Control Of Temperature Distribution Research Articles

Influence of the radiofrequency applicators arrangement on the sizes of ablative zones inside hepatic tumor

Radiofrequency (RF) ablation is a popular therapeutic technique for heating solid tumors that are medically unsuitable for resection or other treatments. Thermal ablation applicators create high-frequency electromagnetic fields (EMFs) within the tumor site, which causes heating, coagulation, and ultimately death of the cancer cells. The aim of this study is the numerical analysis of the temperature distributions, ablation zones, and specific absorption rates (SAR) during RF ablation in relation to an ellipsoidal shaped tumor placed in the model of liver tissue. The source of heat is a three-element system of RF needle applicators operating at a frequency 100 kHz, with a given electrode potential, inserted into the tumor. In order to obtain an appropriate temperature distribution in the target area, the Laplace equation coupled with the Pennes equation were solved using the finite element method (FEM). The arrangement effect of three needle-type applicators on the resultant thermal profiles and the volumes of ablation zones were analyzed and compared. In addition, the ablation zones for various angles of the RF applicator placed in the center of the tumor were analyzed. The paper shows that in order to control temperature distribution and ablation zones the proposed system of RF applicators and the arrangement of electrodes can be successfully applied in hepatocellular carcinoma treatment.

Effective battery pack cooling by controlling flow patterns with vertical and spiral fins

Battery Thermal Management System (BTMS) is essential for dissipating heat and controlling temperature distribution within the battery pack of an electric vehicle to maintain its optimal operating temperature. This research focuses on the influence of cooling fins in achieving balanced temperature distribution inside the battery pack. Vertical and spiral fins are attached around 21,700 cylindrical cells for this investigation. ANSYS FLUENTsoftwareis employed to conduct the numerical simulations, where a finite volume approach is used to solve the mass conservation, Navier–Stokes, and energy transport equations. The study also uses a set of polynomial functions to calculate the heat generation inside the cells. It assesses the effects of the Reynolds number, fin loop number, and outlet section of BTMS at numerous discharge rates. The findings indicate that the spiral fins significantly impact the thermal performance, reducing Tmax by 21.31 % due to the enhanced flow circulations within the BTMS. A high Reynolds number also positively affects Tmax by reducing the temperature uniformity caused by the shorter time for air-cooling contact with the cell surfaces. More specifically, at a Reynolds number ≥9433, a Z-type BTMS with the spiral fins can maintain the temperature uniformity at a temperature difference of 5 °C. Among the six different BTMSs analysed, a U-type BTMS is reported to have the best performance, reducing Tmax and ΔTmax by 4.11 % and 38.1 %, respectively. The pressure drop in this case is also reduced by 8.46 %, thus lowering the overall power consumption.

Multiple hot spot cooling with flow boiling of HFE-7000 in a multichannel pin fin heat sink

Electronics cooling applications require a high cooling performance due to increasing power consumption. Phase change heat transfer is a popular approach for offering high heat flux cooling. Controlling temperature distribution and mitigating boiling instabilities under high heat flux conditions present a significant challenge. While numerous studies investigated the effect of pin fins in a minichannel with single hotspots on boiling enhancement, few research studies are available for minichannels with multiple segmented hotspots. This study's primary objective is to dissipate high heat (1.4 kW) using flow boiling of a dielectric fluid, namely HFE-7000, which has lower thermophysical properties than water, to achieve a uniform temperature distribution, and to suppress boiling instabilities. The boiling performance of a pin fin multichannel heat sink with dimensions of 3 × 14 × 300 mm (H × W × L) subjected to 8 hotspots with uniform heating was investigated in this regard. Flow boiling experiments were performed over a wide range of input heat power from ∼0.1 to ∼1.4 kW with a coolant mass flux of 500 kg/m2 s in the three parallel minichannels having staggered elliptical pin fins with no tip clearance on each hotspot and distribution pins at the inlet. High-speed visualization was used to relate the heat transfer coefficient variations along the channel to flow patterns. The heat transfer performance and flow regimes at different locations were obtained and discussed. Thanks to the mixing effect of elliptical micro pin fins with optimum geometrical parameters along the heat sink, the presence of distribution pin fins at the inlet for suppressing boiling instabilities and early transition to stable annular flow, the temperature uniformity (∼2.3 °C, temperature difference between the inlet and outlet hotspots) could be achieved at the highest heat input. Heat transfer coefficient reduction upto 27 % was reported along the channel when comparing inlet (1st) and outlet (8th) hotspots.

Photothermal metasurface with polarization and wavelength multiplexing.

Controlling temperature distribution at the micro/nano-scale brings new applications in many fields such as physics, chemistry and biology. This paper proposes a photothermal metasurface that employs polarization and wavelength multiplexing to regulate various temperature distributions at the micro/nano-scale. Such a photothermal metasurface is numerically validated by the finite element method. Firstly, the inversion algorithm is used to calculate the thermal power density distribution, which is decided by a given temperature distribution. Then, based on the bottom-up design method, (a) the library of absorption cross sections of gold nanoparticles is established by resizing nanoparticles; (b) the single pixel is constructed for wavelength and polarization multiplexing; (c) the overall structure of a photothermal metasurface is optimized and established. Finally, four given temperature distributions, combining the multiplexing of two orthogonal polarizations and two wavelengths, are achieved in the same area. The simulation results well confirm the feasibility of photothermal multiplexing. Such photothermal metasurface provides solutions for flexible control of temperature distribution at the micro/nano-scale.

Splitting of temperature distributions due to dual-channel photon heat exchange in many-body systems

We investigate the radiative heat transfer and spatial distributions of stationary temperatures in periodic many-body systems composed of alternating slabs of two different materials. We show that temperature distributions exhibit an alternating spatial pattern and split into two distinct components, with each component corresponding to one of the two materials. Spatial temperature variations following the periodicity of the structure can be attributed to a dual-channel photon heat exchange through a long-range coupling of electromagnetic modes supported by bodies of the same material. We also analyze the thermal relaxation of the temperatures in the system to verify potential applications in dynamical situations. The results reveal that tunable nonmonotonic temperature variations can be also designed and utilized at a transient mode. The dual-channel mechanism to control temperature distributions proposed in the present work may pave new avenues for prospective applications in nano devices, especially for thermal photon-driven logic circuitry and thermal management.

Prediction and validation of melt pool dimensions and geometric distortions of additively manufactured AlSi10Mg

A finite element–based thermomechanical modeling approach is developed in this study to provide a prediction of the mesoscale melt pool behavior and part-scale properties for AlSi10Mg alloy. On the mesoscale, the widely adopted Goldak heat source model is used to predict melt pool formed by laser during powder bed fusion process. This requires the determination of certain parameters as they control temperature distribution and, hence, melt pool boundaries. A systematic parametric approach is proposed to determine parameters, i.e., absorption coefficient and transient temperature evolution. The simulation results are compared in terms of morphology of melt pool with the literature results. Considering the part-scale domain, there is increasing demand for predicting geometric distortions and analyzing underlying residual stresses, which are highly influenced by the mesh size and initial temperature setup. This study aims to propose a strategy for evaluating the correlation between the mesh size and the initial temperature to provide correct residual stresses when increasing the scale of the model for efficiency. The outcomes revealed that the predicted melt pool error produced by optimal Goldak function parameters is between 5 and 12%. On the part-scale, the finite element model is less sensitive to mesh size for distortion prediction, and layer-lumping can be used to increase the speed of simulation. The effect of large time increments and layer lumping can be compensated by appropriate initial temperature value for AlSi10Mg. The study aids practitioners and researchers to establish and validate design for additive manufacturing within the scope of desired part quality metrics.

Adaptive damper control for HVAC systems based on human occupancy and indoor parameters: A development study

Occupancy-based strategies for the control of ventilation systems in buildings are effective for achieving energy savings and user comfort. Savings in energy consumption of more than 50% can be achieved by controlling heat, ventilation, and air conditioning (HVAC) systems with accurate sensory and occupancy information. In this study, the flow through the damper of the variable area valve (VAV) system and the speed of the blower’s variable frequency drive (VFD) are controlled in the HVAC system, on the basis of human occupancy and indoor parameters, namely, temperature and humidity, segment-wise in the building. In the proposed model, the flapper angle of the VAV is estimated using the indoor temperature, external temperature, and number of occupants. The occupancy data are fed to the controller proposed to regulate the flow through the ducts of the system, which is based on the flapper angle of the VAV, in order to maintain human comfort. The proposed scheme makes it possible to detect abnormalities in energy utilization and to trace maximum utilization in the building based on occupancy, with the control parameters of the HVAC adjusted for a comfortable indoor environment. Performance evaluation of the VAV system with its proposed control strategy, temperature, and flow distribution is simulated using Fluent software. A laboratory grade prototype incorporating the proposed control strategy is then developed, tested under three different conditions, and the results are reported. The experimental results show that an energy saving of 18% can be achieved.

Numerical investigation on thermal performance of battery module with LCP‐AFC cooling system applied in electric vehicle

AbstractTo improve the thermal performance of electric vehicle batteries, a novel cooling system of liquid cold plates coupled with air flow channels (LCP‐AFC) for battery thermal management was proposed. Three‐dimensional models were established for simulation. The effects of five factors on the heat dissipation of the electric vehicle battery module were studied, which included the battery discharge rate, inlet temperature of cooling liquid, nanofluids, airflow velocity, liquid, and air flow directions. The results showed that the maximum temperature Tmax and temperature difference ΔT of the battery module under 1 C discharge rate could be reduced by 1.1°C and 0.92°C compared to the single liquid cooling. Comparing the LCP‐AFC with single air cooling, the Tmax and ΔT of the battery module under 4 C discharge rate could be reduced by 18.74°C and 2.71°C. The temperature uniformity of the battery module was not satisfied with the inlet temperature of the cooling liquid, which was lower than 15°C. The heat transfer performance was improved by adding Al, Cu, or Ag nanoparticles into the deionized water. Among them, Ag–water nanofluid had the most significant cooling effect. Parallel flow indicated better thermal performance than cross flow and counter flow. The developed cooling system of LCP‐AFC offers a new method to design lithium‐ion battery thermal management system for controlling temperature distribution of a battery module.

Exploring thermal state in mixed immersive virtual environments

Combining immersive virtual environment (IVE) with a controlled environment is a potential solution for analyzing human thermal experience during building design. Existing studies in this field have not adequately analyzed scenarios involving stabilized comfortable and uncomfortable temperature conditions using both thermal state votes and physiological responses, or the influence of the seasons. By combining IVE with a climate chamber, called mixed IVE (MIVE) in this study, experiments were conducted to test the hypothesis that participants' virtual experience did not significantly alter their thermal experience compared to their in-situ experience. Response variables were the control temperature distribution, the thermal state vote (at temperature steps 18.3 °C, 23.8 °C, and 29.4 °C), and physiological responses (heart rate and skin temperature). The results show that the first two response variables were not significantly different between the MIVE and in-situ settings (except for one case). Due to the heat development of the head mounted display device, the mean forehead skin temperature in the MIVE experiments was significantly higher than that in the in-situ experiments in most cases. However, such difference in skin temperature did not seem to affect general thermal state votes. In addition, significant skin temperature differences at some locations were also observed between the MIVE and in-situ settings.

Numerical Analysis to Predict Temperature Distribution of Passion Fruit Seeds During Drying

HighlightsA temperature distribution occurred due to temperature differences between the surface and inside passion fruit seeds.The temperature distribution occurred simultaneously in all directions.The temperature distribution decreased at greater depths inside the seeds.The same temperature distribution pattern occurred in the vertical and horizontal directions.Abstract. Optimization of the drying process can be determined based on temperature distribution patterns using numerical analysis with the finite element method (FEM). This study compiled a numerical analysis using FEM to predict the temperature distribution in passion fruit seeds during drying. The study was conducted using a circulating-air tray dryer. Temperature distribution data on passion fruit seeds were measured using a data logger. The results showed that numerical analysis using FEM quickly and accurately simulated the temperature distribution in passion fruit seeds during drying. The model was validated by comparing the temperature distribution data measured in the drying chamber with the simulation results, with a relative error of 0.45% to 1.27%. Numerical analysis using FEM provides an useful reference for controlling temperature distribution during drying because this method is easy to implement and results in low errors. Keywords: Drying, Finite element methods, Numerical analysis, Passion fruit seeds, Temperature distribution.

Cooling Performance Analysis of the Lab-Scale Hybrid Oyster Refrigeration System

Compared with the waste-to-heat and electricity-based hybrid refrigeration system, the innovative lab-scale refrigeration system integrated with the DC and AC cooling units that able to use solar and electricity as energy resources. Previous studies found that temperature control and uniform temperature distribution in refrigeration systems are both critical factors reducing vibrio growth on raw oysters and saving energy consumption. Therefore, this refrigeration system also equipped a specially designed divider and was used to test various air circulation strategies to achieve uniform temperature distribution in six individual compartments. The objective is to investigate and evaluate the effects of air circulation strategies and operating conditions on the cooling performance, including temperature distribution, standard deviation of compartment temperatures, and cooling time using a factorial design method. Results indicated the maximum temperature difference between the compartments was 8.9 ± 2.0 °C, 6.7 ± 2.0 °C, and 4.8 ± 2.0 °C in the scenarios of no air circulation, natural air circulation, and combined natural and forced air circulation, respectively. The interaction of fan location and fan direction showed a significant effect on the compartment temperatures while there was no significant effect on cooling time. A circulation fan on the lower part of the 12-volt section with an air supply from the 12- to 110-volt section was determined as the optimal condition to achieve relatively uniform temperature distribution. Refrigeration system also achieved a cooling temperature of 7.2 °C within 150 min to meet regulations. To that end, the innovative hybrid oyster refrigeration system will benefit oyster industries, as well as the aquaculture farmers in terms of complying with regulations and energy savings.

Laboratory investigation on the influence of factors on the outflow temperature from stratified reservoir regulated by temperature control curtain.

A temperature control curtain can effectively mitigate the negative effect of outflow temperature on the river eco-environment downstream. To investigate the response of outflow temperature to influence factors (i.e., installation position of temperature control curtain, submerged depth, temperature distribution, and outflow discharge), experiments were conducted in a nonlinearly stratified fluid. The important degree of influence factors was determined by entropy weight method. The results indicated that the effect extent of influence factors on the outflow temperature was temperature distribution, submerged depth, outflow discharge, and installation position in turn. The installation position had little effect on the outflow temperature. Increasing the outflow discharge could withdraw more warm water near the surface and increase the outflow temperature. The outflow temperature also rose with decreasing submerged depth, and more warm water above the temperature control curtain level tended to be extracted when the submerged depth was enough. Although the outflow temperature increased, its variation amplitude depended on the temperature gradient of temperature distribution and was not affected by the structural form of selective withdrawal. From the point of operation management, the minimum submerged depth was determined using sensitivity analysis to obtain maximum improvement of outflow temperature.

Numerical investigation on a lithium ion battery thermal management utilizing a serpentine-channel liquid cooling plate exchanger

The thermal management for a lithium ion battery cell plays a pivotal role in enhancing the cell performance and reliability for electric vehicles. In this work, a novel serpentine-channel liquid cooling plate with double inlets and outlets is developed for better managing an undesirable temperature distribution of a cell module. With a simplified model for the cell module, numerical analyses are implemented using the software of FloEFD to study effects of flow directions, flow rates and channel widths of the cooling plate on cell temperature distribution under different operating conditions; Likewise, a ratio of power consumption as a non-dimensional number is defined to analyze the hydraulic performance of the developed cooling plate. Results show that locations of the inlet and the outlet as well as flow directions have great impacts on the cell temperature distribution and the ratio of power consumption of the cooling plate. Increasing fluid flow rate substantially decreases the maximum temperature rise of the cell module while it has little effect on the temperature distribution. Moreover, the channel width of the cooling plate has a strong influence on its ratio of power consumption as well as the cell temperature distribution but it has a weak influence on the cell maximum temperature rise. Interestingly, the developed serpentine-channel cooling plate offers one a new method to design a lithium ion battery thermal management system for controlling temperature distribution of a cell module.

Near-infrared laser irradiation of a multilayer agar-gel tissue phantom to induce thermal effect of traditional moxibustion

Traditional moxibustion therapy can stimulate heat and blood-vessel expansion and advance blood circulation. In the present study, a novel noncontact-type thermal therapeutic system was developed using a near-infrared laser diode. The device allows direct interaction of infrared laser light with the skin, thereby facilitating a controlled temperature distribution on the skin and the deep tissues below the skin. While using a tissue-mimicking phantom as a substitute for real skin, the most important optical and thermal parameters are the absorption/attenuation coefficient, thermal conductivity, and specific heat. We found that these parameters can be manipulated by varying the agar-gel concentration. Hence, a multilayer tissue-mimicking phantom was fabricated using different agar-gel concentrations. Thermal imaging and thermocouples were used to measure the temperature distribution inside the phantom during laser irradiation. The temperature increased with the increase in the agar-gel concentration and reached a maximum value under the tissue phantom surface. To induce a similar thermal effect of moxibustion therapy, controlled laser-irradiation parameters such as output power, wavelength and pulse width were obtained from further analysis of the temperature distribution. From the known optothermal properties of the patient’s skin, the temperature distribution inside the tissue was manipulated by optimizing the laser parameters. This study can contribute to patient-specific thermal therapy in clinics.

Analysis of cooling media effects on microstructure and mechanical properties during FSW/UFSW of AA 6082-T6

The aim of the present study is to investigate the effect of cooling media on the temperature distribution, microstructure and mechanical properties of the joint produced during Underwater Friction Stir Welding (UFSW) in normal water, cold water (water with crushed ice (CFSW)) and air (FSW), for aluminum alloy (AA) 6082-T6. The results showed that peak temperature during UFSW and CFSW were significantly lower than the FSW. The temperature at the advancing side (AS) of the joint was higher than the retreating side (RS). Substantial reduction in TMAZ/HAZ width was observed during UFSW and CFSW as compared to FSW. Al-Mn-Fe-Si intermetallic phases were seen in all the joints along with the BM. The main strengthening precipitates found in UFSW and CFSW was β″ (Mg5Si6) which changed to β (Mg2Si) precipitates during FSW due to increased temperature. The tensile strength of the joints was best during UFSW followed by FSW and CFSW. The controlled temperature distribution resulted in improved tensile strength whereas both undercooling and overcooling resulted in decreased tensile strength, however, increased cooling rate does not improve the elongation. A typical ‘W’ shape hardness profile was observed in all the joints irrespective of the cooling media used. Maximum hardness was obtained in the UFSW joint due to refined grain structure, high-density dislocations and presence of β″ phases.

Coupled Electro-Thermo-Mechanical Simulation for Multiple Pellet Fabrication Using Spark Plasma Sintering

A coordinated experimental and computational analysis was undertaken to investigate the temperature field, heat generation, and stress distribution within a spark plasma sintering (SPS) tooling-specimen system during single- and multipellet fabrication of uranium dioxide (UO2) fuel pellets. Different SPS tool assembly configurations consisting of spacers, punches, pellets, and a die with single or multiple cavities were analyzed using ANSYS finite element (FE) software with coupled electro-thermo-mechanical modeling approach. For single-pellet manufacture, the importance of the die dimensions in relation to punch length and their influence on temperature distribution in the pellet were analyzed. The analysis was then extended to propose methods for reducing the overall power consumption of the SPS fabrication process by optimizing the dimensions and configurations of tooling for simultaneous sintering of multiple pellets in each processing cycle. For double-pellet manufacture, the effect of the center punch length (that separates the two pellets) on the temperature distribution in the pellets was investigated. Finally, for the multiple pellet fabrication, the optimum spacing between the pellets as well as the distance between the die cavities and the outer surface of the die wall were determined. A good agreement between the experimental data on the die surface temperature and FE model results was obtained. The current analysis may be utilized for further optimization of advanced tooling concepts to control temperature distribution and obtain uniform microstructure in fuel pellets in large-scale manufacturing using SPS process.

Development of a novel strategy of CFD-based model predictive control

With increasing energy consumption, growing attentions are given to reduce the carbon footprint in the world. The building sector is always one of the largest energy end user in many developed countries. Energy management of heating, ventilating and air-conditioning (HVAC) system is a key issue in building energy analysis, since the energy cost of HVAC system is the highest among those of all other building services installation and electrical appliances. The air-conditioned environment is an essential component for a HVAC system and the rationality of airflow pattern has significant influence on the energy use of air-conditioning. Therefore, it appeals to control temperature and air velocity distributions in an air-conditioned environment to achieve the optimized thermal comfort with the minimized energy consumption. In the present work, a novel model is developed by integrating a simplified Computational Fluid Dynamics (CFD) model into the model predictive control (MPC) algorithm for a CFD-based MPC (CFDbMPC) system. Firstly, based on the two dimensional Navier-Stokes equations, a CFD model is simplified for simulation of the air-conditioned indoor environment, in order to significantly reduce computational cost with desired numerical accuracy. The simplified CFD model is then integrated into the MPC algorithm with assistance of the successive linearization method. Finally, the preliminary case studies are conducted by the proposed CFDbMPC system.

Shape Design of Unsteady Forced Heat-convection Fields to Control Temperature Distribution History

Shape Design of Unsteady Forced Heat-convection Fields to Control Temperature Distribution History

Electrically heated 3D-macro cellular SiC structures for ignition and combustion application

The paper describes different aspects of porous combustion reactor operation especially at cold start conditions. Under cold start conditions it is necessary to increase the internal energy of the combustion reactor, to accumulate enough energy inside its solid phase and to reach at least the ignition temperature on the reactors inner surface. The most practicable method to preheat a cold porous reactor is to use its surface as a flame holder and to apply free flame combustion as a heat source for the preheating process. This paper presents a new electrically heated ignition element, which gets integrated in a three dimensional macro-cellular SiSiC reactor structure. For the development of the ignition element it was assumed, that the element is made of the same material as the combustion reactor itself and is fully integrated within the three-dimensional macro-cellular structure of the combustion reactor. Additive manufacturing like three-dimensional (3D) printing permits the production of regular SiSiC structures with constant strut thickness and a defined current flow path. To get a controlled temperature distribution on the ignition element it is necessary to control the current density distribution in the three-dimensional macro-cellular reactor structure. The ignition element used is designed to be an electrical resistance in an electric current system, converting flowing current into heat with the goal to get the highest temperature in the ignition region (glow plug). First experiments show that the ignition element integrated in a combustion reactor exhibits high dynamics and can be heated to the temperatures much above 1000°C in a very short time (approx. 800ms) for current of I=150A.

Focus on materials, semiconductors, vacuum, and cryogenics

Focus on materials, semiconductors, vacuum, and cryogenics