pure and Mixed Refrigerants
within Plain Horizontal Tubes: An Experimental Study 216
Adriana Greco
Index 304
Lixin Cheng and Dieter Mewes (Ed)
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Advances in Multiphase Flow and Heat Transfer Vol. 2 (2009) i
Preface
Multiphase flow and heat transfer have been found a wide range of applications in
nearly all aspects of engineering and science fields such as mechanical engineering,
chemical and petrochemical engineering, nuclear engineering, energy engineering,
material engineering, ocean engineering, mineral engineering, electronics and micro-
electronics engineering, information technology, space technology, micro- and nano-
technologies, bio-medical and life science etc. With the rapid development of various
relevant technologies, the research of multiphase flow and heat transfer is growing very
fast nowadays than ever before. It is highly the time to provide a vehicle to present the
state-of-the-art knowledge and research in this very active field.
To facilitate the exchange and dissemination of original research results and state-
of-the-art reviews pertaining to multiphase flow and heat transfer efficiently, we have
proposed the e-book series entitled Advances in Multiphase Flow and Heat Transfer
to present state-of-the-art reviews/technical research work in all aspects of multiphase
flow and heat transfer fields by inviting renowned scientists and researchers to
contribute chapters in their respective research interests. The e-book series have now
been launched and two volumes have been planned to be published per year since 2009.
The e-books provide a forum specially for publishing these important topics and the
relevant interdisciplinary research topics in fundamental and applied research of
multiphase flow and heat transfer. The topics include multiphase transport phenomena
including gas-liquid, liquid-solid, gas-solid and gas-liquid-solid flows, phase change
processes such as flow boiling, pool boiling, and condensation etc, nuclear thermal
hydraulics, fluidization, mass transfer, bubble and drop dynamics, particle flow
interactions, cavitation phenomena, numerical methods, experimental techniques,
multiphase flow equipment such as multiphase pumps, mixers and separators etc,
combustion processes, environmental protection and pollution control, phase change
materials and their applications, macro-scale and micro-scale transport phenomena,
micro- and nano-fluidics, micro-gravity multiphase flow and heat transfer, energy
engineering, renewable energy, electronic chips cooling, data-centre cooling, fuel cell,
multiphase flow and heat transfer in biological and life engineering and science etc. The
e-book series do not only present advances in conventional research topics but also in
new and interdisciplinary research fields. Thus, frontiers of the interesting research
topics in a wide range of engineering and science areas are timely presented to readers.
In volume 2, there are seven chapters on various relevant topics. Chapter 1 deals
with the passive condensers. The condensation phenomenon plays an important role in
the heat transfer process in the chemical and power industry, including nuclear power
plants. Condensers that are based on natural forces are called passive condensers and
they do not require pumps or blower to move fluid. Examples of passive condensers
include passive condenser systems in nuclear reactor safety systems, closed loop heat
pipes, passive condenser for harvesting dew from surrounding humid air and passive
refrigeration systems. In nuclear reactors, there is a greater emphasis on replacing the
active systems with passive systems in order to improve the reliability of operation and
safety. Heat pipes with passive condensers have been developed to transport high heat
Lixin Cheng and Dieter Mewes (Ed)
All right reserved – © Bentham Science Publishers Ltd.
ii Advances in Multiphase Flow and Heat Transfer 2 (2009) Cheng and Mewes
flux from electronic devices. In practical operations of the passive condensers, small
amounts of non-condensable gas may exist in working vapors due to characteristics of
the system or dissolution of working vapors. It is well known that the presence of non-
condensable gases in a vapor can greatly reduce the performance of condensers. This is
because of the fact that the presence of non-condensable gas lowers the partial pressure
of the vapor, thus reducing the saturation temperature at which condensation occurs. In
this chapter state-of-the art in passive condensers, topics are covered including various
types of passive condensers designs and their applications. The theory of passive
condensation, condensation models, and experimental work on the passive condensers
are presented. Practical heat transfer relations applicable to various for passive
condensers are presented and discussed.
Chapter 2 presents a topic on phase inversion is the phenomenon where the
continuous phase of a liquid-liquid dispersion changes to become dispersed and the
dispersed becomes continuous. Phase inversion has important implications for a number
of industrial applications where liquid-liquid dispersions are used, since the change in
the mixture continuity affects drop size, settling characteristics, heat transfer and even
the corrosion behaviour of the mixture. In pipeline flows, phase inversion is usually
accompanied by a step change or a peak in pressure drop. The chapter reviews the work
on phase inversion during the pipeline flow of liquid-liquid mixtures when no
surfactants are present. Investigations have revealed that in pipes a transitional region
occurs during inversion from one phase continuous to the other, characterized by
complex flow morphologies (multiple drops, regions in the flow with different
continuity) and even stratification of the two phases over a range of dispersed phase
volume fractions. The observations on the phase inversion process in pipelines are
discussed and the parameters which affect the phenomenon are summarized. In
addition, the various models available for predicting phase inversion are analyzed, as
well as the methodologies developed to account for the transitional region with the
complex morphologies and the flow stratification and to predict pressure drop during
inversion.
Chapter 3 presents a study of heat transfer and friction in helically-finned tubes
using artificial neural networks. The last few decades have seen a significant
development of complex heat transfer enhancement geometries such as a helically-
finned tube. The arising problem is that as the fins become more complex, so does the
prediction of their performance. Presently, to predict heat transfer and pressure drop in
helically-finned tubes, engineers rely on empirical correlations. Tubes with axial and
transverse fins have been studied extensively and techniques for predicting the friction
factor and heat transfer coefficient exist. However, fluid flow in helically-finned tubes is
more difficult to model and few attempts have been made to obtain non-empirical
solutions. Friction and heat transfer in helically-finned tubes are governed by an
intricate set of coupled and non-linear physical interactions. Therefore, obtaining a
single prediction formula seems to be an unattainable goal with the knowledge
engineers currently possess. Regression techniques performed on experimental data
require mathematical functional form assumptions, which limit their accuracy. To
achieve accuracy, techniques that can effectively overcome the complexity of the
problem without dubious assumptions are needed. One of these techniques is the
Preface Advances in Multiphase Flow and Heat Transfer Vol. 2 (2009) iii
artificial neural network (ANN), inspired by the biological network of neurons in the
brain. This chapter presents an introduction to artificial neural networks (ANNs), and a
literature review of the use of ANNs in heat transfer and fluid flow is also discussed. In
addition, this chapter demonstrates the successful use of artificial neural networks as a
correlating method for experimentally- measured heat transfer and friction data of
helically-finned tubes.
Chapter 4 presents a comprehensive review on the heat transfer characteristics of
CO and CO -oil mixture in tubes including convective flow boiling, gas cooling, and
2 2
condensation are investigated. Two-phase flow patterns are thoroughly investigated
based on physical phenomena, which show the early flow transition to intermittent or
annular flow especially for small diameter tube. The physical phenomena for nucleate
boiling of CO follow the same trends with other organic fluids under the same reduced
2
pressure. The gas cooling heat transfer is critically dependent on the turbulent
diffusivity related with buoyancy force due to the large density difference. Under the oil
presence conditions, the interaction of oil rich layer and bubble formation is the physical
mechanism for the CO -oil mixture convective boiling. Besides, the gas cooling
2
phenomena with oil should be investigated based on the flow patterns formed by CO
2
and oil, and the oil rich layer, whose thickness are depends on the solubility of CO to
2
oil explains the physical mechanisms of heat transfer. The thermodynamic properties of
CO -oil were estimated by the general model based on EOS, and they are utilized to
2
estimate the properties for oil rich layer and oil droplet vapor core. Through these
predicted properties, the convective boiling and gas cooling heat transfer coefficients
and pressure drop theoretically estimated. Condensation of CO is not so different from
2
the existing one, so the heat transfer coefficients and pressure drop are well estimated
by the existing one developed for other fluids.
Chapter 5 summarizes the work done by our research group in recent five years on
the nonlinear analysis and prediction of time series from the system of fluidized bed
evaporator with an external natural circulating flow. Besides traditional investigations
on steady-state characters of flow and heat transfer, the nonlinear evolution behavior of
the system was emphasized and explored in this chapter. Measured time series of wall
temperature and heat transfer coefficient were taken as the time series for the nonlinear
analysis, modeling and forecasting. The main analysis tools are based on the chaos
theory. Meaningful results were obtained. Under certain conditions, the signals obtained
from the system of vapor-liquid-solid flow boiling are chaotic, which is demonstrated
by obvious wideband characteristic in power spectra, decreasing gradually of
autocorrelation coefficients, non-integer fractal dimension and non-negative and limited
Kolmogorov entropy etc. At least two independent variables are needed to describe the
vapor-liquid-solid flow system according to the estimation of the correlation dimension
in meso-scale. The shapes of correlation integral curves and their slopes change with the
variations of boiling flow states. The identifications of various flow regimes and their
transitions can be characterized by the shape variations. Multi-value phenomena of
chaotic invariants were found including correlation dimension and Kolmogorov entropy
at the same operation conditions, showing the appearance of multi-scale behavior in the
vapor-liquid-solid flow. Time series of heat transfer coefficients in fluidized bed
evaporators were modeled and predicted by the nonlinear tools and the comparisons
iv Advances in Multiphase Flow and Heat Transfer 2 (2009) Cheng and Mewes
between predicted and measured time series were carried out by estimating the statistics
characteristics, power spectrum, phase map and chaotic invariants and good agreements
were observed. This indicates that a simple nonlinear datum driving model can describe
the average or steady heat transfer character with a reasonable accuracy and the
transient heat transfer behavior with a general fluctuation tendency for the vapor-liquid-
solid flow. These findings are useful for finding new design, operation and control
strategies for such complex systems.
Chapter 6 describes the phenomena of air-water two-phase flows with the particular
application to the design of a drainage and vent system. The detailed knowledge of air-
water interfacial mechanism, the propagation of transient air pressure and the flow
resistance in a drainage system is essential in order to prevent the damage of trap seal,
the unfavorable acoustic effect and the foul odors ingress into the habitable space
through the interconnected drainage and vent network. For a drainage system with the
air admittance valve at the exit vent of the vertical stack, the control of the propagation
of the air pressure requires the understanding of the transient air-water two-phase flow
phenomena in each component of a drainage system. This chapter starts with the
background introduction for a drainage and vent system. Research works investigating
the air-water two-phase flows through vertical, horizontal and curved tubes as well as
through the tube junctions are subsequently reviewed. An illustrative numerical analysis
that examines the transient air-water two-phase flow phenomena in a confluent vessel
with multiple joints feeding the stratified air-water flows is presented to demonstrate the
CFD treatment for resolving the complex transient air-water two-phase flow phenomena
in the typical component of a drainage system.
Chapter 7 presents a study on convective boiling heat transfer of pure and mixed
refrigerants within plain horizontal tubes. An experimental study is carried out to
investigate the characteristics of the evaporation heat transfer for different fluids.
Namely: pure refrigerants fluids (R22 and R134a); azeotropic and quasi-azeotropic
mixtures (R404A, R410A, R507). zeotropic mixtures (R407C and R417A). The test
section is a smooth, horizontal, stainless steel tube (6 mm I.D., 6 m length) uniformly
heated by the Joule effect. The flow boiling characteristics of the refrigerant fluids are
evaluated in 250 different operating conditions. Thus, a data-base of more than 2000
data points is produced. The experimental tests are carried out varying: i) the refrigerant
mass fluxes within the range 200 - 1100 kg/m2s; ii) the heat fluxes within the range 3.50
- 47.0 kW/m2; iii) the evaporating pressures within the range 3.00 - 12.0 bar.
Experimental heat transfer coefficients and pressure drops are evaluated varying the
influencing parameters. In this study the effect on measured heat transfer coefficient of
vapour quality, mass flux, saturation temperature, imposed heat flux, thermo-physical
properties are examined in detail. The effect on measured pressure drops of vapour
quality, mass flux, saturation temperature and thermo-physical properties are examined.
In this chapter the attention is focused also on the comparison between experimental
results and theoretical results predicted with the most known correlations from
literature, both for heat transfer coefficients and pressure drops.
As the founding editors of the e-book series, we are very happy to see that the e-
books are now available to our readers. We are very much grateful to the authors who
have contributed to the chapters. It is our great wishes if the e-book series are able to
Preface Advances in Multiphase Flow and Heat Transfer Vol. 2 (2009) v
provide useful knowledge for our community and to facilitate the progress of the
research in the field of multiphase flow and heat transfer.
We would like to express our gratitude to our families for their great support to our
work.
Editor-in-Chief: Dr. Lixin Cheng
School of Engineering, University of
Aberdeen, King’s College, Aberdeen, AB24 3UE,
Scotland, the UK,
Email: [email protected]
Co-editor: Prof. Dieter Mewes
Institute of Multiphase Process, Leibniz
University of Hanover, Callinstraße 36, D-30167
Hannover, Germany,
E-mail: [email protected]
20 10 2009
vi Advances in Multiphase Flow and Heat Transfer Vol. 2 (2009)
Contributors
Panagiota Angeli, Department of Chemical Engineering, University College London,
UK
Louay M. Chamra, School of Engineering and Computer Science, Oakland University,
USA
S.W. Chang, Thermal Fluids Laboratory, National Kaohsiung Marine University,
Taiwan, R.O.C
Adriana Greco, DETEC, University of Naples Federico II, Italy
Mingyan Liu, School of Chemical Engineering and Technology, Tianjin University,
China; State Key Laboratory of Chemical Engineering, China
D.C. Lo, Research Institute of Navigation Science and Technology, National Kaohsiung
Marine University, Taiwan, R.O.C.
Pedro Mago, Department of Mechanical Engineering, Mississippi State University,
USA
Aihong Qiang, School of Chemical Engineering and Technology, Tianjin University,
China
Shripad T. Revankar, School of Nuclear Engineering, Purdue University, USA
Juanping Xue, School of Chemical Engineering and Technology, Tianjin University,
China
Rin Yun, Department of Mechanical Engineering, Hanbat National University,
South Korea
Gregory Zdaniuk, Ramboll Whitbybird Ltd, London, United Kingdom
Lixin Cheng and Dieter Mewes (Ed)
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Advances in Multiphase Flow and Heat Transfer Vol. 2 (2009) vii
Research and Review Studies
Lixin Cheng and Dieter Mewes (Ed)
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Advances in Multiphase Flow and Heat Transfer Vol. 2 (2009) 1-37 1
Chapter 1
Passive Condensers
Shripad T. Revankar∗
School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907, USA
Abstract
The condensation phenomenon plays an important role in the heat transfer process in the chemical
and power industry, including nuclear power plants. Condensers that are based on natural forces are
called passive condensers and they do not require pumps or blower to move fluid. Examples of passive
condensers include passive condenser systems in nuclear reactor safety systems, closed loop heat pipes,
passive condenser for harvesting dew from surrounding humid air and passive refrigeration systems. In
nuclear reactors, there is a greater emphasis on replacing the active systems with passive systems in order
to improve the reliability of operation and safety. Heat pipes with passive condensers have been
developed to transport high heat flux from electronic devices. In practical operations of the passive
condensers, small amounts of non-condensable gas may exist in working vapors due to characteristics of
the system or dissolution of working vapors. It is well known that the presence of non-condensable gases
in a vapor can greatly reduce the performance of condensers. This is because of the fact that the presence
of non-condensable gas lowers the partial pressure of the vapor, thus reducing the saturation temperature
at which condensation occurs. In this chapter, state-of-the art in passive condensers topics are covered
including various types of passive condensers designs and their applications. The theory of passive
condensation, condensation models, and experimental work on the passive condensers is presented.
Practical heat transfer relations applicable to various passive condensers are presented and discussed.
Introduction
Condensation is a process, where saturated vapor is converted in to liquid with
transfer of latent heat from one fluid system to another. Since latent heat is large, a
significant amount of heat can be transferred through condensation process. Hence, this
mode of heat transfer is often used in a number of chemical and power industries
including nuclear power plants because high heat transfer coefficients are achieved. In
order to facilitate condensation of vapor, a cold surface is required whose temperature
should be lower than the saturation temperature of the condensing vapor. For dynamic
operation, the condensed liquid needs to be removed continuously from the condensing
surface to make room for further condensation. The condensing surface is generally
cooled by using an external coolant flow or radiation. In a condenser, the vapor,
external coolant, and condensate liquid are often transferred through the aid of pumps,
compressors, or blowers. However, there is a class of condensers that operate with
gravitational force or surface tension force. These condensers do not need external
pumps or blowers. These condensers are referred as passive condenser systems. The
advantage with passive condenser system is that their reliability is high, since they do
∗ Email address: [email protected], tel:1-765-496-1782
Lixin Cheng and Dieter Mewes (Ed)
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