Theoretical Temperature Distributions Research Articles

Comparison of Maximum Heat Transfer Rate of Thin Vapor Chambers with Different Wicks under Multiple Heat Sources and Sinks

In this paper, we present a new analytical model to investigate the maximum heat transfer rate of a thin vapor chamber (TVC) with multiple heat sources and sinks. The model can specifically consider different heat flux conditions for each heat source. Both capillary limitations and allowable maximum temperature constraints were employed to determine the maximum heat transfer rate. The liquid and vapor pressure distributions within the TVC were analytically derived using the Brinkman-extended Darcy equation and the Hagen–Poiseuille equation, respectively. Additionally, the theoretical wall temperature distribution was calculated based on the 3D energy equation, considering different heat flux conditions for multiple heat sources with a weighting factor. Our results demonstrate that the heat flux conditions applied to the heat sources significantly impact the internal flow pattern of the TVC. These changes in flow patterns influence the pressure distributions of the liquid and vapor, thereby affecting the maximum heat transfer rate. Furthermore, the effects of wick parameters on the maximum heat transfer rate under various heat flux conditions were examined.

Temperature distribution measurement inside an Er:Yb:Lu2Si2O7 crystal under 1.55 μm laser operation

Based on the fluorescence intensity ratio technique, the temperature distribution inside an Er:Yb:Lu2Si2O7 crystal was measured in real time when a 1.55 μm laser was operating. The polarized green up-conversion fluorescence in 500–580 nm of the crystal generated simultaneously under laser operation was used as the temperature probe. At a pump beam waist diameter of 400 μm, the highest temperature inside the crystal reached 507 K when the incident pump power and output mirror transmission were 11.13 W and 1.3%, respectively. The experimental result was compared with the theoretical temperature distribution inside the crystal simulated by the finite element analysis method, and the difference between them was analyzed.

Fibre Optic FBG Sensors for Monitoring of the Temperature of the Building Envelope.

Standard sensors for the measurement and monitoring of temperature in civil structures are liable to mechanical damage and electromagnetic interference. A system of purpose-designed fibre optic FBG sensors offers a more suitable and reliable solution—the sensors can be directly integrated with the load-bearing structure during construction, it is possible to create a network of fibre optic sensors to ensure not only temperature measurements but also measurements of strain and of the moisture content in the building envelope. The paper describes the results of temperature measurements of a building 2-layer wall using optical fibre Bragg grating (FBG) sensors and of a three-layer wall using equivalent classical temperature sensors. The testing results can be transmitted remotely. In the first stage, the sensors were tested in a climatic test chamber to determine their characteristics. The paper describes test results of temperature measurements carried out in the winter season for two multilayer external walls of a building in relation to the environmental conditions recorded at that time, i.e., outdoor temperature, relative humidity, and wind speed. Cases are considered with the biggest difference in the level of the relative humidity of air recorded in the observation period. It is found that there is greater convergence between the theoretical and the real temperature distribution in the wall for high levels (~84%) of the outdoor air relative humidity, whereas at the humidity level of ~49%, the difference between theoretical and real temperature histories is substantial and totals up to 20%. A correction factor is proposed for the theoretical temperature distribution.

The foam concrete temperature measuring during its microwave heat treatment

The actual problem of accelerating and reducing the energy costs of the foam concrete slabs heat treatment technological process is considered. It is shown that to solve this problem, it is advisable to use the microwave radiation energy as a heat source. The main advantages of the microwave method of foam concrete slabs heat treatment in comparison with traditional methods are considered. The design of a microwave installation for the foam concrete slabs heat treatment has been developed. The installed microwave radiation sources have energy outputs in the form of a rectangular waveguide openings, which are used as radiating antennas. Huygens-Kirchhoff method was used to calculate the temperature distribution on the foam concrete slab surface; the method of loaded long lines was used to calculate the temperature distribution over the foam concrete slab thickness. A method for measuring the foam concrete slab temperature distribution is proposed. The results of theoretical and experimental temperature distribution studies on the surface and the cross-section of foam concrete slab with a width of 1500 mm, a height of 1000 mm and a thickness of 200 mm, a density of 1000 kg/m3 on the electromagnetic fields oscillation frequency of 2450 MHz are shown. The obtained experimental results showed a high efficiency of using microwave radiation for the foam concrete slabs heat treatment technological processes. Microwave technologies can be used for heat treatment of products made of concrete, reinforced concrete and polymer composite materials.

Characterizing corrosion properties of carbon steel affected by high-power laser cleaning

A high-power CW laser equipment was used to irradiate bare carbon steel plates to evaluate the effects of laser surface cleaning on the corrosion properties of the base metal. Different laser processing parameters were adopted, representing lower to higher laser ablation effects. The surface oxide content was analyzed using XRD and SEM-EDX, the microstructure was observed under optical microscopy, and the corrosion properties of the specimens were evaluated using electrochemical tests. The results demonstrated that the CW laser-treated steel plates possessed better corrosion resistance than the unirradiated steel plates. Higher laser power density and interaction time result in denser iron oxide formed on the steel surface, which is the main reason for the improved corrosion resistance. Layers with modified microstructures are present in all laser-treated steel plates. The laser ablation effects and gradient microstructures can be well described by the theoretical peak temperature distribution. The laser surface cleaning technique for steel structures is thereby confirmed to have a positive impact on the corrosion properties of the base metal.

Analysis on light power and three-dimentional temperature distribution characteristics of gain guided and index alternate-guided fiber lasers

Gain guided and index alternate-guided (GGIA-G) fiber was suggested by our group recently. In this work, the improved rate equations of the GGIA-G fiber laser were established and solved. The pump and signal light power distribution along the fiber longitudinal axis were simulated under the conditions of forward, backward and bidirectional pump. Furthermore, a theoretical three-dimensional temperature distribution model of the GGIA-G fiber laser was established, and the temperature distribution characteristics along both the fiber longitudinal axis and radius were simulated and compared when the fiber was pumped with different methods. The research results show that different pump method has obvious influence on both signal light power distribution and the fiber temperature. When the fiber is forward pumped, the signal light power in the fiber is the highest, and when the fiber is bidirectionally pumped, the temperature of the fiber is the lowest. The research conclusions are helpful in the application of the GGIA-G fiber.

Temperature Distribution Study of Friction Stir Welded Aluminum Alloy 7075-T6 joints Reinforced with SiC Powders

Abstract Friction Stir Welding (FSW) is a unique process of joining two similar or dissimilar materials by generation of heat between two surfaces (tool shoulder and plate). The bonding made between two materials was achieved by a tool pin profile which makes the material to flow from the advancing side to retreating side. The main advantage of FSW is that during the welding process, the materials are joined with less heat and increased bond strength, due to reduced heat generation it results in better material properties when compared with other conventional welding processes. The experiments were conducted with SiC powders by varying the process parameters by keeping axial load as similar for all the trials. The tool used in the experiments is a high carbon steel D3, with a straight flat cylindrical pin. In the present work, we made an attempt to predict the theoretical temperature distribution for the joints made with FSW process using ANSYS. The temperature profiles were measured across different zones of welded sample for better understanding of temperature flow during the joining process. Metallurgical study was also carried outacross different zones and it is correlated with the theoretical temperature values for better understanding of process parameters and the effect / influence of adding SiC powders in material. From the results it is inferred that both temperature distribution and metallurgical study showed a good agreement due to its refined / coarse grain boundary development. The generation of higher temperature profile proves better mixing of SiC powders during the joining process. However, this work revealed that the process parameters and addition of SiC powders leads a major role in deciding the temperature profile across various zones of the FSW process.

Theoretical and Experimental Temperature Distribution along a Plate

Existing equations for the temperature distribution along a plate produced by a point heat source are analyzed. Experimental values are compared with theoretical results from a formula employed in the development of a thermoelectric element for borehole use. On that basis, the influence of the heat-transfer coefficient on the calculated temperature distribution is established. In order to ensure agreement between the distribution calculated by the proposed formula and the experimental distribution, the value of the heat-transfer must be corrected.

Interstitial photoacoustic technique and computational simulation for temperature distribution and tissue optical properties in interstitial laser photothermal interaction

Interstitial laser immunotherapy (ILIT) is designed to use photothermal and immunological interactions for treatment of metastatic cancers. The photothermal effect is crucial in inducing anti-tumor immune responses in the host. Tissue temperature and tissue optical properties are important factors in this process. In this study, a device combining interstitial photoacoustic (PA) technique and interstitial laser photothermal interaction is proposed. Together with computational simulation, this device was designed to determine temperature distributions and tissue optical properties during laser treatment. Experiments were performed using ex-vivo porcine liver tissue. Our results demonstrated that interstitial PA signal amplitude was linearly dependent on tissue temperature in the temperature ranges of 20–60[Formula: see text]C, as well as 65–80[Formula: see text]C, with a different slope, due to the change of tissue optical properties. Using the directly measured temperature in the tissue around the interstitial optical fiber diffusion tip for calibration, the theoretical temperature distribution predicted by the bioheat equation was used to extract optical properties of tissue. Finally, the three-dimensional temperature distribution was simulated to guide tumor destruction and immunological stimulation. Thus, this novel device and method could be used for monitoring and controlling ILIT for cancer treatment.

Flexible thermal rectifier based on macroscopic PDMS@graphite composite film with asymmetric cone-shape interfaces

Thermal rectifier is a device with the higher heat transport capacity in one direction than the backward one, being similar to the electrical diode working for the control of the electrical current. In this work, we report a new thermal rectifier based on the flexible macroscopic polydimethylsiloxane (PDMS) film with asymmetric cone-shape holes embedded with micrometer sized graphite powder (denoted as PDMS@graphite). The PDMS@graphite shows thermal rectification behavior with an extracted thermal rectification coefficient of 1.1326 ± 0.009 under 129.8 K temperature bias, and this value can be further modulated by changing the asymmetric ratio of the cone-shape interface in the PDMS@graphite film. Two underlying mechanisms are invited to explain the thermal rectification effect in the PDMS@graphite system. The one is the opposite temperature dependence of thermal conductivity for PDMS and graphite powder. The other one is the different temperature dependent thermal conductivity of the asymmetric cone-shape graphite in PDMS@graphite film in the forward and backward heating direction when applying the same temperature bias, which can be demonstrated in the COMOSL theoretical simulated temperature distributions for the PDMS@graphite. The as-fabricated flexible macroscopic PDMS@graphite composite film thermal rectifier may provide the potential applications in thermal control and management.

Simulation of heat transfer in intricately-configured polymer composite structures of instrumented container type

Method of mathematical simulation of heat transfer processes in polymer composite (PC) products with intricate configuration, being an alternative of using up-to-date commercial software complexes has been developed. On the example of PC container with instrumentation and fiberglass electric heaters located in it, a mathematical model describing unsteady temperature field (a system of nonlinear differential heat balance equations for each element) has been formulated. Features of heat transfer between elements (heaters, instrumentation, enclosing structures) were taken into account. The verification of the method was conducted by comparing of theoretical temperature distributions with results of measurements in experiments with simplified variant of the structure. The developed method is effective, in particular, for such PC products as containers, modules, bunkers and vessels. It allows us to specify optimum operation modes for heating elements, operational parameters for conditioners and funs, heat insulation characteristics for providing a given level of air temperature inside objects in winter and summer service periods.

Theoretical Temperature Distribution Investigation in Electrical Transformer by Using Nano-Technology

A proposed thermal model is examined for a distribution transformer. A 2d simulation by a transient analysis in light of the Finite Element Method (FEM) was done to obtain the temperature distribution in the three phase transformer (250 KVA 11/.416 KV core type, mineral oil) using "ANSYS PROGRAM". Meanwhile, the effects of type of oil on HOST are investigated using the proposed model. To test the effect of nanoparticles on heat transfer process, the insulation oil was changed with Nanofluid; it has been used two types of Nano particles (CuO and Al2O3) with 0.5% as a volume concentration, where themaximum temperature reduced about (5%).The core material also has been changed from silicon steel to amorphous steel and caused a reduction in maximum temperature about (9.9%) in HV winding and change the interior angles from 90o to 135o, where the temperature distribution transformer is improved. The present model successfully accomplished for expecting the temperature distribution at any locations in the transformer when compared with practical measurement.

Analytical Modeling and Experimental Validation of Heating at the Leaf Seal/Rotor Interface

The secondary air system of a modern gas or steam turbine is configured to satisfy a number of requirements, such as to purge cavities and maintain a sufficient flow of cooling air to key engine components, for a minimum penalty on engine cycle efficiency and specific fuel consumption. Advanced sealing technologies, such as brush seals and leaf seals, are designed to maintain pressures in cavities adjacent to rotating shafts. They offer significant reductions in secondary air parasitic leakage flows over the legacy sealing technology, the labyrinth seal. The leaf seal comprises a series of stacked sheet elements which are inclined relative to the radial direction, offering increased axial rigidity, reduced radial stiffness, and good leakage performance. Investigations into leaf seal mechanical and flow performance have been conducted by previous researchers. However, limited understanding of the thermal behavior of contacting leaf seals under sustained shaft contact has led to the development of an analytical model in this study, which can be used to predict the power split between the leaf and rotor from predicted temperature rises during operation. This enables the effects of seal and rotor thermal growth and, therefore, implications on seal endurance and rotor mechanical integrity to be quantified. Consideration is given to the heat transfer coefficient in the leaf pack. A dimensional analysis of the leaf seal problem using the method of extended dimensions is presented, yielding the expected form of the relationship between seal frictional power generation, leakage mass flow rate, and rotor temperature rise. An analytical model is derived which is in agreement. Using the derived leaf temperature distribution formula, the theoretical leaf tip temperature rise and temperature distributions are computed over a range of mass flow rates and frictional heat values. Experimental data were collected in high-speed tests of a leaf seal prototype using the Engine Seal Test Facility at Oxford University. These data were used to populate the analytical model and collapsed well to confirm the expected linear relationship. In this form, the thermal characteristic can be used with predictions of mass flow rate and frictional power generated to estimate the leaf tip and rotor temperature rise in engine operation.

H2O beams for zinc oxide film growth produced by a Pt-catalyzed H2–O2 reaction at various divergent aperture angles of a de Laval nozzle

High-energy H2O beams generated by a de Laval nozzle, meant for the growth of zinc oxide thin films through chemical vapor deposition, were assessed based on compressible flow theory at various divergent aperture angles. In this process, high temperature H2O was generated by a catalytic reaction between H2 and O2 on Pt nanoparticles and effused through the nozzle into the reaction zone. The theoretical beam temperature distributions, reduced scaling parameters and mean cluster sizes of the H2O beams generated at angles between 50 and 90° were evaluated. The reduced scaling parameters of the H2O beams for all angles were calculated to be less than 200 and the mean cluster sizes were estimated to be less than one irrespective of the divergent aperture angle of the nozzle, suggesting that clusters are not formed in the H2O beam in our apparatus. The crystallinity and electrical properties of the zinc oxide films grown using various divergent aperture angles were also evaluated.

Measurement of the Temperature of Sheet Materials in Microwave Traveling-Wave Structures

The results of theoretical and experimental investigations in the area of high performance microwave technologies for the heat treatment of sheet materials are presented. Two-dimensional periodic slow-wave systems are used as the heating elements of the microwave devices. The disagreement between the theoretical and experimental temperature distribution characteristics in the sheet material and the temperature deviation from the nominal value does not exceed 3% and 5%, respectively.

Study on temperature distribution of HSS in hot FLD test

In this paper, we study forming limit diagram (FLD) of high strength steel (HSS) under high temperature condition to simulate the hot stamping process. We investigate the sheet specimen temperature distribution in hot FLD test. First, we propose a simple model of heat transfer process in sheet specimen, in which the sheet specimen is separated into two sections due to different mechanism. In thermal radiation, the convection and thermal contact conductance are included in two partial differential equations (PDEs) to express the temperature distribution in these two sections (S1 and S2 sections). Second, hot FLD experiments (Nakazima test) are performed and temperature distributions of sheet specimen are investigated by thermal infrared imager. Furthermore, the experimental temperature distributions are compared with theoretical ones, and these two measurements make good agreement between each other. This conclusion validates the feasibility of proposed thermal model in hot stamping process. In addition, an uneven sheet temperature distribution is examined in expansion process experiment, we observe that the temperature of specimen increases from center to edge until it reaches the temperature of punch. The further theoretical analysis proves that this phenomenon is mainly caused by the punch through thermal contact conductance between punch and S1 section, which indicates that a hot punch is indispensable to sustain the temperature of the deforming sheet. Third, the theoretical temperature distribution on S1 section under different die height is calculated. The radiation heat flux of the sheet decreases as the die height is increasing, but the sheet temperature increment is small, which implies that the height of die affects the sheet temperature slightly.

The thermal structure of a protostellar envelope

A numerical hydrodynamical model for the evolution of spherically symmetric collapsing clouds, designed for the calculation of the thermal structure of these objects in both the prestellar and protostellar stages of their evolution, is presented. Distinctive features of the model include the possibility of independently describing the temperatures of the gas and dust, which is extremely important when calculating the thermal structure of prestellar and protostellar clouds, and the account of the radiation flux from the central protostar. This model is used to compare the theoretical density and temperature distributions with observations for nearby sites of star formation obtained with the Herschel Space Observatory. Application of the diffusion approximation with a flux limiter describes well the radial density and temperature distributions in protostellar clouds. However, significant differences between the model and observational density profiles were found for prestellar stages, suggesting the presence of appreciable deviations from equilibrium in the prestellar clouds. An approximate method for calculating the thermal structure of a cloud based on the adaptive τ-approximation is presented. Application of the τ-approximation yields good agreement with the diffusion approximation for the prestellar phase, but produces appreciable discrepancies for the protostellar phase, when the thermal structure of the accreting envelope is determined by the radiation of the protostar.

Analysis of the Aluminum Bars in Three-High Skew Rolling Mill Rolling Process

One of the modern methods of production of round bars is the process of rolling in three-high skew rolling mill. This method enables the production of bars with both standard materials as well as hard deformation materials. In this paper, the results of theoretical and laboratory research of the 20 mm aluminum A1050 round rods rolling in three-high skew rolling mill process are presented. The numerical analysis was carried out upon applying the Forge 2011® software package. Based on the theoretical research, the stress, strain and temperature distribution during the rolling process were determined. In order to verify the numerical results, rolling aluminum rods were explored in laboratory conditions.

X-RAY EMISSION LINE PROFILES FROM WIND CLUMP BOW SHOCKS IN MASSIVE STARS

The consequences of structured flows continue to be a pressing topic in relating spectral data to physical processes occurring in massive star winds. In a preceding paper, our group reported on hydrodynamic simulations of hypersonic flow past a rigid spherical clump to explore the structure of bow shocks that can form around wind clumps. Here we report on profiles of emission lines that arise from such bow shock morphologies. To compute emission line profiles, we adopt a two component flow structure of wind and clumps using two "beta" velocity laws. While individual bow shocks tend to generate double horned emission line profiles, a group of bow shocks can lead to line profiles with a range of shapes with blueshifted peak emission that depends on the degree of X-ray photoabsorption by the interclump wind medium, the number of clump structures in the flow, and the radial distribution of the clumps. Using the two beta law prescription, the theoretical emission measure and temperature distribution throughout the wind can be derived. The emission measure tends to be power law, and the temperature distribution broad in terms of wind velocity. Although restricted to the case of adiabatic cooling, our models highlight the influence of bow shock effects for hot plasma temperature and emission measure distributions in stellar winds and their impact on X-ray line profile shapes. Previous models have focused on geometrical considerations of the clumps and their distribution in the wind. Our results represent the first time that the temperature distribution of wind clump structures are explicitly and self-consistently accounted in modeling X-ray line profile shapes for massive stars.

Observing simulated galaxy clusters with phox: a novel X-ray photon simulator

We present a novel, virtual X-ray observatory designed to obtain synthetic observations from hydro-numerical simulations, named phox. In particular, we provide a description of the code constituting the photon simulator and of the new approach implemented. We apply phox to simulated galaxy clusters in order to demonstrate its capabilities. In fact, X-ray observations of clusters of galaxies continue to provide us with an increasingly detailed picture of their structure and of the underlying physical phenomena governing the gaseous component, which dominates their baryonic content. Therefore, it is fundamental to find the most direct and faithful way to compare such observational data with hydrodynamical simulations of cluster-like objects, which can currently include various complex physical processes. Here, we present and analyse synthetic Suzaku observations of two cluster-size haloes obtained by processing with phox the hydrodynamical simulation of the large-scale, filament-like region in which they reside. Taking advantage of the simulated data, we test the results inferred from the X-ray analysis of the mock observations against the underlying, known solution. Remarkably, we are able to recover the theoretical temperature distribution of the two haloes by means of the multi-temperature fitting of the synthetic spectra. Moreover, the shapes of the reconstructed distributions allow us to trace the different thermal structure that distinguishes the dynamical state of the two haloes.