Steady-state Thermal Analysis Research Articles

Responses of Aluminium Alloy Pistons under Mechanical and Thermal Loads

A comparative study of three different aluminium alloys, Al2618, Al4032 and Al6061 made internal combustion engine pistons is done on their responses under mechanical and thermal loads using finite element methods. In this study, a 3D solid model of piston is created in CATIA and the simulations of the static structural analysis, steady-state thermal analysis and transient thermal analysis are carried out in ANSYS. Stress and temperature distributions on critical areas of piston are pointed out for appropriate modification in piston design. The temperature and heat flux variations with time are presented in transient thermal analysis. Taguchi method and topological optimization are applied to optimize the process parameters and to select the appropriate material for the piston.

Thermo-Mechanical Analysis of Functionally Graded Material Plate under Transverse Loading for Varying Volume Gradation

Functionally graded material (FGM) has a unique design in which material properties vary smoothly and continuously which leads to having better thermal and mechanical performance. Functionally graded material has a wide area of application from the pressure vessel to aerospace due to its tailoring properties. The main emphasis has been made here, to present a structural mechanical and steady-state thermal analysis of functionally graded flat plate made up of aluminum and ceramic. The flat plate is subjected to various boundary and loading condition. Material properties of FGM is calculated across the thickness using power law with the help of MATLAB programming. An analysis is performed for various volume gradation using MACROS in ANSYS APDL. The analysis results for functionally graded materials are compared with a composite sandwich plate for the same boundary conditions. It was found that von-Mises stress generated in FGM is 14.6% less than compared to sandwich structure, the stress in x and y-direction is 16.5% less, XY-Shear is 13.5% less and deflection is 33% less than a sandwich plate of aluminum and ceramic.

Calculation of clearances in twin screw compressors

Clearances between rotating and stationary parts in a screw compressor are set to ensure the efficient operation and allow for thermal deformation without unwanted contacts. The change in clearances is caused by both pressure and temperature changes within the machine. If clearances are too large, the increased leakage flows will reduce efficiency. However, if the nominal clearances are too small, contacts between the rotating and stationary parts can occur as a consequence of rotor and casing deformations. In order to determine the operational clearances, a numerical analysis of deformation of screw compressor rotors and casing has to be performed. This paper discusses how the temperature of rotor and casing surfaces calculated from the one-dimensional chamber model in the SCORG could be used as a boundary conditions for a steady state thermal and structural analysis of a screw compressor solid parts. Deformations of rotors and casing under temperature load were calculated using a commercial Finite Element Analysis code ANSYS. Operational clearance are estimated from these deformations and some recommendations for further work are proposed.

Thermal management of photonic integrated circuits: impact of holder material and epoxies.

The thermal management of photonic integrated circuits (PICs) poses a few challenges at the packaging level. The integration of a PIC with a proper holder provides mechanical support and electrical interconnection, as well as spreading of the heat generated during PIC operation. This study proposes and evaluates the thermal behavior of silicon and diamond holders and estimates the impact of integrating them with PICs as a packaged system; to this end, the thermal profile of a PIC with distributed feedback lasers mounted on silicon or diamond holders was simulated for different power levels using ANSYS Mechanical software. The impact of the epoxy resin used to mount the PIC on the holder and the thermal crosstalk between the active components were also evaluated. Based on steady-state thermal analysis, when the PIC is assembled via wire bonding, the replacement of the silicon holder with a diamond holder brings only a marginal advantage. The choice of epoxy has a larger impact on the maximum PIC temperature and the thermal crosstalk between active components. Choosing a large-thermal-conductivity-value epoxy is thus a mandatory requirement in order to guarantee the proper thermal management of PICs and their corresponding holders.

Design analysis and performance evaluation of heat pipe embedded oil cooler with enhanced staggered fins

Hydraulic coolers are most commonly preferred cooling source in industry. The progress in past few years have offered high efficiency and reliable hydraulic component, yet hydraulic cooling circuit design is often neglected part of development. One aspect of the hydraulic cooling circuit design is prevention of overheating hydraulic oil. Allowing oil temperature rise beyond particular limit can increase the power consumption and reduce the life of a system due to poor lubrication, higher internal leakage, higher risk of cavitation’s and damage component. Now-a-days shell and tube type oil coolers with water as the cooling medium are used as hydraulic oil cooler, these are extremely bulky and running cost is high hence it is needed to be replaced by another system that will be air cooled to make provision for lower space consumption and cost reduction. This paper discusses the design and development of innovative oil cooler heat extraction system using heat pipe. Designs of fins preferred are namely the straight fin system with fins projected outward in eight channels. The equipment developed is first model using Unigrafix Nx-8 and steady state thermal analysis of fins is done in Ansys workbench 16.0. A simple, compact, high efficiency, low cost device is developed, also a new technology of heat pipe embedded oil cooler is learnt in this present work. This paper discusses the performance of heat pipe embedded oil cooler in terms of LMTD, overall heat transfer coefficient and effectiveness. Further it discusses the performance evaluation of the straight fin setup.

Multiphysics analysis of side-coupled RF cavity

By changing the resonant frequency of the cavity due to the power dissipation in its wall, the impedance matching will impair and the power will reflect. The acceptable frequency shift range which is based on the cooling system in the cavity design depends on the ability of the automatic frequency controller system and the bandwidth of the RF amplifier output frequency. This paper describes how to couple electromagnetic, thermal and mechanical analysis and calculates the cavity frequency shift during operation. Multiphysics analysis investigations had done for an S-band side-coupled cavity. By using the Superfish code, the power loss ratio at different surfaces of the cavity could be accurately calculated and Steady-State Thermal (SST) analysis could be performed correctly. In this paper, the report on the simultaneous use of multiphysics analysis with the modules of the Ansys software is presented and the results of both simulations are compared. The temperature distribution of the cavity was obtained by using the Fluent software and its results were compared with the temperature distribution gained from applying the convection coefficient to the SST. Three cooling systems were investigated for different powers with different cross-sections. In this section of the investigation, after thermal analysis, deformed geometry was obtained due to thermal stresses. By electromagnetic analyzing of deformed geometry, its frequency shift was obtained for all different cases. In order to evaluate the simulations, after the construction of a single-cavity, frequency variations are measured in terms of temperature variation and the results are compared with each other. After constructing a single-cavity, frequency shifts based on temperature variations are measured and the results are compared with each other.

Verification of the TIGRSP Computer Code as Applied to a 19-Rod Fuel Assembly Using CFD Computations

For assessing the core critical heat flux ratio in VVER-type nuclear reactors, the lattice computation code TIGRSP (steady-state thermal and hydraulic analysis of parameters in fuel rod bundles) is used. Despite the fact that quite a large amount of verification studies has been accomplished and that the code has passed the certification procedure, work on improving the code capabilities is still being continued. One of the modern tendencies is the wide-scale involvement of CFD codes for studying local parameters in fuel assemblies (FAs). Along with comparison with experimental data, it is advisable to carry out cross verification of lattice codes with the results of 3D thermal-hydraulic computations for conditions for which experimental data are either lacking or limited for some or other reasons. This article considers thermal-hydraulic processes during coolant flow in a 19-rod assembly with parameters close to the nominal conditions in the FAs of a VVER-1000 reactor. The 3D model is verified with respect to empirical formulas and experimental data. Based on the results of test and verification computations, we determined the mesh and turbulence model parameters using the ANSYS CFX code by means of which it is possible to obtain reliable results in estimating the hydraulic characteristics of FAs fitted with spacer grids, heat transfer in the single-phase region, and coolant flow distribution over the FA cross section. The CFD computation of coolant flow for the 19-rod assembly is carried out, and the coolant mass velocity and temperature in different sections over the length and corresponding cells of the TIGRSP code are calculated. The TIGRSP code has been verified against experimental data and taking into account the CFD simulation of the 19-rod FA, and a software module for graphically visualizing the lattice code output results has been developed. The presented data can be used for verification of thermal-hydraulic codes and in elaborating the design of FAs for VVER-type reactors.

Exergy and improvement potential of hybrid photovoltaic thermal/thermoelectric (PVT/TE) air collector

In this paper, a review of exergy and improvement potential (IP) of solar thermal systems is presented. The review includes exergy analysis of photovoltaic thermal (PVT) systems, solar drying systems and solar collectors. Solar collectors, which are the most essential components of solar thermal systems, receive solar energy and convert it into thermal energy. Since the solar/PVT collector system is an essential component when the design of sustainability is considered, exergy analysis, which provides a more representative performance rating. In addition, a theoretical and experimental performance of hybrid photovoltaic thermal/thermoelectric (PVT/TE) air collector is investigated. A steady-state thermal analysis of a hybrid PVT/TE air collector is developed to predict air outlet and photovoltaic (PV) temperatures. The predicted results are in close agreement with the experimental study. The percentage error of air outlet and PV temperatures between theoretical and experimental value is 1.1% and 2.6% respectively. On the other hand, the simulated model is then used to study the performances of a hybrid PVT/TE air collector using exergy analysis for the mass flow rate ranging between 0.001 kg/s to 0.15 kg/s and a solar radiation of 600 W/m2. The effect of mass flow rate on exergy efficiency and an advance prospective are observed. The optimum exergy efficiency of PVT/TE obtained is relatively 0.38. In addition, IP is proposed in this study.

Thermal analysis of a waveguide section of the ITER plasma-position reflectometry system on the high-field side

Some components of the ITER Plasma Position Reflectometry (PPR) system will be installed inside the vacuum vessel (VV), directly exposed to the plasma, and therefore subjected to thermal loads that may result in excessive operation temperatures. The main objective of this work was to estimate the temperature distribution on a waveguide section of the PPR in-vessel system to be installed on the high-field side. A steady state thermal analysis was conducted using the finite element method and the commercial software ANSYS Workbench. The analysis revealed a maximum temperature of 187 °C in the waveguides, well below the maximum allowable temperature for SS316L(N)-IG under neutron irradiation (450 °C). Based on these results, a static structural analysis shall be performed to determine the thermal stresses on the components.

Thermo-mechanical analysis of a probe for electron paramagnetic resonance spectroscopy operating at cryogenic temperatures.

In this article, we present the thermo-mechanical analysis of an electron paramagnetic resonance (EPR) probe operating at cryogenic temperatures using finite element analysis. Thermo-mechanical analysis plays a key role in the mechanical design evaluation process as EPR probes are often subjected to large stresses under such extreme conditions. For simplification, we assume thermal conduction to be the dominant mode of heat transfer over convection and radiation. The simulation model consists of a cryostat-probe assembly with appropriate thermal and structural boundary conditions. The predicted temperature distributions from the steady-state thermal analysis is then used for the stress analysis of the EPR probe. The stress analysis indicated that stresses in the EPR probe are below the ultimate strengths of each component, and thus safe for running EPR experiments. Furthermore, the simulation results were confirmed experimentally, and we found that the predicted heat losses for the EPR probe assembly and the sample holder are in excellent agreement with the experimental measurements.

Preliminary investigation on W foams as protection strategy for advanced FW PFCs

As one among the core missions towards the realization of nuclear fusion, a future reactor must provide efficient and safe power exhaust through both divertor and first wall (FW). Recent studies have confirmed that the greatest challenges arise from the occurrence of plasma transients. Indeed, extensive damage of the plasma facing component (PFC) may occur during transients, with the risk of loss of coolant accidents (LOCA) that would hinder the safety of a future reactor as well as its prompt return to normal operation. Among the possible wall protection strategies, a sacrificial and micro-engineered surface made of porous tungsten (W) may promote the heat flux reduction while preventing the failure of the cooling pipe. As a preliminary step in this direction, the present study aims to investigate the possible application of W-based open cell foams as a sacrificial armor material. At first, an equivalent solid model, originally validated for Al open cell foams, was transferred to W foams. Then, a steady state thermal FEM analysis was carried out to evaluate the equivalent thermal conductivity provided by several foam configurations. Ultimately, a scaling law of the thermal response was developed as a function of the most influential foam parameters. As a future outlook with respect to DEMO-relevant transients scenarios, the scaling law will support design optimization and tailoring of an advanced FW PFC provided with a sacrificial W foam armor.

Performance Test of the Air-Cooled Finned-Tube Supercritical CO2 Sink Heat Exchanger

This technical paper presents results of an air-cooled supercritical CO2 (sCO2) finned-tube sink heat exchanger (HX) performance test comprising wide range of variable parameters (26–166 °C, 7–10 MPa, 0.1–0.32 kg/s). The measurement covered both supercritical and subcritical pressures including transition of pseudocritical region in the last stages of the sink HX. The test was performed in a newly built sCO2 experimental loop which was constructed within Sustainable Energy (SUSEN) project at Research Centre Rez (CVR). The experimental setup along with the boundary conditions are described in detail; hence, the gained data set can be used for benchmarking of system thermal hydraulic codes. Such benchmarking was performed on the open source Modelica-based code ClaRa. Both steady-state and transient thermal hydraulic analyses were performed using the simulation environment DYMOLA 2018 on a state of the art PC. The results of calculated averaged overall heat transfer coefficients (using Gnielinski correlation for sCO2 and IPPE or VDI for the air) and experimentally determined values shows reasonably low error of + 25% and – 10%. Hence, using the correlations for the estimation of the heat transfer in the sink HX with a similar design and similar conditions gives a fair error and thus is recommended.

A Hybrid Modeling Approach for Characterization and Simulation of Cryogenic Machining of Ti–6Al–4V Alloy

A hybrid modeling approach based on computational fluid dynamics (CFD) and finite element method (FEM) is presented to simulate and study cryogenic machining (CM) of Ti–6Al–4V alloy. CFD analysis was carried out to study the characteristics of the fluid flow and heat transfer process of liquid nitrogen (LN2) jet used as a coolant in turning operation. The velocity, turbulence, gas volume fraction, and temperature of the impingement jet were investigated. Based on the analysis results, the coefficient of heat transfer (CHT) between the LN2 and cutting tool/insert was obtained and used in the FEM analysis to model the heat transfer process between the LN2 and the tool/chip/workpiece. A three-dimensional (3D) finite element (FE) model was developed to simulate a real CM operation. CM tests were carried out to validate the 3D FE model by comparing cutting forces and chip temperature. To evaluate LN2 cooling effect on tool temperature and tool wear, a two-dimensional (2D) FE model was developed for steady-state thermal analysis of cryogenic and dry machining. Based on the predicted temperatures, the tool wear was estimated, showing that LN2 cooling can significantly improve tool life.

Beam Dump Fabrication and Simulation by Using PHITS Code and an ANSYS Analysis

The design of a beam dump for the energy range less than 20 MeV is reported. The beam dump was developed for the beam extraction commissioning stage of the Korea Basic Science Institute’s( KBSI’s) heavy ion facility. At present, the downstream section design of the diagnostic chamber of the beam line was completed, as has the fabrication of a radio-frequency quadrupole(RFQ) section. We are now performing frequency tuning for optimization. For reduction and elimination of the generated beam, the beam dump will be located downstream of the diagnostic beam line, and the beam dump was designed to withstand a heavy-ion beam energy of less than 20 MeV. The PHITS code and ANSYS steady-state thermal analysis were adapted for simulating the heat transfer and determining the numbers and types of secondary particles produced by bombardment of the beam’s dump material, respectively.

Thermal analysis of nanostructured alumina stabilized zirconia coating on exhaust manifold

ABSTRACTRapid rise in pollution has increased the number of automobiles usage worldwide. The exhaust manifold is an important part in the automobile since it acts as a passage for the transport of exhaust gases from the combustion chamber to the atmosphere. It is a sensitive component since it handles high-temperature exhaust gases. Continuous exposure of high-temperature exhaust gas may cause thermal stress which decreases the life of the exhaust manifold. Cast iron or steel is the most common material used for exhaust manifold. The present study deals with the improvement of material properties of exhaust manifold. In order to optimize the cast iron properties such as thermal conductivity and corrosion resistance, a zirconia-based nanocomposite coating such as alumina stabilized Zirconia (ASZ) can be coated on both sides of the exhaust manifold, instead of replacing the whole material. By coating nano structured ASZ, the amount of heat flow from exhaust gases to the exhaust manifold is decreased, thereby reducing the thermal fatigue. The method of coating can be achieved by radio frequency Magnetron sputtering technique. A steady-state thermal analysis is performed by simulation approach using ANSYS R17.2 to validate the output in the numerical approach. The results obtained shows that ASZ nanocomposite coating acts as an efficient thermal barrier coating for the exhaust manifold thus increasing its reliability.

A combined numerical and experimental approach for determining the contact temperature in an industrial ironing operation

Tribological conditions in forming operations depend on several parameters such as tool-workpiece interface pressure, surface expansion, sliding length, sliding speed, tool and workpiece materials and the roughness of the parts. Among indirect parameters, the most influential one is the tool-workpiece interface temperature, which directly influences the lubricant performance. Prior to testing new tribo-systems to determine their limits of lubrication, it is therefore important to find the interface temperature. However, measurement of the interface temperature in metal forming is difficult. The present work investigates the determination of the interface temperature in an industrial ironing operation, where severe process parameters lead to lubricant film breakdown and galling after several strokes. The methodology combines finite element simulations and experimental measurements. The overall procedure is based on a steady-state thermal analysis to determine the temperature distribution within the tool and a transient thermo-mechanical analysis of the ironing process when steady-state conditions are achieved. Results show that the proposed methodology applied to a single stroke can effectively and accurately predict the interface temperature in the test tool, thus avoiding the otherwise required thermo-mechanical FEM analyses of hundreds of strokes to reach steady-state. Furthermore, the influence of parameters, such as the predicted steady-state tool temperature, the friction coefficient and the heat transfer coefficient on the contact temperature, is analysed. It is concluded that the frictional heating is the primary cause for the peak temperature. By calibration of the friction coefficient and the heat transfer coefficient to ensure matching of the numerical results and the experimental measurements, a maximum tool-workpiece interface temperature of 158 °C was determined during the forward stroke and 150 °C during the backward stroke.

Steady state electrical–thermal coupling analysis of TSV* * Project supported by the National Natural Science Foundation of China (Nos. 61574106, 61574104), the National Defense Pre-Research Foundation of China (No. 9140A23060115DZ01062), and the Key Science and Technology Special Project of Shaanxi Province (No. 2015KTCQ01-5).

This paper presents a blended analytical electrical–thermal model for steady state thermal analysis of through-silicon-via (TSV) in three-dimensional (3D) integrated circuits. The proposed analytical model is validated by the commercial FEM tool—COMSOL. The comparison between the results of the proposed analytical formulas and COMSOL shows that the proposed formulas have very high accuracy with a maximum error of 0.1%. Based on the analytical model, the temperature performance of TSV is studied. Design guide lines of TSV are also given as: (1) the radius of the TSV increases, the resistance decreases and the temperature can be increased; (2) the thicker the dielectric layer, the higher the temperature; (3) compared with carbon nanotube, the Cu enlarges the temperature by 34 K, and the W case enlarges the temperature by 41 K.

Thermo-Structural Analysis of First Stage Gas Turbine Rotor Blade Materials for Optimum Service Performance

During gas turbine operation, the vibration that occurs at high speed, hot gases entering the combustion chamber and other operational factors affect the longevity of gas turbine blade. This paper is focused on the selection of suitable materials that can withstand the severe working condition and thermo-structural analysis using Finite Element method (FEM) to determine the behaviour of each material under service condition. Cambridge Engineering Software (CES) was employed in the material selection process where GTD111, U500 and IN 738 were identified prior to analyzing U500 and IN 738 due to desired mechanical properties over GTD111. Employing ANSYS R15.0 in the steady state thermal analysis, maximum service temperature of 736.49oC and maximum Total heat flux of 4.345x105 W/m2 was obtained for IN 738 material while maximum service temperature of 728.29oC and maximum Total heat flux of 4.1746x105 W/m2 was obtained for U500 blade material. For structural static analysis, maximum von-mises stress of 454 MPa and total deformation of 0.16221 obtained for IN 738 while maximum von-mises stress of 416 MPa and total deformation of 0.12125 was obtained for U500 blade material. While the FEA analytical results for both materials exhibited less variations between each other, IN 738 displayed better thermal characteristics, whereas, U500 presented satisfactory structural static results and above all, von-mises stresses obtained for both materials was below their yield strength and melting temperature. Hence, gas turbine blade materials should be assessed thoroughly for structural and thermal conditions before manufacturing.

Intermediate Voltage Variation-Based Interconnecting Transformer Design for Voltage and Phase Angle Control With Coupled Field FEA Studies

A 160-MVA, 220/132/33-kV autotransformer is commonly used as an intermediate connecting transformer (ICT) in an electrical power transmission network. The modified design of such an ICT in order to get a phase angle control along with the voltage control, by intermediate voltage variation, is reported in this paper. Estimation of stray loss and core loss is done both by analytically and realizing 2-D and 3-D models by a finite-element analysis (FEA) method. A 3-D FEA design is further extended with arrangement of shunts to limit the stray loss and the thermal impact. Multiphysics simulation platform is used to link magnetostatic, steady-state thermal and structural FEA models. The composite FEA simulation approach used in this study enables steady-state thermal analysis of a transformer by importing stray loss from the magnetostatic model and the structural deformation in the transformer due to hot-spot temperature. To validate the proposed design, a 1-kVA, 415/230-V, three-phase transformer is designed, built, and tested in the laboratory. Voltage and phase angle at various operating conditions calculated analytically, obtained through FEA and measured experimentally, are in close agreement.

Thermal analysis of Nano ceramic coated piston used in natural gas engine

Nano ceramic coatings have low thermal conductivity which can provide good heat insulation properties, and therefore they have been widely used in industrial design as thermal barrier coatings (TBCs). In the design of internal combustion engines, TBCs have been used on combustion chamber components to improve engine performance. In this paper, improvement in the working performance of natural gas engines is demonstrated when an aluminum alloy piston is sprayed with a Y2O3 partially stabilized zirconia (PYSZ) ceramic coating. Steady-state thermal analyses were used to determine the effects of the ceramic coating on temperature distributions. Output was compared with results from an uncoated conventional piston using the finite element method. Results show that the temperature at the top surface of coated piston is significantly higher (about 44% or 153 °C higher) than that of the uncoated piston. This higher combustion chamber temperature results in better engine thermal efficiency and lower emissions. Simultaneously, the temperature of the coated piston substrate is much lower (about 12% or 43 °C lower) than that of the uncoated piston. The lower metallic substrate temperature provides better thermal fatigue protection for the piston.