Search Results (37)

The efficiency of electric motors is highly dependent on their operating temperature, with lower temperatures contributing to enhanced performance, reliability, and extended service life. This study presents a comprehensive review of state-of-the-art cooling technologies and evaluates their impact on the thermal behavior of a commercial motor–generator system in high-demand applications. A baseline model of a permanent magnet synchronous motor (PMSM) was developed using MotorCAD 2023^® software, which was supported by reverse engineering techniques to accurately replicate the motor’s physical and thermal characteristics. Subsequently, multiple cooling strategies were simulated under consistent operating conditions to assess their effectiveness. These strategies include conventional axial water jackets as well as advanced oil-based methods such as shaft cooling and direct oil spray to the windings. The integration of these systems in hybrid configurations was also explored to maximize thermal efficiency. Simulation results reveal that hybrid cooling significantly reduces the temperature of critical components such as stator windings and permanent magnets. This reduction in thermal stress improves current efficiency, power output, and torque capacity, enabling reliable motor operation across a broader range of speeds and under sustained high-load conditions. The findings highlight the effectiveness of hybrid cooling systems in optimizing both thermal management and operational performance of electric machines. Full article

To enable proactive prediction of marine diesel engine failure time and root causes, thereby reserving sufficient time for maintenance, this study proposes a data-driven multi-algorithm integration framework for performance assessment and fault early warning in marine diesel engines. By integrating the SSD (steady-state detection) algorithm, a data-driven CLIQUE clustering algorithm was chosen for automatic multi-parameter high-dimensional running condition partitioning. This innovative approach overcomes the limitations of traditional single-parameter approaches or dimensionality reduction techniques, significantly enhancing state classification accuracy. The improved classification results subsequently increase the reliability of Mahalanobis distance as a performance indicator for marine diesel engine condition assessment. Finally, the cumulative anomaly method combined with the Yamamoto test was employed for anomaly detection analysis, enabling precise identification of fault occurrence time and establishing an effective early-warning mechanism. The study demonstrates that this technique effectively characterizes the overall performance of marine diesel engines and captures their performance degradation features. Implemented on a 6RT-flex82T marine diesel engine dataset, the method achieved precise prediction of fault occurrence time with early warnings, providing approximately 20 days advance notice for maintenance planning. Furthermore, comparative analyses with existing studies revealed its superior capability in pinpointing the anomaly to the jacket cooling water outlet temperature of cylinder #2. These results confirm the method’s effectiveness in both performance assessment and fault early warning for marine diesel engines, offering a novel approach for intelligent maintenance of shipboard equipment. Full article

Electric machines (EMs) of electrified vehicle drivetrains can be tested on drivetrain test benches at an early stage of development. In order to protect the EMs from premature damage or failure during testing, monitoring their thermal condition is important. Due to the package requirements of compact and powerful EMs with high-speed requirements and high-power densities, the heat build-up inside the motor during operation is particularly high. For this reason, fluid cooling with heat exchangers is increasingly being used in EMs. The EMs analysed in this work are water-cooled by a cooling jacket. This influences the heat flow inside the machine through heat transfer mechanisms, making it difficult to detect damage to the EMs. This paper presents a novel method for non-destructive and non-contact thermal condition monitoring of water-cooled EMs on drivetrain test benches using thermography. In an experimental setup, infrared images of an intact water-cooled EM are taken. A bearing of the EM’s rotor is then damaged synthetically, and the experiment is repeated. The infrared images are then processed and analysed using appropriate software. The analysis of the infrared images shows that the heat propagation of the motor with bearing damage differs significantly from the heat propagation of the motor without bearing damage. This means that thermography opens up another method of condition monitoring for water-cooled EMs. The results of the investigation serve as a basis for future condition monitoring of water-cooled EMs on powertrain test benches using artificial intelligence (AI). Full article

The flow and heat transfer of the coolant directly affect the cooling performance, thermal load, and emissions of gasoline engine. The accurate estimation of heat transfer and temperature distribution within engines is crucial for studying thermal stresses and calculating engine performance. This study focuses on the design of a new cooling water jacket structure for a two-cylinder gasoline engine. In the novel structure, the coolant flows from the cylinder block to the cylinder head and then returns to the cylinder block, providing better cooling for the cylinder head. The three-dimensional simulation results show that the overall flow velocity of this structure ranges between 0.1 m/s and 3 m/s, which meets the design requirement of 0.1 m/s to 5 m/s. However, there are still some flow dead zones in this structure, which may lead to insufficient heat transfer. Therefore, the water jacket structure is further optimized. After optimization, the pressure drop between the inlet and outlet is decreased, and the velocity distribution becomes more rational. Both the flow velocity and the heat transfer coefficient meet the design targets. These results can provide theoretical guidance for the structural improvement of the water jacket and approaches to studying the flow characteristics of the coolants. Full article

Hydrogen energy is a green and environmentally friendly energy source, as well as an excellent energy carrier. Hydrogen storage technology is a key factor in its commercial development. Solid hydrogen storage methods represented by using metal hydride (MH) materials have good application prospects, but there are still problems of higher heat transfer resistance and slower hydrogen absorption and release rate as the material is applied to reactors. This study innovatively proposed an array-type MH hydrogen storage reactor based on external water-cooled jacket heat exchange, aiming to improve the heat transfer efficiency and absorption reaction performance, and optimize the absorption kinetics encountered in practical applications of LaNi₅ hydrogen storage material in reactors. A mathematical model was built to compare the hydrogen absorption processes of the novel array-type and traditional reactors. The results showed that, with the same water-cooled jacket, the hydrogen absorption rate of the array-type reactor can be accelerated by 2.78 times compared to the traditional reactor. Because of the existence of heat transfer enhancement limits, the increase in the number of array elements and the flow rate of heat transfer fluid (HTF) has a limited impact on the absorption rate improvement of the array-type reactor. To break the limits, the hydrogen absorption pressure, as a direct driving force, can be increased. In addition, the increased pressure also increases the heat transfer temperature difference, thereby further improving heat transfer and absorption rate. For instance, at 3 MPa, the hydrogen absorption time can be shortened to 147 s. Full article

The study introduces an innovative three-stage nested power generation system that enables the cascading utilization of LNG cold energy. It makes the most of wasted energy by using ship jacket cooling water (JCW) and exhaust gas (EG) as heat sources, a trans-critical carbon dioxide cycle as internal circulation, and utilizing the pressure exergy of LNG. We choose two azeotrope mixing fluids that match the requirements and create four cases for the outer and middle cycle working fluids in the three-stage nested system. To discover the ideal system performance from the perspectives of exergy (E), economy (E), and environment (E), four cases were subjected to multi-objective optimization using the multi-objective particle swarm optimization technique (MOPSO). Finally, the optimal solution was found by applying the TOPSIS decision-making method. Through comparative analysis, the optimal system is selected among the four optimization results. R170 (22.66%) and R1150 (77.34%) are used as the outer circulating working medium, while R170 (90.86%) and R1270 (9.14%) are utilized as the inter-cycle working fluid. The net output work is 575.75 kW, the optimal exergy efficiency is 46.09%, the optimal electricity production cost is $0.04009 per kWh, the carbon dioxide emissions can be reduced by 36,910 tons, and the payback period is 2.548 years. After optimization, a more energy-efficient and environmentally friendly power generation system is obtained. Full article

The scale-up and control of the acrylamide polymerization process in solution is presented. The viscosity is modeled as a function of temperature and monomer concentration. Four cases are analyzed: (i) Keeping the similarity principles to carry out the polymerization using water to heat and cool the process, (ii) using water with nanoparticles to heat and cool the process, (iii) adding the initiator at different temperatures to start the polymerization, and (iv) modifying the heat-transfer area by changing the aspect ratio $L/D_r$. The reactor and jacket temperature profiles, the reaction conversion, and the average molecular weight are presented. The main finding is that increasing the heat-transfer area by modifying the $L/D_r$ ratio also increases the efficiency of the polymerization process. Futhermore, the numerical results indicate that the addition of the initiator at low temperatures increases the molecular weight of the final product. Full article

Due to the lack of oil injection cooling, it is usually necessary for dry twin-screw compressors to design cooling jackets to carry away the heat generated during operation. In order to investigate to what extent a cooling jacket can improve the performance of screw compressors, this study set up an experimental platform for a dry twin-screw compressor applied in fuel cell vehicles and used water as the working liquid in the cooling jacket. Then, the performance parameters of the screw compressor under different rotating speeds, discharge pressures, and cooling water flow rates were measured. It can be considered that the existence of a water cooling jacket is of great significance for improving the performance of dry screw compressors and improving extreme operating conditions. The research results may provide a reference for the development and improvement of dry twin-screw compressors in the future. Full article

Electrical losses are converted into thermal energy in motors, which heats each component. It is a significant factor in decreasing motor mechanical performance. In this paper, the motor cooling characteristics were analyzed according to the design factors of the water jacket to investigate the cooling performance of a permanent magnet synchronous motor (PMSM). First, the electrical losses generated in PMSM were calculated using electromagnetic finite element (FE) analysis. Secondly, a 3D electromagnetic–thermal fluid coupled FE analysis was performed to analyze the temperature distribution inside the motor by applying electrical loss as the heat source. Finally, the motor cooling performance according to the design factors of the water jacket was statistically analyzed using the design of experiment (DOE) method. It was found that the mass flow rate of 0.02547 kg/s and six passes of the water jacket with one inlet and two outlets could be considered the optimum conditions in terms of the maximum motor temperature. Full article

The ironless linear permanent magnet synchronous motor (ILPMSM) is highly compact, easy to control, and exhibits minimal thrust fluctuations, making it an ideal choice for direct loading applications requiring precise positioning accuracy in linear motor test rigs. To address the issue of temperature rise resulting from increased primary winding current and to simultaneously enhance thrust density while minimizing thrust fluctuations, this paper introduces a bilateral-type ILPMSM with a cooling water jacket integrated between the dual-layer windings of the primary movers. The primary winding of the motor adopts a dual-layer coreless structure where the upper and lower windings are closely spaced and cooled by a non-conductive metal cooling water jacket, while the dual-sided secondary employs a Halbach permanent magnet array. The motor’s overall braking force is a combination of the electromagnetic braking force generated by the energized windings and the eddy current braking force induced on the cooling water jacket. This paper specifically focuses on the analysis of the eddy current braking force. Initially, the motor’s geometry and working principle are presented. Subsequently, the equivalent magnetization intensity method is employed to determine the no-load air gap magnetic density resulting from the Halbach array. An analytical model is then developed to derive expressions for the eddy current density and braking force induced in the water-cooling jacket. The accuracy of the analytical method is validated through finite element analysis. Then, a comparative analysis of the braking forces in two primary cooling structures, namely the inter-cooled type and the two-side cooled type ILPMSM, is conducted. Moreover, the characteristics of the eddy current braking force are thoroughly examined concerning motor size parameters and operating conditions. This paper provides a solid theoretical foundation for the subsequent optimization design of the proposed motor. Full article

Based on the analysis of the waste heat distribution characteristics of a typical ship two-stroke low-speed main engine (model: MAN 8S65ME-C8.6HL, the specified maximum continuous rating SMCR: 21,840 kW) under different loads, two different types of organic Rankine cycle (ORC) systems, namely the basic system (BORC) and the preheated system(PORC), were constructed to recover the ship main engine’s exhaust gas waste heat and jacket cooling water waste heat. Using the thermodynamic simulation model of the system, the main performance indexes, including net output power of the two ORC systems were studied with the variation of seawater temperature and main engine load, and the annual ship fuel saving and annual carbon emission reduction generated by the two systems were compared and analyzed. It was found that the maximum net output power of the BORC system and PORC system were 445.3 kW and 491.3 kW, respectively, when the ship’s main engine load was 100%, and the outboard seawater temperature was 20 °C; the maximum thermal efficiency was 12.84% and 12.71%, respectively; under the annual operation, the fuel saving of BORC system and PORC system can be 456 tons and 510 tons, respectively, and the carbon emission reduction was 1416 tons and 1581 tons, respectively. The analysis found that the net output power of the PORC system is always greater than that of the BORC system. When the outboard seawater is lower, and the main engine load is more than 80%, the net output power difference between the PORC system and BORC system gradually expands, and the improvement of ORC system performance is more evident by adding a preheater. It can be concluded that when the ship was mainly operated in the sea area with low seawater temperature and the main engine was running under high load most of the time, selecting the PORC system to recover the waste heat of the main engine was more advantageous. Full article

Metal hydrides are a class of materials that can absorb and release large amounts of hydrogen. They have a wide range of potential applications, including their use as a hydrogen storage medium for fuel cells or as a hydrogen release agent for chemical processing. While being a technology that can supersede existing energy storage systems in manifold ways, the use of metal hydrides also faces some challenges that currently hinder their widespread applicability. As the effectiveness of heat transfer across metal hydride systems can have a major impact on their overall efficiency, an affluent description of more efficient heat transfer systems is needed. The literature on the subject has proposed various methods that have been used to improve heat transfer in metal hydride systems over the years, such as optimization of the shape of the reactor vessel, the use of heat exchangers, phase change materials (PCM), nano oxide additives, adding cooling tubes and water jackets, and adding high thermal conductivity additives. This review article provides a comprehensive overview of the latest, state-of-the-art techniques in metal hydride reactor design and heat transfer enhancement methodologies and identifies key areas for future researchers to target. A comprehensive analysis of thermal management techniques is documented, including performance comparisons among various approaches and guidance on selecting appropriate thermal management techniques. For the comparisons, the hydrogen adsorption time relative to the reactor size and to the amount of hydrogen absorbed is studied. This review wishes to examine the various methods that have been used to improve heat transfer in metal hydride systems and thus aims to provide researchers and engineers working in the field of hydrogen storage with valuable insights and a roadmap to guide them to further explore the development of effective thermal management techniques for metal hydrides. Full article

In this simulation study, we compare the dynamics and thermal behavior of different ideal flow crystallizers. The first step in creating mathematical models for the crystallizers was the implementation of the population balance equation. The population balance equation was completed with mass balance equations for the solute and the solvent as well as in the case of non-isothermal crystallizers with an energy balance equation. The solution to the population balance equation, which is a partial differential equation, can only be performed numerically. Using the method of moments, which calculates the moments of the population density function, gives a mathematically simpler model for simulating and analyzing the crystallizers. All crystallizers studied are considered mixed suspension and mixed product crystallizers. In this simulation study, the investigated crystallizers are the batch mixed suspension and mixed product isothermal crystallizer, the batch mixed suspension and mixed product non-isothermal crystallizer, and the continuous mixed suspension and mixed product removal (CMSMPR) non-isothermal crystallizer equipped with a cooling jacket. We consider citric acid as the solid material to be crystallized, and a water–glycol system is used as a cooling medium. Considering the nucleation kinetics, we applied both primary and secondary nucleation. In the case of a crystal growth kinetic, we assumed a size-independent growth rate. The highest expected value and the variance of the crystal product occur in the isotherm batch case, which can be explained by the high crystallization rate caused by the high supersaturation. Contrary to this, in the non-isothermal batch case, the final mean particle size and variance are the lowest. In continuous mode, the variance and mean values are between the values obtained in the two other cases. In this case, the supersaturation is maintained at a constant level in the steady state, and the average residence time of the crystal particles also has an important influence on the crystal size distribution. In the case of non-isothermal crystallization, the simulation studies show that the application of the energy balance provides different dynamics for the crystallizers. The implementation of an energy balances into the mathematical model enables the calculation of the thermal behavior of the crystallizers, enabling the model to be used more widely. Full article

In this study, a main marine engine with a rating power of 21,840 kW for a ship sailing in an actual voyage was obtained as the research object. The engine’s exhaust gas and jacket cooling water were adopted as the heat source of the organic Rankine cycle (ORC) system developed for the main marine engine. The engine can consume high-sulfur or low-sulfur fuel oil, respectively, according to the different emission control requirements. The impact of the use of high-sulfur or low-sulfur fuel oil, and variations in engine load, amount of recoverable waste heat, outboard seawater temperature, and the ship’s steam demand were comprehensively considered, and the validated ORC system model was used for the analysis of the system’s performance and the ship’s energy saving for the whole voyage. The results demonstrated that when the ship adopted high-sulfur or low-sulfur fuel oil, the maximum total net power output of the ORC system was 449.3 kW and 753.1 kW, respectively. During the whole voyage of 1610.7 nautical miles, when high-sulfur fuel oil was used, the ORC system reduced carbon emission by 40.3 tons and 33.8 tons, respectively, in summer and in winter, and the fuel saving rates were 2.53% and 2.12%; when low-sulfur fuel oil was used, the ship’s carbon emissions were reduced by 62.1 tons and 61.8 tons, respectively, in summer and in winter, and the fuel saving rates were 3.91% and 3.89%. Full article

As carbon dioxide emissions arising from fossil energy consumption and fossil fuels are gradually increased, it is important for the low-carbon operation of ships to recover diesel engine waste heat. A newly developed dual-loop organic Rankine cycle (ORC) system to recover waste heat from a marine main engine (M/E) was designed in this paper. The exhaust gas (EG) heat was recovered by the high-temperature (HT) loop. The jacket cooling water (JCW) heat and the condensation heat of the HT loop were recovered by the low-temperature (LT) loop. Toluene, cyclohexane, benzene, R1233zd (E), R245fa, and R227ea were selected as the working fluids. The influence of the condenser thermal parameters on the LT loop was analyzed using the pinch point method. The performance of the dual-loop ORC was investigated under various working fluid combinations. The maximum net power of the HT loop can reach 253.4 kW when using cyclohexane as the working fluid, and the maximum thermal efficiency of the HT loop can reach 18.5% with benzene as the working fluid. Meanwhile, higher condensation temperatures and levels of condensation heat of the HT loop have a positive effect on the performance of the LT loop. However, in most conditions, the HT loop condensation heat could not provide enough heat for the LT loop’s working fluid to start the boiling process. The total net power of the dual-loop ORC system was 410.6 kW with Cyclohexane in the HT loop and R1233zd (E) in the LT loop, resulting in a 10.9% improvement in the marine main engine thermal efficiency. Full article