• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.230-239
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• 2004

A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moire interferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moire experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1475-1480
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• 2013

In this paper, the basic design study of a water-cooling jacket, which have reported no cases for applying to railway traction motors so far, were conducted for applying to Interior Permanent Magnet Synchronous Motor (IPMSM) for railway vehicles. The basic thermal characteristics analysis of the 110kW-class IPMSM was performed by using 3-dimentional thermal equivalent network method. The necessary design requirements of the water-cooling jacket were derived by analyzing the results of the basic thermal properties. Next, the thermal characteristics analysis technique was established by using the equivalent model of the solenoid-typed pipe to be installed on the inside of the water-cooling jacket for 110kW-class IPMSM. Finally, a design model of 6kW-class water-cooling jacket was derived through the analysis of various design parameters.

• International Journal of Computer Science & Network Security
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• v.23 no.2
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• pp.183-192
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• 2023

Radiofrequency ablation (RFA) is an alternative treatment for liver cancer to the surgical intervention preferred by surgeons. However, the main challenge remains the use of RF for the ablation of large tumours (i.e., tumours with a diameter of >3 cm). For large tumours, RFA takes a large duration in the ablation process compared with surgery, which increases patient pain. Therefore, RFA for large tumours is not preferred by surgeons. The currently materials used in RF electrodes, such as the nickeltitanium alloy (nitinol), are characterized by low thermal and electrical conductivities. On the other hand, the use of materials that have high thermal and electrical conductivities, such as titanium aluminide alloy (gamma titanium), produces more thermal energy for tumours. In this paper, we developed a cool-tip RF electrode model that uses nickel-titanium alloy and replaced it with titanium aluminide alloy by using the finite element model (FEM). The aim of this paper is to study the effect of the thermal and electrical conductivities of gamma titanium on the ablation volume. Results showed that the proposed design of the electrode increased the ablation rate by 1 cm³ /minute and 6.3 cm³/10 minutes, with a decrease in the required time ablation. Finally, the proposed model reduces the ablation time and damages healthy tissue while increasing the ablation volume from 22.5% cm³ to 62.5% cm³ in ten minutes compared to recent studies.

• Journal of information and communication convergence engineering
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• v.20 no.4
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• pp.303-308
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• 2022

Simulating the heat transfer in a composite material is an important topic in material science. Difficulties arise from the fact that adjacent materials cannot match perfectly, resulting in discontinuity in the temperature variables. Although there have been several numerical methods for solving the heat-transfer problem in imperfect contact conditions, the methods known so far are complicated to implement, and the computational times are non-negligible. In this study, we developed a ResNet-type deep neural network for simulating a heat transfer model in a composite material. To train the neural network, we generated datasets by numerically solving the heat-transfer equations with Kapitza thermal resistance conditions. Because datasets involve various configurations of composite materials, our neural networks are robust to the shapes of material-material interfaces. Our algorithm can predict the thermal behavior in real time once the networks are trained. The performance of the proposed neural networks is documented, where the root mean square error (RMSE) and mean absolute error (MAE) are below 2.47E-6, and 7.00E-4, respectively.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.144-151
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• 2012

A district heating system produces thermal energy and supplies it to a large region. District heating systems can provide higher efficiencies and better pollution control than localized boilers. The heat generated by a district heating system is distributed to the customer via a network of insulated pipes. For the optimal operation of a district heating system, it is important to predict the distributions of pressure, flow rate and temperature of heating fluid within the network of pipes at various operating conditions. In this work, a mathematical modeling was performed to predict the dynamic hydraulic-thermal behaviors of heating fluid in the network of pipes for a district heating system. The mathematical model accounts for the conservations of mass, momentum and energy. In order to verify the validity of modeling, the modeling results were compared with the monitoring data of Gang-nam Branch of District Heating.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.477-491
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• 2022

In the present study, the effects of thermal loading on the buckling and resonance frequency of graphene platelets (GPL) reinforced nano-composites are examined. Functionally graded (FG) material properties are considered in thickness direction for the thermal responses of the composite. The equivalent material properties are obtained using Halphin-Tsai nano-mechanical model for composite layers. Moreover, the effects of nano-scale sizes are taken into account, employing functionally modified couple stress (FMCS) parameter. In this regard, for the first time, it is demonstrated that at certain values of GPL weight fraction, thermal buckling occurs. In obtaining results of vibrational behavior, both analytical solution and deep neural network (DNN) methods are used. The DNN method needs low computational costs to predict the resonance behavior. A comprehensive parametric study is conducted to indicate the effects of several geometrical, material, and loading conditions on the vibrational and buckling behavior of cylindrical shell structures made of GPL-nanocomposites. It is shown that the effect of temperature change on the occurrence of buckling is vital while it has a negligible impact on the resonance frequency of the structure. Moreover, the size-dependency of the results is demonstrated, and it cannot be neglected in nano-scales.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.155-159
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• 2020

Nanoporous silica aerogel insulation material is both lightweight and efficient; it has important value in the fields of aerospace, petrochemicals, electric metallurgy, shipbuilding, precision instruments, and so on. A theoretical calculation model and experimental measurement of equivalent thermal conductivity for nanoporous silica aerogel insulation material are introduced in this paper. The heat transfer characteristics and thermal insulation principle of aerogel nano are analyzed. The methods of SiO₂ aerogel production are compared. The pressure range of SiO₂ aerogel is 1Pa-atmospheric pressure; the temperature range is room temperature-900K. The pore diameter range of particle SiO₂ aerogel is about 5 to 100 nm, and the average pore diameter range of about 20 ~ 40 nm. These results show that experimental measurements are in good agreement with theoretical calculation values. For nanoporous silica aerogel insulation material, the heat transfer calculation method suitable for nanotechnology can precisely calculate the equivalent thermal conductivity of aerogel nano insulation materials. The network structure is the reason why the thermal conductivity of the aerogel is very low. Heat transfer of materials is mainly realized by convection, radiation, and heat transfer. Therefore, the thermal conductivity of the heat transfer path in aerogel can be reduced by nanotechnology.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.883-888
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• 2023

Since data centers are places that provide IT services 24 hours a day, 365 days a year, data center power consumption is expected to increase to approximately 10% by 2030, and the introduction of high-density IT equipment will gradually increase. In order to ensure the stable operation of IT equipment, various types of research are required to conserve energy in cooling and improve energy management. This study proposes the following process for energy saving in data centers. We conducted CFD modeling of the data center, proposed an artificial intelligence-based thermal environment prediction model, compared actual measured data, the predicted model, and the CFD results, and finally evaluated the data center's thermal management performance. It can be seen that the predicted values of RCI, RTI, and PUE are also similar according to the normalization used in the normalization method. Therefore, it is judged that the algorithm proposed in this study can be applied and provided as a thermal environment prediction model applied to data centers.

• ETRI Journal
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• v.42 no.1
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• pp.118-128
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• 2020

A semitransparent photovoltaic-thermal (PV/T) air collector can produce electricity and heat simultaneously. To maximize the thermal and overall efficiency of the semitransparent PV/T air collector, its availability should be maximum; this can be determined through a Markov analysis. In this paper, a Markov model is developed to select an optimized number of semitransparent PV modules in service with five states and two states by considering two parameters, namely failure rate (λ) and repair rate (μ). Three artificial neural network (ANN) models are developed to obtain the minimum cost, minimum temperature, and maximum thermal efficiency of the semitransparent PV/T air collector by setting its type appropriately and optimizing the number of photovoltaic modules and cost. An attempt is also made to achieve maximum thermal and overall efficiency for the semitransparent PV/T air collector by using ANN after obtaining its minimum temperature and available solar radiation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.141-150
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• 2007

This paper presents a lumped model to predict crosstalk characteristics of thermally driven inkjet print heads. Using the lumped R-C model, heating characteristics of the head are predicted to be in agreement with IR temperature measurements. The inter-channel crosstalk is simulated using the lumped R-L network. The values of viscous flow resistance, R and flow inertance, L of connecting channels are adjusted to accord with the 3-D numerical simulation results of three adjacent jets. The crosstalk behaviors of a back shooter head as well as a top shooter head have been investigated. Predictions of the proposed lumped model on the meniscus oscillations are consistent with numerical simulation results. Comparison of the lumped model with experimental results identifies that abnormal two-drop ejection phenomena are related to the increased meniscus oscillations because of the more severe crosstalk effects at higher printing speeds. The degree of crosstalk has been quantified using cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed and validated with the numerical simulations. Our model can be used as a design tool for a better design of thermal inkjet print heads to minimize crosstalk effects.