Heat Exchanger Research Articles

Design Optimization of a Plate‐Fin Heat Exchanger With Metaheuristic Hybrid Algorithm

ABSTRACTThis paper introduces a novel approach to enhance the heat transfer efficiency of a plate‐fin heat exchanger. The metaheuristic hybrid approach combines particle swarm optimization (PSO) with the genetic algorithm (GA). Seven critical design parameters are used as variables. The research demonstrates the effectiveness of this hybrid method through a case study based on existing literature. The numerical results show the superior performance of the hybrid genetic algorithm particle swarm optimization over conventional GA and PSO techniques. The hybrid method achieves an optimal configuration with increased accuracy in a shorter computational time, offering significant time and cost savings in the design process.

Experimental study on heat transfer and resistance of round tube with tube sheet under ultrasonic action

AbstractEnergy is vital to the survival and development of human beings. In the era of ‘carbon neutrality’, all walks of life around the world are upgrading their technological capabilities to reduce carbon emissions. As a new type of active strengthening technology to improve the comprehensive performance of heat exchangers, ultrasonic technology has attracted the attention of more and more scholars. From the actual installation situation, a set of ultrasonic enhanced heat transfer test device with tube sheet round tube was built. After experimental research and data analysis, the influence of ultrasonic sound intensity, frequency, and position on heat transfer, flow resistance, and comprehensive performance of heat exchange tube under different working conditions and without ultrasonic wave is studied. The results show that the ultrasonic enhanced heat transfer and drag reduction capacity increases with the decrease of ultrasonic frequency, and under the action of ultrasonic waves of different frequencies, the critical sound intensity of its enhanced heat transfer and drag reduction performance is different. The drag reduction performance of the ultrasonic heat exchange tube is increased by 18.41%, the heat transfer performance is increased by 36.53%, and the overall performance is increased by 20.57%.

Experimentation of Grate Combustion of Municipal Solid Waste in Ouagadougou: Influence of Primary and Secondary Air Flow on Thermal Potential

The present work concerns the study of the influence of combustion air flows on the thermal potential during the combustion of a 2 kg mixture of solid model waste from the city of Ouagadougou. This mixture consists primarily of wood, cardboard and plastic. The prototype model is a natural laterite internal-walled grate furnace. During these investigations, we were interested in the temperature variation measured by 4 thermocouples K1 to K4 placed respectively from the waste bed to the top of the furnace. These variations are considered according to a variable primary and secondary air flow. The maximum primary and secondary airflow is 3000 L/min. Measurements are taken throughout the experiment at a step of 18 seconds and a maximum duration of 3 minutes for each case of flow considered. Maximum temperatures reaching 450oC are observed following the injection of secondary air only. This is explained by the supply of oxygen making the combustion more complete. The results show that the injection of primary and secondary air at a flow rate of 1500 L/min gives a more stable temperature result, i.e. 362,18oC 186,82oC 109,27oC 72,41oC respectively for the thermocouples K1, K2, K3, K4. An increase in the primary and secondary air flow to a maximum of 3000 L/min leads to a drop in temperatures due to the dilute internal atmosphere. These results allow to set the optimal operating parameters of the furnace in order to produce more heat for its recovery into electricity through a heat exchanger and a steam turbine.

Visual liquefaction process of biomass pyrolysis vapors during indirect heat exchange: Experimental description, prediction, and verification

The present investigation proposed an experimental method combining bio-oil segmental recovery, vapor composition inversion, and function fitting, to describe the vapor evolution curves and heat maps of water, acetic acid, furfural, phenol, MCP, guaiacol and its derivatives in the indirect condensing field regulated by continuous water bath temperatures within 280–364 K. Under 280 K water bath, the recovery proportion of water exceeded 50 % after pyrolysis vapors moved 8 cm from inlet, and soon surpassed 90 % after 12.5 cm. At 337 K, 50 % recovery proportion of water required the vapors to move 20 cm, while guaiacol required only 10 cm for the same proportion. Half of the evolution description data were sampled and utilized to fit the prediction curves of vapor evolution with increasing bath temperature, and another half were used to verify these prediction curves. The overall prediction accuracy of the representative components remained at 70 %, despite the local accuracies less than 50 % within 280–300 K and 355–364 K. These findings provided a visual description and prediction method for the selective condensation of pyrolysis vapors. The cycle from research to application of selective condensation was effectively shortened by the prediction of vapor evolution under water bath based on sampling experiments.

HAZOP ANALYSIS OF AN ATMOSPHERIC PETROLEUM DISTILLATION UNIT AND SIMILARITY IN SUSTAINABLE AVIATION FUELS (SAFs) PRODUCTION PROCESSES

The production of petroleum derivatives stands out worldwide among the non-renewable energy production processes, as the most well-known worldwide. In this study, an atmospheric distillation column that processed 100,000 barrels/day (662.5 m3/h) of crude oil was simulated using CHEMCAD® software. From this procedure, the Process Flow Diagram (PFD) and the Piping and Instrumentation Diagram (PI&D) for the unit, corresponding to its automation, were obtained. Subsequently, a HAZOP (Hazard and Operability Study) analysis was conducted in order to identify risks in the unit that, although not dangerous, could compromise its ability to achieve its productivity. The main risks of the process were related to fires, explosions and environmental contamination from leaks and ruptures in pipes, pumps, heat exchangers, the column itself, among other equipment. The HAZOP analysis was able, through the use of guide words, to identify possible operational risks arising from deviations in operating intentions, such as the possibility of fires, explosions, environmental contamination and their consequences. It was possible to identify the risks associated with the selection of materials, the mechanical design of the equipment and the specifications of the accessories. Therefore, the study carried out is an important survey for reducing possible failures in the oil industry. And, since this study is an in-depth study on the distillation processes for petroleum-derived products. It is understood that their in-depth study, as a result of the development of new renewable products, especially sustainable aviation fuels (SAFs), because they are similar purification processes, employ the same methodology to identify possible failures in production.

Research on the thermal comfort of vertical radiant cold plate coupling with a new dual cold source dehumidification air conditioning system

Radiant cooling provides a completely novel air conditioning terminal that could provide better thermal comfort for the resident. However, the radiative system may encounter condensation issues under high-humidity environments. This article studies a radiant air conditioning system with dual-cold-source dehumidification which comprises a plate heat exchanger, a dual-cold fresh air dehumidifier, a capillary radiant cooling wall, and an air-source heat pump. The experimental results demonstrate a positive correlation between the temperature profile of the indoor air and the temperature distribution of the radiant cooling wall. Simulations were conducted to analyze the office’s air temperature and airflow velocity distributions under different supply air volumes and to assess thermal comfort employing computational fluid dynamics (CFD) software. The comfort levels with different air inlet positions are discussed. The simulation results demonstrate that the air conditioning system can maintain a high standard of comfort under an air supply of 350 m³/h.

Investigation of convective heat transport in a Carreau hybrid nanofluid between two stretchable rotatory disks

Abstract Hybrid nanofluids (HNFs) have outstanding energy transfer capabilities that are comparable to mono-nanofluids. Materials had appliances in obvious fields such as heat generation, micropower generation, and solar collectors. The objective of this study is to investigate the new aspects of convective heat transfer in an electrically conducting Carreau HNF situated between two parallel discs. In addition to the presumed stretchability and rotation of the discs, physical phenomena like nonlinear radiation, viscous dissipation, Joule dissipation, and heat generation and absorption are considered. The Cu and TiO2 nanoparticles dispersed in engine oil to understand the intricate phenomenon of hybridization. The Tiwari and Das nanofluid model is employed to model the governing partial differential equations (PDEs) and then simplified using boundary layer approximation. The suitable transformations of similarity variables are defined and implemented to change the set of formulated PDEs into ordinary differential equations. The reduced system is solved semi-analytically by the homotopy analysis method. The influences of involving physical parameters on the velocity and temperature are plotted with the help of graphical figures. This study brings forth a significant contribution by uncovering novel flow features that have previously remained unexplored. By addressing a well-defined problem, our research provides valuable insights into the enhancement of thermal transport, with direct implications for diverse engineering devices such as solar collectors, heat exchangers, and microelectronics.

Unilateral carotid rete mirabile presenting with limb-shaking transient ischemic attack

A rare presentation of unilateral carotid rete mirabile (RM) in a 70-year-old male manifesting as limb-shaking transient ischemic attacks (LS-TIAs), a disorder typically associated with carotid artery stenosis. The patient experienced recurrent left-sided limb shaking and numbness, with angiography revealing an anomalous microarterial collateral network replacing the right internal carotid artery's (ICA) cavernous segment, indicative of RM. Differential diagnoses included recanalization following occlusion, arteriovenous malformation, with carotid canal dysplasia on CT supporting the RM diagnosis. The patient's management involved antiplatelet therapy and lifestyle changes, following which he reported no further cerebrovascular events. This case underscores the importance of considering RM in differential diagnoses of LS-TIA and suggests conservative management as a favorable approach.

Experimental Evaluation of Gas-Dynamic Conditions of Heat Exchange of Stationary Air Flows in Vertical Conical Diffuser

Conical diffusers are widely used in technical devices (gasifiers, turbines, combustion chambers) and technological processes (ejectors, mixers, renewable energy). The perfection of flow gas dynamics in a conical diffuser affects the intensity of heat and mass transfer processes, the quality of mixing/separation of working media and the flow characteristics of technical devices. These parameters largely determine the efficiency and productivity of the final product. This article presents an analysis of experimental data on the gas-dynamic characteristics of stationary air flows in a vertical, conical, flat diffuser under different initial boundary conditions. An experimental setup was created, measuring instruments were selected, and an automated data collection system was developed. Basic data on the gas dynamics of air flows were obtained using the thermal anemometry method. Experimental data on instantaneous values of air flow velocity in a diffuser for initial velocities from 0.4 m/s to 2.22 m/s are presented. These data were the basis for calculating and obtaining velocity fields and turbulence intensity fields of the air flow in a vertical diffuser. It is shown that the value of the initial flow velocity at the diffuser inlet has a significant effect on the gas-dynamic characteristics. In addition, a spectral analysis of the change in air flow velocity both by height and along the diffuser axis was performed. The obtained data may be useful for refining engineering calculations, verifying mathematical models, searching for technical solutions and deepening knowledge about the features of gas dynamics of air flows in vertical diffusers.

Particle transport and turbulence modification in unstably stratified mixed convection within a horizontal channel

Particle transport and turbulence modification in an unstably stratified, particle-laden turbulent flow within a horizontal channel is studied via direct numerical simulations combined with Lagrangian point‒particle tracking techniques. Two-way coupling in momentum and energy is considered in dilute gas‒solid flows under mixed convection (synergistic effects of shear and buoyancy). For comparison, simulations of neutral turbulence are also conducted with equivalent parameters. The study reveals that large-scale longitudinal vortical structures induce significant spatial heterogeneity in the spanwise distribution of inertial particles. This heterogeneity is characterized by an increase in the particle concentration on the side of the cold plume and a corresponding decrease on the side of the hot plume. In the context of unstably stratified turbulence, particles reduce the fluid streamwise velocity and promote its profile toward symmetry. This phenomenon contrasts with that observed in neutral flows, where particles induce velocity asymmetry by dragging the upper flow and accelerating the lower flow. A quantitative analysis of the heat flux indicates that particles absorb heat as they settle, thereby reducing the average temperature of the flow. Buoyancy effects slow the settling and reinjection of particles, which in turn diminishes thermal energy absorption. Particles with higher inertia preferentially settle on the cooler plume side, minimizing their participation in heat exchange due to prolonged durations of repeated wall collisions.

A Review on Friction Stir Welding of Copper: Tool Geometry, Process Parameters, and Joint Properties.

This paper comprehensively reviews friction stir welding (FSW) as applied to copper and its alloys. FSW is a solid-state joining process that offers significant advantages over traditional fusion welding methods, particularly for materials like copper that are difficult to weld conventionally due to their high thermal conductivity and oxidation issues. Over time, the FSW process has been developed for different industries. Copper structures joined through FSW are utilized for nuclear waste storage, electrical connectors, chemical and petrochemical storage, refrigeration systems, heat exchangers, and the aerospace industry. This covers recent advancements in FSW technology, the geometry of the tools used, the process parameters, and the microstructural characteristics and mechanical properties of the joints. It examines the shapes, sizes, and materials of the tools used for welding copper and its alloys, along with process parameters such as rotational speed and traverse speed, and their influence on the quality of the joints. Additionally, the paper presents syntheses of previously published results, highlighting the values of parameters that indicate the quality of the welds, including grain size, microhardness, mechanical strength, and elongation. The challenges and potential solutions in applying FSW to copper are also discussed, providing a starting point for future research and industrial applications.

A modular, human body-mimicking phantom with active thermoregulation capabilities for validation and verification of convective hyperthermia devices

Objectives This study aims to design and fabricate a modular phantom for hyperthermia applications, addressing interpatient variability in thermal regulation mechanisms like sweating rate, metabolic heat production, and blood redistribution. Materials & methods The phantom can be constructed in various weights and dimensions by connecting identical units. Each unit consists of an agar-based block, an ethyl cellulose-based top layer, a heat source, deep and superficial water circulation, and a sweating mechanism. Agar and ethyl cellulose gels mimic the thermal properties of human tissues and fat respectively. The blocks are wrapped in PVC foil to prevent water evaporation. A heating wire, coiled around an embedded aluminum tubing simulates metabolic heat production. A superficial water circulation mimics skin capillaries. A water pump ensures a steady flow rate throughout the tubing system. Sweat production is simulated using a water pump and perforated tubing. A programmed controller maintains core temperature in a normal operating mode and simulates an anesthetized patient in anesthesia mode. Results Temperature uniformity and regulation were assessed under varying environmental conditions. The phantom effectively regulated its core temperature at 37.0 °C +/- 0.7 °C with an ambient temperature ranging between 21 °C and 30 °C. Activating the water circulation reduced the maximum temperature gradient within the phantom from 4.70 °C to 1.92 °C. Conclusion The versatile phantom successfully models heat exchange processes. Its thermal properties, dimensions, and heat exchange rates can be tuned to mimic different patient models. These are promising results as an effective tool for hyperthermia device validation and verification, representing human physiological responses.

Mitigation-driven global heat imbalance in the late 21st century

While the changes in ocean heat uptake in a warming climate have been well explored, the changes in response to climate mitigation efforts remain unclear. Using coupled climate model simulations, here we find that in response to a hypothesized reduction of greenhouse gases in the late 21st century, ocean heat uptake would significantly decline in all ocean basins except the North Atlantic, where a persistently weakened Atlantic meridional overturning circulation results in sustained heat uptake. These prolonged circulation anomalies further lead to interbasin heat exchanges, characterized by a sustained heat export from the Atlantic to the Southern Ocean and a portion of heat transfer from the Southern Ocean to the Indo-Pacific. Due to ocean heat uptake decline and interbasin heat export, the Southern Ocean experiences the strongest decline in ocean heat storage therefore emerging as the primary heat exchanger, while heat changes in the Indo-Pacific basin are relatively limited.

Contribution of transient heat transfer to overpressure protection in a passive Boiling Water Reactor

The BWRX-300 reactor is a small modular reactor with 300 MW nominal electric power output. As the abbreviation indicates, the reactor is a boiling type reactor using water as the coolant. The main operating principle of the reactor model is the use of natural circulation of the coolant for both steady-state operation and emergency cooling of the reactor. Isolation Condenser Systems (ICS) have been used in early BWRs and were reintroduced in the 1990s to implement passive safety.Modern technologies enable effective simulation of objects of various complexity. In this study, the thermal-hydraulic system code TRACE v.5 is used to simulate BWRX-300 reactor plant operation. The software enables calculation of a system consisting of the reactor pressure vessel and ICS in both steady-state and transient operation.The ICS is an emergency cooling system borrowed from the previous generation of GE Hitachi BWRs, the ESBWRs, and it consists of a vertical tube bundle heat exchanger immersed in a water tank. Although this system design remains unchanged, its purpose is different. The BWRX-300 design completely eliminates safety and relief valves. This is why the ICS must perform both overpressure protection and long term heat dissipation functions.Three reactor plant operation states were simulated: normal operation with nominal parameters; reactor isolation; and the transient process into the cooling down mode by reactor shutdown and ICS activation. The results demonstrate that the ICS is capable to mitigate overpressure transients. Upon ICS startup, its metallic structures absorb heat well in excess of its nominal steady-state rating. Initial thermal inertia of the system is important for overpressure mitigation in transients.

Research on thermal runaway and gas generation characteristics of NCM811 high energy density lithium-ion batteries under different triggering methods

Safety concerns, including thermal runaway and gas generation, present significant challenges for high-energy-density lithium-ion batteries. Thermal abuse, a common trigger for thermal runaway, can be induced by various methods, including heating rods, coils, plates, and lasers. This study compares the impacts of three heating techniques—heating rods, coils, and plates—on thermal runaway and gas generation in a commercially used NCM811 lithium-ion battery, which has a high energy density of 280.24 Wh/kg (the latest cylindrical 46950 model). The study found that the heating coil was the most effective, triggering thermal runaway more quickly and at a higher temperature than the heating plate and rod. Gas production analysis revealed that the heating coil method generated significantly more gas, particularly CO2, than the other methods. The concentrations of gases produced during thermal runaway (CO, CO2, H2, and CH4) varied by heating method, with the heating coil leading to a more complete battery reaction. The safety evaluation highlighted the hazardous nature of the heating rod method, which produced the widest flammable gas concentration range and the highest explosion risk among the tested heating methods. This study provides critical insights into heating techniques in lithium-ion battery thermal runaway scenarios and offers valuable data for improving safety measures in energy storage systems.

Optimal design of a high-performance heat exchanger for modular thermoelectric generator towards low-grade thermal energy recovery

Thermoelectric generator (TEG) has been identified as a promising method for low-grade thermal energy recovery owing to their lack of moving parts, scalability, and compatibility with other devices generating waste heat. Heat exchanger, as one of the most important components of the modular TEG, plays a crucial role in improving the overall performance of the TEG. Nevertheless, flow maldistribution inside the heat exchanger results in uneven surface temperature field of the heat exchanger, which will ultimately limit the output capacity of the TEG. Achieving a homogeneous flow distribution within the heat exchanger while minimizing flow resistance is essential. To address this, optimization of a plate-shaped heat exchanger for the modular TEG is conducted using CFD analysis and the Taguchi method to identify the optimal combination of parameters. The optimized heat exchanger demonstrates a flow maldistribution intensity (ζ) of only 4.75 % and a low flow resistance of 1.16 kPa. Furthermore, a unit of the modular TEG is constructed using two optimized heat exchangers and commercial thermoelectric modules (TEMs), and its performance is analyzed via an analytical model. The results indicate that the power per module, net power density, and conversion efficiency reached 1.2 W, 51.4 kW/m3, and 1.92 %, respectively, at a temperature difference of 70 °C. These findings suggest that the optimized heat exchanger could provide high output performance compared with other literature, offering significant potential for low-grade heat energy recovery.

Impact of the type of heat exchanger on the characteristics of low-temperature thermoacoustic heat engines

Thermoacoustic technologies are considered an effective solution for harnessing low-temperature heat, whether from waste or renewable sources. However, in practice, developing and implementing high-performance thermoacoustic systems is a complex challenge. In real waste heat recovery systems, heat exchange between thermoacoustic engines (TAEs) and external heat sources is facilitated by auxiliary systems, such as circulation loops that include recuperative heat exchangers. It is evident that the upper power limit of a TAE is constrained by the thermal performance of its internal heat exchangers. This article investigates the energy transfer processes between the internal recuperative heat exchangers of a TAE and its matrix, and presents a mathematical model describing the interactions between the matrix and the heat exchangers. The model accounts for the effects of temperature inhomogeneities on the surface of the recuperative heat exchangers, which influence the temperature distribution within the TAE matrix. The use of liquid-gas recuperative heat exchangers in TAEs introduces temperature heterogeneity within the components of the thermoacoustic core. This study shows that such temperature variations can reduce the matrix gain factor for additional acoustic energy by a factor of 1.1 to 1.3. Therefore, when designing low-temperature thermoacoustic systems, it is essential to consider the type and characteristics of the heat exchangers used. The analysis indicates that recuperative heat exchangers can reduce the efficiency of thermoacoustic machines, whether they function as engines or refrigerators.

Performance improvement of magnesium-based hydrogen storage tanks by using carbon nanotubes addition and finned heat exchanger: Numerical simulation and experimental verification

One of the important tasks of improving the properties of metal hydride reactors is the design of system with optimized heat and mass transfer. Many works are devoted to the selection of the optimal heat exchanger for metal hydride hydrogen storage systems. At the same time, it is necessary to consider the composition of the metal hydride bed, which affects thermal conductivity as well. Little attention has been paid to the study of heat transfer properties in hydrogen storage systems with a heat exchanger and a metal hydride bed based on magnesium hydride and carbon nanotubes. In this work we used numerical simulation to determine the effectiveness of carbon nanotubes addition and heat exchangers with different fin number and geometries on high-temperature magnesium-based hydrogen storage tanks performance. It was found, that increasing the number of fins from three to five makes a smaller contribution in the temperature increasing as compared to the addition of three fins to the heater. The three solid, radial and complex fins have a similar effect on the average Mg/MgH2 bed temperature at 60 min. The most optimal fin number and geometry is three radial fins in terms of the efficiency and the volume it occupies. The addition of carbon nanotubes increases the average temperature of the Mg/MgH2 bed by 67 K for a reactor equipped with a heater without fins. Hydrogen storage system with three radial fins and Mg/MgH2 bed enhanced with carbon nanotubes provides an increase in the average bed temperature of about 180 K as compared to system without fins and nanotubes. This leads to a reduction in the hydrogen absorption time to reach 90% saturation by almost 63% for the three radial fins reactor with carbon nanotubes addition to the metal hydride bed. It has been confirmed that the addition of carbon nanotubes to Mg/MgH2 makes a significant contribution to the heat transfer in the metal hydride bed. In addition, it is shown that both an increase in the heat transfer area and the thermal conductivity coefficient leads to a significant improvement in the efficiency of the metal hydride reactor. In the future, the obtained results can be taken into account when designing hydrogen storage systems based on these materials.

Design and performance analysis of a novel downhole heat exchanger for deep geothermal wells: Experimental and field tests

This study addresses the challenge of "extracting heat without extracting water" in geothermal energy systems, which is a key requirement for sustainable resource utilization. A novel downhole heat exchanger (NDHE) was designed to increase the heat exchange efficiency in compact geothermal single-well systems. This research employed theoretical analysis, experimental studies, and field tests. The heat exchanger, which incorporates a single-pass flow for geothermal water and a dual-pass flow for ground loop water, achieved a heat transfer coefficient of 2200–3200 W/(m2·K) and a maximum heat extraction power of 32 kW under laboratory conditions. In field applications, the system demonstrated a heat extraction power of 185 kW—38–58 % higher than that of existing technologies—sufficient to meet the 155 kW heating demand for buildings. Under full load, the predicted maximum capacity reached 555 kW, more than quadrupling the performance of current single-well systems. This innovative heat exchanger significantly enhances both heat extraction efficiency and scalability, paving the way for broader adoption of geothermal energy technologies.

Dynamics and heat transfer characteristics on tube side and shell side of micro-tube compact air-to-air heat exchanger

Applied to the design and selection of compact micro-tube heat exchangers for aviation, an experimental study on the flow and heat transfer performance on both the tube side and shell side of micro-tube heat exchangers was conducted based on the Wilson plot method. The results demonstrated that, although the fluid on the tube side entered the hydraulically smooth region earlier at Reh = 3000, the enhancement in the heat transfer performance and drag reduction characteristics was primarily manifested on the shell side. Compared with traditional empirical correlations, the shell-side Nusselt number showed a maximum enhancement of 47.99 %, and the flow resistance was reduced by a maximum of 59.84 %. Furthermore, a new evaluation index was employed to verify the performance of the heat exchanger. The results indicated that the heat exchanger exhibited advantages in designs requiring low flow resistance, compactness, and lightweight compactness.