Heat Exchanger Configurations Research Articles

Experimental study on the thermal performance of a high-temperature finned latent heat storage system

The primary objective of this study is to develop and evaluate the performance of a latent heat storage (LHS) system. A tube-in-tube heat exchanger configuration was used to design the LHS system. Sodium nitrate and air were employed as the phase change material (PCM) and heat transfer fluid (HTF), respectively. To mitigate the low thermal conductivity of the PCM, six circular fins were integrated on the HTF tube surface and experiments were conducted in an in-house experimental facility. Temperature plots from the charging-discharging experiments revealed that the HTF flow direction governs the heat transfer along the axis of the system. The sensible heat gain by the PCM in the range of 270–330 °C, led to an additional ⁓0.4 MJ of heat storage beyond the storage capacity of 1 MJ. Furthermore, increasing the inlet temperature from 400 °C to 440 °C reduced the charging time by 39.6 %, while reducing the inlet temperature from 210 °C to 170 °C decreased the discharging time by 18.2 %. Despite improved heat transfer, higher inlet temperatures adversely affected the thermal uniformity whereas, the increase in inlet air velocity enhanced both the dynamics of heat transfer and the thermal uniformity within the storage system.

Redesigning heat exchanger channels: A local entropy generation approach

This paper proposes a redesign technique for heat exchanger channels based on a Local Entropy Generation (LEG) analysis and numerical simulations. The approach first divides the computational domain into zones and then identifies the zones responsible for increasing irreversibilities due to viscous and heat transfer effects. By evaluating different geometric features and flow conditions, the wall shape is modified (zone by zone) with the configurations that offer the lowest local entropy generation rates. The redesigned channels demonstrate that sudden changes in geometry along the streamwise direction reduce the size of regions with high thermal entropy generation and promote the creation of vortices, thereby reducing the magnitude of thermal irreversibilities. Smooth wall shape transitions might not be desirable when the goal is to improve heat transfer. The redesign process enhances the thermal performance of the system without significantly increasing power demand. The proposed methodology is evaluated using three wavy channels with a non-uniform amplitude-to-wavelength ratio (β1,β2,andβ3) since they allow for better management of wall geometry. As demonstrated for case β1, the LEG analysis enables the construction of new channels with a thermal performance 3.9 % superior to those with a uniform amplitude-to-wavelength ratio of α = 0.16 (best-case scenario), but with approximately 20 % less pumping power. While this study employs wavy channels as a case study, the methodology is broadly applicable to various heat exchanger configurations, including trapezoidal, triangular, and zigzag channels, making it a versatile tool for improving thermodynamic performance across different designs.

Hybrid of Non-dominated Sorting Genetic Algorithm II and Invasive Weed Optimization for Fan Duct Surface Heat Exchanger Configuration Optimization Design

In this research, configuration optimization was conducted for FDSHX (fan duct surface heat exchanger) that is a new type of heat exchanger adopted in aero-engine heat management in recent years. Firstly, a method of Taguchi-ANFIS (Taguchi-Adaptive Neuro-Fuzzy Inference System), which can reduce training data volume utilizing orthogonal experimental matrix, was proposed to construct a rapid response mathematical model between three configuration parameters, including fin pitch, fin thickness, and oil passages number, and two design indicators, including heat transfer capacity and operating weight, based on the data prepared by an experimental validated FDSHX heat transfer capacity calculation method using heat transfer unit simulation. Secondly, a hybrid method of NSGA II-IWO (Non-dominated Sorting Genetic Algorithm II-Invasive Weed Optimization), which can simultaneously obtain the strong abilities of exploration and escaping from trap into local optima, was proposed to drive the constructed response mathematical model to enhance heat transfer through adjusting the three configuration parameters. Optimization comparison was performed between NSGA II-IWO and four classic optimization algorithms including GA (Genetic Algorithm), IWO (Invasive Weed Optimization), CA (Cultural Algorithm), and HS (Harmony Search). This research provides an integrated solution to help mechanical engineers improve the applicability and reasonableness of FDSHX design.

Enhancing thermal-hydraulic performance in heat exchangers with metal foam inserts: a comprehensive experimental investigation

ABSTRACT This research investigates the use of metal foam inserts to enhance the thermal-hydraulic performance of double-tube heat exchangers, relevant for energy-efficient systems such as solar flat plate collectors. Motivated by the need for improved heat transfer efficiency, this study hypothesizes that metal foam integration can significantly boost performance. Through systematic experimental study, the impact of metal foam inserts on heat transfer and pressure drop characteristics is comprehensively evaluated across various configurations, spanning horizontal and vertical orientations. Experimental evaluations were conducted on four configurations, including both conventional and metal foam-integrated heat exchangers in horizontal and vertical orientations, using water as the working fluid and Nickel metal foam with 0.9 porosity and 10 PPI in the annular space. The findings highlight significant enhancements in heat transfer performance with metal foam integration across both horizontal and vertical heat exchanger configurations compared to conventional counterparts, particularly showcasing superior effectiveness and efficiency in the horizontal configuration. Results show that metal foam integration substantially enhances heat transfer, with horizontal configurations exhibiting a 14.56% higher heat transfer coefficient than vertical ones. Additionally, the comprehensive performance index improved by 1.17 times, indicating a better balance between heat transfer enhancement and pressure loss. These findings were validated against established correlations from the literature, confirming the superior effectiveness of horizontal metal foam heat exchangers.

Thermo-Economic Analysis of Thermoelectric-Based Atmospheric Water Harvesters: Flow Configuration Impacts

In recent years, thermoelectric cooling has seen significant growth, driven by advancements in nanoscience and manufacturing. Concurrently, the increasing water crisis in various regions has led to a surge in research on Atmospheric Water Harvesters (AWHs) for decentralized water harvesting. This study presents a comprehensive thermodynamic and economic analysis of Thermoelectric-based Atmospheric Water Harvesters (TAWHs) with different Heat Exchanger (HX) configurations with different flow configurations. Our research identifies five types of HXs, each characterized by its own optimal geometrical and controlling parameters. These HXs are evaluated based on economy, eco-friendliness, productivity, air cooling efficiency, and compactness. We provide new insights into the hidden potential and performance of Thermoelectric Coolers (TECs) in desalination, particularly highlighting the effect of increasing the ratio of surfaces mounted with TECs to the total surface area of the channels. Our results indicate that among the HX configurations, the counter flow HX is the most economical option, capable of water harvesting at a cost of $0.230 USD per liter from an 80% humidity level. The parallel flow HX demonstrates higher efficiency according to the second law of thermodynamics and environmental friendliness, while the crossflow HX exhibits lower overall efficiency. We found that the optimum cold channel incoming air flow rate varies with humidity in a detailed analysis of a counter flow HX with 2 columns and 15 rows. Interestingly, we found that humidity and incoming air mass flow rate have a negligible effect on power consumption. This work can be used as a guideline for future engineering problems involving the design and optimization of TAWHs.

A Review of Thermochemical Energy Storage Systems for District Heating in the UK

Thermochemical energy storage (TCES) presents a promising method for energy storage due to its high storage density and capacity for long-term storage. A combination of TCES and district heating networks exhibits an appealing alternative to natural gas boilers, particularly through the utilisation of industrial waste heat to achieve the UK government’s target of Net Zero by 2050. The most pivotal aspects of TCES design are the selected materials, reactor configuration, and heat transfer efficiency. Among the array of potential reactors, the fluidised bed emerges as a novel solution due to its ability to bypass traditional design limitations; the fluidised nature of these reactors provides high heat transfer coefficients, improved mixing and uniformity, and greater fluid-particle contact. This research endeavours to assess the enhancement of thermochemical fluidised bed systems through material characterisation and development techniques, alongside the optimisation of heat transfer. The analysis underscores the appeal of calcium and magnesium hydroxides for TCES, particularly when providing a buffer between medium-grade waste heat supply and district heat demand. Enhancement techniques such as doping and nanomaterial/composite coating are also explored, which are found to improve agglomeration, flowability, and operating conditions of the hydroxide systems. Furthermore, the optimisation of heat transfer prompted an evaluation of heat exchanger configurations and heat transfer fluids. Helical coil heat exchangers are predominantly favoured over alternative configurations, while various heat transfer fluids are considered advantageous depending on TCES material selection. In particular, water and synthetic liquids are compared according to their thermal efficiencies and performances at elevated operating temperatures.

Influence of polishing process on surface morphology and thermo-hydraulic performance of additively manufactured Gyroid-structured heat exchanger

As additive manufacturing technology overcomes fabricating obstacles, the Gyroid structure, characterized by its intricate topology, emerges as a promising heat exchanger configuration. Nonetheless, the substantial surface roughness intrinsic to additive manufacturing considerably constrains the practical deployment of Gyroid-structured heat exchangers. This study focuses on the post-treatment of a Gyroid-structured heat exchanger, manufactured by selective laser melting, employing abrasive jet polishing. It further investigates the influence of this process on surface morphology and thermo-hydraulic performance, utilizing characterization, experimental, and numerical methodologies. Surface characterization indicates that the polishing process markedly diminishes the distribution density of protrusion microstructures on the internal surface. Pre-polishing surface roughness results in an area expansion of 106–123%, which is reduced to 20–45% after polishing. Moreover, the coupling effect of concurrent reduction in wall thickness and surface roughness enables the polished prototype to attain a 40% decrease in differential pressure, while maintaining nearly identical heat transfer capacity. The overall performance evaluation criterion of the post-polishing prototype consistently surpasses the offset strip fin heat exchanger by 12.94–26.09%, within a Reynolds number range of 300–3000. This study introduces a validated technology for modifying the internal surface of additively manufactured heat exchangers, especially Gyroid-structured heat exchangers, thereby facilitating its practical utilization in cutting-edge fields.

Multi-objective optimization and sensitivity analysis of offset strip fin compact heat exchangers

In this study, the aerothermal performance of Offset Strip Fin Compact Heat Exchangers (OSF-CHE) is optimized with the multi-objective Particle Swarm Optimization method. Available empirical correlations for the Fanning factor and Colburn factor are utilized in the optimization process. Selected off-design Pareto-optimal solutions for compact heat exchanger configurations are reconstructed and simulated by Computational Fluid Dynamics simulations at various boundary conditions after extensive validation processes. Optimized OSF-CHE designs are shown to have improved aerothermal performances among comparable designs in the literature. It has been shown that a high Reynolds number in the range of 1,500–2,000 as a flow attribute provides the Fanning factor ranging from 0.0228 to 0.0619 and the Colburn factor between 0.0067 and 0.0122 and Re is more dominant than geometric design variables on the objective functions. Low and moderate Reynolds number flows at 500 and 1,000 offer a wider selection range for both objective functions on the Pareto-front.

Thermodynamic optimization of heat exchanger circuitry via genetic programming

In this study, an evolutionary thermodynamic technique was developed for the optimization of heat exchanger circuitry. The proposed technique is capable of handling the unrestrained implementation of genetic operators while ensuring circuitry feasibility and basic manufacturability. The optimization tool was used to clarify the optimal heat transfer features in relation to the characteristics of the refrigerant and to provide a thermodynamic interpretation of the optimization results to extract general design guidelines. Evaporator circuitry optimization was conducted under given cooling capacity, superheating degree, and boundary conditions representative of air-conditioning applications. The consistency between the minimum entropy generation and the maximum coefficient of performance (COP) was demonstrated under these settings. Accordingly, heat exchanger configurations that take maximum advantage of the thermodynamic benefits of each refrigerant are proposed by optimizing the distribution of friction and heat transfer irreversibility. Consequently, the evaporator outlet pressure increases, thus lowering the compression ratio and maximizing the COP. The developed optimization method maximizes the benefits of low-GWP alternative refrigerants and shows that zeotropic mixtures may exhibit performance analogous to that of R32 and higher than that of R410A by approaching a Lorenz cycle operation.

The characteristics of heat exchanger for local utilization of wastewater heat under different operating conditions

RELEVANCE. The authors research the local utilization of wastewater heat (in close proximity to the place of their formation) based on a heat exchanger. To select rational characteristics of the heat exchanger and correctly assess the potential energy effect, it is necessary to take into account the influence of the operating conditions of the device (duration of individual use of the shower, mass flow of heated and heating water, temperature of heated water at the inlet to the heat exchanger, temperature of the flow at the moment the device is turned on).THE PURPOSE. The purpose of the work is to research the dependence of the efficiency of wastewater heat utilization on the operating conditions of the heat exchanger and to identify the parameters that have the greatest impact on the effect of energy-saving measures.METHODS. Based on a verified mathematical model of the thermal operation of a recovery heat exchanger, the temperature distribution inside the flows of the heated and heating water in time is calculated (from the moment of switching on until reaching a stationary operating mode). Based on the data obtained (the temperature of the heated water at the outlet of the heat exchanger at each point in time), the absolute and relative heat savings are determined under various operating conditions.RESULTS. The influence of the non-stationary phase of the heat exchanger operation on its energy efficiency is considered. For a specific heat exchanger configuration, the time required for the device to reach a steady state of thermal operation is determined. It was revealed that the greatest influence on the relative and absolute savings of thermal energy is exerted by such operating conditions as mass flow and temperature of heated water at the entrance to the heat exchanger. The temperature of the flow at the initial moment of time has the least influence on the energy effect.CONCLUSION. The operating conditions that have the greatest impact on the effect of local wastewater heat recovery are determined. The need to take these conditions into account when designing a heat exchanger and choosing its optimal parameters has been confirmed.

Investigation by monitoring and numerical simulation of the performance of a ground-source heat pump system with and without regeneration in different configurations and operating modes

This paper is focused on restoring the thermal imbalance of the ground caused by conventional GCHP systems through seasonal and continuous regeneration using a geothermal-solar facility with a vertical GCHP combined with photovoltaic (PV) and PV-thermal (PV/T) panels in a heating-dominated climate, located in Timisoara, Romania. Therefore, the performance of a GCHP system integrated into the heat supply system of an experimental office, operating in single and double U-tube borehole heat exchanger (BHE) configuration, with regeneration in the summer months by injecting heat into the ground, is experimentally evaluated. Exploratory research has indicated an increase in the average temperature of the working fluid by 2.4% and an improvement in system performance when using heat injection (seasonal performance factor (SPF) by 3.5% and 6.6% higher and CO2 emission by 1.2% and 3.8% lower in the single and double U-tube BHE configurations, respectively). Additionally, numerical simulations with Polysun software are also used to test the performances of the hybrid GCHP-PV/T system with continuous regeneration throughout the year by PV/T panels and of a conventional GCHP integrated into the heating and DHW production systems for a single-family building. The simulations were experimentally validated through measurements on the geothermal-solar facility for heating and DHW production in the experimental office. The simulation results show that the SPFHP-PV/T values of the hybrid GCHP-PV/T system in the single and double U-tube BHE configurations, equal to 6.00 and 5.79, respectively, are 32% and 34% higher than the SPFHP corresponding to the conventional GCHP system, equal to 4.56 and 4.32, respectively. In addition, the SPFHP-PV/T in the single U-tube BHE configuration is 3.6% higher than in the double U-tube BHE configuration for the GCHP combined with the PV/T array (31.8 m2).

MODELLING AND ANALYSIS OF HEAT EXCHANGER

Shell and tube heat exchangers in their various construction modifications are probably the most widespread and commonly used basic heat exchanger configuration in the process industries. The modelling of the heat exchanger has done by using the advanced design software CATIA. In this project the Heat Exchanger is modelled and assembled with the help of CATIA and the component is meshed and analysis is done in ANSYS software and the thermal and static behaviour is studied and the results are tabulated. The various stresses acting on the Heat Exchanger under various loading conditions has been studied. In the preset work has been taken up on the following aspects to cover the research gaps and to present the results based on the systematic studies. Temperature distribution and heat flow through the Heat Exchanger. FEA analysis of the Heat Exchanger to measure temperature at the points where it is not possible to find out practically and to observe the heat flow inside the Heat Exchanger. Key Words: Shell and Tube Heat Exchanger, Catia,and Ansys Softwares, Static and Thermal behavior, and FEA Analysis.

Heat transfer enhancement of different ribbing pitched semi-closed microstructure tube bundles fabricated by deformational cutting method

The study investigates the limitations posed by low-value heat transfer coefficients and higher wall superheat in conventional tube bundles, which adversely impact the performance of heat exchangers. To address this challenge, semi-closed microstructure tubes, created via deformational cutting at ribbing pitches of 300 µm and 400 µm, are proposed as a potential solution. The research centers on analyzing the two-phase boiling heat transfer performance of these microstructure tubes arranged in 2 × 3 staggered tube bundles. A comparative analysis is conducted, evaluating the thermal effectiveness of the microstructure tube bundles against a 2 × 3 smooth tube bundle and a copper-coated tube bundle under varying mass flux, heat flux, and pitch-to-diameter ratios. The experimental findings indicate the superior heat transfer performance of both microstructure tube bundles, with reduced wall superheat compared to other tube bundles. The findings further indicate that the 2 × 3 semi-closed microstructure tube bundle with a higher ribbing pitch outperforms the microstructure with a lower ribbing pitch. The 2 × 3 high-pitched microstructure tube bundle exhibits a maximum enhancement of 420 % over the 5 × 3 smooth tube bundle and 340 % over the 2 × 3 smooth tube bundle. Moreover, it surpasses the performance of copper-coated tube bundles by 230 % and outperforms its lower-pitch counterpart by 70 %. Particularly, the use of microstructure tube bundles allows for a reduction in the number of tubes required in the heat exchanger configuration without compromising its performance, promoting compactness and cost-effectiveness. Overall, the study highlights the feasibility of implementing these tubes in the two-phase heat exchanger owing to their superior performance compared to conventional tubes.

Comprehensive performance evaluation method of working fluids for high temperature heat pump based on multi-objective optimization

The working fluid has garnered significant attention as a critical factor influencing the efficiency of high-temperature heat pumps. A novel method based on multi-objective optimization has been introduced for assessing the performance of heat pump working fluids. The method enhances the clarity of the objective and flexibility in addressing various operating conditions, which helps to improve the efficiency of working fluid screening, especially for the complex mixture system. This study utilizes eight pure refrigerants as the initial fluid set and evaluates 560 binary mixtures with a 5% composition variation. The NSGA-II algorithm is combined with the theoretical heat pump cycle model to obtain Pareto optimal solutions regarding the mixtures, with the coefficient of performance and volumetric heating capacity as the objective functions. Then the evaluation of the optimal solutions is conducted by considering their flammability, toxicity, environmental performance, and temperature glide properties. Subsequently, a comprehensive performance index is derived. The evaluation reveals the dominant solution set for each pure refrigerant. The findings suggest that the blend R142b/R1233zd(E) with a mass fraction of R142b between 0.15 and 0.25 demonstrates a comprehensive performance index of 0.322–0.350, indicating superior performance during the basic cycle. Furthermore, various cycle configurations have been investigated. In the vapor injection configuration, R600a/R601(0.6/0.4) shows good performance in all aspects except flammability. The mixture R245fa/R601(0.2/0.8) exhibits superior overall performance in the internal heat exchanger configuration. It displays excellent temperature glide matching characteristics and good environmental performance. Nevertheless, it shows suboptimal performance in terms of toxicity and flammability. This approach replaces the previous qualitative comparison-based decision making methods, offering high efficiency and practicality.

Technical and economic performance assessment of blue hydrogen production using new configuration through modelling and simulation

Steam methane reforming (SMR) is the dominant process for hydrogen production, which produce large amount of carbon dioxide (CO2) as a by-product. To address concerns about carbon emissions, there is an increasing focus on blue hydrogen to mitigate carbon emissions during hydrogen production. However, the commercialization of blue hydrogen production (BHP) is hindered by the challenges of high cost and energy consumption. This study proposes a new configuration to address these challenges, which is characterized by: (a) the use of piperazine (PZ) as a solvent, which has a high CO2 absorption efficiency; (b) a more efficient heat exchange configuration which recovers the waste exergy from flue gas; (c) the advanced flash stripper (AFS) was adopted to reduce the capital cost due to its simpler stripper configuration. In addition, the technical and economic performance of the proposed energy and cost-saving blue hydrogen production (ECSB) process is investigated and compared with the standard SMR process. The detailed models of the SMR process and the post-combustion carbon capture (PCC) process were developed and integrated in Aspen plus® V11. The results of the technical analysis showed that the ECSB process with 30 wt.% PZ achieves a 36.3 % reduction in energy penalty when compared to the standard process with 30 wt.% Monoethanolamine (MEA). The results of the economic analysis showed that the lowest levelized cost of blue hydrogen (LCBH) was achieved by the ECSB process with 30 wt.% PZ. Compared to the BHP process with 30 wt.% MEA, the LCBH was reduced by 19.7 %.

Unleashing novel configurations of gravitational water vortex thermal energy exchanger

This study presents thermal and hydrodynamics investigations for novel configurations of gravitational water vortex heat exchanger (GWVHE). The proposed novel configurations of GWVHE include SWB (shell with baffles), CSFH (circular spiral flow helix) and RSFC (rectangular spiral flow channel). The thermal energy balance between two fluid domains has been calculated numerically for various operational conditions. An analytical model is developed using the Kern's approach, the effectiveness-NTU method, and the LMTD method for heat exchangers to calculate the heat transfer characteristics of two fluids to validate numerical results. Moreover, a transient two-phase flow numerical model has been solved to investigate the volume fraction of air and water during the development of the vortex at the center of the basin. The results show that a convincing thermal energy balance is present between both fluid streams for all the proposed configurations of GWVHE. However, the heat exchange rate for the RSFC configuration of GWVHE is higher than the SWB and CSFH of GWVHE. Because it has maximum heat exchange surface area of 1.08 m2 and thermal losses in RSFC are significantly lower than those computed in CSFH and SWB at different operating conditions. The thermal losses reported for RSFC are just 1 % compared to CSFH and SWB thermal losses of 2 % and 5 %, respectively. Moreover, the maximum volume fraction of air obtained at the center of basin during vortex formation is 18 %, indicating an effective vortex air core.

CFD Analysis of a Latent Thermal Storage System (PCM) for Integration with an Air-Water Heat Pump

Heat pumps driven by sustainable electricity sources have been identified as a technology that can contribute to reduce carbon dioxide emissions. Furthermore, a heat pump can also provide energy savings when combined with a thermal energy storage system. Heat pumps can optimize their efficiency by accumulating thermal energy during periods of lower electricity demand, resulting in shorter operational durations and decreased overall energy consumption. In this work, the combination of a latent heat storage system with an air-water heat pump has been numerically analysed and experimentally tested. A phase change material (PCM) heat exchanger with an immersed plate was designed using a 3D CFD model (COMSOL Multiphysics®). The heat exchanger configuration with six steel plates immersed in the phase change material tank was proposed to enhance heat transfer in the storage system. The developed model is validated against experimental data from a real case study, demonstrating a maximum error of approximately 3% during the discharging phase. Additionally, the study explores the effects of different inlet heat transfer fluid temperatures and flow rates on the PCM solidification time.

Experimental and numerical investigation of porous heat exchangers with Kelvin cell structured foam at high temperatures: Coupled conduction-convection and radiation heat transfer

Heat recovery is crucial in the energy sector, especially for industries operating at high temperatures. One way to achieve high-efficiency heat recovery is to use porous materials in heat exchangers. In this work, the performance of a high temperature heat exchanger was investigated. For this purpose, a tube containing a porous cast iron structure was externally heated by radiation inside a tubular furnace and air at ambient temperature was blown into the tube. Experiments were conducted at different temperatures of up to ▪ and different airflow velocities in a specialized bench, considering the combined effects of conduction, convection, and radiation. Temperature profiles in three sections of the porous structure were measured by using sheathed thermocouples brazed to the porous structure. Power and exergy flow rate extracted from the porous structure to the air flow were calculated and analyzed to quantify recovered heat. In addition, a numerical modeling performed at the pore level using Fluent showed an average relative error of 15% compared to experimental results, indicating acceptable agreement with observed trends. This numerical model will serve as a valuable reference tool for future parametric analyses of porous structures in heat exchanger configurations.

Mathematical model of the solar combined cycle power plant using phase change materials in thermal energy storage system (Thermodynamic analysis)

This research presents a novel mathematical framework for optimizing solar combined cycle power plants, with a particular emphasis on the exergy analysis of various superheating heat exchanger configurations used in thermal energy storage. The importance of phase change materials (PCMs) in improving the thermodynamic efficiency of solar combined cycle power plants is emphasized in this study. The investigation includes three configurations, two with a single PCM and one with two PCMs. The use of PCMs is intended to increase storage density, reduce volume, and maintain consistent temperatures, thereby favoring latent energy storage. The model developed evaluates exergy efficiency and output temperature profiles during the charging and discharging processes. The results show that the single PCM configuration has an impressive charging efficiency of 93.12 %, reaching an output temperature of 371 °C in 8 h. The two PCM configurations, on the other hand, achieve even higher efficiency at 94.89 % during charging, with an output temperature of 367 °C over a slightly longer 10-hour period. This comparison emphasizes the benefits of using two PCMs, demonstrating increased exergy efficiency and a marginal increase in output temperature over a single PCM setup. Furthermore, a comparison of the outcomes resulting from the use of a single type of PCM in exchangers reveals that the disparity in PCM melting temperatures causes only minor variations in the system's efficiency. The findings emphasize the significance of optimal PCM utilization for efficient solar energy retention, particularly during periods of low radiation.

Thermo-hydraulic performance evaluation through experiment and simulation of additive manufactured Gyroid-structured heat exchanger

Following the breakthrough of additive manufacturing in overcoming machining limitations, triply periodic minimal surface (TPMS), governed by mathematical implicit functions, has emerged as a highly promising configuration for heat exchanger. Current study evaluates the thermo-hydraulic characteristics of a 316L stainless steel Gyroid-structured heat exchanger, manufactured by selective laser melting (SLM), through experimental and numerical methods. The experiment was conducted on a single-phase test rig with water as the working medium. The measured performance is affected by surface roughness and other factors, resulting in deviations from the theoretical performance. Specifically, at a flow rate of 500 kg/h, the experimentally measured overall heat transfer coefficient and cold-side differential pressure exhibit a 9.70 % and 69.82 % increase, respectively, compared to their theoretical values. In comparison to various heat exchangers reported in the literatures, this experimental model possesses a notable advantage concerning the power density achievable per unit length of pressure drop consumed. In addition, a nonlinear regression method based on the least squares approach and the thermal resistance separation method is proposed to obtain the Nu ∼ Re correlation. The fitting effect is satisfactory, as all the points fall within the deviation range of (-7.5 %, 7.5 %). Moreover, this experimental model outperforms four conventional heat exchanger configurations in terms of performance evaluation criteria.