Characteristics Of Coolant Flow Research Articles

CFD Analysis of Coolant Flow Characteristics in Reactor Pressure Vessel: A Comprehensive Review

This comprehensive review explores the application of Computational Fluid Dynamics (CFD) in analyzing coolant flow within Reactor Pressure Vessels (RPVs) of nuclear power plants. By synthesizing existing research, methodologies, and advancements specific to RPVs, the paper offers in-depth insights into critical aspects such as boundary conditions, turbulence modeling, heat transfer mechanisms, and validation techniques. Examining a range of studies encompassing various reactor types from Pressurized Water Reactors (PWRs) to Integral Pressurized Water Reactors (IPWRs), the review underscores CFD's pivotal role in enhancing safety, efficiency, and performance optimization in nuclear reactors. Through systematic exploration, this study underscores the critical importance of precise modeling in facilitating safety assessments, operational optimization, and design enhancements across various reactor systems. Accurate modeling serves as a cornerstone for informed decision-making processes aimed at maximizing reactor performance while ensuring the highest standards of safety and reliability. The paper navigates through challenges such as computational limitations and turbulence modeling intricacies, while also discussing emerging trends like the porous media method aimed at improving computational efficiency. By offering a comprehensive understanding of thermal-hydraulic behavior in nuclear reactors, the review underscores CFD's contribution to enhancing safety and reliability in nuclear power generation. Overall, this review underscores the indispensable role of CFD in advancing our understanding of nuclear reactor dynamics, thereby contributing significantly to the overarching goals of improved safety and reliability in nuclear power generation.

Research Progress of Enhanced Thermal Evacuation and Cooling Technology for High-Speed Motors

In high-speed motors, there is a huge amount of heat generation from core and winding losses, which may result in thermal failures or motor performance deterioration. In the prevention of heat accumulation, efficient cooling technology is critical for smooth and reliable motor movement. This paper summarizes the diverse application of high-speed motor and thermal requirements, such as in electrical devices, turbo-machinery, and high-precision machine tools. Three paths of case convection—cooling, internal ventilation cooling and spindle core cooling—are analyzed. Methods for configuring thermal resistance and improving cooling efficiency are summarized. Among them, coolant flow characteristics and flow channel shapes, gas supply ventilation systems, and methods to reduce air resistance, as well as axial cooling and integrated heat pipe structures, are extensively investigated. Finally, the development prospects of high-speed motor cooling are also forecasted. At present, the primary research directions are to reduce the heat generated by the heat source, utilize the latent heat of the coolant, optimize the cooling flow path of the shell, design an axial air-cooling circulation system, and enhance the heat dissipation of the spindle.

Quantitative Analysis of the Effect of Operating Temperature on Energy Performance of an Electric Heavy Commercial Vehicle

Even though heavy-commercial vehicles have a relatively low population density (11%), they still account for a large share of urban noise and CO2 emission (37%). Therefore, trucks are a priority for full electrification. However, heavy-duty trucks (HDT) have complex array of challenges: high energy consumption combined with high daily driving distances. This paper investigates the effect of operating temperature on HDT energy performance. A high-fidelity multi-physics model of electric machine with fixed and variable parameters as nonlinear functions of temperature and coolant flow characteristics was developed. Temperature-dependent motor maps were then generated and integrated with forward-facing vehicle model. Quantitative analyses under different operating conditions with a realistic cycle (ESK) have shown that temperature plays a crucial role for the energy efficiency of EVs.

Thermofluids performances on innovative design with multi-circuit nested loop applicable for double-layer microchannel heat sinks

This study numerically proposes a novel microchannel heat sink design named multi-circuit nested loop (ML) to strength the thermal performance of double-layer microchannel heat sinks (DMCHS). The ML is introduced into the DMCHS to enhance the thermal characteristics and is compared with the traditional straight DMCHS. Due to the complexity of the ML-DMCHS, 4 different working conditions on inlets and outlets are designed to find the optimal one. Based on the analysis of the thermal gradients on substrate, flow characteristics of coolant, overall thermal resistance and thermal performance factor, it is found that the novel ML-DMCHS not only can significantly reduce the peak temperature, but also offer better temperature uniformity on substrate. The peak temperature on substrate can be reduced up to 34 K when compared with traditional parallel straight double-layer microchannels (P-DMCHS). Furthermore, the inner cooling circuit in ML-DMCHS shows greater impact on the lowest temperature on substrate, while the outer cooling circuit affects more on the peak temperature.

CFD modelling on flow field characteristics of engine cooling water jacket and its cooling performance improvement based on coolant transport path analysis method

Reasonable coolant flow distribution and its heat transfer coefficient (HTC) distribution are of great significance to the cooling performance of water-cooled engine. Therefore, the present paper proposes a coolant transport path analysis method aiming at analyzing coolant velocity distribution and optimizing the coolant flow characteristics of water jacket based on Computational Fluid Dynamics (CFD), with particular emphasis on the assessment of coolant flow velocity distributions of high-temperature area of engine head water jacket. First, the coolant flow characteristics of a single-cylinder water jacket is investigated and it is found that coolant velocity of exhaust bridge is less than 1.5 m/s and the HTC distribution of water jacket under three flow conditions of 15 L/min, 25 L/min and 35 L/min have a small area reaching 5000 W/(m2∙K). Some areas have no coolant flow and the mass flowrate distribution of each gasket hole is unreasonable, proving that original water jacket structure has some shortcomings and need to be optimized. Based on coolant transport analysis, an improved design of the single cylinder water jacket is proposed and HTC distribution of improved water jacket meet cooling requirements that HTC in high heat load area are above 5000 W/(m2∙K). The coolant transport path analysis method for optimizing coolant flow characteristics of water jacket proves to be an effective way through successful application and remarkable achievement in the other single-cylinder water jacket and two-cylinder water jacket that coolant flow distribution become more reasonable and coolant velocity of high-temperature areas are bigger than 1.5 m/s.

Numerical Analysis of Conjugated Heat Transfer and Thermal Stress Distributions in a High-Temperature Ni-Based Superalloy Turbine Rotor Blade

This paper establishes a multidisciplinary method combining conjugate heat transfer (CHT) and thermal stress for a high-temperature Ni-based superalloy turbine rotor blade with integrated cooling structures. A conjugate calculation is performed to investigate the coolant flow characteristics, heat transfer, and thermal stress of the rotor blade under rotating and stationary conditions to understand the effects of rotation on the multidisciplinary design of the blade. Furthermore, the maximum resolved shear stress among the 30-slip systems and the corresponding dominant slip system are obtained to predict the deformation tendency of the blade by employing the crystal plasticity finite element method (CPFEM) and considering the specified anisotropic blade material (GTD-111). The results show that the forces of rotation, including centrifugal and Coriolis forces, and their induced buoyancy force, alter the coolant flow field and thus affect the rotor blade’s heat transfer distribution compared with the stationary condition. The maximum temperature and thermal stress of the rotor blade under rotating conditions are reduced by 5% and 21% compared with that under the stationary condition, respectively. Compared with the stationary condition, the temperature and thermal stress distribution on the blade under the rotating condition are more uniform, especially on the suction side. In addition, the blade root connecting with the hub, the film holes near the leading-edge region at the blade root, the mid-chord of the suction surface, and the grooved blade tip are easily damaged by the enormous resolved shear stress and the interface effect of different types of dominant slip system under the two conditions. In this work, it was feasible to use the cascade cooling effect test to analyze the dynamic test results for the rotor blade. Furthermore, the thermal stress analysis based on the CPFEM can provide a superior level of blade cooling design than CHT by considering the anisotropic material characteristics of a turbine blade.

Numerical study on enhanced heat transfer and flow characteristics of supercritical hydrogen rocket engine's chamber wall using cylindrical ribs structure

One of the most critical issues in supersonic flight is the thermal protection of the rocket engine combustion chamber. The ribs' construction can improve heat transfer and coolant flow characteristics significantly. Ansys fluent was used to investigate the supercritical hydrogen fuel flow and heat transfer characteristics. Ribs spacing of 10 mm, 5 mm, and 2.5 mm were compared to determine the optimal spacing required to achieve maximum cooling influence and lower pressure drop to safeguard the overheated structure and lower the temperature of the walls. Compared to the smooth channel, the thermal performance factor and pressure drop of the 5 mm spacing increased by 32.5% and 16.64%, respectively, while the maximum temperature reduced by 12.07%. Therefore, the cylindrical rib construction with a 5 mm spacing is perfect for improving heat transfer, has acceptable pressure drops, and reduces thermal stratification inside the channel.

Influence of twisted tape insert on the coolant flow characteristics in swirled film cooling

The present paper discusses film cooling behavior through numerical simulation in the presence of a twisted tape insert inside the film hole. The twisted tape insert imparts a swirl to the coolant flow. Coolant swirl intensity is controlled by varying the pitch of the twisted tape resulting in swirl numbers of 0.0289, 0.116, and 0.168. The film cooling performance is evaluated using area-averaged effectiveness and heat transfer coefficient for blowing ratios of 0.5, 1.0, 1.5, and 2.0. Results revealed a significant amount of improvement in averaged effectiveness with the addition of swirl. Coolant swirl predominantly modifies the jet trajectory resulting in a reduced jet penetration and increased lateral expansion. Further investigation on the effect of twisted tape thickness on the coolant distribution has been found to be negligible. Pressure losses occurring due to the insertion of twisted tape inside the film hole is evaluated through the coefficient of discharge which indicated the necessity of higher pumping power than the film cooling case with no-swirl.

Effects of Coolant Flow Characteristics and Channel Surface Temperature on Nucleate Boiling Heat Transfer in IC Engine Cooling System

Effects of Coolant Flow Characteristics and Channel Surface Temperature on Nucleate Boiling Heat Transfer in IC Engine Cooling System

Numerical investigation on the characteristics of coolant flow, heat absorption and phase change in transpiration cooling process

Transpiration cooling using liquid water as coolant has been confirmed as a promising thermal protection method due to the huge phase change latent heat. A multi-region numerical strategy is developed and presented in this paper, to simulate directly the liquid transpiration cooling process within a wedge-shaped porous cone. An experiment was conducted to validate the numerical strategy. Using the validated strategy, five series of numerical simulations under different coolant mass fluxes were carried out. The numerical results revealed some interesting and valuable characteristics of fluid flow, heat absorption and phase change of liquid coolant in the porous cone and on the impermeable surface. When the liquid coolant is vaporized incompletely in the porous region, one can find two interesting phenomena: 1) A large amount of coolant flow towards the end of the porous cone, while only a small part of coolant can be transferred into the leading edge region; 2) An increase in inlet coolant mass flux causes a decrease of the coolant ejected from the leading edge. However, these phenomena are absent when the liquid coolant is vaporized completely in porous region. Another important phenomenon demonstrated in this work is an additional thermal protection effect on the downstream impermeable surface. This additional thermal protection effect increases with the inlet coolant mass flux, but at the price of a larger wastage of coolant phase change latent heat.

Optimization transpiration cooling of nose cone with non-uniform permeability

With the development of active thermal protection techniques (TPTs), optimization transpiration cooling (OTC) design, to enhance the cooling effect in stagnation regions and decrease coolant load, has become a critical issue in the research and development of hypersonic vehicles. One of the possible OTC approaches is using a non-uniform porous material to vary the coolant allocation within pores. This paper presents an experimental and numerical investigation on the transpiration cooling performances of two wedge shaped nose cones. One is for OTC, made of a special porous matrix with non-uniform permeability to ensure the largest porosity near the stagnation point, and the other is for traditional transpiration cooling (TTC), consisting of a general uniform porous matrix. Surface temperature and cooling effectiveness of the two nose cones are investigated in the experiments. The data show that in comparison with TTC, OTC can effectively enhance the cooling effectiveness in stagnation regions through a locally high permeability, and improve the uniformity of the temperature distribution within the entire nose cone. To exhibit the coolant flow characteristics within the pores, two-dimensional numerical simulations are carried out by commercial software FLUENT, and the numerical method is validated by the experimental data. The numerical results indicate that OTC with non-uniform permeability can provide an optimized coolant allocation and decrease the driving force required by the coolant transport to the stagnation region.

Numerical investigation on the optimization of local transpiration cooling effectiveness

With the development of active Thermal Protection System (TPS) of hypersonic vehicles, optimizing active TPS design and reducing weight including the system and coolant loaded are the critical issues to be considered. This paper presents an optimization method of local transpiration cooling effectiveness under supersonic condition with a freestream total temperature of 2310K, and a freestream Mach number of 4.2. The numerical investigations of transpiration cooling are conducted by performing two strategies of coolant allocation over a nose cone surface, (1) constant coolant velocity allocation; (2) step coolant velocity allocation. The aerodynamic and aerothermal performances including Mach number and pressure distributions, cooling performances and coolant demand are analyzed by the two strategies. The analysis indicates that the step strategy can effectively improve the local cooling effectiveness in the stagnation region and reduce the coolant demand. To accomplish the optimization strategy, a non-uniform porosity strategy of the nose cone is analyzed, and the coolant flow characteristics in the porous matrix at different coolant injection conditions are studied. The study indicates that the non-uniform porosity can improve the efficiency of coolant transportation, and increase coolant mass flow rate in stagnation region.

A computational fluid dynamics (CFD) model for effective coolant application in deep hole gundrilling

Effective coolant application in deep hole gundrilling is crucial to prevent rapid degradation and failure of drills through high performance cooling, lubrication and chip evacuation. This paper presents a novel methodology to increase effectiveness of coolant application through strategic optimization of gun drill designs that leads to appreciable tool life improvement, based on computational fluid dynamics (CFD) analysis. Through the analyses of coolant flow characteristics and rheological properties, conventional designs of critical drill geometries like nose grind contour, coolant hole configuration and shoulder dub-off angle, which are detrimental to coolant application and hence tool life are determined. A new, optimized gun drill design for the drilling of deep holes on Ni-based alloys is proposed. All findings are experimentally substantiated.

Experimental study of local coolant hydrodynamics in TVS-Kvadrat PWR reactor fuel assembly using mixing spacer grids with different types of deflectors

Results of experimental studies of local hydrodynamic characteristics of coolant flow in fuel assemblies of RWR reactors using different types of mixing spacer grids are presented. Specific features and regularities of coolant flow in fuel pin bundles of TVS-KVADRAT fuel assemblies with different types of mixing spacer grids were revealed in the course of experiments. Analysis of space distribution of projections of absolute flow velocity allowed detailed description of coolant flow beyond the spacer grid with installation of three different types of deflectors. Optimal design of deflector for spacer grid of the TVS-KVADRAT fuel assembly in the standard cell in the area of guiding channels was identified. Results of studies of local hydrodynamics of coolant flow in the TVS-KVADRAT fuel assembly are accepted for subsequent practical application by the JSC Afrikantov Experimental Design Bureau for Mechanical Engineering (OKBM) in the evaluations of thermal engineering reliability of PWR reactor cores and were included in the database for verification of computational fluid dynamic codes (CFD-codes) and implementation of detailed cell array calculations of PWR reactor cores.

Assessing fuel-cell coolant flow fields with numerical models and infrared thermography

Proper thermal management is important to the successful operation and durability of proton exchange membrane fuel cell (PEMFC) systems. In liquid cooled fuel cell systems, the planar temperature distribution of the cell is largely controlled by the coolant flow field (CFF) design inside bipolar plates (BPPs). We characterize the temperature distribution of the coolant in two different CFF designs made out of Ti–6Al–4V titanium alloy by using infrared (IR) thermography and a coupled heat-transfer numerical model. Numerical models show that the two CFFs have nearly equivalent global heat transfer characteristics and temperature distributions but very different coolant flow characteristics; one design has uneven flow through parallel cooling channels and the other design has even flow through parallel cooling channels. These two designs are used to probe the capability of IR thermography to resolve subtle differences in temperature distribution in the CFFs. We find that the temperature distribution in CFFs measured using IR thermography matches the predicted numerical model results. We conclude that IR thermograph is a useful tool for characterizing CFFs because it can visualize local temperature differences caused by trapped bubbles in addition to the overall in-plane temperature distribution.

Coupled Heat Transfer Analysis in Regeneratively Cooled Thrust Chambers

The coupled hot gas–wall–coolant environment that occurs in regeneratively cooled liquid rocket engines is studied by a computational procedure able to provide a quick and reliable prediction of thrust chamber wall temperature and heat flux as well as coolant flow characteristics, like pressure drop and temperature gain in the regenerative circuit. The coupled analysis is performed by means of a computational fluid dynamics solver of the Reynolds-averaged Navier–Stokes equations for the hot gas flow and by a simplified quasi-two-dimensional approach, which widely relies on semiempirical relations, for the coolant flow and wall structure heat transfer in the cooling channels. Coupled computations of the space shuttle main engine main combustion chamber are performed and compared with available literature data. Results show a reasonable agreement in terms of coolant pressure drop and temperature gain with nominal data, whereas the computed wall temperature peak is closer to hot-firing test data than to the nominal value.

Experimental studies of hydrodynamic and mass-transfer properties of coolant flow in VVER fuel assemblies TVSA

The results of experimental studies of the local hydrodynamics and mass transfer of coolant in the characteristic zone of VVER fuel assemblies using mixing lattices of structurally different types are presented. These studies were performed on an aerodynamic stand by the method of impurity diffusion for several experimental scaled models. The studies were performed on a section of self-similar flow, so that the results can be used to convert to natural conditions of coolant flow in the core in regular TVSA. These studies refine the local and mass-transfer characteristics of coolant flow in order to reduce the conservatism in the evaluation of the heat-engineering reliability of the VVER core with TVSA fuel assemblies. The results also comprise a database for verifying CFD codes and programs for cellular calculation of a VVER core.

Research on the Flow Characteristics of Forced Circulation Evaporative Cooling System of Stator in Turbo-Generator

The forced circulation evaporative cooling system of stator in turbo-generator is a new cooling system under study, with the advantages of high-security, high efficiency and energy-saving. In this paper, an experiment table of this new cooling system with single hollow conductor was established. The flow characteristics of coolant in hollow conductor were analyzed and discussed by theoretical simulating and experimental researching. The results show that with the volume flow of coolant increasing, the variation tendencies of total flow resistance in hollow conductor and Xe are not monotonic and the prediction precision of total flow resistance in hollow conductor is satisfying with maximum relative error less than 10%. The length of subcooled flow boiling region in hollow conductor is relative long and can not be ignored. The conclusions in this paper can provide the theoretical and experimental basis for the further study of this new cooling system.

Investigation of the heat transfer process in a mesh matrix of a rotary heat exchanger

The paper presents the results of computational modeling of thermal processes in mesh matrixes of rotary frame heat exchangers. The authors received the refined dependence of the mesh matrix heat transfer of the coolant flow characteristics.

Practical Slot Configurations for Turbine Film Cooling Applications

Turbine component film cooling is most effective when using a continuous slot to introduce coolant to the surface. However, this is not practical due to the structural weakness that would be inherent with a continuous slot. In this study, several slotlike designs are investigated to establish the film cooling effectiveness. These slot configurations extended only a partial distance through the simulated turbine vane wall and were fed with impinging cylindrical holes. The configurations were studied on the suction side of a scaled-up turbine vane. In this study, varying slot widths, discrete and continuous slots, and diffusing the coolant flow within the slot prior to it being emitted onto the surface of the vane were investigated. Rows of discrete round and shaped holes were also tested for comparison with the slots. The study of varying slot geometries showed that decreasing the width of the slots led to a substantial increase in adiabatic effectiveness. An internal coolant diffusion technique showed promise by maintaining performance levels while potentially providing a design configuration that more readily meets structural demands in real-world operating conditions. The coolant flow characteristics were also studied through the use of thermal profiles measurements. These thermal profiles showed minimal mainstream ingestion on the top surface of the slot prior to the coolant emitting onto the surface of the vane.