Performance Of Exchanger Research Articles

Investigations on thermal profiles and flow structures in a square channel equipped with staggered vortex turbulators

Given the escalating energy demands today, improving the efficiency of engineering equipment is crucial for optimizing energy use. This study focuses on enhancing heat exchanger performance through passive methods, particularly by installing vortex turbulators. Passive techniques can effectively manage energy costs while enhancing efficiency.The research examines thermal profiles and airflow structures within a square channel heat exchanger (SCHE) equipped with staggered vortex turbulators (SVTs). SVTs feature a unique design combining rectangular winglets and V-pattern baffles. The installation of SVTs aims to intensify vortex strength, thereby increasing SCHE efficiency, convective heat transfer coefficients, and overall heat transfer potential. The study investigates the effects of SVT dimensions (b1/H and b2/H), airflow directions (+x and -x), installation patterns (pattern no. 1 and 2), pitch to height ratios (P/H = 1, 1.5, and 2), and flow attack angles (α = 20°, 30°, and 45°). Computational simulations using the finite volume method with a commercial code (FLUENT) under laminar flow conditions (Reynolds number of 100–2000) provide insights into thermal profiles, fluid temperature distributions, and flow configurations within the SCHE. Staggered arrangement and gap spacing are employed to reduce pressure loss and enhance airflow strength. The results highlight flow structures and heat transfer characteristics in the heat exchanger channels, elucidating the underlying mechanisms of the heat exchange process. Understanding these behaviors is crucial for developing more efficient heat exchangers and vortex generators in the future. Simulation findings demonstrate that SVTs significantly enhance convective heat transfer over smooth channels due to increased vortex strength. Notably, pattern no. 2 SVTs (b1/H = b2/H = 0.20) achieve the highest Nu/Nu0 of 19.21 in the +x flow direction at Re = 2000, α = 30°, and P/H = 1. In conclusion, the study identifies a maximum thermal enhancement factor of 4.38. It underscores the potential of pattern no. 2 SVTs for optimizing heat exchanger performance, offering valuable insights for future developments in thermal management technologies.

Numerical study on hydrogen desorption performance of a new MgH2 solid-state hydrogen storage device

To explore the factors affecting the hydrogen evolution performance of a new MgH2 solid-state hydrogen storage heat exchanger, this paper designs the MgH2 solid-state hydrogen storage device. The study numerically investigates the influence of operating parameters and structural parameters on the hydrogen release reaction. The results demonstrate that the hydrogen desorption rate increases as the pressure decreases from 0.3 MPa to 0.1 MPa. Moreover, the hydrogen evolution reaction rate significantly rises with an increase in the inlet temperature of the heat transfer fluid (HTF) from 600 K to 700 K. Similarly, the rate of hydrogen evolution reaction increases with an increase in the flow rate of the HTF from 0.5 m/s to 1.25 m/s. The hydrogen evolution reaction time can be notably reduced by increasing the thickness of the annular HTF layer. Compared to no annular fluid layer, the completion time of the hydrogen desorption reaction is shortened by 558 s with a 5 mm thickness. The arrangement of heat exchanger pipes plays a crucial role in the hydrogen evolution reaction, and thus a comprehensive index M is defined to evaluate its influence. A higher M value indicates slower hydrogen release efficiency of the device. By optimizing the operating conditions, the hydrogen desorption time can be shortened by 93.4 %.

Experimental investigations on thermo-fluid performance of perforated baffle aided with oppositely oriented sawtooth deflector in tubular heat exchanger

Purpose The investigation concentrated on studying a distinct category of tubular heat exchanger that uses swirling airflow over tube bundle maintained at constant heat flux. Swirl flow is achieved using a novel perforated baffle plate with rectangular openings and multiple adjustable opposite-oriented saw-tooth flow deflectors. These deflectors were strategically placed at the inlet of the heat exchanger to create a swirling flow downstream. Design/methodology/approach The custom-built axial flow heat exchanger consists of three baffle plates arranged longitudinally supporting tube bundle maintained at constant heat flux. The baffle plate equipped with saw-tooth flow deflector of various geometry represented by space height ratio(e/h). Next, ambient air was then directed over the tube bundle at varying Reynolds number and the effect of baffle spacing (PR), Space height ratio (e/h) and inclination angle(a) of deflectors on performance of heat exchanger was experimentally analyzed. Findings The heat transfer augmentation of heat exchanger for given operating condition is strongly dependent on geometry, inclination angle of deflector and baffle spacing. Originality/value An average improvement of 1.42 times in thermal enhancement factor was observed with inclination angle of 30°, space height ratio of 0.4 and a pitch ratio of 1.2 when compared to a heat exchanger without a baffle plate under similar operating conditions.

Performance analysis of precooling systems for cryogenic carbon capture: A comparative study of theoretical, numerical, and experimental methods

The urgency of addressing climate change has necessitated innovative and practical approaches to reducing greenhouse gas emissions. Cryogenic Carbon Capture (CCC) technology has emerged as a promising solution for capturing CO2 from industrial emissions. This study investigates a simplified design for a precooling system within CCC technology, focusing on optimizing the efficiency and reliability of the system while minimizing energy consumption. The research examines the effects of CO2 concentration in a gas mixture (simulated flue gas, nitrogen and carbon dioxide), cooling bath temperature, and gas mixture flow rate on the performance of heat exchangers in the precooling system. Theoretical, numerical, and experimental analyses were conducted to assess the system's performance. The use of liquid nitrogen at −196 °C in the cooling bath was found unsuitable due to CO2 freezing within the pipes. Instead, a mixture of dry ice and isopropyl alcohol at −78.5 °C proved effective in maintaining consistent temperature and pressure conditions without causing CO2 blockages. Numerical simulations highlighted the importance of optimizing pipe length to balance temperature control and pressure dynamics, with a 140 cm pipe length identified as optimal for heat exchanger design. Experimental results revealed that longer pipes enhance cooling performance due to increased heat exchange surface area, while higher CO2 compositions and flow rates result in higher outlet temperatures and pressures. The study emphasizes the need for further research and simulation work to refine heat exchanger designs for industrial applications, aiming to develop systems that maximize cooling efficiency while ensuring reliable operation.

Design of metal foam baffle to enhance the thermal-hydraulic performance of shell and tube heat exchanger

Solid baffles are widely used in shell and tube heat exchanger (STHX), while the highly increased flow resistance and dead zones remain serious drawbacks in the applications. To address this issue, metal foam baffle is proposed in this study to replace solid baffle. The numerical model with considering the thermal non-equilibrium between fluid and foam baffles was established. Laminar flow is assumed in the foam baffles region and the realizable k-ε turbulence model is assumed in the open region. Effects of porosity, pore density, thickness and number of foam baffle (N) on the performance were examined. Results show the foam baffles always lead to lower pressure drop of STHX compared to the solid baffles. Compared to five 2 mm thick solid baffles, five 6 mm thick metal baffles with the porosity of 0.80, 0.85 and 0.90 results higher outlet temperature at the pore density greater than 80, 120 and 160 PPI, respectively. The metal foam baffle leads to higher outlet water temperature compared with solid baffles at the baffle number N ≤ 7. The foam baffles with optimum pore parameters reduced the pressure drop by 12.9 % and increase the outlet and inlet temperature difference by 31.0 % compared to the solid baffles.

Enhancing corrosion resistance and heat transfer performance of fin-tube heat exchangers for closed-type heat-source towers by superhydrophobic coatings

Heat-source towers are essential components in heat-source tower heat pump systems, pivotal for achieving energy efficiency. Enhancing corrosion resistance and heat transfer performance for heat-source towers is important but challengeable. For solving this problem, this study aims to introduce a novel superhydrophobic (SHP) coating applied via a one-step electrodeposition method to enhance both corrosion resistance and heat transfer performance of fin-tube heat exchangers in closed-type heat-source towers. The superhydrophobic nature of the coating is validated by contact angle measurements, while its structural integrity and chemical composition are confirmed through various methods i.e., X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Corrosion resistance tests indicate a significant improvement, with the coating showing a corrosion current density of 1.400 × 10−6 A/cm2 and a low-frequency modulus |Z|0.01 Hz of 1.50 × 10⁴ Ω cm2 after 30 days in a 15 wt% calcium chloride solution at 0 °C. Additionally, heat transfer experiments demonstrate a 42.5 % increase in heat transfer efficiency compared to uncoated fins under identical conditions, which present the significant heat transfer performance of the presently developed SHP coating. The key contribution of this research lies in the development and application of a novel SHP coating that significantly enhances the performance of heat-source towers. Moreover, the present findings suggest that implementing this SHP coating can substantially improve the durability and efficiency of heat-source towers, supporting the advancement of more sustainable building infrastructures.

Numerical investigation for the effects of surface roughness in counter flow microchannel heat exchanger with different channels geometries

This article presents a numerical investigation focused on how roughness of surface affects the overall performance of a counter-flow microchannel heat exchanger (CFMCHE). The study examines various microchannel shapes, including triangles, squares, circles, and trapezoids, to evaluate their performance within the context of CFMCHE. Water with consistent properties flows through aluminum microchannels used as the working fluid. The analysis employs the roughness-viscosity method to assess how surface roughness influences the CFMCHE’s performance. The study’s findings emphasize that the trapezoidal channel shape exhibits the most favorable performance among the shapes investigated. Additionally, among the operational parameters considered, the hydraulic diameter emerges as the most influential factor in determining the most suitable characteristics for CFMCHE. The presence of surface roughness was found to marginally improve thermal performance while slightly reducing hydraulic efficiency. This research provides valuable insights into the intricate interplay between surface roughness and channel shape. Notably, the impact of roughness is more pronounced in the case of the trapezoidal shape compared to other geometries.

Analysis of Soot Deposition Effects on Exhaust Heat Exchanger for Waste Heat Recovery System

This study investigates the thermal–hydraulic behavior and deposition characteristics of a shell and tube exhaust heat exchanger using a CFD-based predictive model of soot deposition. Firstly, considering the influences of thermophoretic, wall shear stress, and other deposition and removal mechanisms, a predictive model is developed for long-term performance of heat exchangers under soot deposition. Then, the variations in exhaust heat exchanger performance during a 4 h deposition period are simulated based on the model. Subsequently, the variation of deposition distribution and different deposition velocities are also evaluated. Finally, an analysis of the long-term performance of the exhaust heat exchanger under varying gas velocities and temperature gradients is conducted, revealing the performance variations under all engine-operating conditions. Results show that the deterioration in normalized relative j/f1/2 varies from 5.26% to 24.91% under different work conditions, and the exhaust heat exchanger with high gas velocity and low temperature gradient exhibits optimal long-term performance.

Numerical evaluation of the impact of using spiral innovative turbulator on improving the thermal performance of a helical double-pipe heat exchanger

Due to the necessity of performing thermal operations, heat exchangers are widely employed in many different areas. The heat transfer and fluid flow within a spiral double-pipe heat exchanger fitted with a novel turbulator were numerically assessed in this work. The presented novel turbulator is a curved tube with holes incorporated into its thickness and spiral ribs on its inner wall. The turbulator wall's curved rib design produces secondary flows at the turbulator output when fluid flows through the tube and the perforations. A commercial CFD tool, based on the finite volume technique, was used to conduct the numerical simulations. The fluid flow regime is turbulence (Re = 8,000 – 14,000). Two sections make up this work. The first portion looked at how the hydrothermal behavior of the fluid flow inside the proposed turbulator was affected by the angle at which the curved ribs rotated. For this angle, three values were considered: θ = 30, 90, and 150°, and the outcomes were contrasted with those of a plain spiral double-tube heat exchanger (turbulator not included). Then, the number of embedded holes in the turbulator's thickness changes in the second part, and three values of N = 12, 16, and 20 were considered. According to the first part's findings, the model exhibiting θ = 90° had a greater thermal performance factor at Re = 10,000. This model has a more noteworthy thermal performance factor than the models with θ = 150 and θ = 30° by approximately 15.62 % and 22.65 %, respectively (at Re = 10,000). Furthermore, the second section's numerical findings showed that the model with N = 20 had more extraordinary thermal performance at Re = 10,000. Model N = 20 has a thermal performance factor of about 16.93 % and 17.55 % greater than models N = 16 and N = 12. Within the proposed heat exchanger, the recommended turbulator produced a sizable rotating flow, and including embedded holes significantly reduced the pressure drop this kind of turbulator causes.

Heat transfer experimental and numerical study of a three-sided serpentine with the operating fluid directly contacting the PV cell back

The cooling methodologies of photovoltaic/thermal equipment are crucial not only to maintain optimal operating temperatures but also to improve the performance of the photovoltaic systems and prolong their lifespan. Traditional heat exchangers often require physical contact with the material to be cooled, posing challenges for specific projects. Therefore, this study introduces an innovative heat exchanger made of aluminum plate, allowing direct contact of the cooling liquid with the surface to be cooled. The thermal performance of the serpentine, coupled to a steel plate simulating a photovoltaic-thermal panel, was evaluated experimentally. CFD numerical simulations were conducted to analyze the thermal performance of the heat exchanger, providing valuable temperature profiles for single-phase flows. The outcomes showed that the simulated and experimental data agreed well. Particularly, when considering the outlet fluid temperature the mean absolute error between the simulated and experimental results was around 0.5 °C, with a relative error of aproximatelly 1.8 %. To evaluate the influence of the type of material that forms the serpentine, heat exchangers with two different polydimethylsiloxane (PDMS) serpentines were numerically investigated. The PDMS serpentine provided a more heterogeneous steel plate temperature profile compared to the aluminum one; however, such an issue can be corrected with geometry modifications, such as a greater width and cross-sectional area. For all flow rates, the steel plate temperature using aluminum serpentine presented a lower average temperature than that with PDMS serpentine (an average of 6.3 % lower). The wide PDMS serpentine exhibited a better cooling performance than the narrow PDMS serpentine (an average of 92 %) since the heat transfer surface area was enhanced in the former case.

Optimizing thermal performance in tube-in-tube heat exchangers with metal foam inserts: experimental and RSM analysis

ABSTRACT This study investigates tube-in-tube heat exchanger performance under steady-state conditions, examining co-current and counter-current flows. It explores various configurations, including metal foam enhancements, to optimize heat transfer efficiency and minimize pressure drop. Driven by the potential of metal foam to enhance heat transfer, the study aims to demonstrate significant improvements in thermal performance compared to conventional designs. Experimental methods involve testing four configurations with Nickel foam (10 PPI, 0.90 porosity) inserts, evaluating temperatures and pressure drops across flow rates of 25 to 50 LPH. Hot water at 65°C flows in the annulus, while normal water at 31°C flows in the outer annulus. Results show metal foam’s substantial enhancement in heat transfer, with counter-current metal foam configurations achieving up to 3.71 times greater efficiency than parallel flow setups. Moreover, comprehensive performance evaluation reveals that the counter-flow heat exchanger with metal foam is 2.03 times more efficient than the conventional co-current flow without metal foam. Conclusions highlight metal foam’s effectiveness in improving heat transfer performance and optimizing thermal systems through systematic parameter optimization using response surface methodology.

Study on the Flow and Heat Transfer Performance of Microchannel Heat Exchangers With Different Elliptical Concave Cavities

AbstractEllipticity has a significant impact on the flow and heat transfer performance of microchannel heat exchangers (MHEs) with elliptical concave cavities. In this study, five types of MHEs with different elliptical concave cavities (ellipticities of 0.4, 0.6, 0.8, 1.0, and 1.2) were designed. The influence of ellipticity on the flow and heat transfer performance of MHEs was numerically investigated using ANSYS Fluent 21.0 R1. Moreover, MHEs with corresponding elliptical concave cavities structures were processed and manufactured, and then an experimental platform was designed and built for experimental verification. The results showed that the fluid velocity distribution in MHEs with elliptical concave cavities was symmetrical, and the formation of secondary flow in the elliptical concave cavities led to the continuous destruction and reconstruction of the flow and thermal boundary layer in the microchannel, which is conducive to mass and heat transfer in the MHEs with elliptical concave cavities. The inlet and outlet pressure drop of MHEs with elliptical concave cavities increased as the inlet flow rate increased. At the same inlet flow rate, the inlet and outlet pressure drop of the MHE with elliptical concave cavities first increased and then decreased with increasing ellipticity. At an ellipticity of 1.0, the inlet and outlet of MHE exhibited the lowest pressure drop indicating that the MHE with an ellipticity of 1.0 featured the highest pressure drop performance. The cold‐water outlet temperature of the MHEs with elliptical concave cavities first decreased and then increased as the inlet flow rate increased. At the same inlet flow rate, the cold‐water outlet temperature of the MHEs with elliptical concave cavities first increased and then decreased with increasing ellipticity, while the hot‐water outlet temperature of the MHEs first decreased and then increased with increasing flow rate. This indicated that the MHE with an ellipticity of 1.0 exhibited excellent heat transfer performance.

The role of pit lake thermal dynamics on the thermal performance of ground heat exchangers

The addition of ground heat exchangers (GHEs) to a pit lake’s basin has the potential for abundant, clean and renewable geothermal energy extraction using shallow geothermal systems. Basin-embedded GHEs avoid direct interaction with mine water, which has been shown to impact efficiency and longevity in mine open-loop geothermal systems negatively. The now accelerated closure of open-pit coal mines presents itself as an opportunity to use this technology. However, no guidelines currently exist for designing or operating GHEs embedded in the sediment of water bodies. Furthermore, the two-way coupling between the complex annual thermal fluid dynamics that lakes are naturally subjected to and heat fluxes on the sediments and the GHE system has not been explored. In this study, we develop and validate finite element models to assess the relevance of lake thermal stratification in the performance of a geothermal system embedded in water bodies basins, e.g., on open-pit mine closures, under temperate residential thermal loads. The results show that the pit lake’s role as a thermal sink improves significantly when the lake’s thermal dynamics are accounted for, with an increase of up to 292% in the lake’s available energy budget. A minor variation in energy budget (~8%) was found whether the lake is modelled explicitly or simplified as a transient Dirichlet temperature boundary condition. This small difference vanishes if horizontal circulation along the lake is considered, highlighting the lake’s thermal energy potential. Finally, the impact on the GHE Coefficient of Performance (COP) is evaluated, with a maximum of ~15% difference among all cases.

Enhancing heat exchanger performance with combined twisted tubes and twisted Tapes: Design and retrofit strategies

This study investigates the application of twisted tubes and twisted tapes as heat transfer enhancement tools in both new designs and revamping of shell-and-tube heat exchangers. This research introduces a new design approach based on published data of thermohydraulic performance of combined twisted tubes and twisted tapes. This work discusses general design considerations and proposes methodologies for the sizing of new heat exchangers and the incorporation of twisted tubes and twisted tapes into existing units. In design, surfaces with the best trade-off between heat transfer enhancement and pressure drop are simple twisted tubes and twisted tubes with triple-channel twisted tape (TT-3C) with a PEC of 3.06 and 2.59 respectively. It is found that for new designs, reductions in area relative to the original units are observed. With twisted tubes alone, the reduction is 19.11 %, while with the incorporation of TT-3C, it reaches 29.70 %. In revamping of existing heat exchangers, the replacement of smooth tubes by twisted tubes and TT-3C results in average thermal load increases of 26.32 % and 27.50 %, equivalent to 19,526 kW and 20,442 kW, respectively. The results reveal significant improvements in heat transfer efficiency without substantial pressure drop increments, making twisted tubes and twisted tapes valuable options for enhancing heat transfer.

Design and optimization of a combi boiler heat exchanger: A CFD-based approach

Heat exchangers are widely used in various fields, emphasizing the importance of efficiency and mass/dimensional improvements. Aluminum boiler heat exchangers play a crucial role in systems, where the natural gas-air fuel mixture is burned and heat transfer to water occurs. In such heat exchanger designs, the region where the air-gas mixture burns is referred to as the “combustion chamber,” and the thermal energy produced is transferred to the circulating water in the body.In this study, it was aimed to improve the heat transfer per unit surface by using novel pin–fin geometries in DAIKIN NDJ 24 kW aluminum cast boiler heat exchanger, thus reducing and lightening the dimensions of the combi heat exchanger for the same thermal performance. This approach targets cost reduction in production and downsizing of the boiler dimensions for more compact units. Cleanability limit was also established, and a unique symmetric droplet model was optimized utilizing a Computational Fluid Dynamics (CFD) based Response Surface Methodology (RSM) approach. Predictions of thermal performance through CFD simulations were subsequently validated experimentally using test bench available at DAIKIN’s facility in Sakarya, Türkiye. The results demonstrated a remarkable of 14% reduction in the overall weight, which was achieved by shortening the combi boiler height by 26 mm, while preserving the same efficiency levels. This research underscores the potential of the innovative pin geometry and optimized droplet model to enhance the efficiency and performance of the heat exchanger, with implications for cost savings and improved manufacturing processes. Also the effect of the new pin-fin geometry on the condensation performance was investigated as a multiphase phenomenon for the first time in the international literature. The results showed an excellent agreement between predicted and measured performance data.

Examining the impact of filling ratio on thermosyphon performance in passive energy recovery processes with dual effects of evaporative cooling: An experimental study

AbstractThe thermosyphon heat exchanger contributes significantly to the improvement of energy conservation technology and has been used in multiple applications, raising the possibility of further studies to contribute to increasing the efficiency of heat pipes. This experimental study examines the different filling ratios of pure Acetone liquid inside a WHPHE integrated with the double‐effect of evaporative cooling to improve the energy‐saving technology. This work studies changing the filling ratio of pure acetone working fluid to investigate the effect of the filling ratio on heat exchanger performance in waste energy recovery technology. The heat exchanger was used with four rows and five tubes per row arranged in a staggered manner. The filling ratio of acetone inside the heat pipe was changed from 50% to 100%. The effect of the mass flow rate of air flowing in direct evaporative cooling on energy conservation technology was studied while the mass flow rate of air through indirect cooling remains constant in addition to the effect of ambient temperature. The results showed that the best filling percentage was between 80% at different temperatures, and the highest energy recovery percentage was when it was at the filling percentage of 80% in the presence of evaporative cooling.

Investigation on the performance of a novel heat transfer structure based on a new twisted airfoil fin array

Printed circuit heat exchanger (PCHE) is a type of micro-channel heat exchanger with high performance, which has a broad application in microelectronics, solar energy, and aerospace. Airfoil fins are widely recognized due to their exceptional thermo-hydraulic performance, but there are few studies on their shape adjustment in three dimensions. In this study, a novel twisted airfoil fin was proposed and applied to the heat exchanger. The heat transfer and flow resistance of the twisted airfoil fin PCHE with the traditional PCHE are compared using the numerical simulation method, and the influence of the twist angle, fin spacing, and arrangement is investigated. The results show that the new fins have excellent flow and heat transfer performance. Under the multiple Re number conditions, the Nu number is improved up to 52%, and the performance evaluation criteria is increased up to 16%. Also, increasing the twist angle of the fins, decreasing the fin spacing, and staggering the fins according to diverse twist directions can improve the performance of the heat exchanger.

Numerical study on the influence of flow direction and fluid type on heat transfer and pressure drop in a two-tube spiral heat exchanger with innovative conical turbulators

In this research, numerical analysis will be conducted on the thermal and hydraulic performance of a spiral two-tube heat exchanger. The study employs an innovative turbulator design with curved outer blades and a semi-conical section with two openings. Numerical simulations were conducted using the commercialized Finite Volume Method (FVM) program, ANSYS FLUENT 18.2. The finite volume method was employed to analyze thermal and fluid equations and parameters. A comparison was made between two distinct flow directions, namely positive and negative currents, utilizing a comprehensive range of three working fluids. The numerical findings indicate that employing counter-current flow with a Water/MOS2−Fe3O4 fluid nanohybrid results in superior endothermic performance. These results indicate that a maximum thermal efficiency improvement of roughly 17.54 % and 8 % can be achieved by using the counterflow configuration with the nanohybrid fluid Water/MOS2−Fe3O4 at a mass flow rate of m˙ = 0.008 kg/s, in comparison to alternative models. Furthermore, the results showed that the Water/MOS2−Fe3O4 fluid nanohybrid performs better than the Ag-HEG/Water nanohybrid fluid when used in counterflow and parallel flow configurations, starting at a Reynolds number of 600. With a counterflow configuration in the two tubes, the Water/MOS2−Fe3O4fluid nanohybrid achieves the highest thermal performance coefficient in the two-tube heat exchanger.

Effect of Heat Exchange Area Margins on Thermal Characteristics of the Heat Exchange System in the Pressurized Water Test Loop during Fuel Assembly Irradiation

The performance of heat exchangers in the pressurized water test loop is a critical factor in ensuring the achievement of irradiation parameters for fuel assemblies and the safety of experimental operations. The effect of the heat exchange area margin on the heat exchangers in the pressurized water test loop for the fuel assembly during the steady-state irradiation is analyzed. Additionally, optimization methods for determining the margin of heat exchange area and corresponding design strategies are further investigated. It shows that the effect of the heat exchange area margin on the heat exchange power is less affected by the inlet temperature of the primary water and is primarily influenced by the flow rate of the primary water. A decrease in the flow rate of the primary water reduces the compensatory effect of the cooling section on power and enhances the weakening effect of the regeneration section on power. Meanwhile, the correspondence between the margin of the regeneration section and the cooling section, established based on design conditions, can be applicable when there are changes in the inlet temperature of the primary water, but it is not suitable when there are changes in the flow rate of the primary water. When the flow rate of the primary water decreases, the cooling section margin required to compensate for the decrease in power caused by the regeneration section margin will increase significantly. In addition, short-circuiting the heat exchange tubes in the regeneration section can effectively enhance the heat transfer capability. Furthermore, setting the heat exchange area margins of the regeneration and cooling sections to zero can serve as a termination condition for iterative calculations in the verification of regenerative heat exchangers under off-design conditions.

Enhancing heat exchanger performance with perforated/non‐perforated flow modulators generating continuous/discontinuous swirl flow: A comprehensive review

AbstractHeat exchangers are crucial in transferring heat and finding applications across various industries. Numerous strategies have been devised to improve and optimize the heat transfer process within these systems. Among these, passive methods have garnered significant attention for their ability to operate without external power consumption. This article examines the recent experimental and computational studies conducted by researchers since 2018 on passive enhancement techniques, especially twisted tape, wire coil, swirl flow generator, and others, to boost the thermal efficiency of heat exchangers and aid designers in adopting passive augmentation methods for compact heat exchangers. Recently, researchers' new class of flow maldistribution devices, referred to as swirl flow devices, has gained attention; which enhances convective heat transfer by introducing swirl into the main flow and disrupting the boundary layer at the tube surface through alterations in surface geometry. Twisted tape inserts are devices that demonstrate better performance in laminar flow compared to turbulent flow. Conversely, other passive techniques like ribs, conical nozzles, and conical rings are generally more effective in turbulent flow than laminar flow. A recent research trend is the utilization of nanofluids in combination with other passive heat transfer enhancement techniques like turbulators, ribs, and twisted tape inserts in heat exchangers, which can reduce exergy losses and improve overall convective heat transfer coefficient and effectiveness of heat exchanger.