Internal Temperature Distribution Research Articles

A Revised Tikhonov Regularization Method for a Cauchy Problem of Two-Dimensional Heat Conduction Equation

In this paper we investigate a Cauchy problem of two-dimensional (2D) heat conduction equation, which determines the internal surface temperature distribution from measured data at the fixed location. In general, this problem is ill-posed in the sense of Hadamard. We propose a revised Tikhonov regularization method to deal with this ill-posed problem and obtain the convergence estimate between the approximate solution and the exact one by choosing a suitable regularization parameter. A numerical example shows that the proposed method works well.

Fully transient modeling of the heavy fuel oil droplets evaporation

In this paper, evaporation of heavy fuel oil (HFO) droplet under atmospheric pressure is studied through a fully transient approach. The HFO is considered as a multi-component liquid with temperature-dependent properties. The performance of this fully transient approach is evaluated for different fuels and results are compared with available experimental data for gasoline and diesel fuel. The comparison shows excellent agreements, and also reveals the flexibility of this approach for interpretation and justification of the evaporation process details by using of internal distribution of temperature and composition. Based on distillation curve, several multi-component compositions are presented for the HFO. The composition is broken down into several pseudo-components and the effects of number of components and their method of selecting are studied comparatively. It shows that despite the wide range of compositions of heavy fuels, a compound consists of a few numbers of pseudo-components can be a suitable representative for them. Also pseudo-components should be chosen with equal interval temperature and narrow boiling temperature range. The effects of environment temperature on the evaporation of droplets are investigated in a parametric study. The results show that internal temperature distribution is not very sensitive to the ambient temperature due to the high boiling temperature of heavy components of the fuel. Also wide span of temperature in the heavy fuel droplet makes it possible to predict the initial condition of pyrolysis and thermal cracking of heavier components.

Optimal temperature control of tissue embedded with gold nanoparticles for enhanced thermal therapy based on two-energy equation model

Thermal therapy is a very promising method for cancer treatment, which can be combined with chemotherapy, radiotherapy and other programs for enhanced cancer treatment. In order to get a better effect of thermal therapy in clinical applications, optimal internal temperature distribution of the tissue embedded with gold nanoparticles (GNPs) for enhanced thermal therapy was investigated in present research. The Monte Carlo method was applied to calculate the heat generation of the tissue embedded with GNPs irradiated by continuous laser. To have a better insight into the physical problem of heat transfer in tissues, the two-energy equation was employed to calculate the temperature distribution of the tissue in the process of GNPs enhanced therapy. The Arrhenius equation was applied to evaluate the degree of permanent thermal damage. A parametric study was performed to investigate the influence factors on the tissue internal temperature distribution, such as incident light intensity, the GNPs volume fraction, the periodic heating and cooling time, and the incident light position. It was found that period heating and cooling strategy can effectively avoid overheating of skin surface and heat damage of healthy tissue. Lower GNPs volume fraction will be better for the heat source distribution. Furthermore, the ring heating strategy is superior to the central heating strategy in the treatment effect. All the analysis provides theoretical guidance for optimal temperature control of tissue embedded with GNP for enhanced thermal therapy.

A Spatially-Reduced Dynamic Thermal Model for Liquid Cooling Lithium-Ion Battery Pack

In electric vehicles, thermal management of a battery pack is becoming critical as both excessive and low temperature may affect the overall battery life and even trigger disastrous damage to a battery pack. Therefore, estimating the temperature distribution and its variation over time is an essential requirement to ensure safe and provide design guidance for control strategy. This study carries out a transient thermal model to predict the thermal behavior of a square lithium-ion battery pack with liquid cooling thermal management system. Different from Equivalent thermal circuit (ETC) model, which can only predict a lumped temperature of a battery cell, a one-dimensional thermal model was built in this study to estimate the temperature distribution throughout the cell and its variation over time according to the structural feature and the liquid cooling mode. The model is based on the Green function method, capable of calculating one-dimensional thermal dynamics and achieving high accuracy with low calculation requirements, making it suitable for real-time control. A second order equivalent circuit model was used in the approach to predict the dynamics of the cell voltage and SOC in relation with the current. Then the electric model is coupled with a lumped thermal model to describe the dynamics of internal temperature distribution of one cell. Based on this cell model, a coupled flow-electro-thermal model for a battery pack was built, which was able to predict the uneven heat generation during the charge and discharge procedure under different cooling conditions. 3D CFD calculation was conducted for the model calibration and validation results are presented to support the proposed modeling approach.

Analogue Simulation Research on Heating Characteristics of Inner Channel of High-temperature Gas Flow

The thermal test of structure generally uses the quartz lamp radiation heating method, but this method is not suitable for heating of the internal surface of a long and narrow irregular channel. This paper puts forward a heating method of inletting the high-temperature gas flow to the channel, and uses CFD numerical simulation method to explore the internal surface temperature rise and temperature distribution conditions of the channel at different temperature and under the impact of Mach number of gas flow and verify the heating capacity of high-temperature gas flow, and also gives out Mach number of the best incoming flow when the total temperature ability of the high-temperature gas tunnel can obtain the highest wall temperature under certain conditions, thus providing a theoretical basis for reasonable determination of the best operating conditions for test.

Numerical Study on Density Gradient Carbon–Carbon Composite for Vertical Launching System

This study presents new carbon–carbon (C/C) composite that has a density gradient within single material, and estimates its heat conduction performance by a numerical method. To address the high heat conduction of a high-density C/C, which can cause adhesion separation in the steel structures of vertical launching systems, density gradient carbon–carbon (DGCC) composite is proposed due to its exhibiting low thermal conductivity as well as excellent ablative resistance. DGCC is manufactured by hybridizing two different carbonization processes into a single carbon preform. One part exhibits a low density using phenolic resin carbonization to reduce heat conduction, and the other exhibits a high density using thermal gradient-chemical vapor infiltration for excellent ablative resistance. Numerical analysis for DGCC is performed with a heat conduction problem, and internal temperature distributions are estimated by the forward finite difference method. Material properties of the transition density layer, which is inevitably formed during DGCC manufacturing, are assumed to a combination of two density layers for numerical analysis. By comparing numerical results with experimental data, we validate that DGCC exhibits a low thermal conductivity, and it can serve as highly effective ablative material for vertical launching systems.

Numerical Simulations of a 96-rod Polysilicon CVD Reactor

With the rapid development of the photovoltaic industry, pressurized Siemens belljar-type polysilicon CVD reactors have been enlarged from 24 rods to 96 rods in less than 10 years aimed at much greater single-reactor productivity. A CFD model of an industry-scale 96-rod CVD reactor was established to study the internal temperature distribution and the flow field of the reactor. Numerical simulations were carried out and compared with actual growth results from a real CVD reactor. Factors affecting polysilicon depositions such as inlet gas injections, flow field, and temperature distribution in the CVD reactor are studied.

Numerical Simulation and Experimental Research on Drying Behavior of a Single Lignite Particle (SLP) under High-Temperature Flue Gas

The drying behavior of a single lignite particle (SLP) in high-temperature (600–900 °C) flue gas was investigated by experiment and numerical calculations. A self-designed horizontal fixed-bed reactor was employed for high-temperature drying experiments. Based on the drying curves obtained from these experiments, no constant-drying-rate stage was found, and the SLP drying process included stages with increasing and decreasing drying rates. To explore the drying process in depth, a mathematical model was developed in which the SLP was simplified into a simple spherical model. Based on the dry–wet zone theory, the heat- and mass-transfer equations were established to describe the drying process. The simulated results calculated using MATLAB agreed well with the experimental data. The model can predict SLP drying behaviors including the effects of the drying time, the surface and internal temperature distributions of the lignite particle, the migration of the evaporation interface inside the particle, and so...

Thermal Design Optimization of Electric Machines Using a Global Sensitivity Analysis

This paper presents a systematic procedure to study the impact of each thermal phenomenon occurring in electric machines on their internal temperature distribution. First, the Monte-Carlo method is chosen as a global sensitivity analysis technique. This method is applied on a thermal network of a prototype consisting of a permanent magnet based integrated starter-generator machine. Accordingly, the variation of electric machine critical temperatures in windings and rotor's permanent magnets is evaluated. In addition, a sensitivity index is defined for identifying network parameters that cause significant variation on the machine critical temperatures and should therefore be the focus of attention when designing electric machines. Finally, experimental tests are performed on the prototype, and the deviation between simulated and measured temperatures is presented.

Application of COMSOL Multiphysics in Thermal Effect Analysis of Electromagnetic Active Vibration Absorber

At present, there are some researches in the thermal analysis of electromagnetic absorbers. The heating principle of electromagnetic absorber magnetic circuit is analysed, and the finite element method is used to numerically solve the temperature field in the working process of electromagnetic vibration absorber. The magnetic circuit simulation model of electromagnetic vibration absorber is established in Comsol Multiphysics finite element analysis software. And the grid Division, simulation analysis of the vibration absorber magnetic circuit structure of the internal temperature distribution, you can get the vibration absorber magnetic circuit in the working process of the temperature field of two-dimensional distribution graphics and magnetic circuit structure of different parts of the temperature rise contrast chart. The conclusion provides some theoretical reference for the design and research of electromagnetic active vibration absorber.

Performance Investigation on an Ultra-compact Interstage Turbine Burner with Trapped-vortex Slot Inlet

Ultra-Compact Combustor (UCC), which is one of mainstream design concepts of Interstage Turbine Burner (ITB), has the advantages of compact structure and high combustion efficiency. A design concept of an UCC with trapped-vortex slot inlet was proposed and numerical simulation of the stability, emissions, internal flow velocity and temperature distribution was carried out. The results indicated that the UCC with trapped-vortex slot inlet could enhance the mixing of combustion mixture and the mainstream airflow, improve the combustion efficiency, outlet temperature and the uniformity of outlet temperature field.

Heat and fluid flow in electro-osmotically driven systems

A numerical investigation of heat and fluid flow in electro-osmotically driven systems is presented, by considering plain channels and channels packed with charged solid particles. The results show that the introduction of charged solid particles a_ects the internal potential distribution, fluid flow and temperature distribution in the channel. Under the analysed conditions, the effect on heat transfer is confined to the centre of the channel. This topic needs to be further investigated since it is of interest in practical applications.

Impact of Cargo Stacking Modes on Temperature Distribution Inside Marine Reefer Containers

The refrigerated/chilled quality of marine cargo is vitally influenced by the temperature distribution inside reefer container. The stacking mode is a key factor affecting temperature distribution. CFD method is employed to model and simulate a 20-ft standard reefer container, in which seven cargo stacking modes are emulated to numerically analyze the internal temperature distribution inside the container. The stacking cargo is assumed as solid stack without heat release and the variables, such as stack number, height, length and gap, are considered in seven simulation cases. The results show that the temperature distributions become disordered along with increase in the stack height; the temperature difference increase along with increase in the stack length; the temperature tends to be isothermal when the gap of the stacks or the space between the stack and sidewall surface is enlarging. The simulation results are in very good agreement with the experimental results.

Field measurement of temperature inside tunnel in winter in Gangwon, Korea

In this study, the internal temperature distribution in winter was investigated in tunnels located in Gangwon Province, the coldest region in Korea. In a total of 104 surveyed tunnels, the temperature was measured at various positions, including the air inside the tunnel, the road pavement, and the lining surfaces. The measurement results were incorporated into a database with the meteorological data of Gangwon Province. Analysis of the data showed that the difference of the temperature in a single tunnel between different positions along the tunnel length was not as significant as the temperature difference between different tunnels. The lining temperature and the air temperature inside the tunnel did not change significantly over time regardless of the tunnel length, but the temperature at the entrances and exits varied significantly over time due to the effects of the external temperature. Since the external air temperature during the winter affects the air temperature inside tunnels, which in turn affects the tunnel lining temperature, the lining temperature followed the air temperature at a certain time interval. In addition, the temperature inside a tunnel is affected by the inflow of external air due to the movement of vehicles as well as due to natural wind.

Effects of 27.12 MHz Radio Frequency on the Rapid and Uniform Tempering of Cylindrical Frozen Pork Loin (Longissimus thoracis et lumborum).

Quality characteristics of frozen cylindrical pork loin were evaluated following different tempering methods: 27.12 MHz curved-electrode radio frequency (RF) at 1000 and 1500 W, and forced-air convection (FC) or water immersion (WI) at 4°C and 20°C. The developed RF tempering system with the newly designed curved-electrode achieved relatively uniform tempering compared to a parallel-plate RF system. FC tempering at 4°C was the most time-consuming process, whereas 1500 W RF was the shortest. Pork sample drip loss, water holding capacity, color, and microbiological quality declined after WI tempering at 20°C. Conversely, RF tempering yielded minimal sample changes in drip loss, microstructure, color, and total aerobic bacteria counts, along with relatively uniform internal sample temperature distributions compared to those of the other tempering treatments. These results indicate that curved-electrode RF tempering could be used to provide rapid defrosting with minimal quality deterioration of cylindrical frozen meat block products.

Parametric study on the thermoelectric conversion performance of a concentrated solar-driven thermionic-thermoelectric hybrid generator

Summary A concentrated solar-driven thermionic-thermoelectric hybrid generator composed of solar heat collector, thermionic generator (TIG), thermoelectric generator (TEG), and radiator is introduced in this paper. A theoretical model of thermoelectric conversion performance for the hybrid generator is built up based on the heat source of the concentrated solar radiation rather than isothermal heat source. Based on the model, the impacts of related parameters on the internal temperature distributions, output power, and efficiency have been discussed. Moreover, the optimal operating conditions of the TIG-TEG hybrid device at its maximum output power and efficiency have been determined. Results show that when cascading the TEG with the TIG, there is very little change of the TIG cathode temperature in most conditions, namely, TC ≈ TC′. Meanwhile, the anode temperature becomes higher, and the TEG cold end temperature T2 is close to the anode temperature TA′ for the single TIG system, ie, TA > TA′ ≈ T2. In theory, the optimal concentrated solar radiation I0 for the maximum output power Pmax and the maximum efficiency ηmax differs, which are I0,P = 2.5 × 106 W/m2 and I0,η = 2 × 106 W/m2, respectively, whereas the output power and efficiency of the TIG-TEG hybrid system simultaneously reach their maximum values when the optimal TIG anode temperature TA,opt = 1025 K, the optimal TIG output voltage Vopt = 2 V, and the optimal ratio of load resistance to internal resistance (R2/R)opt = 2. However, in practice, the parameter values of I0, ΦA, and TA should be strictly controlled under 1.8 × 106 W/m2, 1.4 eV, and 660 K, respectively. Generally, the maximum output power and efficiency of the hybrid TIG-TEG system are, respectively, 35% and 4% higher than that of the single TIG.

Transient thermal analysis of a lithium-ion battery pack comparing different cooling solutions for automotive applications

This paper presents a computational modeling approach to characterize the internal temperature distribution within a Li-Ion battery pack. In the mathematical formulation both entropy-based and irreversible-based heat generation have been considered; combined with CFD software in order to simulate the temperature distribution and evolution in a battery pack.A prismatic Li-ion phosphate battery is tested under constant current discharge/charge rates of 1C, 2C, 5C and 8C. Model parameters (in particular, the entropic heat coefficient and the internal resistance) needed for the calibration of the model are determined using experimentation.The model is then used to simulate two different strategies for the thermal control of a battery pack in case of car application: an air-cooling and a liquid-cooling strategy.The simulation has highlighted the pros and cons of the two strategies, allowing a good understanding of the needs during the process of battery pack design and production.

Study on thermal resistance performance of 8YSZ thermal barrier coatings

The application of ceramic thermal barrier coatings (TBCs) can significantly increase gas turbine performance. The microstructure of TBCs fabricated by APS and EB-PVD is remarkably different. The thermal and mechanical properties of TBCs with the same material are determined by its microstructures. In order to establish structure-property relationships of TBCs with complex inhomogeneous geometry, in this work, various 3D-microstructures of TBCs were reconstructed using the geometric reconstruction software developed by our team. A three-dimensional model based on Lattice Bolzmann method (LBM) was developed to investigate the heat transfer behaviors in TBCs. The effect of microstructure parameters such as porosity, pore size and pore shape on the effective thermal conductivity of TBCs was studied in detail. The relationship between microstructures and effective thermal conductivity of TBCs was obtained. The calculated values of the effective thermal conductivity of 3D-TBCs agree well with the experimental values, and all relative errors are less than 4%. It can be found that the layered coatings should have larger size pores, and the columnar coatings should have smaller size pores. This can make the internal temperature distribution of TBCs more uniform. The effect of pores size on the thermal conductivity of two types of TBCs is different, but their thermal conductivity increase with the increase of porosity. The effective thermal conductivity of the columnar TBCs with the same porosity decreases with the decrease of pores size, but that of the layered TBCs increases with the decrease of pores size. The pores shape has a great influence on the effective thermal conductivity of the coating, especially for high porosity columnar coating. The effective thermal conductivity of the columnar coatings logarithmically increases with the length of the elongated pores, and it is increased by 21.6% when the porosity is 20%. However, the effective thermal conductivity of the layered structure coatings logarithmically decreases with the length of the elongated pores. The results will provide us a theoretical guide to design TBCs with a high thermal insulation property.

Microneedle arrays fabricated with two types of multifunctional liposomes as a vaginal mucosal vaccine adjuvant-dual delivery dystem (VADDS)

Thermal therapy is a very promising method for cancer treatment, which can be combined with chemotherapy, radiotherapy and other programs for enhanced cancer treatment. In order to get a better effect of thermal therapy in clinical applications, optimal internal temperature distribution of the tissue embedded with gold nanoparticles (GNPs) for enhanced thermal therapy was investigated in present research. The Monte Carlo method was applied to calculate the heat generation of the tissue embedded with GNPs irradiated by continuous laser. To have a better insight into the physical problem of heat transfer in tissues, the two-energy equation was employed to calculate the temperature distribution of the tissue in the process of GNPs enhanced therapy. The Arrhenius equation was applied to evaluate the degree of permanent thermal damage. A parametric study was performed to investigate the influence factors on the tissue internal temperature distribution, such as incident light intensity, the GNPs volume fraction, the periodic heating and cooling time, and the incident light position. It was found that period heating and cooling strategy can effectively avoid overheating of skin surface and heat damage of healthy tissue. Lower GNPs volume fraction will be better for the heat source distribution. Furthermore, the ring heating strategy is superior to the central heating strategy in the treatment effect. All the analysis provides theoretical guidance for optimal temperature control of tissue embedded with GNP for enhanced thermal therapy.

Thermal design and characterization of a modular integrated liquid cooled 1200 V-35 A SiC MOSFET bi-directional switch

The aim of this work is the thermal design of a modular direct liquid cooled package for 1200V–35A SiC power MOSFETs, in order to take full advantage of the high power density and high frequency performance of these devices, in the development of a modular integrated solution for power converters. An accurate electro-thermal fluid dynamic model is set up and validated by thermal characterization on a prototype; numerical models have been used to study the internal temperature distribution and to propose further optimization.