Applied Thermal Engineering 43 (2012) 1e6
Contents lists available at SciVerse ScienceDirect
Applied Thermal Engineering
journal homepage: www.elsevier.com/locate/apthermeng
Heat integration including heat exchangers, combined heat and power, heat
pumps, separation processes and process control
Jirí Jaromír Klemes*, Petar Sabev Varbanov
Centre for Process Integration and Intensification e CPI2, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia,
Egyetem utca 10, H-8200 Veszprém, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 March 2012
Accepted 31 March 2012
Available online 7 April 2012
This Special issue (SI) of Applied Thermal Engineering presents twenty one selected contributions from
the 14th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution
Reductione PRES’11. It benefits from the long-term cooperation between the PRES conferences and the
journal. The selected papers cover important subjects: heat exchangers and heat pumps, design of
thermal processes, heat integration, combined heat and power (CHP) integration, integration of thermal
processes, power systems.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Heat integration
Thermal process design
Integration of CHP
Heat exchangers
Heat pumps
Integration of separation processes
Power systems and control
1. Introduction
An ever growing number of conferences are organised worldwide providing international avenues for stimulating cooperation
and creativity in the investigation of energy saving, reduction of
waste and emissions. The conference series “Process Integration,
Modelling and Optimisation for Energy Saving and Pollution Reduction
- PRES” has played an increasingly active role in finding answers to
these issues alongside energy supply and demand challenges. The
goals have been pursued through exchange of ideas as well as
fostering collaboration and conception of international projects,
presented and discussed during the conference venues. This is one
of the most prestigious conference series in the field of improvements in energy and materials efficiency in industrial and other
economy sectors.
The first venue of the PRES series was organised under the
CHISA umbrella in 1998, in Prague and subsequently in various
other places e including Hungary, Italy, Canada and the Czech
Republic. The 14th conference e PRES’11 was held from 8 to 11 May
2011 in Florence, Italy. The city is well known as a cultural and also
* Corresponding author. Tel.: þ36 88 421 664.
E-mail addresses: klemes@cpi.uni-pannon.hu (J.J. Klemes), varbanov@cpi.unipannon.hu (P.S. Varbanov).
1359-4311/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.applthermaleng.2012.03.044
a business centre, rich in historical heritage e including arts and
engineering. The PRES’11 conference attracted delegates from 58
countries and 756 authors submitted 348 contributions. Participants were from all inhabited continents e Africa, North and South
America, Asia, Australia, and most European countries.
The PRES conferences are now running into the middle of their
second decade and continue to provide opportunities for crossfertilisation of research, engineering and education. They have
been established to address issues relevant to energy and water
integration of processes for minimising resource demands and
emissions. Besides the extensive networking and exchange of ideas
at the venues, PRES conferences have a comprehensive publication
strategy.
This Special Issue (SI) is already the thirteenth SI of Applied
Thermal Engineering, dedicated to selected contributions from
PRES conferences after starting in the year 2000 with PRES’99 [1]. It
has been followed by SI of PRES 2000 [2], PRES’01 [3], PRES 2002
[4], PRES’03 [5], PRES 2004 [6], PRES’05 [7], PRES 2006 [8], PRES’07
[9], PRES 2008 [10], PRES’09 [11], and PRES 2010 [12]. In addition to
Applied Thermal Engineering, other well-known journals have
been collaborating with PRES and related conferences e Journal of
Cleaner Production [13], Heat Transfer Engineering [14], Cleaner
Technologies and Environmental Policy [15], Resources, Conservation and Recycling [16] and Energy [17].
2
J.J. Klemes, P.S. Varbanov / Applied Thermal Engineering 43 (2012) 1e6
2. The main topics of this special issue
Thirty contributions were selected from PRES’11 as candidates
for this SI. After a thorough reviewing procedure carried out by the
members of the PRES International Scientific Committee and
invited selected world-leading experts, twenty one papers have
been accepted for this SI of Applied Thermal Engineering. The
selected papers deal with four major topics:
(1) Heat integration and heat processes design
(2) Integration of CHP, heat exchangers, heat pumps
(3) Integration of separation processes
(4) Power systems and control
The authors are from sixteen countries, which demonstrates the
worldwide spread of the venue and this Special Issue: Austria,
China, Croatia, the Czech Republic, Finland, France, Germany,
Hungary, Japan, Macedonia, Mexico, Republic of Korea, Slovenia,
Sweden, Switzerland and the United Kingdom.
2.1. Heat integration and thermal process design
The first topic includes six articles: on Heat Exchanger Network
retrofit, an industrial case study on Total Site optimisation, Pinch
and exergy optimisation of a biorefinery and application of Process
Integration to geothermal processes.
The first manuscript in the SI is on "Heat exchanger network
retrofit optimization involving heat transfer enhancement” [18],
contributed by Yufei Wang and Robin Smith from The University of
Manchester in the United Kingdom, plus Jin-Kuk Kim from Hanyang
University - Republic of Korea. Conventional retrofit methods rely
mostly on topology modifications and/or adding heat transfer area
to existing heat exchangers, which often results in a long retrofit
duration and high initial costs. The paper presents a novel approach
to solving the heat exchanger network retrofit problems using heat
transfer enhancement. A Simulated annealing based optimisation
procedure has been developed to find the appropriate heat
exchangers for heat transfer enhancement and the required level of
enhancement. Comparison of this retrofit strategy with previous
ones demonstrates that retrofit duration and payback time are
significantly reduced. The retrofit investment required, when using
only enhancement, is very low: £0.37M, resulting in a very short
payback time e only 0.34 y, as well as short modification duration.
The second paper in the group is from Japan, authored by Kazuo
Matsuda and Shigeki Tanaka from Chiyoda Corporation, Masaru
Endou from Sumikin Management Co. Ltd., and Tsutomu Iiyoshi
from Sumitomo Metal Industries Ltd.. It presents an analysis of an
industrial case. The title is “Energy saving study on a large steel plant
by total site based pinch technology” [19]. Total Site Profile (TSP)
analysis has been applied to a large-scale steel production site. This
methodology has been developed from the beginning in the late
nineties [20] into advanced methodology [21] and [22]. Despite the
very high energy efficiency of the individual processes, huge energy
saving potential has been identified. The major energy saving
potential was found on the cooler side (power generation of
21.1 MW). Analysing the amount of the heat available under 300 C
showed that there was a possibility to develop a combination of
two power generation systems (6.2 MW and 12.3 MW) and a heat
utilisation system for the removal of CO2.
The next contribution deals with “Pinch and exergy analysis of
lignocellulosic ethanol, biomethane, heat and power production from
straw” [23] and comes from Austria e Vienna University of Technology. It has been written by Ala Modarresi, Philipp Kravanja and
Anton Friedl. The authors extended their previous works [24] and
[25] and introduce a process design for a biorefinery producing
bioethanol, biomethane, heat and power from wheat straw and is
subjected to Pinch and exergy analyses. The Pinch Analysis is
focused on the bioethanol production where a well-designed heat
exchanger network saves up to 45 MW hot utility and additionally
power cogeneration potential has been identified, making the
process more attractive from an energy viewpoint. Exergy analysis
was performed to calculate system irreversibilities and to identify
material and heat losses as waste streams. The results show that the
bioethanol production process has the highest exergy efficiency
because of usage of stillage for other processes where it can be
converted to biomethane in an anaerobic digestor and combusted
in a boiler generating steam.
An application of Process Integration techniques to the utilisation of geothermal resources is presented by Léda Gerber and
François Maréchal from the Ecole Polytechnique Fédérale de Lausanne, Switzerland. The work is titled “Defining optimal configurations of geothermal systems using process design and process
integration techniques” [26] and describes a systematic methodology for the optimal design of geothermal systems, based on
constructing a superstructure of possible alternatives. The superstructure includes the various conversion technologies, the
potential resources and the demand profiles of the required
energy services. It covers a wide panel of conventional resources
and technologies like deep and shallow aquifers, heat pumps,
organic Rankine cycles for combined heat and power production,
as well as new enhanced geothermal systems. To account for the
seasonal variations of the demand, a multi-period approach is
used, supplemented by a dual-objective function comprising
minimisation of investments and maximisation of exergy efficiency. At the geological conditions of the case study, it has been
demonstrated that enhanced geothermal systems built at an
optimal depth and using the appropriate conversion technology
can be profitable even in the case where both district heating and
electricity selling prices are low.
A Process Integration application to a pulp-and-paper based
biorefinery is presented by Valeria Lundberg, Erik Axelsson, Maryam Mahmoudkhani and Thore Berntsson from the Chalmers
University of Technology e Sweden. The title is “Process integration
of near-neutral hemicellulose extraction in a Scandinavian kraft pulp
mill e Consequences for the steam and Na/S balances” [27]. The
authors well exploited their previous experience in the field [28]
and [29]. They concluded that most important consequences of
integrating a bioethanol production unit into a pulp mill are
presented in terms of steam and Na/S balances. The considered
hemicellulose extraction and bioethanol processes, if implemented directly, increase the net steam demand by 48 MW. The
authors report that applying Process Integration techniques within
the mill and the bioethanol plant, combined with Total Site integration, result in a site with the same steam demands as the
simple mill.
The last article in this section is “Design of coolers for use in an
existing cooling water network” [30], coming from Mexico e the
University of Guanajuato. It is written by a team of four authors:
Martín Picón-Núnez, Graham Thomas Polley, Lázaro CanizalezDávalos and Elvis Koku Tamakloe. Their paper presents a procedure
for the specification of design conditions for the incorporation of
new coolers into existing cooling water networks. The decision is
made based on the evaluation of the thermo-hydraulic effects of
the various options. The procedure involves thermo-hydraulic
simulation of the cooling water network accounting for the
performance of the pumps and the cooling tower. The authors
propose an approximate sizing approach for new coolers based on
the flow resistance factor. An important outcome of the study is the
identification of pressure drop targets for placing the coolers, which
should not be exceeded in the detailed cooler design.
J.J. Klemes, P.S. Varbanov / Applied Thermal Engineering 43 (2012) 1e6
2.2. Integration of CHP, heat exchangers, heat pumps
The topic includes works on advanced energy integration e
including cogeneration targeting and evaluation, simultaneous
synthesis of a process and its heat recovery network, HEN optimisation, advanced heat transfer element design, and heat pump
integration.
The section starts with the paper “Cogeneration targeting for site
utility systems” [31], authored by Ali Ghannadzadeh, Simon Perry and
Robin Smith from The University of Manchester e United Kingdom.
They again build on the previous Total Site methodology [20,32] and
its recent extensions [21,33]. They present a new targeting model e
the Iterative Bottom-to-Top Model (IBTM), which accounts for the
variation of the steam main temperatures with the steam flow rates
and shaft power generated by the steam turbines, using a simple
steam turbine expansion model with a constant isentropic efficiency.
The procedure is illustrated by a case study of a refinery plant. The
authors point out that the new model features offer more realistic
estimates of the Total Site Cogeneration targets than previous models.
The second article in the group is titled “Emergy evaluation of
combined heat and power plant processes” [34]. The authors are Sha
Sha and Markku Hurme from the Aalto University, Finland. They
present a method for energy-environmental accounting based on
the embodied solar energy - emergy principle [35]. Biomass and
coal-based CHP alternatives were compared with independent
production of heat and power. The authors report that biomassbased cogeneration is 3.3 times more emergy-efficient than coalbased independent production; i.e. the biosphere needed to work
77% less for biomass produced heat and power compared to that
produced independently from coal. When comparing systems
using the same fuel (either coal or biomass), cogeneration was
found by the authors 20e25% more emergy-efficient than independent electricity or heat generation.
Following this, Milos Bogataj and Zdravko Kravanja from the
University of Maribor e Slovenia present a manuscript “An alternative strategy for global optimization of heat exchanger networks”
[36]. They propose a new strategy for formulating and reducing an
augmented superstructure of the heat exchanger network (HEN)
using aggregation. The strategy for achieving global optimality of
the solutions relies on solving a single convex MINLP incorporating
piecewise linear and nonlinear convex underestimators of the
terms in the non-convex MINLP. The authors report that the
application of the strategy allows reducing the gap between the
lower and upper bound of the problem below 1%. As a result they
achieve a HEN synthesis 30% faster and producing a solution with
about 6% lower total cost, compared to a state of the art benchmark
method [37] chosen by the authors.
The next article is by Rozalija Drobe
z e Tanin Sevnica d.d. e
Sevnica, Slovenia; Zorka Novak Pintari
c and Zdravko Kravanja from
the University of Maribor e Slovenia; and Bojan Pahor from
Perutnina Ptuj d.d, Ptuj, Slovenia. The title is “Simultaneous
Synthesis of a Biogas Process and Heat Exchanger Network” [38]. It
presents a synthesis of a biogas process, performed simultaneously
with the synthesis of its heat exchanger network (HEN), achieving
high energy efficiency. The authors build on a previous work where
they have developed a process synthesis model for the biogas
process [39]. The problem is solved by formulating and reducing by
MINLP a combined superstructure, consisting of modules for the
biogas process, the HEN and process stream links superstructure.
The synthesis case study, derived from an existing large-scale meat
company, yields a completely energy-self-sufficient solution for
thermophilic biogas production, closed-loop water configuration,
and a comparatively simple HEN arrangement.
A stress analysis of a high temperature heat exchanger tube with
enhanced surface is presented by Ting Ma, Yitung Chen, Min Zeng
3
and Qiuwang Wang from Xi’an Jiaotong University, Xi’an, Shaanxi,
China and from University of Nevada, Las Vegas, United States. The
title is “Stress analysis of internally finned bayonet tube in a high
temperature heat exchanger” [40]. Continuing their successful series
of investigations of high-temperature heat exchangers [41] the
authors present a study of the thermal stress and deformation of
the internally finned bayonet tube used for high-temperature heat
exchangers. The observed significant temperature gradient along
both the axial and radial directions gives rise to large stress in the
joint of the inner fin and inner tube, and the joint of the inner fin
and outer tube despite the stress reduction properties of the
bayonet structure. The authors propose not to weld together the
inner fin and inner tube and thus they can expand or contract freely
not affecting each other. They further compare the effect of the gap
between the inner tube and the inner fin on the stress and the heat
transfer performance. They recommend that the gap should be less
than 1 mm for the considered bayonet tube with 6 mm annulus
height.
The optimal choice and sizing of a dual-mode heat pump is
presented in the article “Design and optimisation of dual-mode heat
pump systems using natural fluids” [42], written by an international
team: Wenling Zhang from the The University of Manchester e
United Kingdom; Jirí Jaromír Klemes from the University of Pannonia e Hungary; Jin-Kuk Kim from the Hanyang University, Seoul,
Republic of Korea. This is based on the previous extensive experience of the authors with research on heat pumps e one example is
the application of heat pumps in biomass gasification processes
[43]. The paper introduces a new multi-period model for the
optimal design of dual-mode heat pumps using natural fluids. The
multi-period optimisation framework has been developed to reflect
different ambient conditions and their influence on heat pump
performance, as well as to determine the heat pump capacity. The
system capacity sizing is obtained by systematic screening and
evaluation of the economic trade-off between supplementary
heating or cooling and operating cost for heat pump, minimising
the annualised operating cost. A Case Study considering three
geographical locations with different heating and cooling demands
illustrates the method application. Three different refrigerants are
compared for each of the case study locations; R22, ammonia and
propane. The optimisation results indicate that in order to use
propane as a more environment friendly agent, there is an operating cost penalty of 20e50%.
The final contribution to the thematic group is by Helen Becker
and François Maréchal from the Ecole Polytechnique Fédérale de
Lausanne e Switzerland, and Aurélie Vuillermoz from the EDF R&D
Moret sur Loing, France, with a title “Heat pump integration in
a cheese factory” [44]. The authors consider an application of
Process Integration to a real case study of a cheese factory with
non-simultaneous process operations. They use the time average
approach combined with restricted matches. They propose two
strategies. In the first option, process modifications and direct heat
exchange between the process and heat pump streams are not
allowed, thus requiring indirect heat transfer via an intermediate
agent. In the second option, direct heat exchange and process
modifications are possible. Both options are compared for the
French and German context. The authors report potential operating
cost savings, from the heat pump integration, up to 40% for both
countries also indicating potential CO2 emissions and primary
energy savings of similar magnitude.
2.3. Integration of separation processes
The third topic groups articles on energy efficient sugar
production, hydrogen production from biomass, CO2 separation,
and evaporators.
4
J.J. Klemes, P.S. Varbanov / Applied Thermal Engineering 43 (2012) 1e6
The first article from the group authored by Saeed Gul and
Michael Harasek from the Vienna University of Technology, Austria,
presents a study titled “Energy saving in sugar manufacturing
through the integration of environmental friendly new membrane
processes for thin juice pre-concentration” [45]. Using a previous
work [46] on the utilisation of waste streams for improving the
efficiency of sugar production as a departure point, the authors
present a study on a novel design of a process for clarified thin
sugar juice pre-heating and concentration. A new pressure-driven
multistage membrane process is integrated with a multiple-effect
evaporator. The thin sugar juice is concentrated from 15% (mass)
to 50% using the membrane unit at moderate pressure of 32 bar and
80 C. For raising the concentration from 50% up to 70%, the
evaporation module is used. The authors report that the new
process not only reduces the energy consumption of the thin juice
concentration process significantly, but also reduces by 70% the
requirements for energy and heat transfer area for pre-heating part
before evaporation. Extrapolating these results, the authors suggest
that existing sugar factories may increase their evaporation
capacities through the integration of the new membrane process
while new factories to be built would have smaller and more efficient evaporation units, making the sugar production processes
more environmentally friendly with a significantly smaller carbon
footprint.
The second paper in the group is “Membrane gas permeation in
the upgrading of renewable hydrogen from biomass steam gasification
gases” [47] by Aleksander Makaruk, Martin Miltner, Michael Harasek from the Vienna University of Technology, Austria. This is yet
another innovative application of membrane technology, in addition to the previous article [45]. They investigate a combination of
biomass steam gasification and membrane gas permeation as
a potential process for producing renewable hydrogen. First the
potential membrane materials for hydrogen enrichment from
biomass gasification producer gas mixtures are identified. Two
permeator arrangements are evaluated through numerical modelling: a single stage and a two-stage with sweep. The evaluation
discusses the most essential upgrading parameters: achievable
hydrogen purity, hydrogen recovery and energy requirement in the
upgrading. It is shown that a two-stage arrangement using
membranes with an H2/CO2 selectivity of 9 allows obtaining
hydrogen fuel with purity of 98% by volume. The authors conclude
that further improvement of the membrane H2/CO2 selectivity is
needed to obtain a more sustainable and economically viable
design.
Another interesting article has been contributed by authors
from Technische Universität Berlin e Germany: Steffen Stünkel,
Daniel Illmer, Andreas Drescher, and Günter Wozny from the
Department of Process Dynamics and Operation, and Reinhard
Schomäcker from the Department of Chemical Engineering. The
article title is “On the design, development and operation of an energy
efficient CO2 removal for the oxidative coupling of methane in
a miniplant scale” [48]. It describes an analysis of the technical
feasibility of the oxidative coupling of methane (OCM) process,
including product recovery in a miniplant scale. In the article the
treatment of the gaseous reaction product is discussed as a key part
of the production chain. In the OCM process CO2 is treated as
a waste by-product. Since the energy expenditure and overall cost
requirements of the OCM process are crucial for its industrial
applicability, they should be minimised. The authors investigate
several separation methods and process alternatives for separating
CO2 from the OCM product stream. They focus their efforts on
analysing the energy saving of a hybrid separation process for the
CO2 capture based on a combination of membrane and absorption
components. The process is constructed and experimentally validated in the pilot miniplant. A case study has been performed and
experimental results are discussed. The authors report that more
than 20% energy saving, more than 25% reduction of column height
and more than 20% of solvent flow rate reduction could achieved by
applying the proposed process.
The next paper is titled “Hybrid evaporator model: Analysis under
uncertainty by means of Monte Carlo method” [49]. Its authors are
Dario Colorado, J. Alfredo Hernández and Beatriz Alonso from the
Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico, and Xudong Ding from the Shandong Jianzhu
University, Jinan, China. They present a study on improving the
error analysis for a hybrid evaporator model. Error propagation
evaluation using a Monte Carlo method is applied to the heat
transfer rate (Q) predicted by the model. The heat transfer rate was
used by the authors to assess the evaporator used in a vapour
compression refrigeration system. They used a hybrid model
reported earlier [50] to identify the error propagation in heat
transfer rate prediction. The model uses temperatures, mass flow
rates and enthalpies from the evaporator as measured inputs. A
correlation for the calculation of relative standard deviation RSD of
the heat load as a function of its experimentally measured value of
the load and the RSD of the measurement instrumentation was
obtained. As a result the authors make recommendations for
improving the calibration and the measurement precision for the
evaporator pressure detection in order to obtain meaningful heat
transfer rate hybrid predictions with relatively small errors of less
than 2.85%.
The last article in this group is titled “Application of the self-heat
recuperation technology to crude oil distillation” [51]. It has been
written by Yasuki Kansha, Akira Kishimoto and Atsushi Tsutsumi
from the The University of Tokyo e Japan. Crude oil distillation
typically uses about 50% of the energy required in an oil refinery.
The authors build on their previous work where they have developed an innovative process design technology for saving energy,
termed self-heat recuperation e e.g [52]. In the described work the
possibility of achieving a significant reduction in energy demands
of crude oil distillation, based on self-heat recuperation technology,
was investigated. The proposed self-heat recuperative crude oil
distillation system was found by the authors to work without any
heat addition as in other self-heat recuperative processes from
previous studies. As a result, the proposed process can achieve
significant energy savings up to 48% compared to conventional
systems. The authors point out that to devise an industrial implementation, certain technological challenges should be overcome e
including the ability of the compressors to work at high temperatures with heavy oil vapour, and to feature high compression ratios.
2.4. Power systems and control
This section presents three articles dedicated to power systems
and control issues.
Boris Cosi
c, Goran Kraja
ci
c and Neven Dui
c from the Faculty of
Mechanical Engineering and Naval Architecture, University of
Zagreb e Croatia, teamed up with Natasa Markovska and Verica
Taseska from the Macedonian Academy of Sciences and Arts, Skopje,
Macedonia present an energy sectoral study titled “Environmental
and economic aspects of higher RES penetration into Macedonian
power system” [53]. The authors, based on their previous experience
with regional and sectoral energy analysis [54], start by observing
that the energy sector is the main emitter of greenhouse gases in
Macedonia (w70% share), of which emissions up to 75% are associated with the electricity generation due to the domination of
lignite fuelled power plants. This prompted the authorities to focus
on the sector as the main target for CO2 emissions reduction
adopting a strategy targeting a 21% share of renewables in the final
energy consumption by 2020. This paper investigates the
J.J. Klemes, P.S. Varbanov / Applied Thermal Engineering 43 (2012) 1e6
environmental and economic aspects of higher penetration of
Renewable Energy Sources (RES) into the Macedonian energy
system. A reference energy scenario for the power system expansion is first developed by making use of the EnergyPLAN model. The
reference energy system was developed for the year 2020, and then
used in the scenario analyses. After analysing four ‘RES’ scenarios
the authors report that renewables can reduce CO2 emissions up to
9.54% compared to the reference scenario. Additional analyses
performed indicate that increasing the price of CO2 twice compared
to the contemporary one, would increase system operating costs by
over 26% in all the scenarios considered, while doubling the lignite
price, the operating costs rise by up to 7.6%.
The next article is “Combined heat and power production planning
under liberalized market conditions” [55] authored by Michal Dvorák
and Petr Havel from the Faculty of Electrical Engineering, Czech
Technical University (CVUT)
in Prague, the Czech Republic. This
paper presents a methodology for optimising the operation of
a CHP plant and the simultaneous planning of electricity trading
with the objective of maximising the profit. A general model is
presented, which aims at rapid CHP plant prototyping using an
object-oriented modelling language. The general model consists of
first-principle models of technological components and a model of
a market of standardised power products. The authors report that
using the proposed methodology and the general purpose solver
Gurobi [56], optimal solutions to short-term planning problems
(24e48 h) are found within few minutes. For medium- and longterm problems (weeks to months), near optimal solutions with
an error usually under 0.5% and 1.0% are found within 2 h.
The concluding article of the issue is titled “Nonlinear inversionbased control of a distributed parameter heating system” [57] and is
authored by László Richárd Tóth, Lajos Nagy and Ferenc Szeifert
from the University of Pannonia, Hungary. It presents a study of the
control of a pilot-scale water heating system, utilising knowledge
from previously developed control models [58]. The pilot installation includes a tube with water flowing through it, while being
heated by an electrical heater. The outlet temperature is controlled
by manipulating the water flow rate responding to inlet temperature and heat duty disturbances. The device has been designed to
resemble solar collectors and heat exchangers, thus making it
a useful tool for modelling such devices. The method of constrained
inversion was applied. This control strategy is based on a firstprinciple model of the process and feed-forward control. Two
different approaches were compared in handling the distributed
parameter system. To eliminate steady-state error, feedback
compensation was provided. Experimental results reported by the
authors indicate that both controllers are superior in performance
to the conventional PI controller by exhibiting smaller deviations
from the control target and virtually no oscillations.
3. Conclusions
The PRES conferences evolved over the years from the original
focus introduced in 1998, which was ”Process Integration for Energy
Saving and Pollution Reduction” to a wider coverage that is very
closely related to applied thermal engineering. It evolved, in
parallel with the broader development of priorities in the industrial
production and related research commitments on environmental,
social and economic challenges. Even in competition with
a constantly growing number of conferences PRES gained its firm
place in the field and attracts a growing number of delegates.
The current Special Issue of Applied Thermal Engineering features
21 innovative scientific articles with a topical coverage representative of PRES’11. The main focus in the area of energy and thermal
engineering has been on improving and making more practical the
techniques for HEN retrofit and optimisation [18,36], combining
5
process and HEN design [38], advancing the Total Site methodology
with more efficient and accurate cogeneration targeting [31], its
application to very large-scale sites [19] as well as emergy evaluation [34], Heat Integration in biorefineries [23,27], geothermal
energy utilisation [26], and optimising utility cooling systems [30].
Those are supplemented by studies on improving heat transfer and
the technical viability of heat exchangers [40], heat pumps [42,44],
membrane use for reducing process heating and cooling demands
[45,47,48], separation systems efficiency [51], studies of whole
electricity sector [53], production planning [55] and thermal
system control [49,57].
We are confident that the papers in this SI of Applied Thermal
Engineering will be of interest and relevance to a broad range of the
scientific community and hope it will also bring to their attention
the PRES Conference series. The PRES 2012 will be again a joint
conference with CHISA 2012 [59]. It will be been held in Prague late
August 2012. PRES 2012 has received more than 400 abstracts [60]
from which to make a selection.
Acknowledgements
The editors of this Special issue of the Applied Thermal Engineering offer our gratitude to fifty reviewers for their invaluable help
and contributions. Many of them reviewed multiple papers and
served as members of the PRES International Scientific Committee
[59]. Their dedicated effort made it possible to review/revise and to
publish this Special issue in a comparatively short time after the
conference. Their contribution has been most appreciated.
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