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Increasing energy usage efficiency requires enhanced heat energy recuperation between process streams in the industry and civic sector with waste heat utilization. The condensation of different vapours is the process encountered in many industrial applications. Increasing the heat recuperation in this process is possible with efficient heat transfer equipment, among which a Plate Heat Exchanger (PHE) is at the leading position. A number of research works have been conducted in recent years concerning construction development and heat transfer enhancement in conditions of limited pressure drop to increase PHE performance in condensation processes. The results of studies on heat transfer and pressure drop in the two-phase condensing flow inside channels of PHE with different geometries of corrugations are discussed. In many implementations, the total pressure drop allowable for gaseous streams in heat exchangers is relatively small. The structure of two-phase flow in PHE channels of complex geometry is very different than in tubes and flat wall channels. The relative differences in approaches to enhance PHE performance in condensation processes based on its modelling, optimisation and design are analyzed. The directions and prospects for future developments are formulated, and potential savings for the economy and the environmental footprint is presented. [ABSTRACT FROM AUTHOR]

The condensation of vapours in the presence of non-condensable gas is happening in a number of industries. Its efficient realisation must be considered in optimisation of Heat Exchanger Networks (HENs) to increase efficiency of energy usage. In these processes, Plate Heat Exchanger (PHE) with enhanced heat and mass transfer can be effectively used. The method of preliminary selection of the PHE heat transfer area, plate size and corrugation geometry is proposed for the case of steam condensing from its mixture with air. The method uses the developed earlier one-dimensional mathematical model, modernized for PHE consisting from commercially produced plates. The heat transfer area of PHE is minimised by proper selection of plate sizes and geometrical characteristics of its corrugation. The optimisation variables are the corrugation angle to the main flow direction inside PHE channel, the corrugations depth and the length of plate. The case study illustrates the application of the method in case of utilisation low grade heat from exhaust gases after process of drying by superheated steam. The method is implemented as a computer program which can be included as a Dynamic Link Library module in software for HEN optimisation. • New method for estimating optimal parameters of Plate Heat Exchanger is proposed. • Method experimentally confirmed in industrial conditions for condensation process. • The effect of plate corrugations on Plate Heat Exchanger performance is analysed. • The effect of pressure drop on Plate Heat Exchanger performance is discussed. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of publications on fouling in plate heat exchangers (PHEs) on heating water solutions is presented. The peculiarities of flow structure in PHE channels and differences in construction require studies specifically for this efficient type of heat exchanger. The main fouling mechanisms in these conditions are crystallisation and particulate fouling. The predominant way of fouling development in PHE is asymptotic when at some time of fouling growth, the deposition of fouling and its removal to the main flow becomes equal and fouling thermal resistance does not change with time. The data of different experimental research and industry tests show that the rate of fouling in PHE from 5 to 20 times lower than in shell and tube heat exchangers for the same duty and overall process conditions in heating water solutions. The different approaches to modelling fouling formation in PHEs are analysed. The modelling of local process parameters in channels with accounting for the geometry of corrugations on plates is extremely important for the accurate prediction of fouling formation. Among different ways of fouling mitigation in PHE, the accurate design and proper selection of plates and their arrangement is considered the most effective, while covering plates with fouling-reducing coatings has prospects in development and application. The cleaning of PHEs has to be done with the development of optimised maintenance schedules. The cleaning of plate-and-frame PHEs can be done by mechanical methods, but chemical cleaning in place (CIP) with special CIP machines is preferable where it is possible. [Display omitted] • The published results of studies on fouling of PHE in heating of water solutions are reviewed. • The fouling tendencies in PHEs are much lower than in shell-and-tube heat exchangers. • The transport-reaction model can account for the fouling deposition in PHE. • The fouling distribution along channels must be accounted for in PHE modelling and design. • The correct plates arrangement and accurate design necessary to mitigate PHE fouling. [ABSTRACT FROM AUTHOR]

Optimization of Heat Exchanger Networks (HEN) has received considerable attention in last decades, but a few studies on inherent safety. In this paper, risk assessment is considered simultaneously during the synthesis of HENs. As risks depend on the equipment selected, a superstructure enabling selection of direct and indirect heat transfer between hot and cold streams and different types of heat exchangers (HEs) was tested. The individual heat transfer and the overall HEN risk were analyzed. Different individual risk limits have been introduced for certain types of heat transfer, e.g. between two process streams or between utility and process streams. The sensitivity analyses were performed first, considering only toxicity as a risk, but later flammability and explosiveness were also simultaneously tested, in order to consider the most important aspects of safety. The results obtained indicate that rather significant changes in HEN designs can increase safety, while still exhibiting similar economic efficiency. [ABSTRACT FROM AUTHOR]

Heat exchanger network synthesis (HENS) is an effective tool for heat recovery in chemical and petrochemical industries. This study aims to show a method for HENS with the consideration of different shell-side flow arrangements in shell-and-tube heat exchangers. The proposed MINLP model is modified from the stage-wise superstructure model, incorporating newly developed correlations for shell-side pressure drop calculation for the helical baffle. The objective is to minimise the total annual cost (TAC) with a trade-off between the cost of different shell-side heat exchangers, utility cost, and pumping cost. The selection of baffle design is decided by the saved pumping cost and the increased area cost. The proposed model is tested from different points of view: with/without utility constraints and different statuses of the streams. Three case studies are presented and compared with the results from the literature. The proposed method with different shell-side baffles can reduce the heat transfer area and pressure drop. For fixed utility consumptions, the TAC in a case study is decreased by 8.9% with mixed baffle types. Although the unit per area cost of the helical baffle is higher than the segmental baffle, the increased investment cost could be compensated by the reduced operation cost, especially for plants with high viscosity streams and long-term cost-saving. [ABSTRACT FROM AUTHOR]

Heat exchanger network synthesis is an essential optimisation tool for Process Integration, particularly in energy-intensive industries. Proper design or retrofit of heat exchanger network can enable energy conservation, efficiency improvement, and process debottlenecking. Many earlier pieces of research have focused on the impact of the network structure and process features such as network topology, temperature intervals, continuous/batch processes, and so on. As the major device in heat exchanger networks, heat exchangers research has always been a hot topic. However, the individual heat exchanger research is different from the number of heat exchangers in a network. Various performance aspects of the heat exchangers, e.g., pressure drop, fouling, and thermal performance, could influence the whole network and the passive responses between each heat exchanger. Besides, integrating those aspects of individual heat exchangers into the network synthesis is still an open problem, especially for cases that demand simultaneous optimisations. This work presents a thorough assessment of research into those aspects in heat exchanger networks, as well as the state-of-the-art of current approaches for heat exchanger networks optimisation that take heat exchanger performance into account. The essential coupling among fouling, pressure drop and thermal design is explored, and the nexus between them and the heat exchanger network is analysed. Researchers will benefit from this overview of heat exchanger network synthesis retrofitting methods and applications. • The impact of heat exchanger performance on the heat exchanger network is discussed. • Progress of model and approach for heat exchanger network synthesis is reviewed. • Influence factors: fouling, pressure drop, thermal design and intensified heat transfer. [ABSTRACT FROM AUTHOR]

Pressure drop is an important consideration in Total Site Heat Integration (TSHI). This is due to the typically large distances between the different plants and the flow across plant elevations and equipment, including heat exchangers. Failure to consider pressure drop during utility targeting and heat exchanger network (HEN) synthesis may, at best, lead to optimistic energy targets, and at worst, an inoperable system if the pumps or compressors cannot overcome the actual pressure drop. Most studies have addressed the pressure drop factor in terms of pumping cost, forbidden matches or allowable pressure drop constraints in the optimisation of HEN. This study looks at the implication of pressure drop in the context of a Total Site. The graphical Pinch-based TSHI methodology is extended to consider the pressure drop factor during the minimum energy requirement (MER) targeting stage. The improved methodology provides a more realistic estimation of the MER targets and valuable insights for the implementation of the TSHI design. In the case study, when pressure drop in the steam distribution networks is considered, the heating and cooling duties increase by 14.5% and 4.5%. [ABSTRACT FROM AUTHOR]

Abstract: This contribution presents an optimisation methodology for a Heat Exchanger Network (HEN) design over its entire lifespan. Consideration of fluctuating energy prices is essential for achieving an optimal HEN design. The objective function presents a trade-off between investment and operating costs. Accounting for higher energy prices supports greater investments compared to solutions obtained with current prices. However, due to the uncertainty of utility prices' forecasts, retrofit with the extension of HEN regarding the lifespan, will usually be the future strategy. As there can be various designs featuring similar initial investments, the objective is to identify one design that will be the most suitable for effective future extensions, preferably with low sensitivity to energy price fluctuations. These observations resulted in development of a stochastic multi-period mixed-integer nonlinear programming (MINLP) model for the synthesis of HEN designs, with extensions accounting for future energy prices. The objective of this work was to maximise both the Expected Net Present Value with no risk assessment performed, and the Certainty Equivalent with risk assessment regarding future utility prices and investment. The results obtained indicate that when applying the proposed approach, a design with improved economic performance could be obtained, especially when compared with Total Annual Cost. [Copyright &y& Elsevier]

Abstract: The optimal design of heat exchanger networks (HENs) has a great influence on the profitability of a plant. The optimisation is based on trade-offs between investment and operational cost. The full lifetime of the HEN and future utility prices have to be considered rather than optimising HEN on a yearly basis using current utility prices. Single-period optimisation and synthesis models for HENs reflect current utility prices only. These prices can fluctuate rather quickly and the optimal solution may be very different from a year to year. Deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) models for HEN synthesis have been developed to account for future price projections, where the utility cost coefficients are forecasted for the lifetime of the process. An optimal design is then determined for each projection and these designs are compared against a design with fixed current prices by applying the Incremental Net Present Value and other economic measures. In case studies the difference between utility consumption, using previous optimisation methods and new, were significant; e.g. in Case Study 2 the utility savings were 18.4% for hot and 32.6% for cold utility yielding an increase of the Net Present Value (NPV) by 7.8%. [Copyright &y& Elsevier]

Abstract: Large amounts of thermal energy are transferred between fluids for heating or cooling in industry as well as in the residential and service sectors. Typical examples are crude oil preheating, ethylene plants, pulp and paper plants, breweries, plants with exothermic and endothermic reactions, space heating, and cooling or refrigeration of food and beverages. Heat exchangers frequently operate under varying conditions. Their appropriate use in flexible heat exchanger networks as well as maintenance/reliability related calculations requires adequate models for estimating their dynamic behaviour. Cell-based dynamic models are very often used to represent heat exchangers with varying arrangements. The current paper describes a direct method and a visualisation technique for determining the number of the modelling cells and their size. [Copyright &y& Elsevier]

In the industry, there are frequently prohibited and restricted matches in the Heat Exchanger Networks (HENs). These matches could cause risk cost when failures happen. Some matches of streams can be entirely prohibited, but some may only have a certain level of restriction. The margins are set up, based on the risk cost assessment, whether to exchange the heat and by which type of equipment between specific streams. This study proposes a method based on the Advanced Grid Diagram to benefit from an optimised synthesis plan for HEN considering prohibited and restricted matches. A pre-designed HEN could be determined in the synthesis stage, not considering the prohibited or restricted matches. A follow-up topology evolution is performed to trade off the prohibitions and evaluate the restrictions. A Benefit Diagram has been developed to show how many economic benefits can be gained by implementing new heat exchangers. It is used for comparison between allowing all restricted streams and avoiding restricted streams to find the potential risk cost margin. The method is applied to a case study to analyse the restricted and prohibited matches. Optimal HEN design results offer the designers a guide to evaluate to which extent should implement the restricted matches. • Prohibited and restricted matches are considered in the HEN synthesis. • An extended Advanced Grid Diagram method is developed. • The trade-off between the risk cost and utility saving is studied. • A Benefit Diagram to show how many economic benefits can be gained. • Several scenarios are studied to illustrate the proposed method. [ABSTRACT FROM AUTHOR]

Heat Integration with heat exchanger network (HEN) is a widely used way to save energy and improve efficiency. Varied types of heat exchangers and materials would influence the investment cost and affect the design of HEN retrofit. This paper critically reviews the features of various types of heat exchangers, their working conditions and investment costs, as well as the state-of-the-art of the current methods for HEN synthesis and retrofit, to introduce a framework for HEN retrofit which considers heat exchanger and material selection. The proposed framework divides the retrofit design process into two stages, diagnosis and optimisation. In the diagnosis stage, two graphical decision-making tools, the Shifted Retrofit Thermodynamic Grid Diagram with Shifted Heat Exchanger Temperature Range (SRTGD-SHTR) and Shifted Material Temperature Range (SRTGD-SMTR) are proposed for analysis and diagnosis of the existing HEN to determine feasible retrofit plans with pre-selected heat exchangers and materials. In the optimisation stage, the constrained particle swarm optimisation algorithm is applied to optimise the plans made in the first stage and minimise the total annual cost. A case study demonstrates a possible implementation of the proposed framework. The suitable types for new heat exchangers and their materials are selected, and the retrofitted design can reduce the utility cost by 8.9% compared with the existing HEN. This framework can be applied easily with a sound solution for HEN retrofit. • Development of a novel optimisation framework for the retrofit of HENs. • Consideration of the heat exchanger type and material selection in the design process. • Review of the features of various types of heat exchangers. • Review of the state-of-the-art of the current methods for HEN synthesis and retrofit. • Presentation of a case to verify the new optimisation framework. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN) retrofit is a vital task in the process design to improve energy savings. Various types of heat exchangers such as shell and tube, double-pipe, compact plate, and spiral tube have their working temperature ranges and costs. Selecting suitable types of heat exchangers according to their temperature ranges and costs is a crucial aspect of industrial implementation. However, considering the type of heat exchangers in the HEN retrofit process is rarely seen in previous publications. This issue can be solved by the proposed Shifted Retrofit Thermodynamic Grid Diagram with the Shifted Temperature Range of Heat Exchangers (SRTGD-STR). The temperature ranges of six widely used heat exchanger types are coupled in the grid diagram. This diagram enables the visualisation of identifying the potential retrofit plan of HEN with heat-exchanger type selection. The retrofit design aims to minimise utility cost and capital cost. An illustrative example and a case study are presented to show the effectiveness of the method. [ABSTRACT FROM AUTHOR]

Graphical tools are useful in the heat exchanger network (HEN) retrofit to maximise energy savings. The disadvantage of heuristic rules, which are usually applied to make retrofit decisions using graphical tools, is that they could lead to sub-optimal solutions. The presented study developed a two-stage method for HEN retrofit. In the first stage, a mixed-integer linear programming (MILP) model is formulated based on the structure of the shifted retrofit thermodynamic grid diagram (SRTGD) to minimise the utility cost and investment. The non-linear equations for the investment cost calculation were linearised, and the parameters in the linearised equations were obtained using data regression. In the second stage, a particle swarm optimisation (PSO) algorithm was selected and applied to adjust the inlet and outlet temperatures of heat exchangers with the aim of minimising the payback period on the basis of the first-stage solution. The proposed two-stage procedure combines the strengths of the MILP and PSO methods, offering convenient interfaces for user interaction and results interpretation. Two cases were studied to verify the effectiveness of the method. Case 1 and Case 2 decreased the payback period by 11.6% and 21.7% compared to the results obtained in previous retrofit applications. [ABSTRACT FROM AUTHOR]

The mission of Renewable and Sustainable Energy Reviews (RSER) is to communicate the most significant and relevant critical thinking in renewable and sustainable energy research and development, bringing together the research community, the private sector and policy and decision-makers. The aim of the journal is to share problems, solutions, novel ideas and technologies that support the transition to a low-carbon future and achieve the global emissions targets as established by the United Nations Framework Convention on Climate Change (UNFCC). The Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES) 2018 conference brought together the following topics through interdisciplinary dialogue: (a) Process Integration for sustainable development; (b) Process analysis, modelling and optimisation; (c) Total Site Integration; (d) Heat transfer and heat exchangers; (e) Energy-saving and clean technologies; (f) Sustainable processing and production; (g) Renewable and high efficiency utility systems; (h) Footprint minimisation and mitigation; (i) Operations and supply chain management; (j) Waste minimisation, processing and management; (k) Batch process analysis and integration; (l) Process network dynamics, flexibility and control; (m) Industrial implementation and optimisation; (n) Numerical fluid flow and heat transfer simulation; (o) Sustainability and Process Integration teaching, learning and knowledge tools. This Virtual Special Issue (VSI) captures many of the most significant developments in renewable and sustainable energy research. [ABSTRACT FROM AUTHOR]

The design of heat exchanger networks (HEN) in the process industry has largely focused on minimisation of operating and capital costs using techniques such as pinch analysis or mathematical modelling. Aspects of operability and flexibility, including issues of disturbances affecting downstream processes during the operation of highly integrated HEN, still need development. This work presents a methodology to manage temperature disturbances in a HEN design to achieve maximum heat recovery, considering the impact of supply temperature fluctuations on utility consumption, heat exchanger sizing, bypass placement and economic performance. Key observations have been made and new heuristics are proposed to guide heat exchanger sizing to consider disturbances and bypass placement for cases above and below the HEN pinch point. Application of the methodology on two case studies shows that the impact of supply temperature fluctuations on downstream heat exchangers can be reduced through instant propagation of the disturbances to heaters or coolers. Where possible, the disturbances have been capitalised upon for additional heat recovery using the pinch analysis plus-minus principle as a guide. Results of the case study show that the HEN with maximum HE area yields economic savings of up to 15% per year relative to the HEN with a nominal HE area. [ABSTRACT FROM AUTHOR]

Highlights • Large-scale HEN synthesis is a first step towards Total Site synthesis. • Two-step MILP/MINLP approach was developed for larges-scale HEN synthesis. • Number of potential matches is significantly reduced, solutions are directed to global optima using MILP TransHEN model. • MINLP model HENSyn use reduced superstructure for HEN synthesis. • Problem with 173 process streams and multiple hot utilities solved. Abstract Although different methodologies for the synthesis of heat exchanger network (HEN) problems have been introduced in the last forty years, there are still significant challenges to be addressed, such as solving large-scale problems. This study focuses on synthesizing large-scale HENs using mathematical programming to achieve near globally optimal solutions based on a two-step MILP/MINLP approach. In the first step a mixed-integer linear programming (MILP) model, TransHEN, is used that obtains a globally optimal solution at selected Δ T min. By utilisation of this model, the most promising matches are selected based on feasibility and viability. The second step entails using the matches selected in the TransHEN of Step 1 in a mixed-integer nonlinear programming (MINLP) model, HENsyn, using a reduced superstructure, to generate a feasible HEN. This study presents also a simultaneous Total Site synthesis with direct heat transfer between processes, and is the first step in the wider project of synthesising an entire Total Site with direct and indirect heat transfer; and is the first step in the wider scope of synthesising an entire Total Site with direct and indirect heat transfer; however, in order to attain this goal, a tool capable of an appropriately handling large number of streams is required. The newly developed procedure has been tested on several case studies, two of which are presented in this paper. For Case study 1 the results obtained lie within the range of best solutions obtained by other authors. Case study 2, consisting of 173 process stream and involving multiple hot utilities, shows the applicability of the developed method to handle large-scale HEN problems. [ABSTRACT FROM AUTHOR]

A plate heat exchanger (PHE) is a modern, effective type of heat transfer equipment capable of increasing heat recuperation and energy efficiency. For PHEs, enhanced methods of heat transfer intensification can be further applied using the analysis and knowledge already available in the literature. A review of the main developments in the construction and exploration of PHEs and in the methods of heat transfer intensification is presented in this paper with an analysis of the main construction modifications, such as plate-and-frame, brazed and welded PHEs. The differences between these construction modifications and their influences on the thermal and hydraulic performance of PHEs are discussed. Most modern PHEs have plates with inclined corrugations on their surface that create a strong, rigid construction with multiple contact points between the plates. The methods of PHE exploration are mostly experimental studies and/or CFD modelling. The main corrugation parameters influencing PHE performance are the corrugation inclination angle in relation to the main flow direction and the corrugation aspect ratio. Optimisation of these parameters is one way to enhance PHE performance. Other methods of heat transfer enhancement, including improving the form of the plate corrugations, use of nanofluids and active methods, are considered. Future research directions are proposed, such as improving fundamental understanding, developing new corrugation shapes and optimisation methods and area and cost estimations. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with an extension of Total Site Integration to Locally Integrated Energy Sectors producing more realistic utility and heat recovery targets. Process Heat Integration (based on Pinch Analysis) aims to minimise the amount of energy mostly used in industrial processes. It is still an open question how to solve the Total Site targeting problem when different values for the minimum allowed temperature differences (ΔT min) are specified for each process on the site. A single uniform ΔT min for all processes integrated in a Total Site, as practiced to date, cannot be generally optimal. Such an assumption may be too simplifying and lead to inadequate results due to imprecise estimation of the overall Total Site heat recovery targets. The modified Total Site targeting procedure, proposed in this paper, allows obtaining more realistic heat recovery targets for Total Sites. It is illustrated with a case study for Locally Integrated Energy Sectors, also providing a comparison with the traditional targeting procedure and the advantages offered by the modified one. [Copyright &y& Elsevier]

To incorporate exchanger dimensions as a design objective in plate and fin heat exchangers, a variable that must be taken into consideration is the geometry of the finned surfaces to be used. In this work, a methodology to find the surface geometry that will produce the required heat transfer coefficient and pressure drop to achieve the design targets was developed. The geometry of secondary surfaces can be specified by the fin density, which represents the number of fins per unit length. All other geometrical features, as well as the thermo-hydraulic performance, can be derived from this parameter. This work showed the way finned surfaces are engineered employing generalised thermo-hydraulic correlations as a part of a design methodology. It also showed that there was a volume space referred to as volume design region (VDR) where heat duty, pressure drop, and dimensions could simultaneously be met. Such a volume design region was problem- and surface-specific; therefore, its limits were determined by the heat duty, the pressure drop, and the type of finned surface chosen in the design. The application of this methodology to a case study showed that a shell and tube heat exchanger of 227.4 m2, with the appropriate fin density using offset strip-fins, could be replaced by a plate and fin exchanger with any combination of height, width, and length in the ranges of 0–0.58 m, 0–0.58 m, and 0–3.59 m. The approach presented in this work indicated that heat exchanger dimensions could be fixed as a design objective, and they could effectively be achieved through surface design. [ABSTRACT FROM AUTHOR]

Heat exchanger leakage leads to the shutdown of the whole set of equipment, which affects the economy of the production and directly threatens the safe operation of equipment. This contribution aims to add a quantitative leakage risks characterisation of including or excluding specific process streams into the dataset for Heat Integration (HI). This has been achieved by formulating a mathematical model of the HEN, where the objective function contains leakage risk assessment embedded into the total cost, based on risk severity and mean occurrence frequency. Equations for investment calculation are linearised, and a novel iteration algorithm is developed to solve the model. A sensitivity analysis of the resulting cost against the levels of potential risk is performed. The results show that there is a turning point with the increase of risk level that changes HEN topologies. It allows engineers to use a quantitative criterion for HI. [ABSTRACT FROM AUTHOR]

Energy is a fundamental element supporting societal development, particularly with the increasing dependency on the Internet of Things. It is also the main contributor to environmental impacts and subsequently, a potential sector for mitigation. Sustainable energy system design considers energy savings and energy efficiency, waste and consumption reduction, process efficiency enhancement, waste heat recovery, and integration of renewable energy. Emerging tools range from advanced Process Integration, modelling, simulation, and optimisation, to system analysis and assessment. This review covers selected emerging studies promoting sustainable system design, including the recent developments reported in the Special Issue (SI) of the 22nd Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES'19). The primary emphasis was to enhance the economic and environmental performance. However, social factors were also highlighted as essential for future sustainable development. The discussion and analysis in this review focus on the most recent developments of (a) heat integration and heat transfer; (b) integrated and newly developed heat exchangers, (c) integration of renewables, and (d) roles in economic and environmental sustainability. The key results are highlighted, and future research ideas are suggested according to their links to a broader context. [ABSTRACT FROM AUTHOR]

Multi-objective optimization yields a set of Pareto solutions. Although Pareto curves provide useful information, deeper insights are needed for identifying more advanced process solutions. This study presents a methodology for analysing Pareto process solutions considering variations in environmental tax rates. Three new combined economic-environmental indicators are defined that measure the relationship between loss of economic value when deviating from the economic optimum, and savings originating from environmental impact reduction at a given environmental tax rate. It is shown that investing in processes or technologies for the reduction of environmental footprints can reduce emissions without worsening economic performance, provided that investors renounce the savings arising from reduced emissions. A multi-period synthesis of a process flow sheet is performed by targeting the economic performance at a given tax rate to the optimal level without any environmental tax. In a case study of Heat Exchanger Network synthesis, emissions were reduced by 8.7% after implementing carbon emissions tax at 60 €/t CO 2 , in comparison with the optimal design obtained at zero carbon emissions tax. However, the net present values of both solutions remained the same. In this way, more environmentally friendly yet economically attractive process designs can be generated. Image 1052441 [ABSTRACT FROM AUTHOR]

The trans -critical organic Rankine cycle (TCORC) can achieve a better thermal match in the heating process of the working fluid compared to the subcritical cycle. By using zeotropic mixtures as working fluids, the thermal match in the cooling process can be further optimized, reducing the system's irreversibility. As the selection criteria are not systematically formulated, screening zeotropic mixtures for the TCORC is challenging. In this work, the thermodynamic and thermo-economic analysis was carried out to investigate how the thermal match in the heating/cooling processes affects the system performance, which is represented by the overall exergy efficiency and the levelized energy cost. Results show that the mixture's critical temperature is a key factor influencing the system performance. Then, the mixtures having a proper condensation temperature glide can further improve the system performance. The thermo-economic analysis shows that the mixtures selected according to these criteria can also provide better thermo-economic performance, although the heat exchanger area has been enlarged during the improvement of the thermal match in heat exchangers. • Selection criteria of zeotropic mixtures for trans -critical ORC are developed. • The criteria are based on the thermodynamic and thermo-economic analysis. • The heating side thermal match is primarily affected by the mixture critical temperature. • Proper condensation temperature glide can further improve the system performance. • Selected mixtures provide both high thermodynamic and thermo-economic performance. [ABSTRACT FROM AUTHOR]

This paper proposed a novel methodology to retrofit Heat Exchanger Storage Networks (HESN) of batch processes using a modified graphical retrofit tool, namely batch Stream Temperature Enthalpy Plot (batch STEP). Unlike other graphical retrofit tools, batch STEP maintains individual characteristic of process streams as well as serves as the one-stop retrofit tool to retrofit direct and indirect HESN simultaneously. The conventional batch heat integration typically aimed to synthesise new Heat Recovery Loops (HRLs) for heat recovery enhancement without exploiting the benefits of reusing existing HRLs in saving the additional volume of heat storage units (HSUs) and space allocated for retrofit. Thus, this paper extends the STEP continuous retrofit methodology to batch processes by introducing a batch STEP diagram for identification of the potential process streams to be integrated into existing HRLs and potential modifications of existing HRLs operating temperature. The methodology also introduces HRL– problem table algorithm (HRL-PTA) and heuristics to target the maximum indirect heat recovery and integrate process streams into the existing HRLs systematically. The methodology proposed achieves plant savings of 23.9%–60.0% for hot utility, 25.9%–42.2% for cold utility and a reduction of 6.3%–8.1% for additional volume of HSUs required in two illustrative case studies. [Display omitted] • An extended STEP graphical tool for retrofitting HESN of batch processes. • Diagnosis of process streams to be integrated into existing heat recovery loops (HRLs). • Diagnosis of potential modification of existing HRLs operating temperature. • The maximum indirect heat recovery by existing HRLs is targeted. • Integration of heat supply and load into existing HRLs is guided. [ABSTRACT FROM AUTHOR]

This research investigated convective heat transfer and hydraulic resistance of smooth and corrugated double-tube heat exchangers at various flow rates from 60 L/h to 200 L/h. The inner tube with a thread structure is designed with three pitches, i.e., 4 mm, 6 mm and 8 mm. Nanofluids are used as tube-side fluids to analyze the enhancement of heat transfer on the inner tube side. Results show that the boundary layer is destroyed by the thread structure, and the heat flux is intensified at the outer tube side. For the double-tube heat exchanger, the combined enhancement technology using thread structure at the side of the outer tube and nanofluids at the side of the inner tube contributes to improvement in the overall heat transfer performance. The maximum increment in the comprehensive performance index is 59% for the case of 1.5 wt% SiC-water nanofluid with a thread pitch of 4 mm at a flow rate of 200 L/h. Finally, the distribution of local temperature difference is analysed theoretically for nanofluids with the optimum particle concentrations, which confirmed the rationality of 1.5 wt% SiC-water nanofluid with a thread pitch of 4 mm. Results reveal that the combined enhancement of using nanofluids and a thread structure has great potential in enhancing the thermal performance of double-tube heat exchangers. • Thermal performance and temperature difference are studied for a heat exchanger. •Corrugation pitch of 4 mm shows better performance compared with 6 mm and 8 mm. •Nusselt number of SiO2-water nanofluid decreases with particle concentration. •1.5% SiC nanofluid leads to 106.7% increase in Nusselt number compared with water. •Comprehensive index is analysed considering Nusselt number and friction factor. [ABSTRACT FROM AUTHOR]

The heat exchanger is an essential component of the supercritical CO 2 Brayton cycle. To attenuate the temperature fluctuations in the cycle, this study proposes a new structure with phase change materials embedded in the printed circuit heat exchanger. This structure package can contain a variety of phase change materials in a stepwise arrangement and a composite phase change material with expanded graphene. The effects of different flow directions, the number of layers in the phase change material ladder, whether the phase change material is compounded with expanded graphene or not, and the thickness of the phase change material were numerically compared. The results show that the PCM layer with 0.45 mm thickness has a smaller amplitude of both temperature fluctuations and liquid fraction fluctuations than that of 0.25 mm. Relative to the case without PCM, the outlet of hot side' temperature fluctuation amplitude of PCM/EG-3 and PCM/EG-5 with 0.45 mm thickness decreased by 17.11% and 22.37%, and the outlet of cold side' temperature fluctuation amplitude decreased by 36.84% and 38.16%, while the heat exchange decreased by only 2.28% and 1.78%, respectively. • A new structure for PCM embedded in PCHE is designed. • The effects of flow direction on the performance of PCHE-PCM are compared. • The effects of a multi-layer PCM ladder arrangement on PCHE-PCM are investigated. • The composite structure of PCM/EG significantly reduces the heat loss of PCHE. • The effects of different PCM layer thickness on PCHE-PCM are investigated. [ABSTRACT FROM AUTHOR]

This paper presents a method for heat exchanger network (HEN) optimisation considering plate heat exchangers (PHEs), incorporating detailed PHEs design. The developed method starts from a mathematical model based on the Advanced Grid Diagram, which can optimise the HEN structure. The model minimises the energy consumption cost with the constraints that enable a solution thermodynamically feasible. Then comes the heat exchanger type selection part, which is provided by a graphical tool helping to identify which types of the heat exchanger are feasible. The feasible temperature range can be easily visualised to avoid the temperature violation of PHEs. This selection part integrates the area calculation and cost calculation with the detailed heat exchanger design. The method has been tested by a case study of crude oil distillation system illustrating that the application of brazed plate heat exchangers (BHEs) of CB series manufactured by Alfa Laval can save 6.6% of the investment cost for new heat exchangers compared with the retrofit plan that only shell-and-tube and double pipe heat exchangers are used. •A framework for HEN optimisation and heat exchanger type selection. •A method for detailed plate heat exchanger design is proposed. •Advanced Grid Diagram-based method helps to avoid the temperature violation. •A case study to illustrate the proposed method. •The brazed plate heat exchanger of CB series has advantage on investment saving. [ABSTRACT FROM AUTHOR]

• An integrated software suite for heat recovery system design is presented. • It can be used for equipment design, system analysis and network optimisation. • Designs for heat exchanger, HEN, and WGCTO are integrated. • Case studies are given to demonstrate the developed software. Heat Integration (HI) with heat exchangers requires intimate knowledge and intensive calculations to set energy-saving targets to achieve the goal of efficient energy utilisation. The Shell and Tube Heat Exchanger (STHX) Design Software Module, or SPIL-HX package developed by the SPIL team, offers features that support engineers to design and rate original STHXs, STHXs coupled with the shell-side enhancement technologies, i.e., with segmented baffles and with helical baffles. This software tool also provides design solutions for the Waste Gas Compact Thermal Oxidiser (WGCTO), identifying the unit design capable of simultaneous combustion and heat exchange for waste gases. SPIL-HX package is also capable of automatic Heat Exchanger Network (HEN) synthesis and retrofit. With the built-in algorithm, the software can provide the optimal solution for HI, which significantly reduces operating, capital, and design costs. A user-friendly interface facilitates the use of the developed software. [ABSTRACT FROM AUTHOR]

Heat Pinch Analysis retrofit projects are typically performed by evaluating and maximising the heat recovery potentials within the individual process units. Once the potential improvements from the individual units have been assessed, the Total Site (TS) Heat Integration analysis is performed. Such approach may steer designers away from the promising retrofit opportunities and to lead towards suboptimal heat exchanger networks (HEN). This paper presents an effective retrofit framework for a TS system to determine the most cost-effective retrofit options and maximise the potential savings. Instead of performing the typical unit-wise process retrofit, the strategy is to determine the baseline total site consumption and benchmark targets, and to identify retrofit options from the TS context. This TS retrofit framework has been tested on a case study involving a petrochemical plant comprising of multiple process sections. The results of the analysis show that significant energy savings can be realised when both direct and indirect heat recovery retrofit options are evaluated. Further energy savings can be achieved via the Plus–Minus Principle that helps pinpoint the correct locations of heat surpluses and deficits and lead to the appropriate TS retrofit solution. As a conclusion, energy retrofit projects should be approached from the TS context, followed by the unit-wise retrofit (i.e., retrofit of the individual process sections). [ABSTRACT FROM AUTHOR]

Abstract: Total Site Heat Integration (TSHI) is a technique of exchanging heat among multiple processes via a centralised utility system. An analysis of the integrated multiple processes, also known as the Total Site (TS) system sensitivity, is needed to characterise the effects of a plant maintenance shutdown, to determine the operational changes needed for the utility production and to plan mitigation actions. This paper presents an improved Total Site Sensitivity Table (TSST) to be used as a systematic tool for this purpose. The TSST can be used to consider various ‘what if’ scenarios. This tool can be used to determine the optimum size of a utility generation system, to design the backup generators and piping needed in the system and to assess the external utilities that might need to be bought and stored. The methodology is demonstrated by using an Illustrated Case Study consisting of three processes. During the TS normal operation, the Total Site Problem Table Algorithm (TS-PTA) shows that the system requires 1065kW of High Pressure Steam and 645.5kW of Medium Pressure Steam as the heating utility, while for the cooling utility, 553.5kW of Low Pressure Steam and 3085kW of cooling water are required. The results of the modified TSST proposed that a boiler and a cooling tower with the system design requiring a maximum capacity of 2.172MW of steam and 4.1865MW of cooling water are needed to ensure an operational flexibility between the three integrated processes. [Copyright &y& Elsevier]

• Model for heat exchanger network (HEN) retrofit with enhancement technologies is formulated. • HEN retrofit model with long-term investment and maintenance planning model is developed. • Service life, depreciation and reliabilities of heat exchangers are considered in the planning model. • Results obtained yield 14% or higher net present value compared to previous retrofit solutions. • A graphical tool is created to track the reliability and maintenance status of heat exchangers. Process Optimisation has been the core topic in chemical process industries for decades. However, the performance of the asset strongly influences the production efficiency as well. In the case of Heat Exchanger Network (HEN), the retrofit decisions are often aimed to maximise energy savings and minimise the associated cost. However, the age and performance of heat exchangers have a great influence on the HEN efficiency as well. This study brings innovative retrofit algorithms, integrating exchangers' lifetime and reliability functions to visualise the benefits of the hybrid process and asset optimisation. The HEN retrofit structures are optimised, considering various heat intensification methods. The model is formulated based on the novel concept of Shifted Retrofit Thermodynamic Grid Diagram (SRTGD). A Mixed Integer Linear Programming (MILP) model is formulated for the investment and maintenance planning. The operating life of the network is discretised into multiple periods, and a decision is made within each period: whether to upgrade the heat exchangers, purchase new heat exchangers – for replacement or adding to the network, maintain the heat exchangers or perform nothing. Two realistic case studies are used to elucidate the application of the method. Under a 20 y planning horizon, the Net Present Value (NPV) obtained are higher than the previous works, i.e. 17% higher for case study 1 with 51% utility savings, and 14% higher for case study 2 with 74% utility savings. The proposed HEN retrofit decisions are proven to be cost-effective. A graphical tool has been developed to track the reliability and maintenance status of the exchangers to provide a significant guide to the economically optimum decisions. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN), which is designed to achieve the maximum energy recovery (MER) involves the integration and interactions of multiple process streams. In a plant, the system operation may experience various disturbances such as changes in supply temperature and flowrates. Small disturbances on one stream can affect other connecting streams. To manage these disturbances, the process to process and utility heat exchangers with bypass streams installation are typically overdesigned, leading to higher capital investment. This study presents the cost optimisation of flexible MER HEN design which considers the fluctuation probability using Break-Even Analysis (BEA). Stream data is extracted for the Pinch study and assessment for flexibility and MER was performed. The MER heat exchanger maximum size (MER-HEM) able to handle the most critical supply temperature fluctuations while minimising the utility consumption is calculated. However, the overdesign factor can affect the total annualised cost (TAC) at a certain probability of fluctuation occurrence. Besides that, the fluctuations experienced by the stream can result in the utility increasing or decreasing. Therefore, the MER heat exchanger original size (MER-HEO) is favoured when the fluctuation resulted in the utility cost increasing. The BEA is performed to determine the probability that results in high savings of the TAC and developed an optimal HEN design of MER-HEM or MER-HEO. The break-even point (BEP) from BEA indicate the exact fluctuation probability at which the TAC of MER-HEM and MER-HEO is the same. A case study with fluctuation probability over one-year operation is used to demonstrate the methodology. Application of the proposed methodology on the case study shows that the optimum size of heat exchanger can be determined and the additional savings of TAC can be achieved. • A new tool for MER HEN design with impact of the probability fluctuations. • The tool enables the selection of optimal heat exchanger size and total annual cost. • Trade-offs between MER, heat exchanger size, utility requirement and total annual cost. [ABSTRACT FROM AUTHOR]

In the present work, the effect of the baffle pattern on the heat transfer and fluid flow characteristics of shell-and-tube heat exchangers are experimentally investigated, including tri-flower baffle, pore plate baffle, rod baffle, segmental & pore baffle and segmental baffle. In order to compare the hydrodynamics and heat transfer characteristics of the five heat exchangers, a water-water heat transfer experiment system is built. Based on the experimental data, and at the same flow rate, comparison with segmental baffle, the h s of tri-flower baffle and pore plate baffle augment 33.8% and 17.7%. The pressure drop of the rod baffle, tri-flower baffle and segmental & pore baffle decrease are 70.1%, 19.5% and 31.1% lower than that of the segmental baffle. The comprehensive performances h s /Δ p of the rod baffle, tri-flower baffle and pore plate baffle are all superior to that of the segmental baffle. Finally, the experimental correlative formula is raised for the four heat exchangers, and an optimal design scheme for shell side heat transfer enhancement is proposed. • Four types of baffle pattern of heat exchangers are experimentally compared. • Pressure drop and heat transfer performance are experimentally investigated. • Experimental correlative formula is fitted for the four heat exchangers. • An optimal design scheme for shell side heat transfer enhancement is proposed. [ABSTRACT FROM AUTHOR]

In this study, diverse baffled longitudinal flow shell-and-tube heat exchangers (STHX) are contrasted with segmental baffle shell-and-tube heat exchanger (SG-STHX). Experimental data are obtained with municipal water served as the working fluid, and the shell-side volume flow rate ranges from 1.79 m3/h to 7.42 m3/h. The components of the shell-side pressure drop are discussed stand on different flow patterns. The maximum proportion of pressure drop in tube bundle section of rod baffle shell-and-tube heat exchanger (RB-STHX) is 12%, while it has nearly taken up 70% shell-side pressure drop for both SG-STHX and large-and-small hole baffle shell-and-tube heat exchanger (LSHB-STHX). The energy efficiency of three tested STHXs is deliberated from three perspectives, including entropy generation, exergy destruction, and efficiency evaluation criterion. The longitudinal flow pattern performed superior energy efficiency, particularly for RB-STHX with the least irreversible energy loss and the most available work. Grounded on the energy-saving potential of RB-STHX, further numerical simulations on the shell-side thermo-hydraulic performance of RB-STHX are conducted. The nexus between geometrical parameters of RB-STHX and its thermal-hydraulic performance are studied. The thermal-hydraulic performance and energy efficiency discussed in this study support further design and application of longitudinal flow STHX to retain inherent superiorities with advanced performance. • Only 12% of the total pressure drop in the shell-side of RB-STHX is derived from the tube bundle section. • RB-STHX performs 173%∼223% higher EEC than LSHB-STHX with the least irreversible energy loss. • Rod baffle shell-and-tube heat exchanger shows the best comprehensive performance. • Numerical investigation of the heat transfer enhancement. • Factors: tube arrangement, rod shape, baffle arrangement, and baffle number. [ABSTRACT FROM AUTHOR]