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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]

The supercritical CO2 Brayton cycle is widely utilized by various industries because of its compactness and efficiency. However, in the actual process, there are always temperature fluctuations that affect the normal operation of the whole supercritical CO2 Brayton cycle system, in order to weaken the temperature fluctuations without adding additional components, a new structure of PCHE with PCM embedded in PCHE was designed in this study. Fluent was used to simulate the working conditions and compare with the commonly used PCHE under the same working conditions. It was found that the structures with porosity of 0.8 to 0.9, the percentage reduction of temperature fluctuations on the hot side was 26.84 %, 26.78 % and 26.49 %, respectively, and the percentage reduction of temperature fluctuations on the cold side was 40.30 %, 40.81 % and 41.63 %, respectively, and the percentage reduction of heat exchange was 1.8 %, 1.9 % and 2.3 %, respectively. [ABSTRACT FROM AUTHOR]

As an essential part of Heat Integration, the heat exchanger network (HEN) plays a vital role in large-scale industrial fields. The optimisation of HEN can increase energy efficiency and considerably save the operating and investment cost of the project. This study presents a novel approach for simultaneous optimisation of plant operating variables and the HEN structure of an existing natural gas purification process. The objective function is the total energy consumption of the studied process. A two-stage method is developed for optimisation. In the first stage, a particle swarm optimisation (PSO) algorithm is developed to optimise variables including tower top pressure, tower bottom pressure, and reflux ratio on the HEN, thereby changing the initial temperatures of cold and hot streams in the HEN. In the second stage, a shifted retrofit thermodynamic grid diagram (SRTGD)-based model and the corresponding solving algorithm was applied to retrofit the HEN. The case study shows that the optimal operating conditions of towers and temperature spans of heat exchangers can be solved by the proposed method to reduce the total energy consumption. The case study shows that the total energy consumption is reduced by 41.5 %. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN) retrofit is an effective way to reduce energy consumption and improve energy efficiency. A key criterion in industrial practice to evaluate the performance of a retrofit plan is the minimising total annualised cost. However, when pursuing the goal of minimising total annualised cost by graphical tools, sub-optimal solutions are inevitable because of the difficulty in finding the balance of utility cost and investment. In this study, a method based on constrained particle swarm optimisation (PSO) algorithm is developed for the annual cost minimisation when retrofitting HENs. The proposed method is applied based on an initial retrofit plan obtained by graphical tools. It can achieve the aim of total annualised cost reduction by adjusting the inlet and outlet temperatures of each heat exchanger through PSO with the consideration of different utility prices and investment. The results show that this method can find optimal temperature spans for heat exchangers to reduce the total annualised cost. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]