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This study analyzed the acoustic energy transfer process in expanded pipe of heat exchangers based on the field synergy principle. The synergy between the flow field and the acoustic field was deduced theoretically based on the energy and momentum equations pertaining to the acoustic field. The synergy angle of the flow field and the acoustic field was calculated numerically. The noise propagation process in the expanded pipe was measured experimentally. The results show that the sound pressure level and synergy angle both increase with the increase in flow velocity, whereas the acoustic energy transfer process decreased with the increase in synergy angle. An extended outlet of the expanded pipe segment can reduce the flow noise magnitude with a lower pressure drop. The flow noise can reach 123 dB and the pressure drop is 37.3％ and 24.7％ less than other cases. In conclusion, the theoretical analysis, experimental tests, and numerical simulation method are developed to study the acoustic energy transfer process in segments of expanded pipe based on synergy principle of flow and acoustic fields. [ABSTRACT FROM AUTHOR]

Abstract Phase change materials used in thermal energy storage systems are critical for energy utilization. Organic phase change materials have received considerable attention both for applications and research due to their favorable properties, such as large latent heat, low cost, stability, nontoxicity, and corrosion resistance. Because of the inherently low thermal conductivity, there has been a lot of research on various combinations of organic phase change materials with high conductivity materials. Carbon nanotubes, graphene and porous carbon have excellent properties, such as ultrahigh surface area and high thermal conductivity, which have become the preferred materials for thermal properties enhancement. Benefit from the varied dimensional spaces for retaining materials, these carbon-based materials can act as excellent confinement for phase change materials to form shape stabilized, phase change tunable, and thermally enhanced phase change composites. In this paper, a review about recent advancement and challenges for organic phase change materials confined in different types of carbon-based materials is presented, associated with some relevant theories trying to understand the mechanism of heat transfer and phase change in micro/nano confinement. Some promising applications in thermal management and energy conversion that have great potential for more explorations are also introduced. Highlights • Carbon-based materials are suitable for infiltrating organic phase change materials. • The thermal properties of organic phase change materials can be improved effectively. • The challenges and perspectives of organic phase change materials are proposed. [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]

• Heat exchanger selection considering thermal efficiency and network responses. • Enhancement of suitable heat exchanger can get more benefits with little costs. • Lower effectiveness shows better return on investment due to potentials of thermal efficiency. • Three constraints of heat exchanger network retrofit are identified. • Energy savings in the case studies are 13.3% and 14.7% of the original utility loads. Energy conservation and efficiency improvement are critical problems for industrial process systems. Heat exchanger network retrofit has emerged as a powerful tool for energy-saving and Heat Integration, but the topology modification with new heat exchangers and re-piping is expensive and demands a long payback period. In this study, heat transfer enhancement is deployed in the heat exchanger network retrofit to avoid network topology modification. A target-evaluation method is proposed for heat exchanger network retrofit with the consideration of the thermal efficiency and the level of heat transfer enhancement. Two case studies are conducted to demonstrate the proposed method. The energy-saving of case 1 is 10.6752 MW, which is 13.3% of the original utility loads; 8.0303 MW heat loads are saved in case 2, which is 14.7% of the original utility loads. The results of return on investment indicate that enhancement of the best candidate heat exchanger can bring more energy-saving and better economic efficiency with fewer modifications to the existing heat exchangers, which is also confirmed by sensitivity analysis. The lower temperature effectiveness of the heat exchanger shows great potential for thermal efficiency improvement. The present results highlight the energy-saving effects that heat transfer enhancement has on the heat exchanger network retrofit. The proposed two-stage method supports the further development of energy conservation in different industries. [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]

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]

Clean energy storage is of vital importance for cleaner production and environmental protection. This present study focuses on the promotion of clean energy storage efficiency in the widely used shell and tube latent heat thermal energy storage unit. The enhancing effects of fin inside the tube on the charging time and energy storage rate are studied. Numerical investigations are performed through the enthalpy based lattice Boltzmann method couple with curved boundary. Three kinds of configurations for one-fin and two-fin are investigated. Results indicated that fin position can effectively impact the enhancing effects. For one-fin, the maximum difference of the enhanced ratio for different fin positions is 15.17% when R a = 107, while it is 7.52% for two-fin. The optimal fin position varies with different Ra , but with appropriate approximation, it can be concluded that one-fin on the bottom and two-fin on the vertical direction are the optimal fin position for one-fin and two-fin cases. In addition, one long fin shows better enhancing effects than two short fins. Under the same fin length, the average enhanced ratio for one long fin is 41.82%, while it is only 27.03% for two short fins. These results can provide guidance for the fin configuration in the shell and tube latent heat thermal energy storage unit to achieve higher energy storage efficiency. Since this unit is widely used in various clean energy storage systems, the results would also be beneficial for various industrial applications of clean energy storage and utilization. • The characteristics of energy storage process with fins inside tube are obtained. • The different enhancing effects caused by fin position can be as high as 15.17%. • One-fin on bottom and two-fin on vertical direction are the optimal fin position. • The average enhanced ratio for one long fin is 14.79% higher than two short fins. • The charging efficiency can be enhanced by 40% with proper fin configuration. [ABSTRACT FROM AUTHOR]