Heating Patterns Research Articles

Optothermal shaping of lamb waves with square and spiral phase fronts

We introduce a Lamb-wave medium with tunable propagation velocities, which are controlled by a two-dimensional heating pattern produced by a laser beam. We utilized it to demonstrate that waves in an appropriately designed medium can propagate in the form of concentric squares, in contrast to the circular patterns typically emitted by a point source in a homogeneous two-dimensional medium. In order to avoid the concentration of wave energy in the middle of the sides of the squares, we propose two alternatives: a square wave that either rotates or exponentially decelerates as it expands. Additionally, we present how circular waves can be transformed into spiral waves utilizing the same tunable medium. The described experimental platform offers a new tool to generate shaped pulses for ultrasonic applications, which has the potential to improve the efficiency of energy and information transport.

Multiphysics modelling of constant power microwave heating of model juice

Constant power microwave heating (CPMH) based on solid-state generators, a new microwave heating system, shows better repeatability than traditional microwave heating (TMH) powered by magnetron when performing experiments, while its detailed heating patterns and field distribution are still not fully understood. In this study, numerical simulations for model juice (about 1–5 mL) heated by CPMH and TMH systems were carried out to compare the heating performance. The simulation was performed through coupling electromagnetic, thermal and fluid fields, using a laminar flow model to simulate the flow behaviour of the model juice during the heating operation. Both surface temperature distributions and inner point temperatures were investigated for model validation, and the simulated data agreed well with the experimental ones, indicating that the modelling was rational and correct. Results showed that CPMH gave higher heating efficiency and better temperature uniformity, which was verified by determining both inner point temperature and surface temperature distribution. Besides, influences of sample volume and microwave input power on the heating performance of the CPMH system were studied, suggesting that greater sample volume could cause worse temperature uniformity, although a faster temperature increase was observed. When fixing total microwave input energy to 3 kJ, different input powers were found to achieve similar final average volumetric temperatures (50.46 °C–51.22 °C) but significantly different heating uniformity (final coefficient of temperature variance: 0.065–0.115), indicating that smaller microwave input power could contribute to better heating uniformity. It is hoped that this study could provide references to further understand the heating effects of CPMH systems, leading to better design and upgrade for microwave heating systems.

Simulation study to select optimal solid oxide fuel cells heat-up pattern from single, dual co-flow, and dual counter-flow alternatives

ABSTRACT To facilitate power generation, it is necessary to subject solid oxide fuel cells (SOFCs) to a heating process. The introduction of hot gases into the gas flow channels of fuel cells is a widely employed technique for heating purposes. Hot gases can be introduced into one channel (single-channel heating) or two channels (dual-channel heating). Dual-channel heating can have co- and counter-flow patterns. Despite the existence of several heating patterns in the literature, a comparative analysis of these patterns has not been conducted. This study uses a numerical approach to compare various heating patterns, focusing on the objectives of heat-up time, temperature gradient, and energy consumption. The findings indicate that the co-flow pattern demonstrates superior performance in terms of temperature gradient and heat-up time. However, the counter-flow pattern is more favorable in terms of energy consumption. Upon considering all the objectives concurrently through a multi-objective planning approach, the co-flow pattern, characterized by a temperature increase rate of 1 K s−1 and a gas velocity of 10 m s−1, emerges as the most optimal heat-up plan. This particular plan results in a heat-up time of 685 s, a temperature gradient of 337 K cm−1, and an energy consumption of 3856 J.

Spatio-temporal changes of heat and cold waves patterns in western Iran

Spatio-temporal changes of heat and cold waves patterns in western Iran

Influence of thermophysical and acoustic properties on temperature elevation at muscle/bone interface induced by ultrasound hyperthermia

Therapeutic ultrasound heating is a very common technique in the treatment of muscular and joints injuries. However, insufficient or excessive heating delivered to living tissues can be either innocuous or hazardous to the patient. The present work deals with the heat transfer process in living tissues, with particular concern on the behavior at the muscle-bone interface, when ultrasound irradiation is applied. Based on the Generalized Integral Transform Technique (GITT), a hybrid numerical-analytical solution of the Pennes’ equation using the open-source UNIT code (“UNified Integral Transforms”) is proposed, considering different boundary conditions. The influence of physical properties and parameters, such as beam incidence angle, acoustic attenuation coefficients for refracted longitudinal and shear waves in the bone, and blood perfusion in the muscle, were more closely analyzed. Numerical results of temperature profiles showing variations of up to 2 °C for different situations are presented, illustrating a marked dependence of heating patterns on the perfusion rates as well as on the effect of shear waves. The conclusions are that such type of more detailed analysis is essential for the accurate identification of physical properties in living tissues and phantoms and can contribute to the treatment planning for therapeutic ultrasound.

A Colourful Way to Unravel the Important Fluidization-Related Granule Size Effect on Semi-Continuous Drying.

Continuous twin screw wet granulation (TSWG) systems are possible pathways for oral solid dosage manufacturing in the pharmaceutical industry. TSWG requires a drying step after granulation before the tableting process. Typically, semi-continuous fluidized bed dryers (FBDs) are used for this purpose. At the same time, the pharmaceutical sector is interested in mathematical prediction models to save resources during the early drug product development (DPD) stage or to control manufacturing. Several authors have already developed prediction models for semi-continuous drying processes. However, these model structures reported systematic prediction offsets, which could be related to the incomplete implementation of fluidization and granule segregation phenomena. This study evaluates the complex fluidization behavior of wet granules in industrially relevant semi-continuous FBDs. A transparent perspex version of the dryer was used for the analysis of bed height, pressure drop, porosity, segregation, and spatial heating patterns at varying process settings. The investigated behaviors of the fluidizing bed will be helpful to derive phenomenological (sub)models for the detailed description of segregation in the semi-continuous fluidized bed system. In this study, it was found that semi-continuous FBDs are characterized by a change in fluidization regime from plug flow to a bubbling bed at the moment that the granule bed slumps. Secondly, the presence of size-based vertical segregation phenomena as well as spatial temperature differences were proven. The experimental results suggest that larger granules are dried under more intense drying conditions than smaller granules.

Comparison of Thermal Behaviors of Carbon and Stainless Steel Billets during the Heating Process.

The effect of thermal properties on the thermal behavior of a steel billet was investigated during the heating process to understand each effect and to provide process engineers with sufficient data to choose the optimal design conditions in reheating the furnace for hot rolling. Carbon steel and austenitic stainless steel (STS) were compared based on numerical simulations owing to the completely different thermal properties of these two steels: carbon steel having a phase transformation with a relatively high thermal conductivity and STS having no phase transformation with a relatively low thermal conductivity. The thermal conductivity affected the thermal behavior of the billet in the initial stage of heating owing to the high temperature difference between the surface of the billet and the gas in the furnace, i.e., the high Biot number. Accordingly, a non-firing zone and/or a preheating zone with a low gas temperature are necessary for high-alloyed steels including STS because the thermal conductivity of these steels is relatively low. The phase transformation of the carbon steels needs to occur in the primary heating zone, and this zone needs to have a relatively low gas temperature to reduce the temperature deviation or thermal stress in the billet. The heating pattern of the carbon steels and STSs in the reheating furnace should be designed differently considering the thermal conductivity and latent heat by the phase transformation of steels to obtain a high heating quality for the billet.

Development and validation of engineering charts: Heating time and optimal salt content prediction for microwave assisted thermal sterilization

Through decades of research and development efforts, Microwave Assisted Thermal Sterilization (MATS) systems started commercial operation for production of shelf-stable meals in 2019. It is now highly desirable to develop user-friendly tools to facilitate the development of commercial MATS processes. The aim of this research was to develop engineering charts by applying Maxwell's and heat transfer equations to illustrate the relationships among dielectric properties, temperature, salt content, product thickness and heating rate for microwave heating in a MATS system. Three G-T (Gezahegn-Tang) charts were developed for mashed potato, peas, and rice products with MATLAB software. The charts can be used to determine the heating temperature, time and optimum salt content for a maximum heating rate at the center of a product. Experimental validation tests using mashed potato samples confirmed that the temperature profiles measured at the cold spots of the samples in the microwave heating section of the MATS system were positively correlated with predicted temperatures from the chart (R2 = 0.94–0.99). Furthermore, the predicted optimal salt contents for 23 mm thick mashed potato (0.1%), 18 mm thick pea (0.5%) and 25 mm thick rice (1%) samples agreed with the experimental heating pattern test results. The optimal salt content is inversely proportional with a product temperature and thickness, which increases the microwave power decay before reaching the center. With the help of these charts, the food industry practitioners can save significant time and resources during the development of food products and schedules for the MATS processes.

Automated marker-free longitudinal infrared breast image registration by GA-PSO

The automated marker-free longitudinal Infrared (IR) breast image registration overcomes several challenges like no anatomic fiducial markers on the body surface, blurry boundaries, heat pattern variation by environmental and physiological factors, nonrigid deformation, etc, has the ability of quantitative pixel-wise analysis with the heat energy and patterns change in a time course study. To achieve the goal, scale-invariant feature transform, Harris corner, and Hessian matrix were employed to generate the feature points as anatomic fiducial markers, and hybrid genetic algorithm and particle swarm optimization minimizing the matching errors was used to find the appropriate corresponding pairs between the 1st IR image and the nth IR image. Moreover, the mechanism of the IR spectrogram hardware system has a high level of reproducibility. The performance of the proposed longitudinal image registration system was evaluated by the simulated experiments and the clinical trial. In the simulated experiments, the mean difference of our system is 1.64 mm, which increases 57.58% accuracy than manual determination and makes a 17.4% improvement than the previous study. In the clinical trial, 80 patients were captured several times of IR breast images during chemotherapy. Most of them were well aligned in the spatiotemporal domain. In the few cases with evident heat pattern dissipation and spatial deviation, it still provided a reliable comparison of vascular variation. Therefore, the proposed system is accurate and robust, which could be considered as a reliable tool for longitudinal approaches to breast cancer diagnosis.

Unlocking geothermal energy for sustainable greenhouse farming in arid regions: a remote-sensed assessment in Egypt’s New Delta

This study introduces a novel approach for assessing geothermal potential in arid regions, specifically Egypt’s New Delta Agriculture Mega Project area. The challenge of limited sub-soil temperature profile data was addressed by integrating Global Land Data Assimilation System (GLDAS) weather data. Using the Earth-to-Air Heat Exchanger (EAHE) model, the extracted air and sub-soil temperature profiles the potential for geothermal energy production was estimated. We modeled the annual sinusoidal soil surface periodic heating pattern by utilizing GLDAS ambient air temperature (AAT) and land surface temperature (LST). Using either AAT or LST yielded a Root-Mean-Square Error (RSME) of 0.2°C. The generated sub-soil profiles for the New Delta region showed a temperature variation of no more than 1.5°C at a 4-m depth, making it an optimal depth for EAHE installation. One-pipe EAHE demonstrated a cooling/heating capacity ranging from 400 W (cooling) to −300 W (heating). The study highlights the New Delta region’s strong geothermal potential for greenhouse cooling and heating, underlining its suitability as a sustainable energy source in arid areas. It also offers a practical guide for the EAHE application and it emphasizes the global potential for geothermal energy exploration, using innovative GLDAS data to expand sub-soil temperature profile accessibility.

Effect of Latent Heat by Phase Transformation on the Thermal Behavior of Steel Billet during Heating.

The effect of latent heat via phase transformation on the thermal behavior of a billet was investigated during the heating process. The latent heat of the billet strongly affected the temperature distribution of the billet during heating, although the heating rate of the billet was not high during the process. The temperature profile of the center region of the steel billet with latent heat had a strong flat shape compared with the other regions, as the heat supply to the center region was limited during the heating process owing to the finite thermal conductivity and mass effect of the billet. The latent heat by phase transformation typically occurred in the middle stage of heating, and the latent heat increased the temperature deviation of the billet during heating owing to the delay in the temperature rise at the center region of the billet. During the phase transformation of carbon steels during heating, the gas temperature needs to be low to reduce the temperature deviation or thermal stress of the billet. Industrial hot rolling mills are required to consider the latent heat by phase transformation of the billet to properly design the heating pattern for the billet. The heating pattern in the reheating furnace should be varied with the materials to obtain a high heating quality for the billet.

Influence of pore structure on steam disinfection heat and mass transfer in Yunnan red loam

The obstacles to the continuous cropping of Chinese herbs in Yunnan have become increasingly prominent. Many soil-borne diseases can infect the roots of crops, affect the growth of crops, and eventually lead to quality and yield reduction. Soil steam disinfection can still be used as one of the first methods to solve the problem of continuous cropping obstacles of Chinese herbs such as Panax notoginseng. However, the steam will condense into a large amount of liquid water when it is cold, which will cause soil pore blockage and seriously affect the steam diffusion efficiency. Therefore, it is necessary to study the influence mechanism of the pore structure of Yunnan red loam on heat and mass transfer of steam disinfection. The experimental research was conducted on steam disinfection's heat and mass transfer patterns under different soil pore structure conditions. Image processing technology was used to collect accurate soil profiles and to establish real soil pore structure analysis. Then, fluid simulation technology was used to simulate the heat and mass transfer process and trend of steam distribution within the soil profile under different soil pore structures. The results showed that the steam heat flow of <2 mm, 2–4 mm and 4–6 mm treatments were uniformly diffused in the form of matrix flow in a 1/4 ellipse, and the effective disinfection range was 18 cm horizontal distance and 20 cm vertical distance, in which the highest temperature could reach more than 90 °C. The steam heat flow of the 6–8 mm and >8 mm treatment groups diffused irregularly in large pore steam flow. Therefore, some devices for breaking soil and rotary tillage need to finely rotate the soil in the future. The end effector's disinfection pipe spacing can refer to the effective disinfection range.

Comparison of indoor thermal environments and human thermal responses in Northern and Southern China during winter

Human thermal adaptability has a significant impact on energy savings and emission reduction in buildings. To investigate the effect of long-term thermal history on thermal adaptability, this study explored the characteristics of indoor thermal environments and the differences in human thermal responses during winter in northern and southern China. Furthermore, the effects of the region (heating patterns), building types and payment patterns on the thermal responses were clarified. Finally, the thermal neutral temperatures and 80 % thermal acceptable ranges were determined. The results indicate that there are significant differences in the indoor thermal environments and human thermal responses in different types of buildings during winter (P < 0.00). However, the effect size of the thermal responses (d ≥ 0.3) is lower than that of the environmental parameters (d ≥ 0.7). This demonstrates that individuals have strong thermal adaptability. Due to the higher indoor air temperature of district heating in northern China, the northerners have a higher thermal neutral temperature and lower clothing insulation. They are stricter in the requirements for room temperature and weaker in thermal adaptability. Nevertheless, the southerners can actively adapt to lower indoor temperatures by clothing adjustments, with a wider acceptable range of indoor temperatures and lower thermal neutral temperatures. Charging for the actual heating usage can lower the thermal neutral temperature and boost the thermal satisfaction rate, which is conducive to saving energy and reducing emissions. Thus, these findings can contribute to the promotion of the comfortable and sustainable development of built environments.

Uncovering the hidden structure: A study on the feasibility of induction thermography for fiber orientation analysis in CFRP composites using 2D-FFT

The induction heating process elicits a heating response in a carbon fiber reinforced polymer (CFRP) composite distinctly different from those in metal. Prior work in our lab and elsewhere has established that the intensity and spatial distribution of the heating patterns are governed by the fiber orientations in each layer and the degree of electrical contact between layers. Based on more extensive work on this non-conventional heating behavior, we show that the analysis of induction heating patterns enables the characterization of the fiber orientations and stacking order within the material. In the first step, 2D Fast Fourier Transform (2D-FFT) is used to extract the fiber orientations from the spatial characteristics of the heating pattern recorded with an infrared camera. In the next step, the extracted fiber orientation is used to design bandpass filters to carry out the inverse 2D-FFT and obtain the layer stacking order. Our findings demonstrate that this approach can accurately identify the layer orientations (maximum error of 6o) and the stacking sequence in quasi-isotropic CFRP laminates with up to 12 layers. We believe that the proposed approach has the potential as a valuable nondestructive, non-contact tool for large-area inspection and quality control in manufacturing fiber-reinforced composites.

Party Wall Behaviour and Impact in QUB and Coheating Tests

In situ measurement can enable accurate evaluation of a building’s as-built performance. However, when measuring whole house performance, party walls introduce measurement uncertainty. Subsequently, it is common to “adjust” measurements to isolate heat transfer through party walls. This study explores the behaviour and impact of party walls in QUB and coheating measurements of a semi-detached house, presenting empirical evidence on the validity of these measurements where a party wall is present. Two different party wall heat transfer behaviours were observed through heat flux density measurements. Thermal charging is apparent in QUB tests and the initial stages of coheating. After 48 h of coheating, the party wall has become heat saturated and exhibits stable heat transfer. Consequently, using heat flux density measurements to isolate party wall heat transfer in QUB tests, where thermal saturation has not been achieved, can result in misleading inferences. The coheating and QUB measurements without party wall adjustment are in close agreement, irrespective of differing heating patterns in the neighbouring property. The generalisation of these findings is problematic since they describe the impact of the case study-specific built form and the test conditions. Future work to explore the impact of built form and test conditions is needed.

Microwave heating based on solid-state generators: New insights into heating pattern, uniformity, and energy absorption in foods

Microwave heating based on solid-state generators: New insights into heating pattern, uniformity, and energy absorption in foods

Utility of heating pattern with variable air temperature in drying; effects on drying time, energy consumption, and product quality.

Drying with variable air temperature is a technique to decrease the drying time, preserve quality and maintain the nutritional components of products. The aim of this study was to find the effect of different heating patterns with variable air temperatures on the drying time, energy consumption and the quality of garlic as well as investigate the critical times to change the air temperature. The constant air temperatures were 50, 60, and 70 °C, and the variable air temperature included three patterns of 60 °C → 50 °C (I), 70 °C→50 °C (II), and 70 °C (30 minutes) →50 °C (III). Despite preventing garlic slices' color changes in the constant air temperature of 50 °C, the antioxidant contents of the samples reduced significantly (45%), and the drying time was 136 minutes. At the air temperature of 70 °C, the color changes peaked, and the drying time was 65 minutes. The best drying condition was observed among the variable air temperature by pattern III. The drying time and loss of antioxidants were 24% and 45% lower than the one in the constant air temperature of 50 °C; besides, the effective moisture diffusivity was 24% higher. The color changes of these samples were lower compared to other patterns and the final product had acceptable quality and was produced in an optimal time.

Indocyanine Green-Loaded Halloysite Nanotubes as Photothermal Agents.

Photothermal nanoparticles with light-to-heat conversion properties have gained interest in recent years and have been used in a variety of applications. Herein, indocyanine green (ICG), which is commonly employed as a photothermal agent suffering from low photostability, was loaded into halloysite nanotubes (HNTs) resulting in photothermal HNT-ICG nanohybrids. The photothermal heating patterns of the prepared photothermal nanohybrids as a result of near-infrared (NIR) irradiation were carefully examined. The nanohybrids reached a temperature of 216 °C in 2 min under NIR light, and in contrast to free NIR, the ICG loaded into HNTs remained stable over 10 heating and cooling cycles. Moreover, HNT-ICG nanohybrids incorporated into polyacrylonitrile (PAN) were electrospun into nanofibers for use as photothermal nanofibers, and composite nanofibers, which heat up to 79.3 °C under 2 min of NIR irradiation, were obtained. To demonstrate the potential of the PAN/HNT-ICG nanofibers as light-activated antibacterial nanofibers, their NIR light-activated killing activity on Staphylococcus aureus (S. aureus) cells has been explored. The composite nanofibers reduced the number of bacteria on their surface by 7log upon 10 min of NIR irradiation. Encapsulation of ICG in HNTs as a carrier has been demonstrated as an effective way to stabilize ICG and incorporate it into materials and coatings without compromising its functionality.

3-D scanned oven geometry improves the modeling accuracy of the solid-state microwave heating process

Solid-state-based microwave ovens are promising to mitigate the non-uniformity issue for their precise controlled microwave parameters. Multiphysics modeling is a useful tool for understanding complicated microwave heating processes. However, previous models using simple or manually measured oven geometry had challenges in accurately predicting the heating patterns. This study developed a 3-D scanning approach to characterize the accurate geometric details of the cavity and incorporate it in the multiphysics modeling of solid-state microwave heating. The effect of oven geometric details on modeling accuracy was evaluated for models using the simple box, manually measured, and 3-D scanned geometries at multiple microwave frequencies and port locations. A quantitative approach was also developed to replace the previously often-used qualitative approach to compare the spatial temperature profiles between the simulation and experiments. The Multiphysics-based models using 3-D scanned geometry showed significantly or considerably smaller RMSE values (1.57 to 4.11 °C) than the models with simple box geometry (1.73 to 6.33 °C) and manually measured geometry (1.48 to 4.66 °C) at most heating scenarios. The 3-D scanned approach can accurately incorporate the irregular geometric details of the oven cavity and can improve the prediction accuracy of microwave heating models for future food products and oven development.

Heat distribution improvement with the implementation of polyethylene-covered water bolus into breast cancer hyperthermia

This paper presents the implementation of polyethylene-covered water bolus into a non-invasive breast cancer hyperthermia applicator. This modified hyperthermia applicator is introduced to improve the performance of hyperthermia by reducing or removing unwanted hotspots during hyperthermia treatment. This simulation-based experiment is carried out to observe the heating distribution of hyperthermia with water bolus coated by three different thicknesses of polyethylene cover or layer, which are 0.5mm, 0.8mm and 1.0mm. The solvent used in the water bolus is distilled water. The 915MHz microstrip antenna as a hyperthermia applicator and stage 2 breast cancer with a cancer depth of 28.6 mm to 73.6 mm is selected for this study. Based on the results, with the modified HTP integrated by water bolus, the heat pattern of hyperthermia simulation becomes more concentrated into the targeted cancer region, and unwanted hotspots nearby the skin area of breast tissue are removed. The 0.5mm thick polyethylene cover showed the best results with a focusing region between 29.4mm to 69.4mm compared with the result of hyperthermia without implemented water bolus, which heated the 26.6mm to 67.3mm region.