Search

To explore the factors affecting the hydrogen evolution performance of a new MgH 2 solid-state hydrogen storage heat exchanger, this paper designs the MgH 2 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 %. • A new type of solid-state hydrogen desorption system is designed. • The effect of working and structural parameters on hydrogen desorption performance is discussed in detail. • The paper defines a comprehensive performance index M to compare different bed designs. [ABSTRACT FROM AUTHOR]

Pre-cooling for refueling high-pressure hydrogen not only avoids safety hazards but also extends the driving range of vehicles. In this paper, a simulation model for hydrogen refueling with a compact heat exchanger is developed to analyze the dynamic process in HRS with three-stage storage tanks. According to the simulated results, the hydrogen temperature at the heat exchanger's outlet is greatly influenced by the mass flow rate and the inlet temperature. The pre-cooling duration is a feasible method to save energy. Moreover, optimization discussions about the pre-cooling temperature and the pre-cooling duration have been carried out for the sake of the low final gas temperature, high SOC, and minimum energy consumption. If the ambient temperature decreases by 10 K, the optimal pre-cooling temperature could be adjusted to increase by 4 K. And if the initial vessel pressure increases by 2 MPa, the optimal pre-cooling duration could be shortened by 10 s. [Display omitted] • A refueling simulation model considering a heat exchanger model has been developed in a HRS with cascade storage system. • The hydrogen temperature at the heat exchanger's outlet is predicted and analyzed. • Impacts of pre-cooling duration on final gas temperature and energy consumption have been discussed. • The optimal pre-cooling temperature could increase by 4 K–6 K if the ambient temperature increases by 10 K. • The pre-cooling duration at the initial stage could be optimized by 10 s if the initial vessel pressure increases by 2 MPa. [ABSTRACT FROM AUTHOR]

Liquefied hydrogen has a high energy density, so it is suitable for railways that require a lot of energy and use fuel for a long time. In this paper, the effects of changes in hydrogen inlet flow rate, outlet pressure conditions, and ethylene glycol water (EGW) flow rate in liquefied hydrogen heat exchangers for locomotives on hydrogen outlet temperature, EGW outlet temperature, hydrogen pressure-drop, hydrogen outlet density, hydrogen outlet flow velocity, and EGW freezing possible range were analyzed through computational analysis. Increasing the inlet flow rate of EGW increased the outlet temperature of EGW and hydrogen, and showed a greater effect in reducing the freezing possible range than increasing the outlet temperature of hydrogen. Increasing the hydrogen outlet pressure increased the hydrogen and EGW outlet temperature and had a greater effect on the increase in the hydrogen outlet temperature than the decrease in the freezing possible range. [ABSTRACT FROM AUTHOR]

The plate-fin heat exchanger was designed for the liquid cooling thermal management system of the hybrid electric propulsion system for an electric vertical take-off and landing (eVTOL) vehicle. The offset-strip fin design was applied, and the performance of the heat exchanger was evaluated, particularly with respect to the inclination of the airflow entering the heat exchanger. The estimated performance during the design phase matched well with the experimental results. The inclination of the heat exchanger had a minimal effect on thermal performance, with a slight increase in performance as the inclination increased. However, the pressure difference along the airflow was affected, likely increasing as the inclination increased. The sensitivity of various parameters on coolant temperature was also investigated. The air inlet temperature had a significant effect on coolant temperature, followed by the coolant flow rate. Therefore, when designing the thermal management system, careful consideration should be given to the ambient air temperature and coolant flow rate. [ABSTRACT FROM AUTHOR]

Fouling mitigation provides many challenges in process equipment, especially in heat exchangers. In this work, the fouling behaviors of two polymers are compared to 1.4301 stainless steel (SS) in calcium sulfate solutions. An experimental setup that allows to classify the materials quickly and under varying process conditions is used to determine the fouling behavior. Results are compared to a screening apparatus which can test up to three materials simultaneously. Finally, the cleaning behavior of all three materials is investigated. Results show that polyether ether ketone (PEEK) is superior to SS in mitigating fouling and is easier to clean; however, polyether ether ketone with 30 % talcum (TKT) is not. This is attributed to the surface roughness of the materials. [ABSTRACT FROM AUTHOR]

The effectiveness of triangular baffles in enhancing heat transfer within corrugated tubes is examined numerically in this study. Two key parameters influencing performance are examined: baffle placement (staggered and aligned) and their angles of attack (0°, 15°, 30°, and 45°). Heat transfer, friction, as well as performance metrics are comprehensively examined and compared for both configurations. The finite element method (FEM) implemented in CFD software COMSOL Multiphysics 6.1 is employed for simulations across a range of Reynolds numbers (100-400). Results reveal significant heat transfer improvements due to the proposed baffle configurations. Notably, aligned baffles with a 30° angle of attack achieve a 43.6% increase the heat transfer when compared to the baffle-free scenario. Staggered baffles with a 15° angle of attack demonstrate a superior 55.3% improvement compared to the baseline. A comprehensive evaluation of performance criteria identifies staggered baffles with a 30° angle of attack as the optimal configuration for maximizing heat transfer within corrugated tubes. [ABSTRACT FROM AUTHOR]

Heat exchangers are widely used in petrochemical and other industries. Improving the efficiency of heat exchangers to increase energy utilization is crucial. Passive enhanced heat transfer technology is widely studied in heat exchanger research due to its low energy consumption and simple operation. Helical baffle–corrugated tube heat exchangers have not been extensively studied as a promising new class of these devices. This paper investigates the key structural parameters of a helical baffle-corrugated heat exchanger through numerical simulation. This study focuses on the factors affecting heat transfer and flow resistance performance. The results show that reducing the helical angle from 28.42° to 10.81° increases the total heat transfer coefficient by approximately 20%. The overall performance of the heat exchanger is evaluated using the efficiency evaluation coefficient (EEC). Optimal levels of each structural factor are determined for different working conditions based on this evaluation. [ABSTRACT FROM AUTHOR]

According to the European energy consumption reports, the highest energy/fuel consumption in the residential sector is due to space heating, followed by water heating. Generally, the product used to warm water in residential buildings is a boiler system where a heat exchanger is the core of the system. The paper provides a Life Cycle Assessment analysis of a traditional heat exchanger used in domestic boilers with the aim to identify critical aspects and environmental hotspots for the development of a novel concept of the heat exchanger. The methodology used to collect eco-design guidelines from the Life Cycle Assessment analysis is proposed within the paper. Several eco-design actions were put into practice to reduce the environmental issues in each phase of the life cycle from the materials used, the manufacturing processes as well as the product geometry to increase energy efficiency during the use. Concerning the materials and manufacturing phase, a novel design based on a different material (e.g., stainless steel) was developed to replace a mix of materials (i.e., copper and aluminum alloy). Concerning the use phase, the overall product efficiency was increased allowing important savings in terms of gas/energy consumption, by the adoption of a novel design (e.g., spiral pipe). The new heat exchanger design shows better environmental performance in each Life Cycle Assessment indicator, saving more than 40% in CO2 emissions (Global Warming Potential) in the whole product life cycle. [ABSTRACT FROM AUTHOR]

Shell and tube heat exchangers (STHE) are essential thermal equipment and widely used in daily life. A novel thermosyphon system called falling-film thermosyphon (FFTS) is introduced and integrated into STHE system, resulting in a better thermal performance. In this study, a rectangular solid tube bank of FFTS bundles with a baffle design is studied. The numerical simulation for heat and mass transfer of the FFTS heat exchanger is developed to predict the condensation rate of the vapor in the flue gas, and a lab-scale prototype is also built up in COMSOL. The prediction is validated with the experimental data from references, and the model's accuracy is verified within 10%-12% error. Also, the Non-dominated Sorting Genetic Algorithm, version 2 (NSGA-II) is implemented to improve the thermal performance of rectangular tube banks in this paper. Several parameters, e.g., baffle number, tube number, and tube space, are optimized. As a result, compact configurations with more baffles are preferred to enhance the performance associated with a high-pressure drop correspondingly. The optimized layout for the lab-scale prototype can increase by 18 to 32% condensation with a pressure loss of less than 200 Pa. [ABSTRACT FROM AUTHOR]

Practical Application The heat and momentum transfer of tomato puree through a concentric‐tube heat exchanger over a range of generalized Reynolds number (0.05 < Re < 66.5) was experimentally and numerically analyzed. Thermophysical and rheological properties of tomato puree (12°Brix) were measured from 20 to 60°C. The velocity, pressure, and temperature were calculated using the computational fluid dynamics (CFD) software FLUENTTM with temperature‐dependent transport properties. The thermal operation of the concentric‐tube exchanger was satisfactorily predicted using CFD, indicating accurate measurement of tomato puree properties with temperature variations. A concordance was found between the calculated Fanning friction factor and generalized Reynolds with the experimental correlation. A modified Sieder–Tate correlation was established, which allows properly expressing the Nusselt number as a function of the Peclet number. Simple correlations for the mechanical work and the heat transfer rate as a function of the volumetric flow rate were derived. The thermal efficiency was high at low puree flow rates but decreased with higher rates. However, at high flow rates, ceased its decline, instead showing a slight improvement. The analysis confirmed higher heat transfer rates in the concentric‐tube heat exchanger compared to a plain tube at low puree flow rates. The results offer valuable insights for assessing diverse operational conditions in dairy, beverage, sauce, and concentrated food industries. Additionally, they also enhance the analysis and design of concentric‐tube heat exchangers.The knowledge of the rheological and hydrodynamical behavior of fluids in concentric‐tube heat exchangers allows to explore a set of different operating conditions to improve the yield and effectiveness on the system heating/cooling design. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The presented research addresses a problem occurring in a biogas plant, which we know plays an important role in sustainable development. The sludge deposited on the walls of the digester's heat exchanger impairs heat transfer to the substrate. It leads to a temperature drop inside the biogas plant and threatens its correct operation. The thickness of the sludge layer cannot be directly measured when the plant is operating. Therefore, the aim of this work was to develop and then validate a method for estimating, based on the operating parameters of the exchanger, the thickness of the sludge layer and to give theoretical foundations for designing an automatic sludge monitoring system. Two mathematical models (and methods) were developed: one- and two-dimensional. The former model was solved analytically while the latter by the Trefftz method. The numerical results from these two approaches showed very good agreement with each other and with the actual measurement taken directly after removing the substrate from the fermentation chamber. According to the calculation results, the growth of the sludge layer was linear with time, and its rate was 0.0064 mm per day. Finally, a schematic diagram of an intended sludge monitoring system was proposed. It could optimize biogas plant operation and thus become a step towards more sustainable energy production. [ABSTRACT FROM AUTHOR]

Heat exchangers play a vital important role in industries and processing equipment's. Among them, the double pipe heat exchanger facilitates the exchange of heat between two fluids through surface tubes. This study aimed to investigate various thermal performance parameters of baseline water and Aluminum oxide nanofluid at various volume concentrations and flow rates. The results were compared between baseline water and Aluminum oxide nanofluid using a test rig at the temperature range of 60 °C for industrial applications. The nanofluid sample was prepared by adding very small-sized (20nm) Al2O3 nanoparticles in the baseline water within the range of 0.10% to 0.175% using a standard two step method for the sterilization process. The nanoparticle and baseline water were under set by a hot plate mechanical stirrer for approximately 2 hours to ensure the proper dispersion before the tests, rendering the nanofluid stable for 12 hours. The Laminar-Transition flow double pipe heat exchanger (test rig) operated at flow rates ranging from 1.6×10-5-3.3×10-5 m3/sec (1-2 LPM) within the range of Reynolds number from 1700 to 3400 at volume concentration of 0.10% to 0.175% Moreover, an addition of 0.175% of Al2O3 nanoparticle in the baseline improved the average heat transfer coefficient from 140% to 155%, thermal conductivity of 21.6% and, 5.94% efficiency in counter flow direction and also showed higher friction factor i.e. 2.81% than baseline water. The results suggest that Al2O3-nanofluid at 0.175% could function very well as working fluid for industrial requirements compared to the conventional baseline water. [ABSTRACT FROM AUTHOR]

The potential of hybrid nanofluids to boost thermal efficiency of heat exchanger systems is the focus of this review study. The primary focus is on addressing the associated issues of nanoparticle clumping, system obstruction, and reduced efficacy of heat exchanger due to increased fluid thickness. Accordingly, this review intends to demonstrate the innovative practices (experimentally and theoretically) that helps improving the heat transfer and thermal performance of heat exchangers. In this regard, a critical analysis is conducted to appraise the experimental and numerical simulations, which introduce the impact of different nanoparticle concentrations and compositions on heat exchanger thermal performance. The findings of this review has shown that the hybrid nanofluid of CuO–Cu/water has the greatest thermal performance factor (1.065), following Al2O3–Cu/water (1.055), and Cu–TiO2/water (1.039). Also, the utilization of turbulator heat exchangers has enabled improving the thermal performance by 126 % with a 6 % rise in volume fraction at the maximum Reynolds number. This study underlines the need for further research into novel nanomaterial combinations, fine-tuning of fluid characteristic, and comprehensive stability assessments to enhance the utilization of hybrid nanofluids in heat exchanger systems. Finally, discussions of limitations associated with such systems and proposed potential solutions will lead to a valuable contribution in the possible future development of cost-effective heat exchanger systems. [ABSTRACT FROM AUTHOR]

With advances in technology and the increasing use of nanomaterials, ongoing research is focused on improving the performance of thermal systems. This study investigates the thermal conductance (UA) of a radiator using aqueous suspensions of carbon nanotubes (CNTs), which are among the nanomaterials with the highest heat transfer coefficient. For this purpose, three different nanofluids were prepared, each with varying concentrations of single‐walled carbon nanotubes (SWCNTs) and multi‐walled carbon nanotubes (MWCNTs). The heat transfer performance of three hybrid nanocoolant fluids (NF), namely, NF1 (0.8 wt% MWCNT + 0.4 wt% SWCNT), NF2 (0.4 wt% MWCNT + 0.4 wt% SWCNT), and NF3 (0.4 wt% MWCNT + 0.8 wt% SWCNT), was experimentally examined and compared with water. The results show that CNT suspensions can enhance heat transfer by up to 16.9% compared with the base fluid, and SWCNTs were observed to have better thermophysical qualities than MWCNTs. [ABSTRACT FROM AUTHOR]

Industrial processes often generate substantial amounts of wastewater with significant thermal energy content, which is typically discarded as waste. A promising approach to increase energy efficiency and advance sustainable resource management is waste water heat recovery. Utilizing a phase change material (PCM) to extract waste heat from wastewater and transfer it to cold water is an innovative method that separates the demand and supply of heat, while also integrating storage and transmission within a single heat exchanger (HE). A 3D numerical model of PCM‐based HE is developed and simulated. The thermal behavior of PCM and preheating of cold water are investigated in this study. In order to increase the thermal conductivity of the PCM, fins are strategically positioned. Around 71.13% of melting time is reduced by adding fins. Further, the 10° orientation of the fins is also numerically observed and it is found that it helps to improve natural circulation of molten PCM. Thus, melting time is reduced by 34% compared to the vertical fin. A 3.5°C–4.5°C temperature rise in cold water is obtained with the inclined fin, which is 14.28% higher than the vertical fin model. [ABSTRACT FROM AUTHOR]

This work examines the fluid flow, heat transfer, and thermal hydraulic performance of turbulent flow through a horizontal pipe integrated with TT that has various cut shapes using numerical analysis. In the current investigation, trapezoidal-cut geometry with single and double cuts is adopted. Three-dimensional simulations have been validated using experimental data from the literature. The equations have been solved using the RNG k-ε model and the finite volume method (FVM). With three distinct types of twisted tape (PT, SC, and DC) and TR (4.0, 6.4, and 8) for a heat flux of 5000 W m−2, the computational findings have been carried out in the range of Reynolds numbers 4000 ≤ Re ≤ 8000. Impact of these factors on Nusselt number, friction factor, and thermal performance are explored and compared to plain pipe under similar conditions. The addition of trapezoidal-cut TTs leads to enhanced mixing of fluid due to swirl flow generation. The result shows that average Nusselt number and friction factor are functions of TR. The thermal performance factor (TPF) for double-cut trapezoidal TT is about 1.2–1.65 which is maximum compared to single-cut and plain TT inserts. [ABSTRACT FROM AUTHOR]

A new type of compact, portable fixed-bed reactor integrated with a heat transfer system was developed for the removal of volatile and flammable air pollutants such as lean methane and volatile organic compounds (VOCs). The reactor may operate in catalytic or thermal combustion conditions with the purpose of achieving autothermal processes with the possibility of energy recovery. An excess heat recovery point was designed behind the reactor bed at the place where the gas temperature is the highest to enable its usage. The mathematical model is presented together with a number of simulation calculations performed for the assessment of the developed reactor. The case study in this paper was for catalytic methane oxidation at a temperature of 400 °C, a methane concentration between 0.1% and 2% by weight, a gas flow rate of 1 m3/s STP, and a heat exchange surface for the assumed plate exchanger from 10 to 200 m2. The calculations show that the thickness of the insulation is of little importance for the operation of the equipment, and a sufficient thickness was about 20–50 mm. The optimal area for the considered case is 80–100 m2. It was found that recovery of thermal energy is possible only for higher methane concentrations, above 0.3% by weight. Using an appropriate surface for the exchanger, it is possible to recover even 50% of the combustion enthalpy at a methane concentration of 0.45% by weight. For an exchanger area below 50 m2, the recoverable energy drops rapidly. It was found that the exchanger area is the most important equipment parameter under consideration. [ABSTRACT FROM AUTHOR]

Heat exchangers are necessary in most engineering systems that move thermal energy from a hot source to a colder location. The development of additive manufacturing technology facilitates the design and optimization of heat exchangers by introducing triply periodic minimal surface (TPMS) structures. TPMSs have shown excellent mechanical and thermal performance, which can improve heat energy transfer efficiency in heat exchangers. This current study intends to design and develop efficient, lightweight heat exchangers for aerospace and space applications. Using the TPMS structure, a porous construction encloses a horizontal tube that circulates heated fluid. Low-temperature water circulates inside a rectangular box that houses the complete system to remove heat from the horizontal pipe. Three porous structures, the gyroid, diamond, and FKS structures, were employed and examined. Porous models with various porosities and surface areas (15 cm2 and 24 cm2) were investigated. The results revealed that the gyroid structure exhibits the highest Nusselt number for heat removal (Nu max = 2250), confirming the highest heat transfer and lowest pressure drop among the three structures under investigation. The maximum Nusselt number obtained for the FKS structure is less than 1000, whereas, for the diamond structure, it is near 1250. A linear variation in the average Nusselt number as a function of the structure surface area was found for the FKS and diamond structures. In contrast, nonlinearity was observed in the gyroid structures. [ABSTRACT FROM AUTHOR]

Advances in additive manufacturing technology have made it possible to produce complex structures. Utilizing this manufacturing technology, compact heat exchangers with triple periodic minimal surface (TPMS) structures have been proposed and implemented for highly thermal-efficient devices with limited space. However, design process of complex compact heat exchangers is still time-consuming and labor dependent. This study aims to develop a design framework for TPMS-based compact heat exchangers. In the first step, a TPMS structure and compact heat exchanger geometries are modeled based on implicit modeling techniques. In the next step, a parametric study based on computational fluid dynamics (CFD) simulations is performed to evaluate the heat exchanging performance for three structures: gyroid, Schwarz-P, and diamond. In the final step, a design modification algorithm for compact heat exchangers is proposed. The proposed approach performs automatic shape correction based on resulting pressure drop distribution from the CFD simulation. [ABSTRACT FROM AUTHOR]

Traditional air conditioning systems use lot of energy; thus, dew point evaporative air-cooling systems could be a good alternative. Many experts studied the impact of constructional and operating characteristics on Maisotsenko cycle (M-cycle) to improve its performance. Cooler performance is influenced by the heat exchanger. Heat exchangers were constructed using flat and corrugated plates. The present study proposes the use of geometrically modified trapezoidal corrugated plates for counter flow heat exchanger, which consists of alternate air and water flow passageways. The numerical model is developed to predict the performance under variety of inlet air conditions and channel dimensions. In the standard range of incoming air properties such as relative humidity, the performance parameters assist in making cooler recommendations. Comparison and validation of simulation results are done with published experimental data for corrugated and trapezoidal corrugated plate heat exchangers. For trapezoidal corrugated plates, simulation findings revealed 10% increase in wet bulb efficiency and 7% increase in dew point efficiency over corrugated plates. The efficiency of wet bulb and dew point decreases as channel gap widens. For trapezoidal corrugated plates, the larger channel spacing minimises pressure drop. [ABSTRACT FROM AUTHOR]

The current energy crisis is causing a transformation of tremendous scope and complexity. The natural gas, coal, and electricity sectors have experienced the largest tremors. In this regard, an effort was made to conserve energy by providing a compact heat exchanger that may be utilized to recover waste heat from power plants and industries. This article explores the effect of combined passive techniques on the performance of a CTHE fitted by twisted tapes at hot-side and Al2O3 nanofluid used as cold-side fluid. The experiments were conducted by incorporating the differently configured PVTTs and CFTTs (TR: 20, 13.3, and 9.8) in the inner tube with fixed flowrate (Re = 2500) of hot water and using different volume fractions of Al2O3 nanofluid (Vol.%: 0.05, 0.1 and 0.15) as cold fluid with varied flow rates (500 ≤ Re ≤ 5000) in the annulus. The results reveal that the PVTT (TR = 20) and 0.05% nanofluid combination increases the Nusselt number by 12.28% and the TPF by 1.127, while the CFTT (TR = 9.8) and 0.15% nanofluid combination increases the Nusselt number by 24.27% and the TPF by 1.263. Hence, CFTT (TR = 9.8) with 0.15% of Al2O3 nanofluid provided greater performance in the combinations tested, albeit at the expense of a little pressure loss. [ABSTRACT FROM AUTHOR]

In present study, the thermal modeling and multi-objective optimization of shell and tube heat exchangers (STHE) with a diamond-shaped turbulator has been investigated. To obtain the Correlation relationship between the Nusselt number and the friction factor for a diamond-shaped turbulator, a CFD analysis with acceptable accuracy has been done. Two factors of total cost and maximum thermal effectiveness are chosen as two objective functions. Nine optimal design variables for the present study are arrangement, diameter, step ratio, length and number of tube, distance ratio and cut ratio of baffle, turbulator step ratio and turbulator internal rod diameter. The ε-NTU procedure is employed for thermal modeling STHE and the Bell-Delaware technique is applied to evaluate the coefficient of heat transfer and pressure drop of the shell side. Also NSGA-II is used to acquire two objective functions. Comparison of the obtained results of the optimal Pareto optimal solutions showed that the use of diamond-shaped turbulator DST on the tube side improves thermal performance and lower overall costs STHE compared to the non-use state. Using turbulator inside the tube and the impact of important design parameters clearly contributed to the difference between effectiveness and overall cost. [ABSTRACT FROM AUTHOR]

The experimentation and analysis of a machine learning (ML) algorithm for automatic problem detection and real-time heat exchanger optimization (RTHEO) is presented in detail in this paper. Preparing datasets, optimizing heat exchanger parameters, identifying problems, self-training, and applying machine learning algorithms are the main areas of study. The suggested method utilizes MATLAB Simulink simulations that use polynomial regression to suggest parameters and a combination of algorithms to identify anomalies. The program continuously obtains real-time data, compares it with previous patterns, and notifies the user if any anomalies are detected. The algorithm adapts to observations through self-training, ensuring accurate and reliable predictions. The implementation is carried out using MATLAB, with robust error-handling mechanisms for real-world applications. The simulation procedure is discussed, and a future experimental setup is proposed to verify the program's performance. [ABSTRACT FROM AUTHOR]

PI-PD controllers have superior performance compared to traditional PID controllers, especially for controlling unstable and integrating industrial processes with time delays. However, computing the four tuning parameters of this type of controller is not an easy task. Recently, there has been significant interest in determining the tuning rules for PI-PD controllers that utilize the stability region. Currently, most tuning rules for the PI-PD controller are presented graphically, which can be time-consuming and act as a barrier to their industrial application. There is a lack of analytical tuning guidelines in the literature to address this shortfall. However, the existing analytical tuning guidelines do not consider a rigorous design approach. This work proposes new robust analytical tuning criteria based on predefined gain and phase margin bounds, as well as the centroid of the stability region. The proposed method has been tested using various simulation studies related to a DC–DC buck converter, a DC motor, and a heat exchanger. The results indicate that the proposed tuning rules exhibit strong performance against parameter uncertainty with minimal overshoots. Furthermore, the suggested technique for simultaneous control of yaw and pitch angles has been tested in a real-time application using the twin rotor multi-input multi-output system (TRMS). Real-time results indicate that, compared to other methods under investigation, the suggested approach provides nearly minimal overshoots. [ABSTRACT FROM AUTHOR]

The implementation of energy-saving measures has a substantial and beneficial impact on the preservation of energy resources as well as the reduction of carbon dioxide emissions. This study focuses on the design and experimental analysis of a water-to-air heat recovery system aimed at capturing waste heat from wastewater and transferring it to a fresh cold air stream using heat pipe technology. The research problem addressed in this study is the efficient recovery of low-grade thermal energy from wastewater, which is often underutilized. The prototype heat recovery unit was designed, manufactured, and tested in the laboratory to assess its performance across various operating conditions. The experimental setup included a system where the primary agent, hot water, was heated to 60 °C and circulated through the evaporator section of the heat recovery unit, while the secondary agent, fresh air, was forced through the condenser section. The system's performance was evaluated under different air velocities, ranging from 3.5 m/s to 4.5 m/s, corresponding to airflow rates of 207.1 m3/h and 268.6 m3/h, respectively. The study employed analytical methods alongside empirical testing to determine the effectiveness of the heat recovery system, with the global heat transfer coefficient calculated for different scenarios. The efficiency of the system varied between 25% and 51.6%, depending on the temperature and speed of the fresh air stream. The most significant temperature difference observed between the inflow and outflow of the fresh air stream was 16.8 °C, resulting in a thermal output of 1553 W. Additionally, the average (mean) overall heat transfer coefficient of the unit was calculated to be 49 W/m2 K, which aligns with values reported in the literature for similar systems. The results demonstrate the potential of the designed system for practical applications in energy conservation and carbon emission reduction. [ABSTRACT FROM AUTHOR]

Pin-fin and flat-tube heat exchangers (PFFTHXs) offer a promising alternative to traditional louvered-fin and flat-tube heat exchangers (LFFTHXs), especially when used as evaporators. The streamlined structure of pin fins helps to effectively remove condensate and defrost water. In this study, we conducted a numerical analysis of 60 different pin-fin configurations across three pin diameters to enhance heat transfer in PFFTHXs. Our investigation focused on how pin pitch affects both airflow and heat transfer efficiency. The results show that a closer pin pitch increases both the heat transfer rate per unit area and the pressure drop for a given airflow velocity. We evaluated the overall performance of these configurations using the heat transfer rate per unit frontal area obtained at equivalent fan power levels. The analysis identified optimal configurations for each pin diameter, with the 0.2 mm diameter configuration demonstrating the highest heat transfer efficiency—this was on par with louvered fins but used fewer resources. This makes it an ideal choice for evaporative applications in PFFTHXs. [ABSTRACT FROM AUTHOR]

Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering, energy conversion, and sustainability. This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies. This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro- and photo-thermal energy conversion and also storage systems. A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6 (GPA6) and Ti3C2Tx MXene/silver nanowire with Cellulose Micro/NanoFibers (CMNF) cryogens by using spark plasma sintering (SPS) based high-pressure hydrothermal treatment model. An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500°C to 850°C. The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems, to increase energy output while minimizing losses. The silver nanowire is with a heat transfer coefficient of 78%, a mass remaining rate of 98.7%, and an energy storage efficiency of 23.8%. This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses, and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials. [ABSTRACT FROM AUTHOR]

With the increasing demand for heat dissipation of engineering vehicles, a dual-cycle cooling system is introduced in this paper to prevent the adverse effects of engineering vehicles' equipment when operating at the overheating temperature. The performance of the new system is analyzed through tests, and the results show that the dual-cycle cooling system can meet the thermal balance requirements of the engineering vehicle during the shovel operation. Compared with the traditional cooling system, the new cooling system improved performance in terms of volume, engine energy consumption and working oil efficiency. The oil consumption of a wheel loader using the dual-cycle cooling system is reduced by 1% per hour, and the temperature of its transmission oil and hydraulic oil is reduced by more than 10 °C. The new cooling system has bright future in energy saving and emission reduction of engineering vehicles. [ABSTRACT FROM AUTHOR]

Thermal storage technology has received increasing attention under the policy of encouraging the development of renewable energy and new clean energy. Optimizing the heat exchange system of phase change thermal storage heat exchangers to obtain better performance has become increasingly urgent. This study comprehensively investigated the actual process of heat transfer and assessed the heat transfer correlation laws between the heat transfer fluids, heat exchange tubes, fins, and phase change materials. Taking the heat exchange efficiency of the heat exchanger as a guide, a simulation was conducted on the effect of the presence and quantity of fins as well as the flow rate of the cooling liquid on the heat exchange efficiency of the heat exchanger. The simulation results showed that too many or too few fins were not conducive to improving heat transfer efficiency. In addition, no positive correlation was observed between the flow rate of the cooling liquid in the heat exchanger and the heat transfer efficiency of the heat exchanger. Specifically, models with slightly slower cooling liquid flow rates had a higher heat transfer efficiency. After a sensitivity analysis, it was found that the number of fins had a more significant effect on the heat transfer efficiency of the heat exchanger than the flow rate of the cooling liquid. The heat exchanger with five fins and a cooling liquid flow rate of 0.1 m/s demonstrated the best heat transfer effect, achieving a temperature drop of 14.76% within 5 min. [ABSTRACT FROM AUTHOR]

The design of a microchannel heat exchanger can be achieved using various approaches. The design includes various materials, such as ceramics, silicon, metals, and polymers, that are used to make microchannels, depending on their specific requirements. Polymers such as silicon, glass, and other polymeric materials are utilized on metallic substrates. The current study includes microchannels fabricated from metallic copper. Further, the design solutions do not consider the implications of the second law of thermodynamics. Hence, performing an energetic analysis of microchannels is imperative to design and assess thermodynamic systems that use them efficiently. One technique to improve a thermodynamic system's efficiency is using a well-designed microchannel heat exchanger with excellent energetic performance. This can be achieved by creating a thermodynamic system that eliminates energetic losses and limits only unavoidable losses. The use of high-conductivity material like copper also achieves this. To identify possible reasons for exergy loss and perhaps address them, a thorough energetic analysis of an existing heat exchanger is necessary. A microchannel heat exchanger with 19 microchannels in a flat tube is considered for this study. The study finds the energetic losses, which are useful for the thermal design of the heat exchanger. [ABSTRACT FROM AUTHOR]

The aim of the present work is to investigate the performance indication and flow of a counter heat device using different baffle configurations numerically. This research illustrates the consequence of segmental stumps and wavy cross-section stumps with varying wave numbers and amplitude. The governing equations of energy and Navier-Stokes equations were solved using the Computational Fluid Dynamics (CFD) software package FLUENT 22R1, employing the finite volume method. The SIMPLE algorithm with second-order upwind discretization for the convection term was used for velocity and pressure calculations. Different cold water rates of flow (2, 4, 6, and 8 L/min) at 23℃ through shell and Constand hot water flow rate at 1 LPM at 50℃ were analysed for their effect on heat transfer efficiency. The heat exchanger's thermal performance was comparing its duty with various baffle configurations to its performance without baffle. The research results indicate that installing baffles increased the heat exchanger's effectiveness (ε)., with the enhancement ratio (ε/εNE) reaching 1.2 and 1.23 for segmental and wavy baffles respectively compared to no baffle. On the other hand, the overall heat transfer coefficient (Uo) showed an improvement with baffles, achieving a performance increase of up to 1.38 at 8 LPM for Wavy baffles with wave number and amplitude (15 and 3 mm) respectively. The pressure drop in the system increased to 406 Pa at wavy baffles (15 and 3 mm) of 6 LPM. The maximum amount of exergy destruction being approximately 0.29 at 8 LPM for segmental. The results providing insights into optimal baffle design for specific applications. [ABSTRACT FROM AUTHOR]

The high temperature of photovoltaic panels represents the most prominent challenge to the possibility of increasing their efficiency. To eliminate excess heat, a PVT system is used with an efficient cooling system. The current study focuses on economic and easy new construction. The main objective of this study is to provide more information about the cooling effect on performance under certain operating conditions. This study involved initial numerical testing of five prototypes used to cool PV panels in a water-based system. The best model was chosen by considering the impact of cooling box geometry, heat flux variation, and coolant flow rate variation on performance. The problem was solved numerically in a 3D model using CFD technology via ANSYS R19.2 software. As for the experimental part, it includes two sections. The first represents the manufacturing of two models, one of which represents the basic model of a cooling box with non-ribbed fins (NRFCB), while the other represents the fifth model that was chosen according to the initial numerical test, which represents a cooling box with ribbed fins (RFCB). The second section consists of adding thermoelectric units (TEGs) to take advantage of the accumulated heat instead of dispersing it. The results showed good convergence between the two tests, with a deviation rate that did not exceed 7.58%. The experimental test results indicate that the PV panel cooled according to the RFCB model achieved an improvement over the NRFCB model of 0.77% and 1.26% under a heat flux of 400 and 1035 W/m², respectively, at a water rate of 4 L/min. On the other hand, the addition of 8 TEG units achieved its highest power at 14:30, which reached 0.144 W during the day on July 15, 2023, in Kut, Iraq, with a water rate of 0.5 L/min. [ABSTRACT FROM AUTHOR]

The probe chuck is an inspection device assessing the thermal durability of semiconductor wafers in various temperature environments before shipping. It is most important to ensure that the temperature of the chuck upper surface, on which the wafers are placed, is uniform. This study presents an axisymmetric chuck model to improve surface temperature uniformity in both radial and circumferential directions. The local distribution of the flow path height in the axisymmetric chuck was adjusted to make the chuck upper surface with a constant wall heat flux to simultaneously become as uniform temperature as possible. Three optimization algorithms, namely the genetic algorithm (GA), deep q-network (DQN), and actor-critic (AC) were applied. The optimized shape of the flow pathway, improved temperature uniformity, pressure drop, and local heat transfer coefficient profile by three different optimization algorithms are presented in detail. As a result, the surface temperature difference was significantly reduced from 7.137 K in the existing spiral model to 0.682 K. The optimal axisymmetric chuck could reduce surface temperature differences up to 90 % compared with the conventional spiral chuck. [ABSTRACT FROM AUTHOR]

As environmental regulations on exhaust gas are enforced worldwide and marine transportation is progressively strengthened, various methods are being explored to comply with emission regulations by using alternative energy sources. This study involved the optimization of a thermoelectric power generation (TEG) system, which converts thermal energy into electrical energy. The design of the TEG system was optimized by using CFD to analyze the heat transfer phenomena resulting from the relative positions of the TEG modules, and the results of this analysis were validated with 1/100 experimental scale measurement data. The comparison of the CFD results with the experimental measurements revealed that the maximum discrepancy exists for the temperature near the cooling jacket and for the amount of power generated by the system. The significant difference between the CFD and experimental results is attributable to the adiabatic conditions assumed for CFD since the experimental facility experiences heat loss to the atmosphere. In this study, we established an analysis methodology by conducting a comparative validation between CFD calculations and experimental data. The methodology is expected to play a significant role in optimizing the design of thermoelectric power generation systems. [ABSTRACT FROM AUTHOR]

In the present study, using a combination of theoretical discussions, practical examples, and case studies, we sought to gain a comprehensive understanding of how numerical solutions could be used to improve the design and optimize the thermal efficiency of a heat exchanger that utilizes wastewater to reduce the domestic consumption of hot water. To this end, we developed a validated numerical model. We also carried out simulations and experiments, the results of which are presented in this paper. The novelty of this work derives from our use of a new heat exchanger design for a domestic shower, and from the presented experimental–numerical evidence that proves its efficiency. We found that use of our newly designed appliance improved thermal efficiency from 14% to 27%. Moreover, we estimated that the cost of manufacturing and installing such a device did not exceed that of a widely available drain grid. Using our newly designed exchanger, a family of four living in Poland could save EUR 38 (at 2022 values) and reduce CO2 emissions by 192 kg. An average European family could save EUR 68 and reduce CO2 emissions by 76 kg. [ABSTRACT FROM AUTHOR]

This study used an experimental setup consisting of a flat tube with a louvered finned crossflow configuration to examine the effects of utilizing a ZnO-TiO2-water hybrid nanofluid on heat transfer rate, heat transfer coefficient, Nusselt number, and pressure drop. The studies were carried out under laminar flow conditions (200 < Re < 800), at four different temperatures (50, 60, 70, 80 °C), four different volume concentrations of nanoparticles (0.025, 0.05, 0.1, 0.2%), and three different volume flow rates (4, 6, 8 LPM). The findings were compared with pure water (0%). The results indicate that using hybrid nanofluid improves the heat transfer performance and increases pressure loss in comparison with pure water. When comparing hybrid nanofluid to pure water, the largest increases in heat transfer rate, heat transfer coefficient, Nusselt number, and pressure drop were 87.8%, 21.7%, 26.4%, and 10%, respectively. In addition, it was found that, up to a specific value (0.05%), increasing the nanoparticle volume concentration enhanced the heat transfer rate, heat transfer coefficient and Nusselt number, but which began to decrease on increasing the concentration past this value. Therefore, it was concluded that nanoparticle volume concentrations greater than 0.05% negatively affect heat transfer under the current operating conditions. The maximum heat transfer rate, heat transfer coefficient, and Nusselt number were obtained under the conditions of an 8 LPM volume flow rate, 80 °C inlet temperature, and 0.05% volume concentration. [ABSTRACT FROM AUTHOR]

Water is the secret of life. People demand more and more water. Solar stills generate distilled water. The present project involved designing and evaluating a heat exchanger-connected solar collector and solar still system. The effects of nanofluids on solar collector performance and solar still productivity were studied. Hybrid and mono ZnO/WO3- water nanofluids have been produced in two steps. Individual and mixed nanofluids have a volume concentration of 0.035%. Four hybrid nanofluids with varying ZnO and WO3 concentrations were examined. Nanofluid stability has been established. The thermal conductivity of nanofluids increased by 5.18–24.8%. The thermal optical efficiency of the solar collector was 0.708, with energy removal parameters of 34.888. The heat removal factor was raised to 0.8 for mono ZnO nanofluid. At a concentration of 0.035%, ZnO/water nanofluid can produce 3.14 kg of distilled water daily. The solar still's total efficiency, including pump consumption, was 39.9% for mono ZnO and 36.4% for WO3. The highest efficiency received for hybrid ZnO + WO3 nanofluids were 37.6%, 37.9%, 38.6%, and 39.2% for ZnO 0.01% + WO3 0.025%, 0.015% + WO3 0.022%, 0.025% + WO3 0.015%, and 0.025% + WO3 0.01%, respectively. As the ZnO percentage rose in hybrid ZnO + WO3 nanofluids, energy absorption, thermal conductivity, solar still productivity, and efficiency were promoted. [ABSTRACT FROM AUTHOR]

Since the notion of dispersing nanoscale particles into the base fluid was first presented in the latter half of twentieth century, the area of nanofluids (NFs) has attracted considerable attention. This is reflected in the growing number of researches published annually on nanofluids. In the current study, an experiment was performed on double-pipe heat exchanger using ZnO–water NF to investigate the thermal performance factor (TPF) and pressure drop. The experiment was conducted for a single-phase fully developed flow in the turbulent region with four different volume fractions (VFs) of 0.005%, 0.02%, 0.04%, and 0.07% in the Reynolds number (Re) range of 5500–15000. During the experiments, it was seen that Brownian motion and thickness of interfacial layer also play a vital role in the enhancement of heat transfer rate along with thermal conductivity. At Re of 5500 for VF of 0.07%, the highest enhancement in Nusselt number was recorded as 55.51% with the penalty of 147.37% increase in friction factor. The highest TPF during the study was recorded as 1.15 for volume fraction of 0.07% at 5500 Reynolds number. For better understanding of nanofluid behavior, characterization of ZnO nanoparticles was performed in the laboratories which includes analysis of XRD, HRTEM, EDS, FTIR, and particle size. Within given range of Reynolds number and particle volume fractions, new correlations were also established for Nusselt number and friction factor. [ABSTRACT FROM AUTHOR]

Fluid guiding elements (FGEs), additive manufactured inserts that enhance heat transfer, have shown the potential to reduce the size of pipe‐in‐pipe heat exchangers up to a factor of 20. Due to their unique design, the calculation of the geometrical parameters for a specific application remains challenging and was initially solved by computationally expensive computational fluid dynamics simulations. This work presents a simplified approach, which treats the fluid and the FGE as pseudo‐homogeneous to enable the fast calculation of effective heat transfer coefficients. The approach is developed based on water in laminar flow state and subsequently tested with different fluids. [ABSTRACT FROM AUTHOR]

A Type 22 Broadsword class of frigate uses a combined gas or gas (COGOG) propulsion system that utilizes four different gas turbines, depending on the mode of operation. Its twin ST40M cruise gas turbines are operational most frequently, and an increase in their efficiency would significantly impact fuel usage and ship range. This study evaluates the option to upgrade the cruise gas turbines to a combined gas turbine–electric and steam (COGES) system, which utilizes a steam Rankine cycle to recover energy from the exhaust gases of the gas turbine. An alternative system using hot air is also analyzed for performance comparison. The analysis contains calculations for the energy extraction and dimensions of heat exchangers, for the power extracted from the additional steam or air turbine and for pressure losses of the exhaust gas. Different configurations for the heat exchangers were investigated, as well as various parameters for the steam and hot air. The size and mass of the system were an important aspect of the analysis. It was concluded that an auxiliary system operating at a maximum steam pressure of 20 bar could generate an additional 771 kW of power while adding a mass of 7.4 tons to the frigate. These findings suggest that upgrading to a COGES system could cover the electricity needs of the entire ship and thus reduce the overall fuel consumption, resulting in lower operational costs and less emissions. [ABSTRACT FROM AUTHOR]

In this study, a numerical investigation of fluid flow and heat transfer of Al2O3‐water nanofluids in a pillow plate heat exchanger with a two‐phase model is investigated. The flow regime studied in this study is in the laminar flow regime such that the Reynolds numbers are 250, 500, 750, and 1000 and the volume fraction of the nanoparticles remained so that the fluid stayed in Newtonian. The volume fraction of nanoparticles is ϕ=$\phi = $ 0, 1, 2, and 3 %. In this study, the effect of the shape of the welding points used in the pillow plate has also been investigated in such a way that three modes of circular welding point, large‐diameter elliptic welding point along with the flow and large‐diameter elliptic welding point perpendicular to the stream have been investigated. Numerical simulation results show that using nanofluid and increasing Reynolds number improves heat transfer, as well as circular welding point, shows the best heat transfer rate. The shape of the welding points has a direct relationship with the pressure drop and heat transfer, as well as the wake created behind the welding points, which have the highest wake and pressure drop respectively for the elliptic welding points perpendicular to the flow, circular and elliptical parallel to the flow. On the other hand, the addition of nanoparticles increases the friction factor and, on the contrary, increases the Reynolds number, which reduces the friction factor. Finally, the highest Reynolds number, the highest volume fraction of nanoparticles, and the circular welding point state show the highest PEC. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The absorption heat exchanger with a large temperature difference has a higher heat transfer superiority than the other heat exchangers (including plate heat exchanger), which is more suitable for long-distance heating. To improve its system performance, parameter collaborative optimization (including building accurate predictive models) has become an effective method because it does not require too much investment. In this study, a heat exchange station was chosen as a case study, and a model of a long short-term memory (LSTM) neural network was used to predict the temperatures of primary return water and secondary return water. Accordingly, the reliability of the fitting result based on the model was confirmed through a contrastive analysis with the prediction results of a support vector machine (SVM) model, a random forest (RF) model, and an extreme gradient boosting (XGBoost) model. In addition, the algorithm of particle swarm optimization was used to optimize the flow rate of primary supply water. The results showed that the temperature of primary-side return water decreased from 29.6 °C to 28.2 °C, the temperature of secondary-side return water decreased from 39.8 °C to 38.6 °C, and the flow rate of primary-side supply water decreased from 39 t/h to 35.2 t/h after the optimization of the flow rate of primary supply water. The sensibility assessment emerged that the secondary-side flow rate to the secondary-side supply water temperature was about 7 times more sensitive than the primary-side supply water temperature, and concretely, the lower the temperature, the higher the sensibility. In summary, the accuracy of the proposed prediction model was validated and the optimization direction was pointed out, which can be used to provide guidance for designing and planning absorption heat exchange stations with large temperature differences. [ABSTRACT FROM AUTHOR]

The dynamic of the heat transfer analysis constitutes an important factor that has drawn the attention of many researchers. Heat transfer is evaluated by considering the heat transfer coefficient, the surface area, and the temperature difference between the surface and the surrounding fluid. The computation of the temperature difference across various surface areas shows that increased heat transfer enhances the proportion of the heat conduction rate. In most cases, the system becomes unstable because inappropriate structural elements and outside disturbances, like ambient temperature can readily change the yielding temperature. As a result, the heat exchanger's efficiency needs improvement. A numerical simulation analyzing the performance of a shell and tube heat exchanger indicates that an increase in the surface area leads to a corresponding increase in the heat transfer rate. To optimize system performance, mathematical models were employed for the stability analysis of temperature changes. MATLAB simulations computed temperature differences in quantities of heat and area, thereby obtaining valuable insights for improving heat exchanger design and operation.

Abstract Microchannel heat exchangers have become the preferred choice in contemporary technologies like electronics, refrigeration, and thermal management systems. Their popularity stems from their compact design and exceptional efficiency, which outperform traditional heat exchangers (HE). Despite ongoing efforts, the optimal microchannels for enhancing heat management, minimizing pressure drop, and boosting overall performance have yet to be identified. This study seeks to deepen our understanding of heat transmission and fluid dynamics within a cross-flow microchannel heat exchanger (CFMCHE). Utilizing numerical modeling, it examines how various physical aspects—such as channel geometry, spacing between channels, the number of channels, and the velocity at the inlet—affect key performance indicators like pressure drop, effectiveness, Nusselt number, and overall efficiency. To enhance the design, we analyze six unique shapes of crossflow microchannel heat exchangers: circular, hexagonal, trapezoidal, square, triangular, and rectangular. We employ the Galerkin-developed weighted residual finite element method to numerically address the governing three-dimensional conjugate partial differential coupled equations. The numerical results for each shape are presented, focusing on the surface temperature, pressure drop, and temperature contours. Additionally, calculations include the efficacy, the heat transfer rate in relation to pumping power, and the overall performance index. The findings reveal that while circular shapes achieve the highest heat transfer rates, they underperform compared to square-shaped CFMCHEs. This underperformance is largely due to the increased pressure drop in circular channels, which also exhibit a 1.03% greater reduction in effectiveness rate than their square-shaped counterparts. Consequently, square-shaped channels, boasting a performance index growth rate of 53.57%, emerge as the most effective design among the six shapes evaluated. Additionally, for the square-shaped CFMCHE, we include residual error plots and present a multiple-variable linear regression equation that boasts a correlation coefficient of 0.8026.

Abstract With the increasing demand for heat dissipation of engineering vehicles, a dual-cycle cooling system is introduced in this paper to prevent the adverse effects of engineering vehicles’ equipment when operating at the overheating temperature. The performance of the new system is analyzed through tests, and the results show that the dual-cycle cooling system can meet the thermal balance requirements of the engineering vehicle during the shovel operation. Compared with the traditional cooling system, the new cooling system improved performance in terms of volume, engine energy consumption and working oil efficiency. The oil consumption of a wheel loader using the dual-cycle cooling system is reduced by 1% per hour, and the temperature of its transmission oil and hydraulic oil is reduced by more than 10 °C. The new cooling system has bright future in energy saving and emission reduction of engineering vehicles.

Leak proof tube-to-tube sheet joints are mandatory for the optimal operation and longevity of the shell and tube heat exchanger. Tube-to-tube sheet joints play a crucial role as fluid barriers, ensuring effective separation between the tube and shell side fluids within shell and tube heat exchangers. Non-conventional friction stir welding, known for imparting less residual stresses, is not commercially used for the fabrication of tube-to-tube sheet joints due to complex joint configuration and geometrical limitations. An extensive study on friction stir welding considering the geometrical parameters of tube-to-tube sheet arrangement is highly demanded. This research examined the mutual influence of radial clearance ranging from 0 mm to 0.5 mm and tube projection lying from 1 mm to 2 mm in friction stir welding of tube to tube sheet configuration on the pull-out strength, extension and, hardness at the stirring and fusion zones. Optimum radial clearance and tube projection for achieving high mechanical weld properties was estimated using multi-objective integrated Taguchi-PCA-GRA optimization. The result proves that the friction stir welded joint is capable of achieving joint strength close to the tungsten inert gas welded joint. The optimum parameters are 2 mm for tube projection and 0 mm for radial clearance to achieve maximum strength and weld penetration, while minimizing hardness at both stir zone and fusion zone. The findings of this research proved the adaptability of friction stir welding for the fabrication of tube-to-tube sheet joints with the right choice of tube projection and radial clearance.

In this study, the effect of an electronic control system (ECS) on the performance of a solar heater fabricated from recycled materials was investigated . The study found that the maximum thermal energy output before installing the ECS stood at 378 W, which was significantly improved to 450 W after integration, indicating a commendable enhancement in the efficiency of the solar heater. The thermal efficiency of the solar heater also saw a substantial jump from 71.7% to 82% after connecting the ECS. The study also uncovered the temperature disparity between the trapped and ambient air (max. ΔT = 20.4 °C) influenced heat loss from the space between the glass cover and the two heat exchangers. To address this issue, the sides and base of the heater assembly were insulated with foam material to minimize heat loss. Furthermore, the ECS was programmed to regulate the water flow rate in the solar collector to prevent the water temperature from surpassing 65 °C in winter and 40 °C in spring and autumn. The study harnessed solar panels to provide electricity to the ECS, which enabled the technology to adapt the solar heating process according to environmental conditions and user needs. The study's findings demonstrate the potential of utilizing an ECS for recycling waste solar heaters, leading to enhanced heat transfer efficiency and long-term financial and environmental benefits.

The effectiveness of triangular baffles in enhancing heat transfer within corrugated tubes is examined numerically in this study. Two key parameters influencing performance are examined: baffle placement (staggered and aligned) and their angles of attack (0°, 15°, 30°, and 45°). Heat transfer, friction, as well as performance metrics are comprehensively examined and compared for both configurations. The finite element method (FEM) implemented in CFD software COMSOL Multiphysics 6.1 is employed for simulations across a range of Reynolds numbers (100-400). Results reveal significant heat transfer improvements due to the proposed baffle configurations. Notably, aligned baffles with a 30° angle of attack achieve a 43.6% increase the heat transfer when compared to the baffle-free scenario. Staggered baffles with a 15° angle of attack demonstrate a superior 55.3% improvement compared to the baseline. A comprehensive evaluation of performance criteria identifies staggered baffles with a 30° angle of attack as the optimal configuration for maximizing heat transfer within corrugated tubes.